Fisheries and Aquatic Sciences
BioMed Central
Review

Food-borne outbreaks, distributions, virulence, and antibiotic resistance profiles of Vibrio parahaemolyticus in Korea from 2003 to 2016: a review

Kunbawui Park1, Jong Soo Mok1,*http://orcid.org/0000-0003-2066-0826, Ji Young Kwon1, A Ra Ryu1, Song Hee Kim1, Hee Jung Lee1
1Food Safety and Processing Research Division, National Institute of Fisheries Science46083BusanRepublic of Korea
*(+82)-51-720-2630mjs0620@korea.kr

© The Author(s) 2018. Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Received: Oct 9, 2017; Accepted: Jan 2, 2018

Published Online: Feb 14, 2018

Abstract

Background

Vibrio parahaemolyticus is one of the most common causes of seafood-borne illnesses in Korea, either directly or indirectly, by consuming infected seafood. Many studies have demonstrated the antibiotic susceptibility profile of V. parahaemolyticus. This strain has developed multiple antibiotic resistance, which has raised serious public health and economic concerns. This article reviews the food-borne outbreaks, distributions, virulence, and antibiotic resistance profiles of V. parahaemolyticus in Korea during 2003–2016.

Main body

V. parahaemolyticus infections appeared to be seasonally dependent, because 69.7% of patient infections occurred in both August and September during 2003–2016. In addition, the occurrence of V. parahaemolyticus in marine environments varies seasonally but is particularly high in July, August, and September. V. parahaemolyticus isolated from aquaculture sources on the Korean coast varied in association with virulence genes, some did not possess either the tdh (thermostable direct hemolysin) or trh (tdh-related hemolysin) genes, and a few were positive for only the trh gene or both genes. The high percentage of ampicillin resistance against V. parahaemolyticus in the aquatic environment suggests that ampicillin cannot be used to effectively treat infections caused by this organism.

Short conclusion

This study shows that the observed high percentage of multiple antibiotic resistance to V. parahaemolyticus is due to conventionally used antibiotics. Therefore, monitoring the antimicrobial resistance patterns at a national level and other solutions are needed to control aquaculture infections, ensure seafood safety, and avoid threats to public health caused by massive misuse of antibiotics.

Keywords: Vibrio parahaemolyticus; Food-borne outbreak; Virulence; Antibiotic resistance; Korea

Background

Vibrio parahaemolyticus is a naturally occurring bacterium in estuarine and marine environments and the leading cause of seafood-borne illness in many countries including Korea (Oh et al. 2011; Haendiges et al. 2014; Elmahdi et al. 2016). V. parahaemolyticus is one of the most common causes of seafood-associated bacterial gastroenteritis in Korea, either directly or indirectly, by consuming infected seafood (Kang et al. 2016; Yang et al. 2017).

Fortunately, the majority of environmental V. parahaemolyticus strains are not pathogenic (Han et al. 2007; Elmahdi et al. 2016). In addition, very few V. parahaemolyticus isolates from aquaculture sources in Korea express the virulence genes tdh (thermostable direct hemolysin) and trh (tdh-related hemolysin) (Oh et al. 2011; Yu et al. 2014; Park et al. 2016; Yang et al. 2017). Nevertheless, according to the food poisoning statistics from 2003 to 2016 (KMFDS (Korea Ministry of Food and Drug Safety) 2017), this strain caused infections in 4256 patients, including 2876 patients during 2003–2007, 986 during 2008–2012, and 394 during 2013–2016.

Since the discovery of penicillin in the 1920s, hundreds of antibiotic agents have been developed and applied for clinical use or animal treatment (Aarestrup and Wegener 1999). Vibrio species are usually susceptible to most veterinary and human antimicrobials (Oliver 2006). However, several studies have reported that antibiotic resistance has emerged and evolved in many bacterial genera including Vibrio spp. during the past few decades due to excessive use of antibiotics in human, agriculture, and aquaculture systems (Mazel and Davies 1999; Cabello 2006). As a result of the misuse of antibiotics to control infections during aquaculture production, V. parahaemolyticus exhibits multiple antibiotic resistance, which has increased concerns about public health and the economic threat of this bacterium (Lesmana et al. 2001; Ottaviani et al. 2013; Al-Othrubi et al. 2014; Shaw et al. 2014; Kim et al. 2016a, b; Kang et al. 2017). Elmahdi et al. (2016) reported that both environmental and clinical isolates of V. parahaemolyticus show similar antibiotic resistance profiles. Antibiotic resistance within a wide range of infectious agents is a growing public health threat of broad concern to multiple countries and sectors (WHO (World Health Organization) 2014).

In Korea, the occurrence, presences of virulence genes, and multiple antibiotic resistance of V. parahaemolyticus in seafood and aquatic environments are particularly concerning in fish and shellfish farming and human health.

Food-borne outbreaks caused by V. parahaemolyticus in Korea

V. parahaemolyticus is one of the most common causes of seafood-borne illnesses in Korea. According to the food poisoning statistics from 2003 to 2016 (KMFDS (Korea Ministry of Food and Drug Safety) 2017), 225 cases and 4256 patients were reported in outbreaks caused by V. parahaemolyticus, accounting for 5.8% of total outbreaks and 4.1% of total patients, respectively, based on all food-borne illnesses occurring in Korea. This outbreak was ranked fourth in Korea.

This strain caused illness in 4256 patients from 2003 to 2016, including 2876 (300–732) patients during 2003–2007, 986 (106–329) during 2008–2012, and 394 (25–251) during 2013–2016 (see Fig. 1a). According to these data, the outbreaks associated with V. parahaemolyticus have been decreasing recently. In particular, the patient numbers caused by V. parahaemolyticus were remarkably low during 2013–2015 due to the decreases in the outbreak cases. It is assumed in the results that the Korean government further strengthens the publicity activities to reduce the seafood-borne outbreaks, especially during summer season. The rates of seafood-borne infections associated with V. parahaemolyticus increase during summer, especially between August and September, leading to 1355 patient infections (31.8%) and 1612 patient infections (37.9%), respectively (see Fig. 1b). In addition, according to the originating facility, the patient infection rate caused by V. parahaemolyticus was highest at restaurants (average 60.3%) with a range of 37.2–100.0% during 2003–2016 in Korea (Fig. 1a).

fas-21-0-3-g1
Fig. 1. Yearly (a) and monthly (b) outbreaks caused by Vibrio parahaemolyticus from 2003 to 2016 in Korea
Download Original Figure

Distribution of V. parahaemolyticus isolates on the Korean coast

Distribution of V. parahaemolyticus in seawater

Table 1 and Fig. 2 summarize the distribution of V. parahaemolyticus isolated in seawater samples collected from the Korean coast, as reported in many studies. Presumptive strains of V. parahaemolyticus in the samples were isolated using the plates of thiosulfate citrate bile salt and then confirmed using the VITEK, API 20E, or polymerase chain reaction (PCR) systems. In some reported results, V. parahaemolyticus was enumerated by the most probable number method. Han et al. (2012) investigated the abundance of V. parahaemolyticus in 281 seawater samples collected from the west coast of Korea (Kyunggi province and Incheon city). According to their results, the level of V. parahaemolyticus was high in summer, especially in August (92.9%) followed by July (85.0%) and September (76.5%). Park et al. (2016) compared the distribution of V. parahaemolyticus in seawater samples (n = 429) collected from the same shellfish farms at each site along the south coast of Korea during 2013–2015. They reported that the detection rate of V. parahaemolyticus was also highest in August of each year; however, the strain was barely detectable from November to April of the following year. In addition, Yang et al. (2017) reported that V. parahaemolyticus was detectable in 9.7 and 32.9% of the Vibrio sp. isolates obtained from seawater and zooplankton samples in the Geoje coastal area of Korea during September 2016. V. parahaemolyticus was detected more frequently in mesozooplankton samples than in seawater samples.

Table 1. Seasonal distribution of Vibrio parahaemolyticus isolated from samples of seawater, fish, and shellfish in Korea

Samples

Detection rate (%) (positive/total number)

References

Site (year)

Type (number)

Positive number

Dec~Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Seawater

 Coast in Kyunggi and Incheon

Seawater (281)

174

42.3a

37.5a

58.0a

85.0a

92.9a

76.5a

61.5a

Han et al. 2012

 Shellfish farms in south coast (2013)

Seawater (152)

9

0.0 (0/59)

0.0 (0/13)

0.0 (0/13)

7.7 (1/13)

35.7 (5/14)

15.4 (2/13)

0.0 (0/13)

7.1 (1/14)

Park et al. 2016

 Shellfish farms in south coast (2014)

Seawater (143)

10

0.0 (0/61)

8.3 (1/12)

8.3 (1/12)

0.0 (0/12)

40.0 (4/10)

33.3 (4/12)

0.0 (0/12)

0.0 (0/12)

Park et al. 2016

 Shellfish farms in south coast (2015)

Seawater (134)

21

2.1 (1/48)

16.7 (2/12)

8.3 (1/12)

16.7 (2/12)

66.7 (8/12)

33.3 (4/12)

23.1 (3/13)

0.0 (0/13)

Park et al. 2016

Fish and shellfish

 Seafood markets in Busan and Gyeong Nam (2004)

Sea foods (213)

65

0a

6.3a

9.1a

50.0a

66.5a

64.5a

41.5a

18.0a

Kim et al. 2005

 Seafood markets in Kyunggi and Incheon

Fish and shellfish (685)

286

37.5a

46.5a

35.0a

47.5a

61.5a

45.5a

30.5a

Han et al. 2012

 Seafood markets in Seoul (2005)

Oyster (72)

48

0.0 (0/16)

87.5 (7/8)

100 (8/8)

100 (8/8)

100 (8/8)

100 (8/8)

100 (8/8)

12.5 (1/8)

Lee et al. 2008

 Shellfish farms in Geoje and Tongyeong Coast (2011)

Oyster (40)

29

100 (8/8)

87.5 (7/8)

87.5 (7/8)

50.0 (4/8)

37.5 (3/8)

Yu et al. 2014

 Gomso Bay (2011)

Shellfish (40)

39

100 (8/8)

100 (8/8)

100 (8/8)

100 (8/8)

87.5 (7/8)

Yu et al. 2014

 Shellfish farms in south coast (2013)

Shellfish (169)

19

1.4 (1/73)

6.3 (1/16)

23.1 (3/13)

16.7 (2/12)

46.2 (6/13)

30.8 (4/13)

0.0 (0/16)

11.8 (2/17)

Park et al. 2016

 Shellfish farms in south coast (2014)

Shellfish (161)

14

3.8 (3/79)

0.0 (0/12)

7.7 (1/13)

7.7 (1/13)

25.0 (3/12)

36.4 (4/11)

0.0 (0/10)

12.5 (2/16)

Park et al. 2016

 Shellfish farms in south coast (2015)

Shellfish (151)

50

4.8 (3/62)

15.4 (2/13)

27.3 (3/11)

72.7 (8/11)

80.0 (8/10)

69.2 (9/13)

56.3 (9/16)

50.0 (8/16)

Park et al. 2016

 Shellfish farms in Incheon Coast (2014–2015)

Oyster (96)

36

0.0 (0/40)

0.0 (0/8)

50 (4/8)

100 (8/8)

100 (8/8)

100 (8/8)

100 (8/8)

0.0 (0/8)

Kim et al. 2016a

aDetection rate was assumed based on the figures in references Kim et al. 2005; Han et al. 2012

Download Excel Table
fas-21-0-3-g2
Fig. 2. Monthly detection rates of Vibrio parahaemolyticus in samples of seawater (a) and seafood (b) in Korea. The data of detection rate were obtained from Table 1, which was defined as positive sample number/total sample number × 100
Download Original Figure

These results indicate that V. parahaemolyticus occurs at high levels during summer to early autumn in seawaters off the Korean coast, especially in July, August, and September. However, the strain was often detected very little during winter to early spring when the water temperature is low in the seawaters off the Korean coast (Table 1 and Fig. 2). Na et al. (2016) investigated the prevalence of pathogenic Vibrio species, including V. parahaemolyticus isolated from 2220 seawater samples during 2013–2015 in Korea and their relationship with marine environmental factors. According to their results, among the environmental factors, the correlation between seawater temperature and V. parahaemolyticus strains was the highest (R2 = 0.90).

Distribution of V. parahaemolyticus in fish and shellfish

Various studies have investigated the distribution of V. parahaemolyticus isolated in samples of shellfish and fish collected from the Korean coast (Table 1 and Fig. 1). Kim et al. (2005) investigated the abundance of V. parahaemolyticus in 213 seafood samples, including sliced raw fish and living marine invertebrates (oysters, ascidians, and sea cucumbers) collected from seafood markets and restaurants in Busan city and Kyeongnam province of Korea. According to their results, V. parahaemolyticus was detected at a range of 41.5–66.5% from July to October, but its incidence was < 20% during the other months. The strain isolation rate (49.2%) in raw marine invertebrates including shellfish was higher (28.9%) than that in sliced raw fish. Another study was conducted in samples (n = 685) of fish and shellfish collected from retail seafood markets in Kyunggi province and Incheon city, Korea. In that study, the monthly detection rate of V. parahaemolyticus ranged from 30.5 to 61.5%; the highest level was found in August (Han et al. 2012).

In addition, most shellfish samples (including oysters) collected from seafood markets and shellfish farms in Korea also contain relatively high levels of V. parahaemolyticus during summer and early autumn (Lee et al. 2008; Yu et al. 2014; Kim et al. 2016a; Park et al. 2016). However, V. parahaemolyticus was often detected at very low rates during winter and early spring in low water temperatures off the Korean coast.

These results show that the seasonal variation and cycle are correlated with water temperature, which is a major factor affecting the abundance of V. parahaemolyticus (Sudha et al. 2014). Some previous studies have reported a positive correlation between water temperature and V. parahaemolyticus counts (DePaola et al. 2003). The outbreaks associated with V. parahaemolyticus in Korea appear to be seasonally dependent because 31.8 and 37.9% of patient infections occurred in August and September during 2003–2016, respectively (Fig. 1b). The Korean results also show seasonal variations in the occurrence of V. parahaemolyticus in the samples of seawater, fish, and shellfish (Table 1 and Fig. 2).

Virulence genes of V. parahaemolyticus isolates in Korea

Virulence of V. parahaemolyticus has been attributed to the presence of the tdh and trh toxic genes using the PCR (Nishibuchi et al. 1985). The tdh and trh genes are widely considered predominant indicators of virulence in V. parahaemolyticus (Su and Liu 2007; Shimohata and Takahashi 2010). Honda and Iida (1993) reported that only 1–2% of environmental V. parahaemolyticus strains normally produce the tdh gene.

In this article, some V. parahaemolyticus isolates were investigated for the presence of virulence genes (tdh and trh) by PCR system. The expected size of the amplified DNA was 251 bp for the tdh gene and 250 bp for the trh gene, respectively. Oh et al. (2009) conducted a study to investigate the presence of the tdh and trh toxic genes in V. parahaemolyticus isolated from brackish water samples collected off the south coast of Korea, such as Geoje city, Tongyeong city, and Goseong Gun (Table 2). According to their results, 23 of 177 isolates were positive for the tdh gene, whereas all strains tested negative for the trh gene. On the other hand, many studies have shown that all V. parahaemolyticus stains isolated from seawater samples collected from the Korean coast were negative for the tdh and trh virulence genes (Lee and Park 2010; Kim et al. 2014, 2016a, b; Park et al. 2016). Yang et al. (2017) reported that all 30 V. parahaemolyticus strains and mesozooplankton samples isolated from seawater were negative for the tdh and trh virulence genes. Therefore, these reports indicate that all V. parahaemolyticus stains isolated from seawater samples collected off the Korean coast are negative for the tdh and trh virulence genes; however, the tdh gene was detected in 13.0% of isolates from brackish water samples collected from sites located in the mouths of streams (Table 2).

Table 2. Summary of antibiotic resistance profiles of Vibrio parahaemolyticus isolated from samples of seawater, fish, and shellfish in Korea

Samples

Number of isolates

Virulence genes (%)

Resistant (%)a

References

Site (year)

Type (number)

Antimicrobials used

Three or more of antimicrobials

Water

 Fish farms in south coast (2004)

Seawater (60)

145

AM (98.0), OA (30.6), AN (26.5), AMC (20.4), TE (12.2), CIP (6.1), D (4.1), CEP (2.0), CTX and SXT (0.0)

15.2 (22/145)

Son et al. 2005

 Coast in Geoje, Tongyeong, and Goseong (2005)

Brackish water (27)

177

tdh (13), trh (0)

AM (85.9), RA (26.6), AN (16.4), S (13.6), TMP (13.0), E (3.4), GM (1.1), AMC, TE, CIP, CEP, CTX, SXT, C, and NA (0.0)

20.3 (36/177)

Oh et al. 2009

 West coast (2006)

Seawater (22)

21

AM (100), CF (85.7), AN (81.0), FOX (38.1), GM (9.5), AMC (4.8), CIP, CTX, SXT, and C (0.0)

Lee et al. 2009

 Shellfish farms in Gomso Bay (2008)

Seawater (−)

28

tdh (0), trh (0)

Lee and Park 2010

 Shellfish farms in Wando Coast (2011–2012)

Seawater (−)

67

tdh (0), trh(0)

AM (100), OX (100), VA (64.2), S (56.7), AN (31.3), K (22.4) CF (20.9), E (10.4), CIP (4.5), TE (3.0), SXT, TMP, GM, C, and NA (0.0)

88.1 (59/67)

Kim et al. 2014

 Shellfish farms in south coast (2013–2015)

Seawater (429)

37

tdh (0), trh (0

Park et al. 2016

 Shellfish farms in Gomso Bay (2014–2015)

Seawater (100)

79

tdh (0), trh (0)

OX (100), VA (100), P (100), AM (96.2), E (10.1), S (7.6), FOX (6.3), AN (2.5), CF (2.5), TE, CIP, CEP, CTX, SXT, RA, TMP, GM, C, NA, K, CTT, and CZ (0.0)

100 (79/79)

Kim et al. 2016b

Fish

 Fish farms in south coast (2004)

Fish (66)

49

AM (97.9), OA (24.1), AN (17.2),

TE (4.8), D (4.1), CIP (2.8), AMC (1.4), CTX and SXT (0.7), CEP (0.0)

38.8 (16/49)

Son et al. 2005

 Fish farms in south coast (2005–2007)

Fish (180)

218

tdh (5.5), trh (0.5)

AM (57.8), RA (11.9), S (8.7), TMP (6.4), TE and C (3.7), AN and NA (2.8), GM (1.8), CEP and SXT (1.4), CTX and E (0.9), CIP (0.5), AMC (0.0)

10.1 (22/218)

Oh et al. 2011

Shellfish

 Shellfish farms in Geoje and Tongyeong Coast (2011)

Oyster (40)

129

tdh (0), trh (0)

AM (79.1), TMP (3.1), S (1.6), CTX, SXT, RA, GM, and NA (0.8), AN, AMC, TE, CIP, CEP, E, and C (0.0)

1.6 (2/129)

Yu et al. 2014

 Shellfish farms in Gomso Bay (2011)

Short neck clam (40)

307

tdh (0), trh (0)

AM (61.0), TMP (5.2), S (2.9), RA (2.3), GM and NA (1.0), C (0.3), AN, AMC, TE, CIP, CEP, CTX, SXT, and E (0.0)

3.6 (11/307)

Yu et al. 2014

 Shellfish farms in south coast (2013–2015)

Shellfish (481)

84

tdh (2.4), trh (9.5)

Park et al. 2016

 Shellfish farms in Incheon Coast (2014)

Oyster (15)

71

tdh (0.0), trh (53.5)

AM (100), S (50.7), CF (52.2), RA (50.7), GM (2.9), E (15.5), CIP (2.8), TE, CEP, CTX, SXT, C, and NA (0.0)

87.3 (62/71)

Kang et al. 2016

 Shellfish farms in Incheon Coast (2014–2015)

Oyster (96)

115

tdh (0.0), trh (9.6)

AM (94.8), S (60.0), CF (53.9), RA (47.8), E (13.9), GM (7.0), CIP (4.4), CEP(3.5), NA (1.7), TE (0.9), K (0.4), CTX, SXT, C, and CTT (0.0)

46.1 (53/115)

Kim et al. 2016a

 Shellfish farms in Incheon Coast (2015)

Oyster (16)

44

tdh (0.0),

trh (9.1)

AM (86.4), S (75.0), CF (56.8), RA (43.2), GM (13.6), E (11.4), CIP (6.8), NA (4.5), TE (2.3), CEP, CTX, SXT, and C (0.0)

77.3

(25/44)

Kang et al. 2017

Other

 Seafood markets in Busan and Gyeong Nam (2004)

Seafood (213)

65

AM (96.9), AN (29.2), TE (27.7), CTX (9.2), AMC, CIP, CEP, and SXT (0.0)

Kim et al. 2005

 Coast and seafood markets in Kyunggi and Incheon

Seawater (281)

Fish and shellfish (685)

716

VA(97.3), AM (87.3), CF (48.8), RA (46.1), E (28.7), NA(16.5), TE (13.5), CTX, SXT, GM, C, K, and NN (< 10)

68.7 (492/716)

Han et al. 2012

 Geoje Coast (2016)

Zooplank-ton (14)

Seawater (14)

24

6

tdh (0.0), trh (0.0)

tdh (0.0), trh (0.0)

AM (100), PIP (90.0), RA (73.3), CF (73.4), CZ (66.7), TMP (10), AN (6.7), CIP and SXT (3.3), TE, AMC, CEP, CTX, S, GM, C, NA, and CTT (0.0)

93.3 (28/30)

Yang et al. 2017

AM ampicillin, OA oxolinic acid, AN amikacin, AMC amoxicillin/clavulanic acid, TE tetracycline, CIP ciprofloxacin, D doxycycline, CEP cefepime, CTX cefotaxime, SXT sulfamethoxazole-trimethoprim, RA rifampin, S streptomycin, TMP trimethoprim, E erythromycin, GM gentamicin, C chloramphenicol, NA nalidixic acid, CF cephalothin, FOX cefoxitin, OX oxacillin, VA vancomycin, K kanamycin, P penicillin, CTT cefotetan, CZ cefazolin, NN tobramycin, PIP piperacillin

aResistance was classified according to guidelines of the Clinical and Laboratory Standards Institute (CLSI)

Download Excel Table

In addition, Oh et al. (2011) carried out a study to determine the virulence genes of 215 V. parahaemolyticus isolates from farmed fish in Korea. Of them, 12 (5.5%) and 1 (0.5%) strains were positive for the tdh and trh genes, respectively. Finally, according to various shellfish studies of Korean coastal shellfish farms, some V. parahaemolyticus isolates do not possess the tdh and trh genes (Yu et al. 2014), and a few were positive for only the trh gene with a range of 9.1–53.5% (Kang et al. 2016, 2017; Kim et al. 2016a, b). Another Korean study reported that 2 (2.4%) and 8 (9.5%) of 84 strains isolated from shellfish samples were positive for the tdh and trh genes, respectively (Park et al. 2016). Therefore, some V. parahaemolyticus isolates from cultured shellfish and fish do rarely possess both genes, and a few were positive for only the trh gene (Table 2).

Antibiotic resistance profiles of V. parahaemolyticus isolates in Korea

Antibiotic resistance profiles of V. parahaemolyticus in seawater

Pathogenic bacteria with antimicrobial resistance genes are often released with wastewater discharge into the aquatic environment (Baquero et al. 2008), indicating that naturally occurring aquatic bacteria including V. parahaemolyticus are capable of serving as reservoirs for resistance genes. Many studies have investigated antibiotic resistance of V. parahaemolyticus in water samples from the Korean coast (Table 2). The recommended antibiotics to treat V. parahaemolyticus illnesses are tetracycline or ciprofloxacin (CDC (Centers for Disease Control and Prevention) 2013). Some Korean studies that were carried out to characterize the antibiotic susceptibility profile of V. parahaemolyticus isolates in seawater samples indicated that 3.0–12.2% of isolates were resistant to tetracycline and ciprofloxacin (Son et al. 2005; Kim et al. 2014).

A study was carried out in 2004 on the antibiotic resistance of 145 V. parahaemolyticus isolates collected from seawater samples at fish farms on the south coast of Korea (Son et al. 2005). Vibrio spp. were resistant to the majority of antibiotics tested (2.0–98%), except for cefotaxime and sulfamethoxazole-trimethoprim, with the highest resistance found for ampicillin. About 15 of the isolates were resistant to three or more antibiotic agents, including tetracycline or ciprofloxacin, which are usually prescribed for V. parahaemolyticus infections.

Oh et al. (2009) investigated the antibiotic susceptibility of V. parahaemolyticus by analyzing the toxigenic and non-toxigenic strains isolated from brackish water samples on the south coast of Korea, such as in Geoje city, Tongyeong city, and Goseong Gun, to 15 antibiotics. A total of 177 V. parahaemolyticus strains were analyzed including 13% of the isolates with the tdh gene. No significant difference was observed in the distribution of multiple resistances with respect to pathogenic potential, and 20.3% of all strains were resistant to three or more classes of antibiotics. Some strains were resistant to ampicillin (85.9%), rifampin (26.6%), amikacin (16.4%), streptomycin (13.6%), trimethoprim (13.0%), erythromycin (3.4%), and gentamicin (1.1%).

Another study was conducted to investigate the susceptibility patterns to different antibiotic agents of 67 V. parahaemolyticus isolates in seawater samples from shellfish farms on the Wando coast of Korea. All isolates (100%) were resistant to ampicillin and oxolinic acid, and 88.1% of all strains were resistant to three or more classes of antibiotics. However, all isolates were sensitive to sulfamethoxazole-trimethoprim, trimethoprim, gentamicin, chloramphenicol, and nalidixic acid (Kim et al. 2014).

Similarly, Kim et al. (2016a, b) reported that all V. parahaemolyticus strains (79 isolates), isolated in seawater samples from shellfish farms in Gomso Bay, Korea, were resistant to oxolinic acid, vancomycin, and penicillin, and 96.2% of all isolates also demonstrated resistance to ampicillin. Unexpectedly, all isolates were resistant to three or more classes of antibiotics.

These reports indicate that V. parahaemolyticus isolates collected from water samples on the Korean coast show very high resistance to ampicillin, accounting for 85.9–100% (see Table 2). A very high ampicillin resistance rate was observed in V. parahaemolyticus in the USA as early as 1978, even before the recognition of Vibrio vulnificus as a food-borne pathogen (Blake et al. 1979).

Antibiotic resistance profiles V. parahaemolyticus in fish

Forty-nine isolates of V. parahaemolyticus were obtained from fish at different fish farms on the south coast of Korea and tested for their susceptibility to various antibiotics. The highest incidence of antibiotic resistance was reported against ampicillin (97.9%) followed by oxolinic acid (24.1%) and amikacin (17.2%). Among these isolates, 100 and 38.8% showed resistance to at least one and three of the ten tested antibiotics, respectively (Son et al. 2005). Oh et al. (2011) also investigated the antibiotic resistance of V. parahaemolyticus isolated from fish farms on the south coast of Korea, where 57% of all isolates were resistant to ampicillin, and 65.1% of the isolates were resistant to at least one of the 15 tested antibiotics.

Antibiotic resistance profiles of V. parahaemolyticus in shellfish

Yu et al. (2014) compared the incidence of antibiotic resistance of V. parahaemolyticus strains isolated from oysters and short-neck clams in each shellfish-growing area of the Korean coast. Of the 129 and 307 isolates from each shellfish species, 79.1 and 61.0% were resistant to ampicillin, respectively, which was the highest of the tested antibiotics. Multiple resistance to at least three antibiotics was relatively low with a range of 1.6–3.6%. Kang et al. (2016, 2017) and Kim et al. (2016a, b) conducted an antibiotic resistance study of V. parahaemolyticus isolates from oysters on shellfish farms located on the Incheon coast of Korea during 2014–2015. Their results indicate that the highest resistance in each study was against ampicillin (86.4–100%) followed by streptomycin (50.7–75.7%), cephalothin (52.2–56.8%), and rifampin (43.2–50.7%). Among these isolates, 46.1–87.3% were resistant to at least three of the tested antibiotics.

Antibiotic resistance profiles of V. parahaemolyticus in other samples

Kim et al. (2005) tested the antibiotic resistance of V. parahaemolyticus isolated in 213 seafood samples, including sliced raw fish and living marine invertebrates from different seafood markets and restaurants in Busan city and Kyeongnam province Korea. V. parahaemolyticus isolates were resistant to ampicillin (96.9%), amikacin (29.2%), and tetracycline (27.7%).

Han et al. (2012) determined the antibiotic resistance profile of 716 V. parahaemolyticus strains isolated from samples of seawater, fish, and shellfish on seven coastal areas of Kyunggi province and Incheon city, Korea. According to their results, 97.3 and 87.3% of the isolates showed very high resistance to vancomycin and ampicillin, respectively, followed by cephalothin (48.8%) and rifampin (46.1%). In addition, 68.7% of the isolates presented multiple resistance to at least 3 of the 13 antibiotics tested, including vancomycin and ampicillin. Two exhibited resistance to 11 antibiotics used in this study. However, about 92% of these isolates were highly susceptible to sulfamethoxazole-trimethoprim and chloramphenicol. They also found high sensitivity to gentamicin (82.3%), tobramycin (74.8%), nalidixic acid (71.6%), tetracycline (69.4%), and cefotaxime (63.0%).

Yang et al. (2017) characterized the antimicrobial resistance profile of V. parahaemolyticus isolated from seawater and zooplankton samples in the Geoje coastal area Korea, which is an important area for coastal fisheries, the fishing industry, and tourism. All V. parahaemolyticus isolates were resistant to ampicillin, and 66.7–90.0% exhibited resistance to rifampin, cephalothin, cefazolin, and piperacillin. In addition, 93.3% of the isolates were resistant to three or more antimicrobial agents. This was the first antimicrobial susceptibility data of V. parahaemolyticus recovered from zooplankton samples in Korea.

Several studies have reported that V. parahaemolyticus isolates collected from samples of seawater, fish, shellfish, and zooplankton in Korea have a very high resistance to ampicillin of 57.8–100% (see Table 2). Similarly, a very high ampicillin resistance rate is also observed in V. parahaemolyticus isolated from marine environments and seafood in many countries, including the USA (Elmahdi et al. 2016).

Tetracycline has long been the most commonly used antibiotic in Korean fisheries, particularly to treat heavy infections caused by Vibrio species (Morris and Tenney 1985; Oh et al. 2011). The recommended antibiotics for treating V. parahaemolyticus illnesses are tetracycline and ciprofloxacin (CDC (Centers for Disease Control and Prevention) 2013; Elmahdi et al. 2016). Unfortunately, although a low percentage of tetracycline resistance to V. parahaemolyticus was observed, some V. parahaemolyticus isolates developed resistance to tetracycline (see Table 2).

In addition, many studies have reported high multiple antibiotic resistance in V. parahaemolyticus isolates from samples of water, fish, and shellfish on the Korean coast (Table 2).

Conclusions

V. parahaemolyticus is a naturally occurring bacterium in estuarine and marine environments and a leading cause of seafood-borne illness. Outbreaks associated with V. parahaemolyticus in Korea appear to be seasonally dependent because 69.7% of patient infections occurred in August and September during 2003–2016. In addition, the occurrence of V. parahaemolyticus increased during summer and early autumn in the samples of seawater, fish, and shellfish from the Korean coast, especially in July, August, and September.

All V. parahaemolyticus isolates in the seawater samples from the Korean coast were negative for the tdh and trh virulence genes; however, the tdh gene was detected in 13.0% of isolates from brackish water samples in the stream estuary areas. V. parahaemolyticus isolates from aquaculture production (shellfish and fish) showed various patterns associated with the virulence genes; some did not possess either the tdh or trh gene, whereas a few were positive for only the trh gene or both genes.

Our findings suggest that ampicillin has been excluded as a treatment option for infections caused by V. parahaemolyticus, because the strains from aquaculture sources (e.g., seawater, fish, shellfish, and zooplankton) in Korea have very high resistance to ampicillin, which ranged from 57.8 to100% of the isolates. In addition, multiple resistance to three or more antimicrobial agents were high with a range of 10.1–100% in V. parahaemolyticus isolates from samples of water, fish, and shellfish off the Korean coast, except two shellfish sampling areas (1.6–3.6%). These findings indicate that a high incidence of antimicrobial resistance of V. parahaemolyticus in marine environments is due to exposure to conventionally used antibiotics.

Therefore, monitoring the distribution and antimicrobial susceptibility of V. parahaemolyticus strains in seafood and marine environments, with surveys expanded to a national level, is needed to ensure seafood safety. Moreover, the development of new alternative methods (e.g., probiotics and natural antimicrobials) is urgently needed to reduce antibiotic use in fish and shellfish farming and to avoid threats to public health caused by massive misuse of antibiotics.

Acknowledgements

We thank William King, PhD, from Edanz Group (www.edanzediting.com/ac) for editing the draft of this manuscript.

Funding

This work was supported by a grant from the National Institute of Fisheries Science in Korea (R2017057).

Availability of data and materials

Not applicable.

Authors’ contributions

KP and JSM designed this study, carried out the analysis of the antibiotic resistance data, and drafted the manuscript. JYK, ARR, SHK, and HJL carried out the data analysis of food-borne outbreaks, monthly distributions, and virulence genes, and polished the manuscript. All authors have read and approved the final version of the manuscript.

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

1.

Aarestrup FM, Wegener HC. The effects of antibiotic usage in food animals on the development of antimicrobial resistance of importance for humans in Campylobacter and Escherichia coli. Microbes Infect. 1999; 1:639-644

2.

Al-Othrubi SM, Kqueen CY, Mirhosseini H, Hadi YA, Radu S. Antibiotic resistance of Vibrio parahaemolyticus isolated from cockles and shrimp sea food marketed in Selangor, Malaysia. Clin Microbiol. 2014; 3:148154.

3.

Baquero F, Martinez JL, Canton R. Antibiotics and antibiotic resistance in water environments. Curr Opin Biotechnol. 2008; 19:260-265

4.

Blake PA, Merson MH, Weaver RE, Hollis DG, Heublein PC. Disease caused by a marine Vibrio. Clinical characteristics and epidemiology. N Engl J Med. 1979; 300:1-5

5.

Cabello FC. Heavy use of prophylactic antibiotics in aquaculture: a growing problem for human and animal health and for the environment. Environ Microbiol. 2006; 8:1137-1144

6.

CDC (Centers for Disease Control and Prevention). Antibiotic resistance threats in the United States. 2013http://www.cdc.gov/drugresistance/threat-report-2013. Accessed 29 Aug 2017.

7.

DePaola A, Ulaszek J, Kaysner CA, Tenge BJ, Nordstrom JL, Well J. Molecular, serological, and virulence characteristics of Vibrio parahaemolyticus isolated from environmental, food, and clinical sources in North America and Asia. Appl Environ Microbiol. 2003; 69:3999-4005

8.

Elmahdi S, DaSilva LV, Parveen S. Antibiotic resistance of Vibrio parahaemolyticus and Vibrio vulnificus in various countries: a review. Food Microbiol. 2016; 57:128-134

9.

Haendiges J, Rock M, Myers RA, Brown EW, Evans P, GonzalezEscalona N. Pandemic Vibrio parahaemolyticus, Maryland, USA, 2012. Emerging Infect Dis. 2014; 20:718-720

10.

Han AR, Yoon YJ, Kim JW. Antibiotic resistance and plasmid profile of Vibrio parahaemolyticus strains isolated from Kyunggi-Incheon coastal area. Kor J Microbiol. 2012; 48:22-28

11.

Han F, Walker RD, Janes ME, Prinyawiwatkul W, Ge B. Antimicrobial susceptibilities of Vibrio parahaemolyticus and Vibrio vulnificus isolates from Louisiana Gulf and retail raw oysters. Appl Environ Microbiol. 2007; 73:7096-7098

12.

Honda T, Iida T. The pathogenicity of Vibrio parahaemolyticus and the role of thermostable direct hemolysin and related hemolysins. Rev Medical Microbiol. 1993; 4:106-113

13.

Kang CH, Shin YJ, Jang SC, Yu HS, Kim SK, An SR, Park K, So JS. Characterization of Vibrio parahaemolyticus isolated from oysters in Korea: resistance to various antibiotics and prevalence of virulence genes. Mar Pollut Bull. 2017; 118:261-266

14.

Kang CH, Shin YJ, Kim WR, Kim YG, Song KC, Oh EG, Kim SK, HS Y, So JS. Prevalence and antimicrobial susceptibility of Vibrio parahaemolyticus isolated from oysters in Korea. Environ Sci Pollut Res. 2016; 23:918-926

15.

Kim SH, Sin YM, Lee MJ, Shin PK, Kim MG, Cho JS, Lee CH, Lee YJ, Chae KR. Isolation of major foodborne pathogenic bacteria from ready-to-eat seafoods and its reduction strategy. J Life Sci. 2005; 15:941-947

16.

Kim SK, An SR, Park BM, Oh EG, Song KC, Kim JW, Yu HS. Virulence factors and antimicrobial susceptibility of Vibrio parahaemolyticus isolated from oyster Crassostrea gigas. Kor J Fish Aquat Sci. 2016a;49:116–23.

17.

Kim TO, Eum IS, Jo SM, Kim HD, Park KS. Antimicrobial-resistance profiles and virulence genes of Vibrio parahaemolyticus isolated from seawater in the Wando area. Kor J Fish Aquat Sci. 2014; 47:220-226.

18.

Kim TO, Eum IS, Kim HD, Park KS. Antimicrobial resistance and minimum inhibitory concentrations of Vibrio parahaemolyticus strains isolated from Gomso Bay, Korea. Kor J Fish Aquat Sci. 2016b;49:582–8.

19.

KMFDS (Korea Ministry of Food and Drug Safety). Food poisoning outbreak statistics. 2017http://www.mfds.go.kr/fm/index.do. Accessed 14 Aug 2017.

20.

Lee HW, Lim SK, Kim MN. Characteristics of ampicillin resistant Vibrio spp. isolated from a west coastal area of Korean Peninsula. Kor J Fish Aquat Sci. 2009; 42:20-25.

21.

Lee JK, Jung DW, Eom SY, SW O, Kim Y, Kwak HS, Kim YH. Occurrence of Vibrio parahaemolyticus in oysters from Korean retail outlets. Food Control. 2008; 19:990-994

22.

Lee KW, Park KS. Antibiotic-resistance profiles and the identification of the ampicillin–resistance gene of Vibrio parahaemolyticus isolated from seawater. Kor J Fish Aquat Sci. 2010; 43:637-641.

23.

Lesmana M, Subekti D, Simanjuntak CH, Tjaniadi P, Campbell JR, Oyofo BA. Vibrio parahaemolyticus associated with cholera-like diarrhea among patients in North Jakarta, Indonesia. Diagn Microbiol Infect Dis. 2001; 39:71-75

24.

Mazel D, Davies J. Antibiotic resistance in microbes. Cell Mol Life Sci. 1999; 56:742-754

25.

Morris JG, Tenney J. Antibiotic therapy for Vibrio vulnificus infection. J Am Med Assoc. 1985; 253:1121-1122

26.

Na HY, Hong SH, Chung GT. The relationship of pathogenic Vibrio spp. with marine environmental factors, Korea, 2013–2015. Public health weekly report. Korea Centers for Disease Control and Prevention (KCDC). 2016http://cdc.go.kr/CDC/info/CdcKrInfo0301.jsp?menuIds=HOME001-MNU1154-MNU0005-MNU0037&year=2016. Accessed 28 Aug 2017.

27.

Nishibuchi M, Ishibashi M, Takeda Y, Kaper JB. Detection of the thermostable direct hemolysin gene and related DNA sequences in Vibrio parahaemolyticus and other Vibrio species by the DNA colony hybridization test. Am Soc Microbiol. 1985; 49:481-486.

28.

Oh EG, Son KT, Ha KS, Yoo HD, Yu HS, Shin SB, Lee HJ, Kim JH. Antimicrobial resistance of Vibrio strains from brackish water on the coast of Gyeongnamdo. Kor. J Fish Aquat Sci. 2009; 42:335-343.

29.

Oh EG, Son KT, Yu HS, Lee TS, Lee HJ, Shin SB, Kwon JY, Park K, Kim JH. Antimicrobial resistance of Vibrio parahaemolyticus and Vibrio alginolyticus strains isolated from farmed fish in Korea during 2005–2007. J Food Protec. 2011; 74:380-386

30.

Oliver JD. In: Thompson FL, Austin B, Swings J, editors. Vibrio vulnificus. The biology of vibrios. 2006; Washington DC: ASM Press. p. 349-366

31.

Ottaviani D, Susini F, Montagna C, Monno R, D’Annibale L. Extensive investigation of antimicrobial resistance in Vibrio parahaemolyticus from shellfish and clinical sources, Italy. Int J Antimicrob Agents. 2013; 42:191-193

32.

Park YS, Park K, Kwon JY, Yu HS, Lee HJ, Kim JH, Lee TS, Kim PH. Antimicrobial resistance and distribution of virulence factors of Vibrio parahaemolyticus isolated from shellfish farms on the southern coast of Korea. Kor J Fish Aquat Sci. 2016; 49:460-466.

33.

Shaw KS, Goldstein RER, He X, Jacobs JM, Crump BC, Sapkota AR. Antimicrobial susceptibility of Vibrio vulnificus and Vibrio parahaemolyticus recovered from recreational and commercial areas of Chesapeake Bay and Maryland Coastal Bays. PLoS One. 2014; 9:1-11.

34.

Shimohata T, Takahashi A. Diarrhea induced by infection of Vibrio parahaemolyticus. J Med Investig. 2010; 57:179-182

35.

Son KT, Oh EG, Lee TS, Lee HJ, Kim PH, Kim JH. Antimicrobial susceptibility of Vibrio parahaemolyticus and Vibrio alginolyticus from fish farms on the southern coast of Korea. J Kor Fish Soc. 2005; 38:365-371.

36.

Su YC, Liu C. Vibrio parahaemolyticus: a concern of seafood safety. Food Microbiol. 2007; 24:549-558

37.

Sudha S, Mridula C, Silvester R, Hatha AA. Prevalence and antibiotic resistance of pathogenic vibrios in shellfishes from Cochin market. Indian J Geo-Mar Sci. 2014; 43:815-824.

38.

WHO (World Health Organization). Antimicrobial resistance global report on surveillance. 2014http://www.who.int/drugresistance/documents/surveillancereport/en/. Accessed 17 May 2017.

39.

Yang JH, Mok JS, Jung YJ, Lee KJ, Kwon JY, Park K, Moon SY, Kwon SJ, Ryu AR, Lee TS. Distribution and antimicrobial susceptibility of Vibrio species associated with zooplankton in coastal area of Korea. Mar Poll Bull. 2017; https://doi.org/10.1016/j.marpolbul.2017.07.054

40.

Yu HS, Oh EG, Shin SB, Park YS, Lee HJ, Kim JH, Song KC. Distribution and antimicrobial resistance of Vibrio parahaemolyticus isolated from Korean shellfish. Kor J Fish Aquat Sci. 2014; 47:508-515.

Abbreviations

tdh

Thermostable direct hemolysin

trh

tdh-related hemolysin

V. parahaemolyticus

Vibrio parahaemolyticus