Vibrio parahaemolyticus serotypes in Calcutta, India

Brief communladons Vibrio parahaemolyticus serotypes in Calcutta, India B. D. CHATrERJEE 1 & T. SEN 2 Abstract A study of V. parahaemolyticus strains isolated from different sources in Calcutta showed that the serotypes associated with human gastroenteritis do not frequently coincide with those of marine and non-narine isolates. Some atypical, complex, and new serotypes are reported. In Japan, the common serological types of Vibrio parahaemolyticus causing food poisoning are preva- lent in sea fish and marine water (4). No parallel study in any other country has yet been described in the literature. V. parahaemolyticus seems to pose special problems in Calcutta because it occurs in fish and water of non-marine origin (1). In the pres- ent study, V. parahaemolyticus serotypes associated with sporadic diarrhoea were compared with those from potential marine and non-marine sources in Calcutta. Since V. parahaemolyticus is facultatively halo- philic, it is of interest to note that the salinity of samples of water from 10 different ponds in Calcutta was found to vary considerably (120, 220, 290, 440, 470, 550, 630, 650, 650, and 830 mg/litre as chloride ion). The ponds from which isolates were prepared for this study do not connect with sewerage, latrines, or river system, and are used for domestic purposes. Material and methods Strains. The non-marine sources comprised 27 strains from small pond fishes and 25 strains from pond water. The marine reservoir was represented by 60 strains from water from the river Hooghly and 53 from sea shrimps. Sixty-two strains from human diarrhoea were also included. The procedure for the isolation and screening of strains from dif- ferent sources has been described by Chatterjee (1). Serotyping. K antigen type determination was 1 Reader, Department of Bacteriology and Serology, School of Tropical Medicine, Calcutta 700012, India. ' Epidemiologist, Field Research Unit, School of Tro- pical Medicine, Calcutta 700012, India. done by slide agglutination of 18-24-hour agar cul- ture suspensions in 2% saline solution, using 52 indi- vidual K antisera following prior testing with 8 pooled antisera. The 0 groups were ascertained by aggluti- nation tests on slides with 11 antisera after autoclav- ing each suspension for 0.5, 1, and 2 h. The set of Toshiba V. parahaemolyticus antisera employed in this study was kindly donated by Professor Takeshi Yokota, Juntendo University, Tokyo, Japan. A new K antiserum was prepared according to the methods of Edwards & Ewing (2). Results and discussion Table 1 shows the serotypes identified from strains from different sources. The majority of the faecal isolates were serotypable but not so many of the marine and non-marine isolates could be typed. The serotype 05: Cal/Ka, a new K antigenic type, ap- pears to occur in a significant proportion of diar- rhoea samples in Calcutta. Of the types detected in human diarrhoea, 01: K56, 04: K55, 05: K30, and 06: K46 were not reported from Japan and the United States (4, 5). Sakazaki et al. (4) concluded that an individual K antigen is invariably linked with one particular 0 group. This postulate needs modification in view of the presence of atypical types in the Calcutta series. That a strain may reveal 2 K antigens (i.e., that it may be of a complex type) is intriguing. The number of untypable strains was higher in the present study than in the experience of Sakazaki et al. (4), and the antigenic types found in the diar- rhoeic strains (excepting types 01: K38, 04: K12, 04: K55, 05: K15 and 05: K30) were not usually seen in the environment. A similar pattern has been noted in Yersinia enterocolitica, to which V. para- haemolyticus is thought to be taxonomically re- lated (1, 3). It is conceivable that unlike V. cholerae, V. parahaemolyticus is widely distributed in our sur- roundings, but that nevertheless the risk of infection is limited by the paucity of enteropathogenic sero- types. 3223 -559 BRIEF COMMUNICATIONS Table 1. Serotypes of V. parahaemolyticus strains isolated Calcutta from different sources in Non-marine fish Human diarrhoea Marine fish Results andstr (62 strains) wad tter(52 strains) (6 an)(113 strains) No. typable No. untypable Serotypes identified (no. of strains) 17 (32.6 %) 35 (67.4 %) 01 :K33(1)a 02: K3 (1) c 02: K28 (4) c 05: K15 (1) b 05: K17 (2) c 05: K47 (2) 05: K15/17 (1) d 08: K20 (2) c 010: K39 (1) a 011: K22 (1) a 011 :K34(1)a 51 (80.2 %) 11 (19.8%) 01: K38 (5) 01: K56 (5) 03: K4 (2) 03: K33 (4) 04: K8 (1) 04: Kl 2 (2) 04: Kl 3 (2) 04: K55 (2) 05: K12 (1) a 05: KI5 (5) 05: K30 (2) 05: Cal/Ka (12) 06: K46 (1) 08: K21 (2) 08: K22 (2) 09: K23 (2) 010: Kl19/46 (1 ) d 46 (40.7 %) 67 (59.3 %) 01 : K38 (1) b 02: K3 (1) c 02: K5 (1)a 02: K8 (1) 02: K28 (4) c 03: K29 (2) 04: Kl 2 (2) b 04: K29 (2) a 04: K34 (1) 04: K37 (1) a 04: K55 (1) b 05: Kl 7 (2) c 05: K30 (1) b 05: K41 (4) a 05: K43 (1) a 06: K18 (1) 08: K20 (3) c 08: K38 (1) a 010: K9 (1)a 010: K24 (3) 010: K26 (5) a 011 : K38 (3) a Oll :K54 (1) a 011: K38/54 (3)d a Atypical types, i.e., K antigen not linked with specific 0 group. b Strains resembling human isolates. c Common serotypes in marine and non-marine sources. d Complex types, i.e., occurrence of two K antigens in a single strain. Additional findings After the preparation of this paper for publication, the authors forwarded the results of continued investigations into V. parahaemolyticus serotypes in Calcutta. The following additional serotypes (number of strains shown in parentheses) were recorded from a second series of isolates of V. parahaemolyticus examined after the series described above: Non-marine strains (35) 03: K57 (1) 04: K29 (1) 04: K42 (3) 05: K5 (2) 05: K30 (1) 011 :K20 (1) Faecal Marine strains (29) strains (38) 02: K3 (2) 04:K9 (3) 04: Kl (1) 08: K20 (2) 010: K19 (1) 010: K24 (1) 01: K37 (1) 01: K54 (1) 03:K5 (1) 011 : K50 (1) 560 BRIEF COMMUNICATIONS 561 When tested for the Kanagawa phenomenon (1), 82 (90.1 %) of the total of 91 human faecal strains examined in both series showed positive results; the serotypes of the 9 negative strains were 03: K33 (2), 04: K8 (1), 04: K12 (1), 04: K13 (1), 05: Cal/Ka (1), 06: K46 (1), and 08: K20 (2). On the other hand, only 2 of the 238 strains from marine and non- marine sources, belonging to serotype 05: K47, were Kanagawa-positive. Evidently Kanagawa-posi- tive cultures are readily obtained from stools of patients but not from strains from the Calcutta environment. The question whether Kanagawa-posi- tivity is related to enteropathogenicity has still to be elucidated. ACKNOWLEDGEMENTS The authors thank Professor A. B. Chowdhury, Direc- tor of the School of Tropical Medicine, Calcutta, for providing facilities for study; Dr A. C. Mukherji and Dr S. N. Sanyal for their cooperation during the work; Dr S. C. Pal, Director, and Dr J. Sil, Bacteriologist, Cholera Research Centre, Calcutta, for supplying some human faecal strains; and Professor Takeshi Yokota, Juntendo University, Tokyo, Japan, who was most helpful in sending antisera. REFERENCES 1. CHATTERJEE, B. D. Epidemiologic and taxonomic status of Vibrio parahaemolyticus. In: Proceedings of the International Symposium on Vibrio parahaemoly- ticus. Tokyo, Saikon Publ. Co., 1974, pp. 177-185. 2. EDWARDS, P. R. & EWING, W. H. Identification of enterobacteriaceae, 2nd ed. Minneapolis, Burgess, 1962, pp. 214-215. 3. NutHN, B. Acta path. microbiol. scand. (Suppl.), 206: 1-48 (1969). 4. SAKAZAKI, R. ET AL. Jap. J. med. Sci. Biol., 21: 313-324 (1968). 5. ZEN-YOJI, H. ET AL. J. infect. Dis., 127: 237-241 (1973).