Furazolidone

Sir,

Continuing surveillance on Vibrio cholerae reveals reappearance of serogroup O139 in Rohtak 10 yr since its first isolation1. Historically, O1 strains have been responsible for all major epidemics including seven pandemics2. In 1992, an epidemics clone of serogroup O139 (Bengal) appeared in southern India3 that rapidly spread throughout most of Southeast Asia4,5 and readied Western Africa in 19946. Serogroup O139 related cholera epidemics/outbreaks have been reported from Calcutta (1993-1996)7, Lucknow (1998)8. Maharashtra (Yavatmal in 19949, Sewagram 1994(10), Mumbai 1999(11)), Orissa (Berhampur in 2000)12: and Hyderabad (2000-2001)13.

A total of 202 stool samples were collected in July-October 2003 from cases of acute watery diarrhoea at Post Graduate Institute of Medical Sciences, Rohtak. Exclusion criterion included patients using antimicrobial agents within previous 2 wk. All stool samples were subjected to routine macroscopic and microscopic examination. Direct plating of faecal sample was done on 5 per cent sheep blood agar, MacConkey agar and bile salt agar (Hi Media, Mumbai). Alkaline peptone water was used for enrichment and subculture was done on bile salt agar (BSA) after 18-24 h. After overnight incubation at 37°C, the typical colonies were identified by colony morphology and standard biochemical tests14. For final identification of vibrios, slide agglutination was performed with polyvalent O1 and monospecific Ogawa-Inaba antisera (obtained from Central Research Institute, Kasauli). Strains biochemically resembling vibrio but not agglutinable with polyvalent O1 antisera were sent to National Institute of Communicable Diseases (NICD), New Delhi for further confirmation. Antibiotic sensitivity was performed on Mueller Hinton agar plates by Kirby Bauer disc diffusion method15 for antibiotics (μg) chloramphenicol (10), tetracycline (30), cefuroxime (30), ampicillin (10), gentamicin (30), cotrimoxazole (25), norfloxacin (30), amikacin (30), cefotaxime (30), ciprofloxacin (5), and ceftizoxime (30) obtained from Hi-Media, Mumbai, India.

Of the 202 faecal specimens, 13 isolates of Vibrio cholerae were obtained, giving a positivity rate of 6.4 per cent. Of the 13 cholera cases, eight (61.5%) were males and five (38.5%) were females. All were paediatric cases ranging from 2-11 yr with mean age 6.9 yr. Except one case from Jhajjar, rest 12 (92.3%) were from Rohtak. Ten (76.9%) isolates agglutinable with poly O1 antisera were typical strain scrotype 'Ogawa'. Three (23.1%) non agglutinable isolates were O139 serogroup identified by NICD, Delhi. Of the 10 typical V. cholerae isolates, 40 per cent were only resistant to ampicillin, 40 per cent were resistant to both ampicillin and co-trimoxazole. One isolate resistant to gentamicin and cefuroxime and the other resistant to gentamicin, tetracycline and cefuroxime were also detected in our study. Among the three non agglutinable isolates of V. cholerae 0139, one was resistant to cefuroxime, second to ampicillin and co-trimoxazole, and the third multiply resistant to choloramphenicol, tetracycline, cefuroxime, ampicillin and gentamicin. All patients were successfully treated with antimicrobial therapy.

Antibiotic resistance in V. cholerae is encoded by horizontally transferable conjugative transposon which resides in the chromosome of host bacterium16. Increase in resistance to ampicillin, co-trimoxazole, nalidixic acid and neomycin was constantly recorded from 1994. Almost all the V. cholerae O1 strains were uniformly resistant to furazolidone and streptomycin while most were susceptible to gentamicin and tetracycline17. Our study showed 100 per cent susceptibility of V. cholerae to norfloxacin, amikacin, cefotaxime, ciprofloxacin and ceftizoxime with just one isolate resistant to chloramphenicol which belonged to serogroup O139. Only 2 of 13 isolates were tetracycline resistant. Like V. cholerae O1, 0139 strains were also found to be resistant to ampicillin, furazolidone and streptomycin and mostly susceptible to nalidixic acid, norfloxacin and tetracycline17. In our study, 76.9 per cent isolates were resistant to ampicillin and 15.3 per cent isolates were multiply resistant (≥3 antimicrobial agents). Multidrug resistant classical V. cholerae strains and simultaneous epidemic outbreaks of both classical and El Tor biotypes have been reported in Bangladesh18. Ciprofloxacin is an important substitute drug for treatment of multidrug resistant enteric and other pathogens. Extensive use of this drug and empirical therapy for treating diarrhoeal infection might have promoted incidence of ciprofloxacin resistant V. cholerae which emerged for the first time in Calcutta during 1992 among V. cholerae non-Ol non-O139 and during 1995 among V. cholerae O1 and 0139 strains19. On the other hand. 100 per cent susceptibility for norfloxacin and ciprofloxacin20 with minimum inhibitory concentration (MIC) being lower for 0139 serogroup as compared to V. cholerae O121 has been reported by other workers. Our study also showed that all the isolates were susceptible to ciprofloxacin and norfloxacin.

Hence. non-O1 V. cholerae should not be considered as epidemiologically or clinically unimportant. Continuous long-term surveillance programmes are essential to prevent outbreaks/ epidemics caused by V. cholerae and to monitor trends in their antimicrobial resistance patterns.

References

1. Sabherwal U. Sikka R. Emergence of Vibrio cholerae serogroup 0139 in Haryana in May-June 1993. Indian J Med Res 1994; 99 : 105

2. Karaolis DKR. Lan R. Reeves PR. The sixth and seventh cholera pandemics are due to independent clones separately derived from environmental. nontoxigenic, non-O1 Vihrio cholerae. J Bacterial 1995; 177 : 3191-8.

3. Ramamurthy T, Garb S, Sharma R. Bhattacharya SK, Nair GB. Shimada T. et al. Emergence of novel strain of I'ihrio cholerae with epidemic potential in southern and eastern India. Lancet 1993; 341 : 703-4.

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7. Mitra R. Basu a. Dulta D. Nair GB. Takeda Y. Resurgence of I'ihrio cholerae 0139 Bengal with altered antibiogram in Calcutta. India. Lancet 1996; 349: 1181.

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10. Narang P. Mendiratta DK. Kannathe .1. Characteristics of I'ihrio cholerae 0139 strains isolated in Sevagram (Maharashtra) during April-August 1993. Indian J Med Res 1994; 99 : 103-4.

11. Joshi A. Turbadkar D, Deshmukh A. Dalai P. Emergence of I'ihrio cholerae 0139 in Mumbai (Maharashtra, India). Indian J Med Microhiol 1999; 17 : 196.

12. Samal B. Ghosh SK. Mohanty SK. Patnaik K. Epidemic of I'ihrio cholerae serogroup 0139 in Berhampur. Orissa. Indian J Med Res 2001; 114 : 10-1.

13. Bilolikar AK. Dass SM, Sarguna P, Ramana KNS. Rao A. Emergence of I'ihrio cholerae O139 in and around Hyderabad. Indian J Med Microhiol 2003; 21 : 146.

14. Koneman EW, Allen SD, Janda WM, Schreckenberger PC. Winn WC Jr, editors. Colour atlas and text book of diagnostic microbiology. 5th ed. Lippincott, USA; 1997.

15. National Committee for Clinical Laboratory Standards (NCCLS). Performance standards for antimicrobial susceptibility testing, vol. 22, No. 1, January 2002.

16. Waldor MK, Tschpe H. Mekalanos JJ. A new type of conjugative transposon encodes resistance to sulfamethoxazole, trimethoprim, and streptomycin in l'ibrio cholerae O139. J Bacterial 1996; 178 : 4157-65.

17. Garg P. Chakraborty S, Basu I, Datta S. Rajendran K, Bhattacharya T. et al. Expanding multiple antibiotic resistance among clinical strains of Vibrio cholerae isolated from 1992-98 in Calcutta. India. Epidemiol Infect 2000: 124 : 393-9.

18. Siddique A, Zaman K, Majumder Y. Simultaneous outbreaks of contrasting drug resistant classic and El Tor Vibrio cholerae O1 in Bangladesh. Lancet 1989; ii : 396.

19. Mukhopadhyay AM, Basu I, Bhattacharya SK, Bhattacharya MK, Nair GB. Emergence of fluoroquinolone resistance in strains of Vibrio cholerae isolated from hospitalized patients with acute diarrhoea in Calcutta, India. Antimicrob Agents Chemother 1998; 42 : 206-7.

20. Sur D, Sengupta PG, Mondai SK, Dutta P, Gupta DN, Ghosh S, et al. A localised outbreak of Vibrio cholerae 0139 in Kolkata, West Bengal. Indian J Med Res 2002; 115 : 149-52.

21. Jesudason MV. Balaji V, Thomson CJ. Quinolone susceptibility of Vibrio cholerae Ol & O139 isolates from Vellore. Indian J Med Res 2002: 116 : 96-8.

Naveen Gupta*, Shalini Dewan & Santosh Saini

*For correspondence :

Department of Microbiology

Pt. B.D. Sharma Post Graduate

Institute of Medical Sciences

Rohtak (Ilaryana), India

e-mail: micronaveen@hotmail.com

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