Asian Program

Japanese

Data

Former Fellows

Dissertation Abstracts

India

  Worldwide changing patterns of Shigella serotypes and increase in their antimicrobial patterns have been reported including India. Since WHO recommends antimicrobial therapy for treatment of shigellosis and development of multidrug resistance in Shigella strains is a global concern, monitoring of Shigella serotypes with their antimicrobial resistance is an integral part of diarrhoeal diseases surveillance system.
  With this background knowledge the status of Shigella infection among diarrhoea children in Kolkata, India has been investigated during Jan 2000 to Dec 2004. Shigella strains could be isolated as a sole pathogen from about 10% (S. flexneri, 5.6%; S. sonnei, 2.5%; S. dysenteriae, 1.2%; S. boydii, 0.7%) of total diarrhoea children admitted to a children's hospital in Kolkata during the study period. Among S. flexneri strains (100%), S. flexneri type 2a (42.2%) was the most frequently isolated strain followed by S. flexneri 3a (14.2%), S. flexneri type 6 (12.8%), S. flexneri type X (5%). During 2002 and 2003 a sudden emergence of S. dysenteriae serotype 1 strain was noted causing both outbreaks and sporadic cases. The strain was resistant to fluoroquinolones i.e., norfoxacin (Nf), ciprofloxacin (Ci) and ofloxacin (Of). During study period, few strains of provisional serovars of S. dysenteriae and S. boydii were recovered from Kolkata, which were confirmed in the Reference laboratory in Japan.
  Most of the Shigella isolates were multidrug resistance (MDR) i,e, resistant to antimicrobials like ampicillin (A), chloramphenicol (C), tetracycline (T), nalidixic acid (Na) and cotrimoxazole (Q), amoxicillin (Am). Although resistance to five or more drugs was more common in S. flexneri than S. sonnei, nalidixic acid resistance was significantly (P<0.05) higher in S. sonnei (95.8%) than S. flexneri (65%). Common R profiles for S. flexneri were ACTQNaAm followed by ACTQNaCiNfAm and that for S. sonnei were TQNa and QNa. The R pattern of Shigella strains was not serotype specific. Similar profiles were observed in more than one serotype. Overall common R profile was TQNa (22%). MICs of most commonly used antimicrobials were very high when compared with previous years. Virulence genes profiles and antimicrobial resistance profiles of Shigella isolates were determined.
  Plasmid profiles of S. dysenteriae serotype 1, flexneri 2a and sonnei strains indicated presence of large plasmid (approx. 210 kb) and multiple copies (4-6 copies) of smaller plasmids in almost all strains. Each of the serotypes presented with unique plasmid profile, hence this can be used as an epidemiological marker tool for strain differentiation. Shigella serogroups when characterized by RAPD analysis, each of them generated one major profile encompassing many small clusters corresponding to different serotypes. It is a rapid, simple and convenient method of strain typing when compared to PFGE. PFGE patterns of representative strains of S. dysenteriae serotype 1, S. flexneri 2a and S. sonnei yielded more than 12-14 bands. It was observed that outbreak strains of SD1 usually generated a single pulsotype with a number of subtypes. By UPGMA cluster analysis the strains were found clonally related with Dice co-efficient ≥ 80. Similar result was also obtained with S. flexneri type 2a and S. sonnei strains where PFGE pattern of each strain differs from each other by one or two bands.
  When effect of antimicrobials on Shiga toxin production by SD1 was studied, about 2- 4 fold increase in Shiga toxin titer was observed in mitomycin C treated culture of S. dysenteriae serotype 1 and the conc. was significantly higher in membrane vesicles after 24 to 48 hr of incubation at 37°C (p<0.05). It was observed that mitomycin C could induce Shiga toxin production as well as its release from periplasmic space by outer membrane vesicles.