Subtype prevalence, plasmid profiles and growing fluoroquinolone resistance in Shigella from Kolkata, India (2001-2007): a hospital-based study.
OBJECTIVE
Shigellosis is a major public health problem, and increasing antimicrobial resistance has complicated its treatment. We report isolation frequency, plasmid profiles and antimicrobial resistance of Shigella subtypes in Kolkata, India, from a prospective hospital-based study.


METHODS
Fresh stool or rectal swabs were collected from children (<5 years) attending the Diarrhea Treatment Unit of a governmental paediatric referral hospital in Kolkata. Samples were processed following standard methods over a 7-year period from January 2001 to December 2007.


RESULTS
Of 4478 samples collected, 516 (11.5%) were positive for Shigella spp. S. flexneri (312; 6.9%) was the most frequently isolated serogroup, ranking before S. sonnei (123, 2.7%), S. dysenteriae (48, 1.1%) and S. boydii (33, 0.7%). Although 10 subtypes of S. flexneri were identified, the common ones circulating locally were S. flexneri 2a (179), S. flexneri 6 (38) and S. flexneri 3a (36). Knowledge of Shigella subtypes is important for vaccine development. The majority of Shigella isolates (81.0%) were multidrug (two or more antimicrobial classes) resistant and showed high minimum inhibitory concentration (MIC) with commonly used drugs like ampicillin, tetracycline, co-trimoxazole and nalidixic acid. Emergence of fluoroquinolone (FQ)-resistant S. dysenteriae type 1 (100.0%) in 2002-2003 was followed by frequent isolation (>25.0%) of FQ-resistant S. flexneri 2a, and S. flexneri 3a in 2004, which restricted use of fluoroquinolones for treatment. A number of smaller plasmids (<20 kb) with distinct patterns have been observed for several years in predominant subtypes.


CONCLUSIONS
Long-term surveillance of Shigellae and their antimicrobial resistance are mandatory in endemic areas to formulate treatment policy until any suitable candidate vaccine is available to control the disease.
Bacteriology Division, National Institute of Cholera and Enteric Diseases, Kolkata, India.
Suman
S
Nandy
Utpala
U
Mitra
K
K
Rajendran
Phalguni
P
Dutta
Shanta
S
Dutta
D000208:Acute Disease; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000235:genetics; D003967:Diarrhea / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D004405:Dysentery, Bacillary / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D007194:India / Q000453:epidemiology; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics; D012760:Shigella / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D024841:Fluoroquinolones