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.
Nandy
Suman
S
Bacteriology Division, National Institute of Cholera and Enteric Diseases, Kolkata, India.
Mitra
Utpala
U
Rajendran
K
K
Dutta
Phalguni
P
Dutta
Shanta
S
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