Frequency of isolation of various subtypes and antimicrobial resistance of Shigella from urban slums of Karachi, Pakistan.
OBJECTIVE
Shigellosis remains a major public health problem in developing countries. Antimicrobial resistance has complicated the empirical treatment. Knowledge of serotypes is crucial in vaccine development, as cross-protection between various serotypes is limited. Therefore we conducted a prospective study to determine the frequency of isolation of Shigella serotypes and antimicrobial resistance.


METHODS
Stool samples from 8155 individuals, collected through a surveillance study conducted in four slums of Karachi from January 2002 to March 2004, were cultured.


RESULTS
Shigella was isolated in 394 (4.8%) of 8155 patients presenting with diarrhea. Two hundred and forty-two (62%) isolates were Shigella flexneri, 72 (18%) were Shigella sonnei, 43 (11%) were Shigella boydii, and 37 (9%) were Shigella dysenteriae. Thirteen S. flexneri serotypes were identified, of which the most frequent were 2a (38), 6 (37), and 1b (25), followed by 2b (23). Only 22 (5.6%) Shigella isolates were found to be pan-susceptible. Large proportions of isolates were resistant to co-trimoxazole (89% S. flexneri, 81% S. dysenteriae, 80% S. sonnei, and 56% S. boydii) and ampicillin (87% S. flexneri, 68% S. dysenteriae, 35% S. boydii, and 4% S. sonnei).


CONCLUSIONS
Concurrent circulation of multiple strains with high resistance is worrying and mandates surveillance at the national level to facilitate the control of shigellosis.
Zafar
Afia
A
Department of Pathology and Microbiology, Aga Khan University Hospitals, Stadium Road, PO Box 3500, Karachi 74800, Pakistan. afia.zafar@aku.edu
Hasan
Rumina
R
Nizami
Shaikh Qamaruddin
SQ
von Seidlein
Lorenz
L
Soofi
Sajid
S
Ahsan
Tanwir
T
Chandio
Saeeda
S
Habib
Atif
A
Bhutto
Naveed
N
Siddiqui
Fahad J
FJ
Rizvi
Arjumand
A
Clemens
John D
JD
Bhutta
Zulfiqar A
ZA
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D004405:Dysentery, Bacillary / Q000453:epidemiology* / Q000382:microbiology; D005243:Feces / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D010154:Pakistan / Q000453:epidemiology; D012703:Serotyping; D012760:Shigella / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification; D013045:Species Specificity; D014505:Urban Population
D000900:Anti-Bacterial Agents