Frequency of isolation of various subtypes and antimicrobial resistance of Shigella from urban slums of Karachi, Pakistan

Document Type

Article

Department

Pathology and Microbiology

Abstract

Objectives:

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 cotrimoxazole (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).

Conclusion:

Concurrent circulation of multiple strains with high resistance is worrying and mandates surveillance at the national level to facilitate the control of shigellosis.

Publication (Name of Journal)

International Journal of Infectious Diseases

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