Increasing multidrug and fluoroquinolone resistance among Salmonella Typhi from sporadic outbreaks in Kenya

Abstract

Purpose: Background: Typhoid fever (TF) caused by Salmonella Typhi remains a major public health problem in Kenya. A systematic surveillance in two slum areas in Nairobi, revealed a crude incidence of TF of 247 cases per 100,000 person-years of observation (pyo), with highest rates in children 5–9 years old (596 per 100,000 pyo). Currently over a third of S. Typhi isolates are multidrug-resistant (MDR), and show reduced susceptibility to Fluoroquinolones; the drugs of choice for treatment of MDR cases. The situation is worrying especially for resource-limited settings where the few remaining effective antimicrobials are either unavailable or too expensive to be afforded by the general public. Objectives: To determine the epidemiology and trends in Antimicrobial Resistance patterns among S. Typhi isolated from patients acquiring treatment in four clinics in Nairobi in the last 5 years. Methods & Materials: We assessed the susceptibility to commonly available antimicrobials of 225 S. Typhi isolates from 5 years of study (2009–2014) from sporadic outbreaks in clinics around Nairobi. Results: S. Typhi outbreaks were due to a single haplotype H58, which is the main cause of epidemics in South East Asia. Over last 5 years only 17.9% were fully sensitive. The majority (60.5%) were multiply resistant to commonly available drugs - Ampicillin, Chloramphenicol, Tetracycline (Minimum Inhibition Concentration (MIC) > 256 μg/ml) and Co-trimoxazole (MIC > 32 μg/ml). Nalidixic resistance was observed in 10% in 2009 to 18% in 2014 of isolates while resistance to Ciprofloxacin susceptibility increased from 5% to 10% in 2014. Conclusion: The rate of increase in MDR over the last 5 years is worrying as more S. Typhi have become less susceptible to Fluoroquinolones. Improved hygiene and sanitation and use of World Health Organization-recommended vaccines should be considered for effective management of MDR TF.