Epidemiology, clinical presentation, and patterns of drug resistance of Salmonella Typhi in Karachi, Pakistan

Abstract

Introduction: Enteric fever remains a major public health problem in Asia. Planning appropriate preventive measures such as immunization requires a clear understanding of disease burden. We conducted a community-based surveillance for Salmonella Typhi infection in children in Karachi, Pakistan. Methodology: A de jure household census was conducted at baseline in the study setting to enumerate all individuals. A health-care facilitybased passive surveillance system was used to capture episodes of fever lasting three or more 3 days in children 2 to 16 years old. Results: A total of 7,401 blood samples were collected for microbiological confirmation, out of which 189 S. Typhi and 32 S. Paratyphi A isolates were identified with estimated annual incidences of 451/100,000 (95% CI: 446 -457) and 76/100,000 (95% CI: 74 -78) respectively. At the time of presentation, after adjusting for age, there was an association between the duration of fever and temperature at presentation, and being infected with multidrug-resistant S. Typhi. Of 189 isolates 83 were found to be resistant to first-line antimicrobial therapy. There was no statistically significant difference in clinical presentation of blood culture sensitive and resistant S. Typhi isolates. Conclusion: Incidence of S. Typhi in children is high in urban squatter settlements of Karachi, Pakistan. Findings from this study identified duration of fever and temperature at the time of presentation as important symptoms associated with blood culture-confirmed typhoid fever. Preventive strategies such as immunization and improvements in water and sanitation conditions should be the focus of typhoid control in urban settlements of Pakistan.

Estimating the Burden of Paratyphoid A in Asia and Africa

“…The incidence estimates reported from pediatric population-based studies (51–76 cases/100,000 person-years) did not differ substantially from incidence reported in adults and children from South Asian countries [23], [24]. In all pediatric studies, S. Paratyphi A accounted for a lower proportion of enteric fever cases (8.6–17.0%) than in studies which included adults, with the exception of one study conducted in New Delhi, India [23]–[27].…”

How multidrug resistance in typhoid fever affects treatment options

“…investigated 293 isolates associated with travel, particularly to Southeast Asia and Mexico, and observed that 17% were MDRST and 7% were NARST . A similar trend of combined resistance to first‐line drugs and relatively higher resistance to nalidixic acid or DCS (MIC = 0.12–1 μg/mL; full‐resistance is ≥2 μg/mL) was observed in India, in a retrospective study of isolates from Pakistan and Bangladesh, and in two studies investigating isolates from children in Pakistan and in Cambodia . Other recent studies have demonstrated a trend of higher percentages of isolates showing nalidixic acid resistance compared to MDR from the first‐line drugs.…”

Antibiotic resistance—the need for global solutions

“…However, fl uoroquinolone resistance is increasing in India (44%) and Pakistan (58%), and susceptibility is decreasing in Congo (15%) and Cambodia (80%). [263][264][265][266] In Kenya, 267 more than 77% of the S typhi were multidrug resistant, much higher than the reported 52% in Ghana 268 and 29% in Egypt. 263 Additionally, the proportion of S typhi in Kenya that are multidrug resistant and resistant to nalidixic acid with decreased susceptibility to fl uoroquinolones had risen from 1% in 2000 to nearly 25% in 2008.…”