Laboratory characterisation of Salmonella enterica serotype Typhi isolates from Zimbabwe, 2009–2017

Abstract

Background Typhoid fever remains a major public health problem in Zimbabwe with recurrent outbreaks reported since 2009. To provide guidance on appropriate treatment choice in order to minimise the morbidity and mortality of typhoid fever and prevent large scale outbreaks, we investigated the antimicrobial susceptibility patterns, prevalence of Salmonella enterica serotype Typhi ( S. Typhi) H58 haplotype and molecular subtypes of S. Typhi from outbreak strains isolated from 2009 to 2017 in Zimbabwe and compared these to isolates from neighbouring African countries. Methods Antimicrobial susceptibility testing was performed on all isolates using the disk diffusion, and E-Test, and results were interpreted using Clinical and Laboratory Standards Institute (CLSI) guidelines (2017). S. Typhi H58 haplotype screening was performed on 161 (58.3%) isolates. Pulsed-field gel electrophoresis (PFGE) was performed on 91 selected isolates across timelines using antibiotic susceptibility results and geographical distribution (2009 to 2016). Results Between 2009 and 2017, 16,398 suspected cases and 550 confirmed cases of typhoid fever were notified in Zimbabwe. A total of 276 (44.6%) of the culture-confirmed S. Typhi isolates were analysed and 243 isolates (88.0%) were resistant to two or more first line drugs (ciprofloxacin, ampicillin and chloramphenicol) for typhoid. The most common resistance was to ampicillin-chloramphenicol (172 isolates; 62.3%). Increasing ciprofloxacin resistance was observed from 2012 to 2017 (4.2 to 22.0%). Out of 161 screened isolates, 150 (93.2%) were haplotype H58. Twelve PFGE patterns were observed among the 91 isolates analysed, suggesting some diversity exists among strains circulating in Zimbabwe . PFGE analysis of 2013, 2014 and 2016 isolates revealed a common strain with an indistinguishable PFGE pattern (100% similarity) and indistinguishable from PFGE patterns previously identified in strains isolated from South Africa, Zambia and Tanzania. Conclusions Resistance to first line antimicrobials used for typhoid fever is emerging in Zimbabwe and the multidrug resistant S . Typhi H58 haplotype is widespread. A predominant PFGE clone circulating in Zimbabwe, South Africa, Zambia and Tanzania, argues for cross-border cooperation in the control of this disease. Electronic supplementary material The online version of this article (10.1186/s12879-019-4114-0) contains supplementary material, which is available to authorized users.

Enteric fever

“…Multidrug resistance, defined as resistance to these three antimicrobials, led to use of fluoroquinolones (ciprofloxacin, ofloxacin, levofloxacin) for enteric fever 33. High rates of fluoroquinolone resistance are now reported in South Asia and increasingly in Africa 3334. Extended spectrum cephalosporins, oral cefixime and parenteral ceftriaxone, and oral azithromycin2829303133 are now recommended options.…”

Challenge of diagnosing acute infections in poor resource settings in Africa

“…The diagnosis must be performed on-site with minimum expertise and processing of results, yet accuracy must wherever possible, match reference level laboratory tests. In some countries like Zimbabwe, diagnosis and confirmation of notifiable diseases have been reserved for a few laboratories used as sentinel sites 9 but the urgency of dealing with acute infections, such as COVID-19, necessitates the focus on decentralized testing 10,32,36 . Rapid diagnosis is apt for initial or crisis screening where sample preparation is simple, enabling many samples to be processed within a short time.…”

“…The impact of these diseases is exacerbated by weak health systems and lack of rapid intervention tools. Rapid and timely diagnosis of such infectious diseases is critical for immediate patient isolation and appropriate treatment to reduce transmission, mortality and morbidity 1,[7][8][9] . Consequently, there is a need for a concerted effort to develop rapid point-of-care diagnostic tools [10][11][12] for the effective surveillance, intervention and control of such acute infections to contribute to the long term health security of the African continent.…”

Frequency Assessment of Emergence of Extensively Drug Resistant Salmonella Typhi Strains in Quetta, Balochistan

“…In general, the attack rate is higher with greater infectious dose and the shorter incubation period gets 5 . Multidrug resistant (MDR) strains of S. typhi (resistant to three first line drugs i.e., Ampicilin, chloramphenicol and trimethoprim-sulfamethoxazole) have already been observed worldwide 6 . Typhoid fever showing extensively drug-resistance (XDR) is increasing in Pakistan.…”