Using hospital‐based studies of community‐onset bloodstream infections to make inferences about typhoid fever incidence

Abstract

objectives Hospital-based studies of community-onset bloodstream infections (CO-BSI) are less resource-intensive to carry out than population-based incidence studies. We examined several metrics capturing the potential role of Salmonella Typhi as a cause of CO-BSI for making inferences about incidence.methods We systematically reviewed three databases for hospital-based studies of CO-BSI. We determined, by study, the prevalence and rank order of Salmonella among pathogenic bloodstream isolates, and the prevalence ratio of Salmonella Typhi to Escherichia coli (S:E ratio). We then describe these hospital-based study metrics in relation to population-based typhoid fever incidence data from a separate systematic review.results Forty-four studies met the inclusion criteria, of which 23 (52.3%) isolated Salmonella Typhi at least once. Among studies isolating Salmonella Typhi, the median (interquartile range) prevalence and rank order of Salmonella Typhi compared to other pathogens isolated in BSI was 8.3% (3.2-37.9%) and 3 (1-6), respectively. The median (interquartile range) S:E ratio was 1.0 (0.4-3.0). With respect to incidence, in Pemba Island, Tanzania, prevalence, rank order, S:E ratio, and incidence was 64.8%, 1, 9.2 and 110 cases per 100 000, respectively, and in Boulkiemd e, Burkina Faso, was 13.3%, 3, 2.3 and 249 cases per 100 000.conclusions We describe considerable variation in place and time for Salmonella Typhi prevalence, rank order, and S:E ratio among hospital-based studies of CO-BSI. Data from simultaneous typhoid prevalence and incidence studies are limited. We propose that hospital-based study metrics warrant evaluation for making inference about typhoid incidence and as covariates in typhoid incidence models.

Facility-based disease surveillance and Bayesian hierarchical modeling to estimate endemic typhoid fever incidence, Kilimanjaro Region, Tanzania, 2007–2018

“…In doing so it is important to choose a pathogen with high prevalence and without an available vaccine, such as E. coli. E. coli rose from the second-ranked isolate during the 2007-08 study period to the first-ranked isolate in the latter two studies; and the smaller ratio value of Salmonella Typhi BSI prevalence to E. coli BSI prevalence tracked with the lower typhoid incidence estimates, consistent with a recent meta-analysis of this prevalence ratio as a surrogate for typhoid incidence [19]. Typhoid fever cases were evenly distributed by sex and the majority of our cases, 36 (72.0%) of 50, were persons 15 years of age or older (Table 2).…”

“…A case of typhoid fever was defined as a participant with a blood culture positive for Salmonella Typhi, identified using API 20E biochemical test system (bio-Merieux, Marcy l'Etoile, France). As ratio of Salmonella Typhi BSI to Escherichia coli BSI may be a surrogate for typhoid incidence [19], we included this ratio in our description of BSI for each study period. In-hospital mortality was recorded for inpatient cases and for outpatient cases determination of vital status was attempted via a 4-6 week follow-up visit.…”

“…However, Salmonella Typhi dropped in causal rank from the number one cause of BSI in the 2007-08 study period to a multi-way tie for the third-ranked cause of BSI in 2016-18 (Table 1). Given the variation in Salmonella Typhi over time, it can be helpful to present this prevalence data in comparison with the prevalence of other BSI pathogens [19]. In doing so it is important to choose a pathogen with high prevalence and without an available vaccine, such as E. coli.…”

Incidence of non-typhoidal Salmonella invasive disease: A systematic review and meta-analysis

“…Hospital-based prevalence studies of NTS BSI could be used as a lower-cost alternative to more resource intensive population-based incidence studies to gain insights into the role of NTS as a cause of bacteremia in unstudied locations. 39 Second, data that were available were subject to moderate or high risk of bias. Varying types and numbers of multipliers were used across studies.…”

Retrospective Review of Blood Culture-Confirmed Cases of Enteric Fever in Navi Mumbai, India: 2014–2018

“…17 If applied to our crude estimates, this would suggest an adjusted S. Typhi incidence of 161/100,000 [(23/100,000)*7] -high typhoid incidence. 18 We utilized culture positivity over time, as prior work suggests this as a potential method of making inferences on typhoid fever incidence, 19 though it can be confounded by other infectious diseases circulating in the community and may result in enteric fever burden underestimates. Our age and gender data are limited, as only a fraction of our total data set (age data: 922/1309, 70%; age and gender data: 701/1309, 54%) included this information, and thus may not accurately represent Navi Mumbai.…”