Reviving the "Moore swab": a classic environmental surveillance tool involving filtration of flowing surface water and sewage water to recover typhoidal Salmonella.

The Moore swab is a classic environmental surveillance tool whereby a gauze pad tied with string is suspended in flowing water or wastewater contaminated with human feces and harboring enteric pathogens that pose a human health threat. In contrast to single volume "grab" samples, Moore swabs act as continuous filters to "trap" microorganisms, which are subsequently isolated and confirmed using appropriate laboratory methods. Continuous filtration is valuable for isolation of transiently present pathogens such as human-restricted Salmonella enterica serovars Typhi and Paratyphi A and B. The technique was first proposed (1948) to trace Salmonella Paratyphi B systematically through sewers to pinpoint the residence of a chronic carrier responsible for sporadic outbreaks of paratyphoid fever. From 1948-1986, Moore swabs proved instrumental to identify long-term human reservoirs (chronic carriers) and long-cycle environmental transmission pathways of S. Typhi and Paratyphi, for example to decipher endemic transmission in Santiago, Chile during the 1980s. Despite limitations such as intermittent shedding of typhoidal Salmonella by humans and the effects of dilution, S. Typhi and S. Paratyphi have been recovered from sewers, surface waters, irrigation canals, storm drains, flush toilets, and septic tanks using Moore swabs. Driven by the emergence of multiple antibiotic-resistant S. Typhi and S. Paratyphi A that limit treatment options, several countries are embarking on accelerated typhoid control programs using vaccines and environmental interventions. Moore swabs, which are re-gaining appreciation as important components of the public health/environmental microbiology toolbox, can enhance environmental surveillance for typhoidal Salmonella, thereby contributing to the control of typhoid fever. [ABSTRACT FROM AUTHOR]