Salmonella

Salmonella enterica remains a major cause of morbidity and mortality worldwide. In industrialized countries, nontyphoidal serovars of S. enterica are important causes of diarrhea. In low-resource settings, particularly in sub-Saharan African countries, nontyphoidal Salmonella are also leading causes of bloodstream infection. Typhoidal serovars of S. enterica cause enteric fever which is common in areas with unsafe water and poor sanitation. Following identification to the species level, subsequent identification is by serogrouping and serotyping, with over 2400 serovars identified. Methods for discrimination within serovars of clinical and epidemiological importance include established tests such as phage typing and pulsed field gel electrophoresis. However, these are rapidly being replaced with DNA sequencing, either sample sequencing such as multilocus sequence typing or increasingly with whole genome sequencing (WGS). Large databases containing tens of thousands of whole genome sequences now exist in national reference laboratories in some high resource settings allowing outbreak detection using WGS. Antimicrobial drug resistance is increasing in prevalence worldwide, with considerable implications for treatment of individuals infected with invasive strains and for public health. Control of Salmonella may be by vaccine, as for typhoid in humans and Salmonella Enteritidis infection in poultry, and by nonvaccine measures such as improvements in water, sanitation, and food safety.