Abstract
BackgroundWhile Group B Streptococcus (GBS) human colonization and infection has long been suspected as originating from cows, several investigators have suggested that ongoing interspecies GBS transmission is unlikely due to genotyping data demonstrating that human and bovine-derived GBS strains represent mostly distinct populations. The possibility of ongoing transmission between humans and their livestock has not been systematically examined.Methodology/Principal FindingsTo examine ongoing interspecies transmission, we conducted a prospective cross-sectional cohort study of 68 families and their livestock. Stool specimens were collected from 154 people and 115 livestock; GBS was detected in 19 (12.3%) humans and 2 (1.7%) animals (bovine and sheep). Application of multilocus sequence typing (MLST) identified 8 sequence types (STs or clones), with STs 1 and 23 predominating. There were 11 families in which two members submitted stools and at least one had GBS colonization. In 3 of these families, both members (consisting of couples) were colonized, yielding a co-colonization rate of 27% (95% CI: 7%–61%). Two of these couples had strains with identical MLST, capsule (cps) genotype, susceptibility, and RAPD profiles. One couple co-colonized with ST-1 (cps5) strains also had a bovine colonized with the identical strain type. On multivariate analysis of questionnaire data, cattle exposure was a predictor of GBS colonization, with each unit increase in days of cattle exposure increasing the odds of colonization by 20% (P = 0.02). These results support interspecies transmission with additional evidence for transmission provided by the epidemiological association with cattle exposure.Conclusions/SignificanceAlthough GBS uncommonly colonizes livestock stools, increased frequency of cattle exposure was significantly associated with human colonization and one couple shared the same GBS strains as their bovine suggesting intraspecies transmission. These results set the framework for GBS as a possible zoonotic infection, which has significant public health implications.
Highlights
Group B Streptococcus (GBS) frequently causes neonatal sepsis and meningitis as a result of transmission from mothers to neonates during childbirth
It has subsequently been suggested by several investigators that interspecies GBS transmission is not likely because genotyping data has demonstrated that human- and bovine-derived GBS strains represent mostly distinct populations [7,8,9,10,11,12,13]
Because the fecal-oral transmission route has been shown to be important for colonization in various human populations [14], it is plausible that direct contact with feces from colonized animals can contribute to human colonization
Summary
Group B Streptococcus (GBS) frequently causes neonatal sepsis and meningitis as a result of transmission from mothers to neonates during childbirth. Based on the sudden emergence of GBS in neonatal disease in the 1960’s after a long history of contributing mostly to bovine infections [6], it was postulated that GBS originated from bovines It has subsequently been suggested by several investigators that interspecies GBS transmission is not likely because genotyping data has demonstrated that human- and bovine-derived GBS strains represent mostly distinct populations [7,8,9,10,11,12,13]. While Group B Streptococcus (GBS) human colonization and infection has long been suspected as originating from cows, several investigators have suggested that ongoing interspecies GBS transmission is unlikely due to genotyping data demonstrating that human and bovine-derived GBS strains represent mostly distinct populations. The possibility of ongoing transmission between humans and their livestock has not been systematically examined
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