Group B Streptococcus (GBS), is a leading cause of neonatal death and an emerging pathogen in adults. Additionally, GBS is a bovine pathogen causing intramammary infections. The likelihood of GBS interspecies transmission is largely unknown. We explored the potential transmission of GBS between cattle and people on dairy farms in Colombia and compared the antimicrobial resistance (AMR) profiles of isolates from both host species. Across 33 farms, throat swabs and rectal swabs were collected from 191 people, and rectal swabs and composite milk samples from 2092 cattle, yielding 60 human isolates and 301 bovine isolates. The majority (64%) of isolates belonged to shared sequence types (ST). Sequence type (ST) 1 was the most common strain in both host species, suggesting that interspecies transmission may be possible. Two members of the bovine-specific clonal complex 61/67 were detected in human samples (ST718 and ST1175), providing evidence for the lack of genuine species barriers. Apparent prevalence of penicillin resistance was surprisingly high in human and bovine isolates. Further investigation of this phenomenon is needed and could lead to modification of standard testing and treatment recommendations in human and veterinary medicine.
For many years Streptococcus agalactiae has been considered an obligate intramammary and strictly contagious pathogen in dairy cattle. However, recent reports of S. agalactiae isolation from extramammary sources have contradicted that premise. To gain further insight into the epidemiology of S. agalactiae infection in cattle, we examined its distribution and heterogeneity of strains in bovine milk, bovine feces, and the environment in Colombian dairy farms. First, a longitudinal study was conducted at herd level in 152 dairy herds. Bulk tank milk samples from each herd where collected twice a month for six months. A follow-up study with a cross sectional design at the cow level was conducted in a subset of 25 farms positive for S. agalactiae. Cow-level milk samples from 1712 lactatting cows and 1545 rectal samples were collected, as well as 120 environmental samples. Samples were used for S. agalactiae detection and genotyping using Multi Locus Sequence Typing. Results showed sporadic rather than repeated isolation of S. agalactiae from bulk tank milk in 40% of the positive herds, challenging the idea that S. agalactiae is a highly contagious pathogen causing chronic infections. S. agalactiae was isolated from rectal or environmental samples in 32% and 12% of cross-sectional study farms, respectively, demonstrating that the bacteria can survive in extramammary sources and that S. agalactiae is not an obligate intramammary pathogen. The same strain was isolated from rectal and bulk tank milk samples in eight farms, suggesting that fecal shedding is frequent, and contributes to the presence of S. agalactiae in bulk tank. High within-herd heterogeneity of strains was found, which is distinct from the situation in developed dairy industries. These new epidemiological findings should be considered to adjust surveillance and control recommendations for S. agalactiae.
Artículo de revisión
Antimicrobial resistance of Streptococcus agalactiae of human and bovine origin
Resistencia antimicrobiana de Streptococcus agalactiae de origen humano y bovinoResistência antimicrobiana de Streptococcus agalactiae de origem humana e bovina
Mycoplasma spp. is reported as a highly contagious mastitis-causing bacteria in dairy cattle, without successful or low response to most common antibiotic treatments due to the lack of cell wall. In Colombia it has been reported in the Central Andean region during 2014. The aim was to estimate the prevalence of Mycoplasma spp. in bulk tank milk using microbiological and molecular diagnosis. A random longitudinal study enrolling 220 commercial dairy farms located in four provinces of the mid-western region of Colombia from four pasteurizer companies was performed. Bulk tank milk samples were collected once monthly for three months period for determining somatic cell count (SCC) and microbiological and molecular diagnosis of Mycoplasma spp. cultures were done without pre-enrichment procedures directly in mycoplasma agar with cefoperazone to inhibit growth of opportunistic microorganisms, plates were incubated under 37° C and atmosphere of 10% CO2 and inspected during a 10d period. Molecular analysis was done by a multiplex PCR using specific primers targeting the 16S-23S rARN gene of Mycoplasma spp. and from non-pathogenic bacteria occasionally found in milk. LnSCC average of included dairy farms was 6.19 x103 cells/mL, Mycoplasma spp. was not isolated during microbiological cultures, and no DNA belonging to the species was detected by PCR in the 220 bulk tanks milk, with an estimated prevalence lower than 2.3%. This finding shows that there is not microbiological or molecular evidence that demonstrates the presence of the pathogen in the milk from the mid-western region of Colombia at herd level.
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