Conjugative transfer of resistance determinants among human and bovine Streptococcus agalactiae

Abstract

Streptococcus agalactiae (GBS) is a major source of human perinatal diseases and bovine mastitis. Erythromycin (Ery) and tetracycline (Tet) are usually employed for preventing human and bovine infections although resistance to such agents has become common among GBS strains. Ery and Tet resistance genes are usually carried by conjugative transposons (CTns) belonging to the Tn916 family, but their presence and transferability among GBS strains have not been totally explored. Here we evaluated the presence of Tet resistance genes (tetM and tetO) and CTns among Ery-resistant (Ery-R) and Ery-susceptible (Ery-S) GBS strains isolated from human and bovine sources; and analyzed the ability for transferring resistance determinants between strains from both origins. Tet resistance and int-Tn genes were more common among Ery-R when compared to Ery-S isolates. Conjugative transfer of all resistance genes detected among the GBS strains included in this study (ermA, ermB, mef, tetM and tetO), in frequencies between 1.10−7 and 9.10−7, was possible from bovine donor strains to human recipient strain, but not the other way around. This is, to our knowledge, the first report of in vitro conjugation of Ery and Tet resistance genes among GBS strains recovered from different hosts.

Analysis of virulence factors and antibiotic resistance genes in Group B Streptococcus from clinical samples

“…Isolates 243 and 322, were both erythromycin sensitive however, at least one gene ermTR or mefA was found, respectively (see Additional le 2: Table S2 and S3). Similar ndings were reported in GBS and other streptococcal species (64,(66)(67)(68). A con rmatory test to check Minimum Inhibitory Concentration (MIC) levels of these three isolates is recommended.…”

“…It was also observed that 100% (n=10) isolates that carried the ermB gene also carried the tetM gene. The association of erythromycin and tetracycline resistance may be due to the conjugative transposon Tn1545, which encodes erythromycin resistance via the ermB gene and tetracycline resistance via the tetM gene (62)(63)(64). This association was supported by our analysis which showed a positive correlation (see Additional le 2: Table S5) between the two genes, but this lacked statistical signi cance according to the Spearman Rank test.…”

In vitro antimicrobial susceptibility and genetic resistance determinants of Streptococcus agalactiae isolated from mastitic cows in Brazilian dairy herds

“…These are the most commonly identified tet genes among both bovine and human S. agalactiae isolates (DOGAN et al, 2005;DUARTE et al, 2005;DUTRA et al, 2014;PINTO et al, 2014), while others determinants such as tetS and tetK being observed less frequently (DUARTE et al, 2004;RATO et al, 2013). Four isolates exhibiting phenotypic tetracycline resistance harbored neither tetM nor tetO, suggesting the presence of a different tet gene, such as tetS or tetK.…”

Indirect enzyme-linked immunosorbent assay method based on Streptococcus agalactiae rSip-Pgk-FbsA fusion protein for detection of bovine mastitis

“…Accordingly, certain ELISA detection methods have been established based on these relatively conserved single antigens, but the sensitivities of the methods targeting one single conserved antigen are not sufficiently high (Keefe 1997, Pinto et al 2014). In our previous study, we used the DNAstar software to analyze the antigen epitope sequences of Sip, Pgk, and FbsA3 of SA, respectively, and the dominant antigen genes of these three proteins were amplified and concatenated by overlap-extension PCR, followed by expression and purification to ultimately obtain the recombinant multi-subunit fusion protein rSip-Pgk-FbsA.…”