Diversity of Staphylococcus aureus associated with mastitis from dairy cows in Rwanda.

OBJECTIVES: The objective of the present study was to examine the diversity of Staphylococcus aureus from mastitis milk samples of cows in Rwanda. METHODS: A total of 1080 quarter milk samples from 279 dairy cows were collected in 80 different farms from all five provinces of Rwanda. In total, 135 S. aureus isolates were obtained and subjected to genotyping (spa typing, DNA microarray, whole-genome sequencing (WGS)), antimicrobial susceptibility testing (AST) and phenotypic profiling by Fourier Transform Infrared (FTIR) spectroscopy (including capsular serotyping). RESULTS: Resistance to penicillin and/or tetracycline was most frequently observed. Ten sequence types (STs) (ST1, ST151, ST152, ST5477, ST700, ST7110, ST7983, ST7984, ST8320, ST97) belonging to seven clonal complexes (CCs) (CC1, CC130, CC152, CC3591, CC3666, CC705, CC97) were detected. The Panton-Valentine leukocidin (PVL) genes (lukF-PV/lukS-PV), the bovine leukocidin genes (lukM/lukF-P83) and the human and bovine toxic shock syndrome toxin gene tst-1 variants were detected. FTIR-based capsular serotyping showed CC-specific differences. Most CC97 (cap5 allele) isolates were primarily nonencapsulated (82%), whereas isolates of CC3591 and CC3666 (cap8 allele) were mostly encapsulated (86.4% and 57.8%, respectively). Our results underline the widespread global distribution of cattle-adapted CC97. CONCLUSION: The presence of CC3591 and CC3666 in bovine mastitis suggests an important role in cattle health and dairy production in Rwanda. The results of the present study support the need for a rigorous One-Health Surveillance program of the bovine-human interface.

Diversity of Staphylococcus aureus isolated from nares of ruminants.

AIMS: To examine the diversity of Staphylococcus aureus isolated from nasal swabs of ruminants in Rwanda. METHODS AND RESULTS: A total of 454 nasal swabs from 203 cows, 170 goats, and 81 sheep were examined for the presence of S. aureus, and 30 S. aureus isolates were detected and characterized pheno- and genotypically. Resistance to penicillin and/or tetracycline was observed. The isolates were assigned to eight different spa types (t21057 (novel), t10103, t18853, t20842, t318, t355, t458, and t9432) belonging to six clonal complexes (CCs) (CC152, CC30, CC3591, CC3666, CC522, and CC97). Panton-Valentine leukocidin (PVL) genes (lukF-PV/lukS-PV), the bovine leukocidin genes (lukM/lukF-P83), and the human and bovine variants of the toxic shock syndrome toxin gene tst-1 variants were detected. CONCLUSION: These findings demonstrate that the nares of ruminants in Rwanda are colonized with mastitis-associated S. aureus, including lineages that are also carried by humans, underscoring the zoonotic risk, especially for livestock keepers. These results highlight the crucial importance of hygiene measures when handling livestock.

Characterization of Antibiotic and Biocide Resistance Genes and Virulence Factors of Staphylococcus Species Associated with Bovine Mastitis in Rwanda.

The present study was conducted from July to August 2018 on milk samples taken at dairy farms in the Northern Province and Kigali District of Rwanda in order to identify Staphylococcus spp. associated with bovine intramammary infection. A total of 161 staphylococcal isolates originating from quarter milk samples of 112 crossbred dairy cattle were included in the study. Antimicrobial susceptibility testing was performed and isolates were examined for the presence of various resistance genes. Staphylococcus aureus isolates were also analyzed for the presence of virulence factors, genotyped by spa typing and further phenotypically subtyped for capsule expression using Fourier Transform Infrared (FTIR) spectroscopy. Selected S. aureus were characterized using DNA microarray technology, multi-locus sequence typing (MLST) and whole-genome sequencing. All mecA-positive staphylococci were further genotyped using dru typing. In total, 14 different staphylococcal species were detected, with S. aureus being most prevalent (26.7%), followed by S. xylosus (22.4%) and S. haemolyticus (14.9%). A high number of isolates was resistant to penicillin and tetracycline. Various antimicrobial and biocide resistance genes were detected. Among S. aureus, the Panton-Valentine leukocidin (PVL) genes, as well as bovine leukocidin (LukM/LukF-P83) genes, were detected in two and three isolates, respectively, of which two also carried the toxic shock syndrome toxin gene tsst-1 bovine variant. t1236 was the predominant spa type. FTIR-based capsule serotyping revealed a high prevalence of non-encapsulated S. aureus isolates (89.5%). The majority of the selected S. aureus isolates belonged to clonal complex (CC) 97 which was determined using DNA microarray based assignment. Three new MLST sequence types were detected.