| Congresso Brasileiro de Microbiologia 2023 | Resumo: 324-1 | ||||
Resumo:Antibiotic resistance is a worldwide concern and affects the treatment of diseases in animals and humans. Bacteria isolated from milk and resistant to antibiotics can affect consumers' health if this milk contains antibiotic residues at levels above those allowed by law. The indiscriminate use of antibiotics, the failure to observe the withdrawal period, and the erroneous diagnosis of the causative agent of the diseases, contribute to the increase of this resistance. This work aimed to analyze the sensitivity to antimicrobials of strains of Staphylococcus chromogenes isolated from the milk of healthy cows and cows with mastitis, from five Brazilian states. For this study, 1468 milk samples from healthy cows with clinical and subclinical mastitis were analyzed, with these samples coming from the states of Goiás, São Paulo, Santa Catarina, Pará, and Paraíba. Milk samples were streaked on blood agar and up to 3 characteristic colonies of Staphylococcus sp were isolated, biochemical tests such as Gram, catalase, and coagulase were performed and finally, the species were identified by MALDI-TOF. Among the strains of Staphylococcus sp that were analyzed and identified, 88 were identified as S. chromogenes. The susceptibility of the 88 strains of S.chromogenes was tested using the disk diffusion method in agar and interpreted according to the CLSI (Clinical and Laboratory Standards Institute), with the following antibiotics being tested: gentamicin (10 μg), oxacillin (1 μg), cefoxitin (30 μg), tetracycline (30 μg), erythromycin (15 μg), clindamycin (2 μg), tobramycin (10 μg), chloramphenicol (30 μg), penicillin (10 μg). Among the 88 strains tested, 13 (14.8%) showed resistance to at least one antibiotic, 5 (5.7%) showed resistance to 2 tested antibiotics, 10 (11.4%) showed resistance to 3 or more tested antibiotics and 11 (12.5%) showed intermediate resistance, that is, they were between the sensitive and resistant threshold. The antibiotics with the highest number of resistant strains were: penicillin (21/88), oxacillin (12/88), cefoxitin (6/88), clindamycin (6/88), chloramphenicol (6/88), tetracycline (5 /88), erythromycin (3/88) and tobramycin (3/88), none of the 88 strains of S. chromogenes showed resistance to gentamicin (0/88). Among the 88 strains of S. chromogenes tested, 46 (52.3%) were isolated from milk from cows with subclinical mastitis, 41 (46.5%) were isolated from milk samples from healthy cows, and 1 (1.2%) were isolated from a cow's milk sample with clinical mastitis. Despite being considered secondary pathogens of bovine mastitis, our results show that species such as S. chromogenes belonging to the Non-aureus Staphylococcus (NAS) group present critical results regarding resistance to the tested antibiotics. Eleven percent of the strains tested were multi-drug resistant (MDR). This result is worrying for the treatment of this disease and also for milk consumers, since 98.8% of the samples where these strains were isolated come from healthy cows with subclinical mastitis, that is, these samples will go to the tanks that will be marketed. Palavras-chave: Staphylococcus chromogenes, mastitis, milk, resistance, antibiotics Agência de fomento:São Paulo Research Foundation – (FAPESP), grant #2018/24191-3. | |||||