Identification and antimicrobial suceptibility profile of bacteria causing bovine mastitis from dairy farms in Pelotas, Rio Grande do Sul

Abstract

Mastitis is an inflammatory process of the udder tissue caused mainly by the bacteria Staphylococcus aureus. The indiscriminate use of antibiotics fosters conditions that favor the selection of resistant microorganisms, suppressing at the same time susceptible forms, causing a serious problem in dairy cattle. Given the importance in performing an antibiogram to select the most adequate antimicrobial therapy, the aim of this study was to identify bacteria isolated from cow's milk with mastitis, in dairy farms situated in the city of Pelotas, Rio Grande do Sul, and to determinate the susceptibility profile of these isolates against the antibiotics used to treat this illness. A total of 30 isolates of Staphylococcus spp., were selected from milk samples from the udder quarters with subclinical mastitis whose species were identified through the Vitek system. The susceptibility profile was performed by the disk diffusion assay, against: ampicillin, amoxicillin, bacitracin, cephalexin, ceftiofur, enrofloxacin, gentamicin, neomycin, norfloxacin, penicillin G, tetracycline and trimethoprim. In the antibiogram, 100.0% of the isolates were resistant to trimethoprim and 96.7% to tetracycline and neomycin, three strains of Staphylococcus spp., (10.0%) presented resistance to the 12 antibiotics tested and 24 (80.0%) to at least eight. These results showed the difficulty in treating mastitis, due to the pathogens' resistance.Keywords: bovine mastitis, identification of microorganisms, bacterial resistance. Identificação e perfil de suscetibilidade antimicrobiana de bactérias causadoras de mastite bovina em propriedades leiteiras de Pelotas, Rio Grande do Sul ResumoA mastite se constitui no processo inflamatório da glândula mamária causada principalmente por bactérias Staphylococcus aureus. O uso indiscriminado dos antibióticos promove condições que favorecem a seleção de micro-organismos resistentes e, ao mesmo tempo, suprime formas suscetíveis, causando um grave problema para a bovinocultura leiteira. Tendo em vista a importância da realização do antibiograma para a seleção da terapia antimicrobiana mais adequada, o objetivo deste estudo foi identificar bactérias isoladas de leite de vaca com mastite, oriundas de propriedades leiteiras localizadas na cidade de Pelotas, RS, bem como determinar o perfil de suscetibilidade desses isolados frente a antibióticos usados para o tratamento desta doença. Foram selecionados 30 isolados de Staphylococcus spp. de amostras de leite provenientes de quartos mamários com mastite subclínica, cujas espécies foram identificadas através do sistema Vitek. O perfil de suscetibilidade foi realizado pela técnica de difusão em disco, frente a:

Antimicrobial Resistance in Farm Animals in Brazil: An Update Overview

“…The highest rate reported (96.7%) was observed among isolates obtained in herds from the Rio Grande do Sul (S). In this study, the isolates also presented high resistance frequencies to other antimicrobial agents [113]. In the same State, a lower frequency of resistance to tetracycline (39%) was observed.…”

“…Penicillin G resistance frequencies have ranged from 30.4% to 100% in the studies published in the last ten years [100,101,109,110]. Some studies have also tested other PSLPs, sometimes with slightly higher resistance frequencies than penicillin G [106,[111][112][113].…”

“…In some studies, PSLP resistance was not prevalent compared to other antimicrobial agents, but significant frequencies were observed. Among 27 S. aureus and three coagulase-negative Staphylococcus (CNS) isolates characterized by Freitas et al (2018), the highest resistance frequencies were observed for trimethoprim (100%), neomycin and tetracycline (96.7% each). However, 70% of the isolates were resistant to penicillin G [113].…”

“…Among 27 S. aureus and three coagulase-negative Staphylococcus (CNS) isolates characterized by Freitas et al (2018), the highest resistance frequencies were observed for trimethoprim (100%), neomycin and tetracycline (96.7% each). However, 70% of the isolates were resistant to penicillin G [113]. Haubert et al (2017) reported a penicillin G resistance frequency of 48% among S. aureus isolates, but the resistance rate to sulfonamides was higher (65%) [112].…”

“…Resistance frequencies for tetracycline have varied in different studies published over the period evaluated [106,108,113,114]. The highest rate reported (96.7%) was observed among isolates obtained in herds from the Rio Grande do Sul (S).…”