antibiotic resistance and biofilm production in catalase-positive gram-positive cocci isolated from brazilian pasteurized milk

Background: milk is a reservoir for several groups of microorganisms, which may pose health risks. the aim of this work was to assess the antibiotic resistance and biofilm pro-duction in catalase-positive gram-positive cocci isolated from brazilian pasteurized milk. methods: the bacteria were isolated using baird-parker agar and identified by matrix-assisted laser desorption/ionization-time-of-flight (maldi-tof) mass spectrometer. disk diffusion technique was used to evaluate antimicrobial susceptibility. for qualitative evaluation of biofilm production, the growth technique was used on congo red agar. results: totally, 33 out of 64 isolates were identified, including staphylococcus epidermidis (n=3; 4.7%), macrococcus caseolyticus (n=14; 21.9%), and kocuria varians (n=16; 25%). twenty-two isolates were resistant to at least one antibiotic. biofilm production was detected in only 5 isolates of k. varians and 1 isolate of s. epidermidis. all 14 m. caseolyticus isolates were resistant to at least one antibiotic; but, multidrug re-sistant (mdr) isolates were not detected. among all k. varians isolates, 4 were resistant to at least one antibiotic from three different classes and were considered to be mdr. conclusion: the presence of antibiotic-resistant m. caseolyticus, s. epidermidis, and k. varians isolates, especially mdrs, in milk samples highlights the possible role of milk as a reservoir of resistance genes.