Antibiotic Resistance and Biofilm Production in Catalase-Positive Gram-Positive Cocci Isolated from Brazilian Pasteurized Milk

M.A.A.   Machado; W.A.  Ribeiro; V.S.  Toledo; G.L.P.A.  Ramos; H.C.  Vigoder; J.S.  Nascimento

doi:10.18502/jfqhc.7.2.2886

M.A.A. Machado
W.A. Ribeiro
V.S. Toledo
G.L.P.A. Ramos
H.C. Vigoder
J.S. Nascimento

DOI: https://doi.org/10.18502/jfqhc.7.2.2886

Keywords: Gram-Positive Cocci Drug Resistance, Microbial Biofilms Milk Brazil

Abstract

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 production in catalase-positive Gram-positive cocci isolated from Brazilian pasteurized milk.

Methods: The bacteria were isolated using Baird-Parker agar and identified by MatrixAssisted 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 resistant (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