Evolution of Antimicrobial Resistance in Staphylococci Isolated from Bovine Mastitis in Argentina

SREDNIK M. E.; PEREYRA A.; RUMI M. V.; PUIGDEVALL T.; GRIEBEN M.; GENTILINI E. R.; CRESPI E.; TESTORELLI F.; CANGGIANO N.

New Orleans

Congreso; ASM Microbe 2017; 2017

AMERICAN SOCIETY FOR MICROBIOLOGY

Background: Bovine mastitis causes important economic losses in the dairy industry. Staphylococcus aureus and coagulase-negative staphylococci (CNS) are the most frequent bacteria isolated from bovine mastitis. Some CNS can carry antimicrobial resistance, are known to form biofilms, and are increasingly recognized as a cause of persistent bovine intramammary infections.In the present study, we evaluated the evolution of resistance in staphylococci isolated from bovine mastitis in Argentina.Methods: We compared results of antimicrobial resistance in different periods of time (1998/2000, 2003/2006, 2010/1013 and 2014/2016). All staphylococcal isolates were tested by disk diffusion for susceptibility to penicillin (PEN 10U), oxacillin (OXA, 1 μg), cefoxitin (FOX, 30 μg), erythromycin (ERY, 15 μg) and clindamycin (CLI, 2 μg) according to the guidelines of the Clinical Laboratory Standard Institute (CLSI).Results:Table 1. Evolution of antimicrobial resistance (%) in S. aureus isolates.Table 2: Evolution of antimicrobial resistance (%) in coagulase-negative staphylococci isolates.Conclusions:CNS show methicillin resistance, but this is low. For that reason, it is not a problem in dairy cows in Argentina. Values of penicillin resistance are similar but, in some periods of time, they decreased probably because of better dairy management.Resistance to macrolides and lincosamides increased in all the periods of time evaluated because of the pressure of the use of antibiotics.Keywords:antimicrobial resistance, resistance genes, S. aureus, coagulase-negative staphylococci, bovine mastitis.