Antimicrobial Susceptibility of Biofilm Producer Staphylococcus Chromogenes Isolated from Bovine Mastitis in Northern Brazil
Authors: dos Santos Medeiros Luciana , Ferreira Lilian Bernardina , de Freitas Santiago Israel Larissa , Domingos Susan Christina Braga , dos Santos Janaina Valente , de Castro Eduardo Moreira , Rabello Renata Fernandes 
Published: June 2021

Staphylococcus species are important pathogens associated to mastitis in lactating cows. Among coagulase‐negative staphylococci, Staphylococcus chromogenes is one of the most prevalent. However, most of the virulence and antimicrobial resistance studies have been done to Staphylococcus aureus isolates. Therefore, the aim of present study was to determine the antimicrobial susceptibility profile of biofilm producing S. chromogenes isolates recovered from cows with mastitis from the Northern region of Brazil. Of one hundred thirty‐five crossbred cows from ten dairy farms with milk production decline, sixty‐seven were with mastitis according to mammary gland clinical examination or California Mastitis Test. Milk samples were collected of these animals to microbiological analysis. Phenotypic tests and MALDI‐TOF were adopted for the bacterial identification. Most of the staphylococci isolates (n=36; 60%) was identified as S. chromogenes. Absorbance‐based method was carried out to determine quantitatively the biofilm production by isolates of this species. Fifteen isolates, with different biofilm production levels, were submitted to the disk diffusion method to ceftiofur, clindamycin, chloramphenicol, ciprofloxacin, enrofloxacin, erythromycin, gentamicin, linezolid, penicillin G, rifampicin, streptomycin and tetracycline. All isolates were susceptible to gentamicin, linezolid and rifampicin. The majority of the isolates were non‐susceptible to penicillin G (n=10; 66.7%), ceftiofur (n=9; 60%), clindamycin (n=9; 60%), enrofloxacin (n=9; 60%) and chloramphenicol (n=8; 53.3%). Multidrug resistance (MDR) was observed to 60% of the isolates. The non biofilm producing isolates (n=3) were susceptible for all antimicrobials, except one was resistance only to penicillin G. MDR was observed among the isolates independently of the biofilm production level (weak, moderate or strong). Isolates susceptible for all antimicrobial agents were also detected among strong and weak biofilm producers. Although few S. chromogenes isolates have been analyzed, high rate of MDR was observed in the present study. Besides antimicrobial resistance these isolates are biofilm producers that is an important virulence strategy. The MDR rate observed may be related to spread of the same strain among the cows of the herds studied. Most studies should be made to this Staphylococcus species due its importance in dairy herds. Moreover, it may contribute to resistance dissemination among other bacterial species, including those of impact in public health, as one source of these genes.Support or Funding InformationDevelopment Agency: Conselho Nacional de Desenvolvimento Científico e Tecnológico‐CNPq, Fundação de Amparo à Pesquisa do Estado do Acre ‐ FAPAC.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.