title: Antibiotic resistance in Staphylococcus aureus strains isolated from cows with mastitis in eastern Poland and analysis of susceptibility of resistant strains to alternative nonantibiotic agents: lysostaphin, nisin and polymyxin B.
abstract: The aim of this study was to analyze the resistance of Staphylococcus aureus isolates from bovine mastitis in the eastern part of Poland to a set of 20 antibiotics and three alternative agents: lysostaphin, nisin and polymyxin B. Eighty-six out of 123 examined isolates were susceptible to all 20 tested antibiotics (70%). The highest percentage of resistance was observed in the case of β-lactam antibiotics: amoxicillin (n=22, 17.9%), ampicillin (n=28, 22.8%), penicillin (n=29, 23.6%) and streptomycin (n=13; 10.6%). Twenty-five of the penicillin-resistant strains were found to carry the blaZ gene coding for β-lactamases. Two strains were found to be mecA positive and a few strains were classified as multidrug resistant (MDR), one of them was simultaneously resistant to six antibiotics. All strains, resistant to at least one antibiotic (n=37) and two control strains, were susceptible to lysostaphin with MIC values of 0.008-0.5 µg/ml (susceptibility breakpoint 32 µg/ml). Twenty-one (54%) isolates were susceptible to nisin. The MIC value of this agent for 17 (44%) strains was 51.2 µg/ml and was not much higher than the susceptibility breakpoint value (32 µg/ml). Polymyxin B was able to inhibit the growth of the strains only at a high concentration (32-128 µg/ml). The presented results confirmed the observed worldwide problem of spreading antibiotic resistance among staphylococci isolated from bovine mastitis; on the other hand, we have indicated a high level of bactericidal activity of nisin and especially lysostaphin.
authors.affiliation: Department of Pharmaceutical Technology and Biochemistry, Faculty of Chemistry, Gdańsk University of Technology, G. Narutowicza 11/12, 80-233 Gdańsk, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Szweda
authors.forename: Marta
authors.initials: M
authors.lastname: Schielmann
authors.forename: Aneta
authors.initials: A
authors.lastname: Frankowska
authors.forename: Barbara
authors.initials: B
authors.lastname: Kot
authors.forename: Magdalena
authors.initials: M
authors.lastname: Zalewska
mesh_terms: D000818:Animals; D002417:Cattle; D017931:DNA Primers / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005260:Female; D008248:Lysostaphin / Q000494:pharmacology*; D008413:Mastitis / Q000188:drug therapy* / Q000382:microbiology*; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D009561:Nisin / Q000494:pharmacology*; D011044:Poland; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011112:Polymyxin B / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics
chemical_list: D017931:DNA Primers; D009561:Nisin; D008248:Lysostaphin; D011112:Polymyxin B