Characterizing Methicillin-Resistant Staphylococcus spp. and Extended-Spectrum Cephalosporin-Resistant Escherichia coli in Cattle

In the field of cattle medicine in Austria, to date, few studies have investigated the presence of methicillin-resistant <i>Staphylococcus aureus</i> and extended-spectrum β-lactamase-producing <i>Escherichia coli</i> in Austria. For this reason, milk and nasal samples were examined for the presence of methicillin-resistant <i>Staphylococcus aureus</i> as well as fecal samples for extended-spectrum cephalosporin-resistant <i>Escherichia coli</i>. The nasal and fecal swabs were collected during the veterinary treatment of calf pneumonia and calf diarrhea. For the milk samples, the first milk jets were milked into a pre-milking cup and then the teats were cleaned and disinfected before the samples were taken. The cows were selected during the veterinary visits to the farms when treatment was necessary due to mastitis. Depending on the severity of the mastitis (acute mastitis or subclinical mastitis), antibiotics and non-steroidal anti-inflammatory drugs were given immediately (acute disease) or after completion of the antibiogram (subclinical disease). Isolates were characterized by a polyphasic approach including susceptibility pheno- and genotyping and microarray-based assays. No methicillin-resistant <i>Staphylococcus aureus</i> was found in the milk samples, but one nasal swab was positive for methicillin-resistant <i>Staphylococcus aureus</i>. Twenty-two <i>Escherichia coli</i> isolates were detected among the fecal samples. All the <i>Escherichia coli</i> isolates were resistant to ceftazidime. In all the <i>Escherichia coli</i> isolates, genes from the <i>bla</i>_CTX family were detected with other <i>bla</i> genes or alone; the most frequently observed β-lactamase gene was <i>bla</i>_CTX-M-1/15 (n = 20). In total, 63.6% (n = 14) of the isolates exhibited a multidrug-resistant phenotype and one <i>E. coli</i> isolate (4.5%) harbored the AmpC gene. Precisely because the presence of data regarding extended-spectrum cephalosporin-resistant <i>Escherichia coli</i> and methicillin-resistant <i>Staphylococcus aureus</i> in calves and cows in Austria is rare, this study further expands our understanding of antimicrobial resistance in Austrian cattle, which is highly relevant for successful antibiotic therapy in sick cattle.