Influence of oxytetracycline susceptibility as a first-line antibiotic on the clinical outcome in dairy cattle with acute <i>Escherichia coli</i> mastitis

Abstract

The purpose of this study was to clarify the therapeutic effects of oxytetracycline (OTC) as a first-line antibiotic in cattle with acute Escherichia coli mastitis and systemic signs. Drug susceptibility was determined by the minimum inhibitory concentration (MIC) of E. coli isolated from cows with acute E. coli mastitis (n=38). Cattle were divided into OTC-susceptible (S, n=30) and OTC-resistant (R, n=8) groups. They were further subdivided according to susceptibility to the antibiotic used as a second treatment, into susceptible-susceptible (SS, n=30), resistant-susceptible (RS, n=5), and resistant-resistant (RR, n=3) groups. Clinical signs on the day after initial treatment were compared between S and R groups as short-term indicators of treatment effects. The 28-day survival rate of cattle was then compared among SS, RS, and RR groups as a long-term indicator of treatment effects. There were no differences in clinical signs between S and R groups on the day after the first dose, but the 28-day survival rate was significantly greater in the SS group than in the RR group ( P =0.04). The results demonstrated that an effective drug is essential for first-line treatment of acute coliform mastitis. However, anticipating the effectiveness of a first-line antibiotic based on clinical symptoms at the second day of treatment is impossible. It is important to build a picture of drug resistance trends in cattle herds for empirical selection of antibiotics to be administered.

Antibiotic Resistance in Bacteria—A Review

“…E. coli infections in animals are subjected to various pharmaceutical treatments. For instance, broad-spectrum cephalosporins and fluoroquinolones are commonly used to treat bovine mastitis [ 99 ]. One of the antibiotics used to treat colibacillosis in poultry is enrofloxacin, which belongs to fluoroquinolones [ 100 ].…”

Advances in therapeutic and managemental approaches of bovine mastitis: a comprehensive review

“…Fourth generation cephalosporin was found to be slightly better than the conventional cloxacillin and ampicillin combination to treat subclinical S. agalactiae mastitis (Rossi et al 2019 ). Oxytetracycline could be used as first line of treatment in acute E. coli mastitis in cattle; however, anticipation of its effectiveness is not possible (Shinozuka et al 2019 ). In case of mild to moderate E. coli mastitis, antibiotics should be avoided whereas in severe cases antibiotics like fluoroquinolones and cephalosporins through parenteral route is recommended to prevent bacteremia-associated risk (Suojala et al 2013 ).…”

Susceptibility of caprine mastitis pathogens to tildipirosin, gamithromycin, oxytetracycline, and danofloxacin: effect of serum on the in vitro potency of current macrolides

“…Minimum inhibitory concentrations that inhibited 90% of caprine mastitis pathogens obtained with tildipirosin (4 µg/ml) and gamithromycin (8 µg/ml) were high, but after modifying the conditions with serum, MIC values decreased dramatically (MIC 90 = 0.5 and 2 µg/ml for tildipirosin and gamithromycin, respectively). References are available in the literature about the susceptibility of E. coli strains isolated from milk to antimicrobial agents in dairy cows (Shinozuka et al 2019 ; Thomas et al 2015 ); however, data are unavailable for dairy goats. Similar high MIC 90 values were found for different tetracyclines in strains isolated from dairy cows (MIC 90 ≥ 64 µg/ml; Thomas et al, 2015 ) and lower values for other fluoroquinolones, such as enrofloxacin o marbofloxacin (MIC 90 = 0.03 and 0.06 µg/ml, respectively; Thomas et al 2015 ).…”