Comparative Killing of Canine Urinary Pathogens by Cephalexin (CP), Marbofloxacin (MR), Pradofloxacin (PR) and Trimethoprim/Sulfamethoxazole (TMP/SMX)
M. Blondeau; D. Shebelski
Urinary tract infections are common in dogs, necessitating antimicrobial therapy. In humans, short-course therapy is used for uncomplicated cases, thereby questioning if shorter courses are possible in dogs. Rapid and complete killing of bacteria by antibiotics affects clinical cure and may influence shorter durations of therapy.
The aim of this study was comparing killing of canine urinary pathogens by 4 antimicrobial agents at clinically relevant drug concentrations. Approximately 100,000 colony-forming units/milliliter of canine isolates (3 strains each) of Escherichia coli (EC), Enterobacter faecalis (EF), Proteus mirabilis (PM) and Staphylococcus pseudintermedius (SP) were exposed to the maximum serum (Cmax) and maximum urine (Umax) concentrations of each drug and the log10 (LT) and percent (%) kill measured at 5, 10, 15, 20, 25, 30, 60, 120 and 180 minutes after drug exposure. All measurements were in triplicate and averaged such that each data point was based on 9 averaged values, i.e., triplicate and 3 strains. Exposure of EC to the Cmax of CP, TMX/SMX, MR and PR resulted in 22 (0.22 LT), 3 (0.01 LT), 94 (2.1 LY) and 99 (2.41 LT) % kill following 30 minutes of drug exposure; at the Umax 23 (0.11 LT), growth (+0.02 LT), 95 (1.6 LT) and >99 (2.5 LT) % kill following 5 minutes of drug exposure. Following 180 minutes of drug exposure at the Umax, 82% kill was seen for CP and growth for TMP/SMX. Exposure of PM to the Cmax of CP, TMP/SMX, MR, PR resulted in 64%, >99%, 96% kill and growth respectively following 60 minutes of drug exposure; at the Umax 42%, 4%, 96% and >99% kill was observed following 15 minutes of drug exposure. Exposure of SP to the Cmax of CP, TMP/SMX, MR, PR resulted in 3, 9, 53 and 93% kill following 30 minutes of drug exposure; at the Umax 2, 3, 64 and 94% kill was seen respectively following 15 minutes of drug exposure. Exposure of EF to Umax for TMP/SMX, MR, PR resulted in growth, 86 and 96% kill respectively following 120 minutes of drug exposure.
Killing of bacterial pathogens is necessary for clinical cure and rapid and complete killing influence duration of therapy. MR and PR more rapidly and completely killed urinary pathogens than did CP and TMP/SMX. Such observations may be important clinically for empiric antimicrobial treatment of canine urinary tract infections and is consistent with antimicrobial stewardship goals.
Disclosures
Disclosures to report
Unrestricted research grant from Bayer Animal Health