title: In vitro susceptibility of canine and feline Escherichia coli to fosfomycin.
abstract: Therapeutic options for multi-drug resistant (MDR) Escherichia coli in dogs or cats are limited. The objective of this study was to establish in vitro susceptibility of canine and feline E. coli to fosfomycin. Two sources of isolates were categorized based on susceptibility as to no resistance (NDR), single drug resistance (SDR), multidrug resistance (MDR) or extreme drug resistance (XDR). Clinical isolates were collected from throughout the US from dogs (n=157) or cats (n=43) with naturally occurring infection between March 2008 and January 2010. Experimental isolates were collected from fecal samples of dogs treated with no drug (NDR), amoxicillin (expressing SDR) or enrofloxacin (expressing MDR or XDR). Fosfomycin minimum inhibitory concentrations (MIC) were determined using E-Test(®). For clinical isolates, most (165/200) originated from the urinary tract, with the number of isolates per resistant category being: NDR (N=44, 22%), SDR (N=65, 32.5%), MDR (N=74, 37%), and XDR (N=17, 8.5%). Of these isolates, 99% (197/200) were susceptible to fosfomycin with the MIC(90) and MIC(50) being 2 and 1 μg/ml, respectively (range: 0.25-196 μg/ml). The number of experimental isolates in each category was NDR (3), SDR (23), MDR (38), and XDR (11) (29.3, 44, and 14.7%, respectively). Of these, 100% were susceptible to fosfomycin with MIC(90) and MIC(50) being 1.5 and 1 μg/ml (range: 0.38-4 μg/ml), respectively. The susceptibility of canine and feline MDR and XDR E. coli to fosfomycin at concentrations well below the susceptible breakpoint supports further investigation for its use when treating E. coli resistant to alternative antimicrobials.
authors.affiliation: Anatomy, Physiology and Pharmacology, Auburn University, College of Veterinary Medicine, 109 Greene Hall, AL 36849-5518, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Hubka
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Boothe
mesh_terms: D000658:Amoxicillin / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002415:Cats; D004285:Dogs; D024881:Drug Resistance, Bacterial; D000077422:Enrofloxacin; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D024841:Fluoroquinolones / Q000494:pharmacology; D005578:Fosfomycin / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D010641:Phenotype; D014556:Urine / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D005578:Fosfomycin; D000077422:Enrofloxacin; D000658:Amoxicillin