Stewardship / Resistance Scan for May 19, 2017

Allergy testing and stewardship
Antibiotic resistance in cattle
Veterinary antibiotic use

Antibiotic allergy testing improves appropriate prescribing, study finds

Incorporating antibiotic allergy testing (AAT) into an antimicrobial stewardship (AMS) program can improve antibiotic usage and appropriateness, according to a study yesterday in Clinical Infectious Diseases.

In the multicenter prospective cohort study, researchers evaluated the effects of a multidisciplinary AAT-AMS implemented at two large Australian hospitals over a 14-month period beginning May 2015. Although they are often inaccurate, the prevalence of patient-reported antibiotic allergies (so-called antibiotic allergy labels [AALs]) has increased in recent years. Because AALs are associated with restricted and inappropriate antibiotic usage, the researcher hypothesized that an AAT-AMS could improve antibiotic use.

Study outcomes included the proportion of patients who were "de-labeled" of their AAL, the spectrum of antibiotic courses for the 12 months prior to testing and 3 months following testing, and antibiotic appropriateness.

From the 118 patients who were referred for AAT, 226 allergies were identified, with 56% harboring a penicillin AAL, 44% a cephalosporin AAL, and 30% aminopenicillin AAL. After formal AAT was performed, 94% of patients had AALs revised, with 83% having one or more AALs removed, including 83% of all patients with penicillin AALs. In the 3 months post-AAT, prescribing of more narrow-spectrum penicillins (adjusted odds ratio [aOR] 2.81), narrow-spectrum beta-lactams (aOR 3.54,), and appropriate antibiotics (aOR 12.27) was more likely than in the 12 months prior to testing, and less likely for restricted antibiotics (aOR 0.16).

"We demonstrated that AAT-AMS increased narrow-spectrum penicillin use, increased uptake of preferred therapies, and reduced restricted antibiotic use," the authors write. "To our knowledge, this is the first study to demonstrate the impact of AAT-AMS on improving the appropriateness of antibiotic prescribing."
May 18 Clin Infect Dis study


Researchers find no resistance in Enterococci from Australian cattle

Australian researchers found no resistance to antibiotics considered critically or highly important to human medicine in Enterococcus samples from cattle manure at slaughter, according to a study yesterday in PLoS One.

In this study, researchers collected fecal samples from 910 beef cattle, 210 dairy cattle, and 300 veal calves to determine the prevalence of antimicrobial resistance (AMR) among Enterococcus isolates. Enterococci are considered important targets for AMR surveillance in humans, animals, and food because they are ubiquitous, commonly isolated nosocomial pathogens that are known to rapidly acquire resistance when exposed to antimicrobials. Enterococcus faecium and Enterococcus faecalis, in particular, have become increasingly important pathogens because of their ability cause to life-threatening hospital infections.

A total of 1,296 Enterococcus isolates were collected from the cattle, and 800 isolates comprising 96 E faecalis, 120 E faecium, and 584 samples from other Enterococcus species were submitted for AMR analysis. The results showed that high levels of resistance to antibiotics that are not considered important to human medicine—flavomycin (80.2%) and lincomycin (85.4% to 94.2%)—was common. Resistance to erythromycin and tetracycline was low. None of the isolates were found to be resistant to vancomycin or ampicillin, an important finding given that ampicillin is the preferred therapy for uncomplicated enterococcal infections and that the absence of vancomycin resistance helps maintain optimal treatment options. 

While the initial tests found low levels of resistance to daptomycin and tigecycline, further testing found that minimum inhibitory concentrations (MICs) were all below clinical breakpoints, and therefore all isolates should be considered susceptible. 

"Importantly, it would appear that the production practices in Australian cattle populations are not generating pools of resistance that are likely to result in the inability to treat human infections caused by enterococci," the authors write.
May 18 PLoS One research article


Study finds antibiotic use in Australian dogs and cats generally appropriate

In another study out of Australia, researchers report in the Journal of Veterinary Internal Medicine that antimicrobial usage by Australian veterinarians in treatment of dogs and cats is generally appropriate.

The findings are based on a survey filled out by 892 Australian veterinary practitioners in which respondents were asked about their approach to antibiotic treatment of dogs and cats for 11 different medical conditions, 2 surgical conditions, and 8 dermatological conditions. Specifically, they were asked about how often they use empirical antimicrobial therapy versus therapy based on culture and susceptibility testing, choice of antimicrobials, and duration of therapy.

The results of the survey showed that antimicrobial therapy was used in 51% of cases and guided by culture and susceptibility testing in 26% of cases, and empirical therapy was employed pending the results of culture and susceptibility testing in 24% of cases. Empirical antimicrobial therapy was more common in acute conditions (76%) than in chronic conditions (24%).

The most common antimicrobial classes used were potentiated aminopenicillins (36%), fluoroquinolones (15%), first- and second-generation cephalosporins (14%), and tetracyclines (11%). Use of antimicrobials with a high importance rating ranged from 12% to 47% in cats and 4% to 42% in dogs. Third-generation cephalosporin use was more frequent in cats than in dogs (16% vs 1.8%), while fluoroquinolone use was more frequent in dogs than in cats (18% vs 11%).

Agreement with Australasian Infectious Disease Advisory Panel guidelines was variable, ranging from 0 to 69% among conditions.

The authors conclude that while the survey results indicate that antimicrobial usage among Australian veterinarians is appropriate, the empirical use of antimicrobials of high importance for human medicine, particularly third-generation cephalosporins in cats and fluoroquinolones in cats, warrants further investigation.
May 17 J Vet Intern Med study

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