Antimicrobial use in critically ill horses

Basic Postoperative Care of the Equine Colic Patient

The 3 time periods around colic surgery (preoperative, operative, and postoperative) are all critical to successful outcomes. Although much focus is often paid to the first 2 time periods, the importance of sound clinical judgment and rational decision-making in the postoperative period cannot be overstated. This article will outline the basic principles of monitoring, fluid therapy, antimicrobial therapy, analgesia, nutrition, and other therapeutics routinely used in patients following colic surgery. Discussions of the economics of colic surgery and expectations for normal return to function will also be included.

Pharmacokinetics and pharmacodynamics of doxycycline in a Streptococcusequi subsp. zooepidemicus infection model in horses

The objectives of this study were to investigate the pharmacokinetics (PK), pharmacodynamics (PD), and the efficacy of oral administration of doxycycline (DXC) in horses with Streptococcus zooepidemicus tissue infections. Tissue chambers (TC) were implanted subcutaneously in the cervical region of 7 horses and inoculated with a single S. zooepidemicus isolate with a minimum inhibitory concentration (MIC) of 0.25 µg/ml, determined by agar dilution. Doxycycline hyclate (10 mg/kg, orally, q 12 h, for 5 days) mixed with poloxamer gel was started following inoculation. The TC fluid was sampled prior to and following inoculation for cytology analysis, quantitative culture, and DXC determination. Plasma DXC concentrations were measured over 48 h following the last dose of DXC administered. The mean plasma peak concentration (C_max ) of DXC was 0.32 µg/ml, and concentrations above the MIC were only reached in 3 TC samples. In plasma, mean T > MIC was 2.4 h, mean C_max /MIC was 1.30, and mean AUC_last /MIC was 11.63 h. These PK/PD indices did not reach the suggested targets for DXC treatments of infections, and the TC abscessed in all horses. This is the first study to evaluate the recommended dose of DXC in horse in an infection model.

Prevalence of extended-spectrum cephalosporin-, carbapenem-, and fluoroquinolone-resistant members of the family Enterobacteriaceae isolated from the feces of horses and hospital surfaces at two equine specialty hospitals

OBJECTIVE

To estimate the prevalence of extended-spectrum cephalosporin-, carbapenem-, and fluoroquinolone-resistant bacteria of the family Enterobacteriaceae in the feces of hospitalized horses and on hospital surfaces.

SAMPLE

Fecal and environmental samples were collected from The Ohio State University Galbreath Equine Center (OSUGEC) and a private referral equine hospital in Kentucky (KYEH). Feces were sampled within 24 hours after hospital admission and after 48 hours and 3 to 7 days of hospitalization.

PROCEDURES

Fecal and environmental samples were enriched, and then selective media were inoculated to support growth of Enterobacteriaceae bacteria that expressed resistance phenotypes to extended-spectrum cephalosporins, carbapenems, and fluoroquinolones.

RESULTS

358 fecal samples were obtained from 143 horses. More samples yielded growth of Enterobacteriaceae bacteria that expressed resistance phenotypes (AmpC β-lactamase, OR = 4.2; extended-spectrum beta-lactamase, OR = 3.2; and fluoroquinolone resistance, OR = 4.0) after 48 hours of hospitalization, versus within 24 hours of hospital admission. Horses hospitalized at KYEH were at greater odds of having fluoroquinolone-resistant bacteria (OR = 2.2). At OSUGEC, 82%, 64%, 0%, and 55% of 164 surfaces had Enterobacteriaceae bacteria with AmpC β-lactamase phenotype, extended-spectrum beta-lactamase phenotype, resistance to carbapenem, and resistance to fluoroquinolones, respectively; prevalences at KYEH were similarly distributed (52%, 32%, 1%, and 35% of 315 surfaces).

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that antimicrobial-resistant Enterobacteriaceae may be isolated from the feces of hospitalized horses and from the hospital environment. Hospitalization may lead to increased fecal carriage of clinically important antimicrobial-resistance genes.

Extended-Spectrum β-lactamase-Producing Enterobacteriaceae Shedding in Farm Horses Versus Hospitalized Horses: Prevalence and Risk Factors

Simple summary

This prospective study investigated the prevalence, molecular characteristics and risk factors of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E) shedding in three equine cohorts: (i) farm horses (13 farms, n = 192); (ii) on admission to a hospital (n = 168) and; (iii) horses hospitalized for ≥72 h re-sampled from cohort (ii) (n = 86). Bacteria were isolated from rectal swabs, identified, antibiotic susceptibility patterns were determined, and medical records and owners’ questionnaires were analyzed for risk factor analysis. ESBL shedding rates significantly increased during hospitalization (77.9%, n = 67/86), compared to farms (20.8%, n = 40/192), and horses on admission (19.6%, n = 33/168). High bacterial species diversity was identified, mainly in cohorts (ii) and (iii), with high resistance rates to commonly used antimicrobials. Risk factors for shedding in farms included horses’ breed (Arabian), sex (stallion), and antibiotic treatment. Older age was identified as a protective factor. We demonstrated a reservoir for antibiotic-resistant bacteria in an equine hospital and farms, with a significant ESBL-E acquisition. In light of our findings, in order to control ESBL spread, we recommend conducting active ESBL surveillance programs alongside antibiotic stewardship programs in equine facilities.

Abstract

We aimed to investigate the prevalence, molecular characteristics and risk factors of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E) shedding in horses. A prospective study included three cohorts: (i) farm horses (13 farms, n = 192); (ii) on hospital admission (n = 168) and; (iii) horses hospitalized for ≥72 h re-sampled from cohort (ii) (n = 86). Enriched rectal swabs were plated, ESBL-production was confirmed (Clinical and Laboratory Standards Institute (CLSI)) and genes were identified (polymerase chain reaction (PCR)). Identification and antibiotic susceptibility were determined (Vitek-2). Medical records and owners’ questionnaires were analyzed. Shedding rates increased from 19.6% (n = 33/168) on admission to 77.9% (n = 67/86) during hospitalization (p < 0.0001, odds ratio (OR) = 12.12). Shedding rate in farms was 20.8% (n = 40/192), significantly lower compared to hospitalized horses (p < 0.0001). The main ESBL-E species (n = 192 isolates) were E. coli (59.9%, 115/192), Enterobacter sp. (17.7%, 34/192) and Klebsiella pneumoniae (13.0%, 25/192). The main gene group was CTX-M-1 (56.8%). A significant increase in resistance rates to chloramphenicol, enrofloxacin, gentamicin, nitrofurantoin, and trimethoprim-sulpha was identified during hospitalization. Risk factors for shedding in farms included breed (Arabian, OR = 3.9), sex (stallion, OR = 3.4), and antibiotic treatment (OR = 9.8). Older age was identified as a protective factor (OR = 0.88). We demonstrated an ESBL-E reservoir in equine cohorts, with a significant ESBL-E acquisition, which increases the necessity to implement active surveillance and antibiotic stewardship programs.

A Common Practice of Widespread Antimicrobial Use in Horse Production Promotes Multi-Drug Resistance

The practice of prophylactic administration of a macrolide antimicrobial with rifampin (MaR) to apparently healthy foals with pulmonary lesions identified by thoracic ultrasonography (i.e., subclinically pneumonic foals) is common in the United States. The practice has been associated epidemiologically with emergence of R. equi resistant to MaR. Here, we report direct evidence of multi-drug resistance among foals treated with MaR. In silico and in vitro analysis of the fecal microbiome and resistome of 38 subclinically pneumonic foals treated with either MaR (n = 19) or gallium maltolate (GaM; n = 19) and 19 untreated controls was performed. Treatment with MaR, but not GaM, significantly decreased fecal microbiota abundance and diversity, and expanded the abundance and diversity of antimicrobial resistance genes in feces. Soil plots experimentally infected with Rhodococcus equi (R. equi) and treated with MaR selected for MaR-resistant R. equi, whereas MaR-susceptible R. equi out-competed resistant isolates in GaM-treated or untreated plots. Our results indicate that MaR use promotes multi-drug resistance in R. equi and commensals that are shed into their environment where they can persist and potentially infect or colonize horses and other animals.

Antimicrobial susceptibility of bacterial isolates from ambulatory practice and from a referral hospital

BACKGROUND

Responsible use of antimicrobials in equine practice relies on knowledge of common bacterial isolates and their antimicrobial sensitivities.

OBJECTIVES

To assess the frequency of bacterial resistance to a combination of parenteral penicillin and gentamicin and to trimethoprim and sulfamethoxazole for PO use in a selection of clinical isolates, and subsequently to determine the prevalence of resistance to antimicrobials that might then be used as alternatives to first-line antimicrobials for the same isolates.

METHODS

Retrospective analysis of minimal inhibitory concentrations (MICs) of antimicrobials for 6354 bacterial isolates from 365 ambulatory practices and 519 isolates from a referral hospital. The MICs were used to indicate sensitivity or resistance to commonly used antimicrobials and the prevalences of resistance were compared between origin of the isolates, and among antimicrobial drugs.

RESULTS

Isolates from the referral hospital were significantly (P < .05) more likely to be resistant to the antimicrobials tested than those derived from ambulatory practice. Overall, 91% of the ambulatory isolates and 64% of the hospital isolates were sensitive to penicillin-gentamicin. For trimethoprim-sulfamethoxazole combination, 82% of the ambulatory practice isolates and 56% of the referral hospital isolates were sensitive.

CONCLUSIONS AND CLINICAL IMPORTANCE

Most isolates were sensitive to penicillin and gentamicin as well as trimethoprim-sulfamethoxazole. No predictable efficacious second choice antimicrobial was identified for those isolates resistant to the first-line antimicrobials. The likelihood of isolates being sensitive to second choice antimicrobials was variable but generally higher for ambulatory isolates compared to referral isolates. Bacterial identification and measurement of MIC are essential to make the appropriate antimicrobial choice.

Antimicrobial Susceptibility of Bordetella bronchiseptica Isolates from Swine and Companion Animals and Detection of Resistance Genes

Bordetella bronchiseptica causes infections of the respiratory tract in swine and other mammals and is a precursor for secondary infections with Pasteurella multocida. Treatment of B. bronchiseptica infections is conducted primarily with antimicrobial agents. Therefore it is essential to get an overview of the susceptibility status of these bacteria. The aim of this study was to comparatively analyse broth microdilution susceptibility testing according to CLSI recommendations with an incubation time of 16 to 20 hours and a longer incubation time of 24 hours, as recently proposed to obtain more homogenous MICs. Susceptibility testing against a panel of 22 antimicrobial agents and two fixed combinations was performed with 107 porcine isolates from different farms and regions in Germany and 43 isolates obtained from companion animals in Germany and other European countries. Isolates with increased MICs were investigated by PCR assays for the presence of resistance genes. For ampicillin, all 107 porcine isolates were classified as resistant, whereas only a single isolate was resistant to florfenicol. All isolates obtained from companion animals showed elevated MICs for β-lactam antibiotics and demonstrated an overall low susceptibility to cephalosporines. Extension of the incubation time resulted in 1-2 dilution steps higher MIC50 values of porcine isolates for seven antimicrobial agents tested, while isolates from companion animals exhibited twofold higher MIC50/90 values only for tetracycline and cefotaxime. For three antimicrobial agents, lower MIC50 and MIC90 values were detected for both, porcine and companion animal isolates. Among the 150 isolates tested, the resistance genes blaBOR-1 (n = 147), blaOXA-2, (n = 4), strA and strB (n = 17), sul1 (n = 10), sul2 (n = 73), dfrA7 (n = 3) and tet(A) (n = 8) were detected and a plasmid localisation was identified for several of the resistance genes.