Prevalence of Methicillin‐Resistant Staphylococcus aureus from Equine Nasopharyngeal and Guttural Pouch Wash Samples

Abstract

BackgroundMethicillin‐resistant Staphylococcus aureus (MRSA) is recognized as a cause of nosocomial infections in both human and veterinary medicine. Studies that examine the nasopharynx and guttural pouches of the horse as carriage sites for MRSA have not been reported.Hypothesis/Objective MRSA colonizes the nasopharynx and guttural pouch of horses. To determine the prevalence of MRSA in equine nasopharyngeal wash (NPW) and guttural pouch lavage (GPL) samples in a field population of horses.SamplesOne hundred seventy‐eight samples (123 NPW and 55 GPL) from 108 horses.MethodsProspective study. Samples were collected from a convenience population of clinically ill horses with suspected Streptococcus equi subsp. equi (S. equi) infection, horses convalescing from a known S. equi infection, and asymptomatic horses undergoing S. equi screening. Samples were submitted for S. aureus aerobic bacterial culture with mannitol salt broth and two selective agars (cefoxitin CHROMagar as the PBP2a inducer and mannitol salt agar with oxacillin). Biochemical identification of Staphylococcus species and pulsed‐field gel electrophoresis (PFGE), to determine clonal relationships between isolates, were performed.ResultsMethicillin‐resistant Staphylococcus (MRS) was isolated from the nasopharynx of 7/108 (4%) horses. Three horses had MRSA (2.7%), and 4 had MR‐Staphylococcus pseudintermedius (MRSP). MRSA was isolated from horses on the same farm. PFGE revealed the 3 MRSA as USA 500 strains.Conclusions and Clinical ImportanceSampling the nasopharynx and guttural pouch of community‐based horses revealed a similarly low prevalence rate of MRSA as other studies sampling the nares of community‐based horses. More study is required to determine the need for sampling multiple anatomic sites when screening horses for MRSA.

Culture‐independent and dependent evaluation of the equine paranasal sinus microbiota in health and disease

“…Samples were barcoded and PCR primers were used under the conditions described above. The software Quantitative Insights Into Microbial Ecology‐2 (QIIME2; https://qiime2.org) was used for sequence processing and analysis . The raw sequence data were de‐multiplexed, and low‐quality reads were filtered using database’s default parameters.…”

Prevalence and whole genome-based phylogenetic, virulence and antibiotic ­resistance characteristics of nasal ­Staphylococcus aureus in healthy Swiss horses

“…Although the MRSA prevalence in horses in Switzerland in 2020 was likely due to a small outbreak in one region, this study provided insights into MRSA carriage in healthy horses in Switzerland. As observed in other countries, the MRSA carriage prevalence in the healthy horse community tends to be usually lower (<0,53 % to 4 %) 6,7,28,31,58 compared to the reported prevalence in horses at hospital admission and in hospitalized horses, which ranges between 1,9 % to 16,4 %. 42,50,51,60,61,67 Similarly to our study, regional dissemination has already been shown to be responsible for increase in prevalence, but such prevalence would decrease when considered on a nationwide scale.…”

A review of horses as a source of spreading livestock-associated methicillin-resistant Staphylococcus aureus to human health

“…Nebulized amikacin (1750 mg in 21 mL total volume) or nebulized enrofloxacin (175 mg in 10 mL total volume) has begun to be used in horses that are continuously colonizing LA-MRSA with shown success in eradicating LA-MRSA colonization [113]. In addition, antibiotic nebulation is not appropriate in cases of LA-MRSA colonization that occurs in the gastrointestinal tract and guttural pockets in horses [114]. Therefore, the efficacy and safety of nebulized antibiotics still require further research.…”