Methicillin-Resistant Staphylococcus aureus Clonal Complex 398 as a Major MRSA Lineage in Dogs and Cats in Thailand

Emergence of MRSA ST612 in horses and of MSSA CC398 in cats in France

OBJECTIVES

Staphylococcus aureus is an important zoonotic pathogen that has often been seen in animals through the prism of the MRSA clonal complex (CC) 398 in pigs and in-contact humans. The goal of this study was first to assess the prevalence of MRSA, and second to look for MSSA CC398 in cats, dogs and horses in France.

METHODS

Clinical S. aureus isolates (n = 479) were collected from 186 cats, 143 dogs and 150 horses during 2022-2023 all over the French territory. Antibiograms were performed on all isolates. MRSA and MSSA CC398 isolates were subject to WGS. Core genome (cg) MLST-based and SNP-based phylogenetic analyses were performed using published methodologies, and characterization of the isolates was performed using publicly available tools.

RESULTS

Sixty-six MRSA isolates were identified in 14 cats (7.5%), 9 dogs (6.3%) and 43 horses (28.7%). The epidemiology of MRSA in cats and dogs remained stable since a previous study in 2015, with the presence of both CC398 and human-associated clones. In horses, in contrast, an important increase in MRSA (from 10% to 28.7%) was observed, potentially attributable to the emergence of the ST612 clones. In parallel, CC398 MSSA, a clone usually described as animal-independent, was found in 24.2% of the cat isolates.

CONCLUSIONS

Our study, which is leading the way to a genomic surveillance of S. aureus in France, revealed the emergence of both MRSA ST612 in horses and MSSA CC398 in cats. These clones should be closely monitored to avoid their zoonotic spread and to understand their dynamics of transmission between humans and animals.

Chromosomal and plasmid localization of ileS2 in high-level mupirocin-resistant Staphylococcus pseudintermedius and Staphylococcus aureus isolated from canine and feline origins

OBJECTIVES

To characterize the mobile genetic elements and genetic localization of ileS2 in high-level mupirocin-resistant (Hi-MupR) methicillin-resistant Staphylococcus pseudintermedius (MRSP) and MRSA isolates recovered from canine and feline clinical samples.

METHODS

The identification of bacterial species and presence of mecA and ileS2 genes in MRSP and MRSA isolates were performed using MALDI-TOF MS and PCR, respectively. Antimicrobial resistance (AMR) phenotypes were determined by broth microdilution assays. The genome characteristics, ileS2-containing elements and staphylococcal cassette chromosome mec (SCCmec) were illustrated using complete circular genomes obtained from hybrid assembly of Illumina short-reads and Oxford Nanopore Technologies long-reads. These were analysed through phylogenetic and bioinformatics approaches.

RESULTS

A total of 18 MRSP clinical isolates and four MRSA clinical isolates exhibited the Hi-MupR phenotype and carried multiple AMR genes, including mecA and ileS2 genes. MRSP ST182-SCCmec V (n = 6) and ST282-ΨSCCmec57395-t10 (n = 4) contained the ileS2 transposable unit associated with IS257 on the chromosome. Three MRSA ST398-SCCmec V-t034/t4652 isolates carried ∼42 kb pSK41-like ileS2 plasmids, whereas similar ileS2 plasmids lacking tra genes were found in MRSP ST282-ΨSCCmec57395-t72/t21 isolates. Furthermore, a new group of ileS2 plasmids, carried by MRSP ST45-ΨSCCmec57395, ST433-ΨSCCmecKW21-t05 and ST2165-SCCmec IV-t06, and by one MRSA ST398-SCCmec V-t034 strain, shared the plasmid backbone with the cfr/fexA-carrying plasmid pM084526_1 in MRSA ST398.

CONCLUSIONS

This study provides the first evidence of ileS2 integration into the S. pseudintermedius chromosome, which is a rare occurrence in staphylococcal species, and plasmids played a pivotal role in dissemination of ileS2 in both staphylococcal species.

The Epidemiology of Animal-Associated Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) remains an important etiological factor of human and animal infectious diseases, causing significant economic losses not only in human healthcare but also in the large-scale farming sector. The constantly changing epidemiology of MRSA observed globally affects animal welfare and raises concerns for public health. High MRSA colonization rates in livestock raise questions about the meaning of reservoirs and possible transmission pathways, while the prevalence of MRSA colonization and infection rates among companion animals vary and might affect human health in multiple ways. We present the main findings concerning the circulation of animal-associated MRSA (AA-MRSA) in the environment and factors influencing the direction, mechanisms, and routes of its transmission. Studies have shown it that S. aureus is a multi-host bacterial pathogen; however, its adaptation mechanisms enabling it to colonize and infect both animal and human hosts are still rarely discussed. Finally, we elaborate on the most successful strategies and programs applied limiting the circulation of AA-MRSA among animals and humans. Although MRSA strains colonizing animals rarely infect humans, they undergo host-adaptive evolution enabling them to spread and persist in human populations.

Pet animals as reservoirs for spreading methicillin-resistant Staphylococcus aureus to human health

Methicillin-resistant Staphylococcus aureus (MRSA) is a strain of pathogenic bacteria that is a major problem in the world's health. Due to their frequent interaction with humans, pets are one of the main risk factors for the spread of MRSA. The possibility for zoonotic transmission exists since frequently kept dogs and cats are prone to contract MRSA and act as reservoirs for spreading MRSA. The mouth, nose, and perineum are the primary locations of MRSA colonization, according to the findings of MRSA identification tests conducted on pets. The types of MRSA clones identified in cats and dogs correlated with MRSA clones infecting humans living in the same geographic area. A significant risk factor for the colonization or transmission of MRSA is human-pet contact. An essential step in preventing the spread of MRSA from humans to animals and from animals to humans is to keep hands, clothing, and floor surfaces clean.

Nasal Staphylococcus aureus and S. pseudintermedius carriage in healthy dogs and cats: a systematic review of their antibiotic resistance, virulence and genetic lineages of zoonotic relevance

The molecular ecology of Staphylococcus aureus, Staphylococcus pseudintermedius and their methicillin-resistant strains in healthy dogs and cats could serve as good models to understand the concept of bacterial zoonosis due to animal companionship. This study aims to provide insights into pooled prevalence, genetic lineages, virulence and antimicrobial resistance (AMR) among healthy dogs and cats. Original research and brief communication articles published from 2001 to 2021 that reported the nasal detection of S. aureus and S. pseudintermedius in healthy dogs and cats in the community, homes and outside veterinary clinics were examined and analysed. Forty-nine studies were eligible and included in this systematic review. The pooled prevalence of nasal carriage of S. aureus/methicillin-resistant S. aureus (MRSA) in healthy dogs and cats were 10.9% (95% CI: 10.1-11.9)/2.8% (95% CI: 2.4-3.2) and 3.2% (95% CI: 1.9-4.8)/0.5% (95% CI: 0.0-1.1), respectively. Conversely, the pooled prevalence of S. pseudintermedius/methicillin-resistant S. pseudintermedius (MRSP) in healthy dogs and cats were 18.3% (95% CI: 17.1-19.7)/3.1% (95% CI: 2.5-3.7) and 1.3% (95% CI: 0.6-2.4)/1.2% (95% CI: 0.6-2.3), respectively. Although highly diverse genetic lineages of S. aureus were detected in healthy dogs and cats, MSSA-CC1/CC5/CC22/CC45/CC121/CC398 and MRSA-CC5/CC93/CC22/CC30 were mostly reported in dogs; and MSSA-CC5/CC8/CC15/CC48 and MRSA-CC22/CC30/CC80 in cats. Of note, MSSA-CC398 isolates (spa-types t034 and t5883) were detected in dogs. Genetic lineages often associated with MSSP/MRSP were ST20/ST71, highlighting the frequent detection of the epidemic European MRSP-ST71 clone in dogs. S. aureus isolates carrying the luk-S/F-PV, tst, eta, etb and etd genes were seldomly detected in dogs, and luk-S/F-PV was the unique virulence factor reported in isolates of cats. S. pseudintermedius isolates harbouring the luk-S/F-I, seint and expA genes were frequently found, especially in dogs. High and diverse rates of AMR were noted, especially among MRSA/MRSP isolates. There is a need for additional studies on the molecular characterization of isolates from countries with under-studied nasal staphylococci isolates.

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

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) was first discovered in horses in 1989. Since then, LA-MRSA has begun to be considered an important strain of pathogenic bacteria in horses, which can cause LA-MRSA infection and colonization in humans with public health impacts. The anterior nares are the primary site of LA-MRSA colonization in horses, although LA-MRSA colonization may also occur in the gastrointestinal tract in horses. LA-MRSA-infected horses typically exhibit clinical infection or may not exhibit clinical infection. There are two potential risks associated with LA-MRSA colonization in horses: The possibility of disease development in horses infected with LA-MRSA and the possibility of LA-MRSA transfer to humans and other horses. The diagnosis of LA-MRSA in horses can be made by conducting in vitro sensitivity testing for oxacillin and cefoxitin, and then followed by a molecular test using polymerase chain reaction. LA-MRSA transmission in animal hospitals and on farms is most likely due to contact with horses infected or colonized by LA-MRSA. The history of prior antibiotic administration, history of prior LA-MRSA colonization, and length of equine hospitalization were described as risk factors in cases of infection and colonization of LA-MRSA in horses. Nebulized antibiotics may be a viable alternative to use in horses, but nebulized antibiotics are only used in horses that are persistently colonized with LA-MRSA. Controlling the spread of LA-MRSA in horses can be done by regularly washing horses, eradicating vectors in horse stalls such as rats, and maintaining the cleanliness of the stable and animal hospital environment. Meanwhile, cleaning hands, using gloves, and donning protective clothes are ways that humans can prevent the transmission of LA-MRSA when handling horses. This review will explain the definition of LA-MRSA in general, LA-MRSA in horses, the epi­demiology of LA-MRSA in horses, the diagnosis of LA-MRSA in horses, the transmission of LA-MRSA in horses, risk factors for spreading LA-MRSA in horses, public health impact, treatment of LA-MRSA infection in horses, and control of the spread of LA-MRSA in horses.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): antimicrobial-resistant Staphylococcus aureus in cattle and horses

Staphylococcus aureus (S. aureus) was identified among the most relevant antimicrobial-resistant (AMR) bacteria in the EU for cattle and horses in previous scientific opinions. Thus, it has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on its eligibility to be listed, Annex IV for its categorisation according to disease prevention and control rules as in Article 9, and Article 8 for listing animal species related to the bacterium. The assessment has been performed following a methodology previously published. The outcome is the median of the probability ranges provided by the experts, which indicates whether each criterion is fulfilled (lower bound ≥ 66%) or not (upper bound ≤ 33%), or whether there is uncertainty about fulfilment. Reasoning points are reported for criteria with uncertain outcome. According to the assessment here performed, it is uncertain whether AMR S. aureus can be considered eligible to be listed for Union intervention according to Article 5 of the AHL (60-90% probability). According to the criteria in Annex IV, for the purpose of categorisation related to the level of prevention and control as in Article 9 of the AHL, the AHAW Panel concluded that the bacterium does not meet the criteria in Sections 1, 2 and 4 (Categories A, B and D; 1-5%, 5-10% and 10-33% probability of meeting the criteria, respectively) and the AHAW Panel was uncertain whether it meets the criteria in Sections 3 and 5 (Categories C and E, 33-90% and 60-90% probability of meeting the criteria, respectively). The animal species to be listed for AMR S. aureus according to Article 8 criteria include mainly mammals, birds, reptiles and fish.

Prevalence and Characteristics of Multidrug-Resistant Livestock-Associated Methicillin-Resistant Staphylococcus aureus (LA-MRSA) CC398 Isolated from Quails (Coturnix Coturnix Japonica) Slaughtered for Human Consumption

Simple Summary

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen in both humans and animals worldwide. MRSA associated with livestock is a zoonotic pathogen that has been reported in several animals and, although its infections in humans are rare, this strain is recognized as an occupational hazard for people working in direct contact with livestock. Thus, we aimed to isolate MRSA from quails and to characterize their antimicrobial resistance and genetic lineages. One hundred swab samples were recovered from quails at the slaughterhouse. To investigate the prevalence and antimicrobial resistance of MRSA in poultry, we conducted this study on 100 quails slaughtered for human consumption. The antimicrobial resistance was investigated in all isolates as well as virulence genes and genetic lineages. Twenty-nine MRSA were isolated. The results showed that all MRSA isolates had resistance to multiple antibiotics. All strains were classified as livestock-associated. Most strains belonged to a well-known livestock-associated lineage: CC398.

Abstract

Livestock-associated MRSA (LA-MRSA) is a zoonotic pathogen that has been reported in several animals, and it is often associated with clonal complex (CC) 398. We aimed to isolate MRSA from quails and to characterize their antimicrobial resistance and genetic lineages. One hundred swab samples were recovered from quails at the slaughterhouse. The swabs were inoculated onto CHROMagar™ MRSA agar plates for MRSA isolation. The presence of antimicrobial-resistant genes and virulence factors was investigated by PCR. All strains were typed by MLST, SCCmec-, spa- and agr-typing. From the 100 samples, 29 MRSA were isolated. All strains were resistant to penicillin, cefoxitin, ciprofloxacin, erythromycin and clindamycin and carried the blaZ, mecA, ermB and ermC genes. All strains, except one, showed resistance to tetracycline and harbored the tetM, tetK and tetL genes in different combinations. Twenty strains belonged to ST398 and SCCmec type V, and nine strains belonged to the new ST6831. Twenty-eight out of twenty-nine strains were ascribed to t011 and one to t108. As far as we know, this is the first report of MRSA from quails slaughtered for human consumption. Most strains belonged to ST398-t011, which is the most common LA-MRSA clone found in livestock in Europe.