New categories designated as healthcare-associated and community-associated methicillin-resistantStaphylococcus pseudintermediusin dogs

Methicillin Resistance Elements in the Canine Pathogen Staphylococcus pseudintermedius and Their Association with the Peptide Toxin PSM-mec

Staphylococcus pseudintermedius is a frequent cause of infections in dogs. Infectious isolates of this coagulase-positive staphylococcal species are often methicillin- and multidrug-resistant, which complicates therapy. In staphylococci, methicillin resistance is encoded by determinants found on mobile genetic elements called Staphylococcal Chromosome Cassette mec (SCCmec), which, in addition to methicillin resistance factors, sometimes encode additional genes, such as further resistance factors and, rarely, virulence determinants. In this study, we analyzed SCCmec in a collection of infectious methicillin-resistant S. pseudintermedius (MRSP) isolates from predominant lineages in the United States. We found that several lineages characteristically have specific types of SCCmec elements and Agr types and harbor additional factors in their SCCmec elements that may promote virulence or affect DNA uptake. All isolates had SCCmec-encoded restriction-modification (R-M) systems of types I or II, and sequence types (STs) ST84 and ST64 had one type II and one type I R-M system, although the latter lacked a complete methylation enzyme gene. ST68 isolates also had an SCCmec-encoded CRISPR system. ST71 isolates had a psm-mec gene, which, in all but apparently Agr-dysfunctional isolates, produced a PSM-mec peptide toxin, albeit at relatively small amounts. This study gives detailed insight into the composition of SCCmec elements in infectious isolates of S. pseudintermedius and lays the genetic foundation for further efforts directed at elucidating the contribution of identified accessory SCCmec factors in impacting SCCmec-encoded and thus methicillin resistance-associated virulence and resistance to DNA uptake in this leading canine pathogen.

Risk Factors, Genetic Diversity, and Antimicrobial Resistance of Staphylococcus spp. Isolates in Dogs Admitted to an Intensive Care Unit of a Veterinary Hospital

Intensive Care Units (ICU) usually provide an excellent environment for the selection of pathogens associated with hospital-acquired infections (HAI), leading to increased mortality and hospitalization costs. Methicillin-resistant Staphylococcus pseudintermedius (MRSP) is a major cause of HAI in dogs worldwide, but the risk factors and dynamics of colonization by MRSP are largely unknown. This study aimed to evaluate the risk factors associated with the acquisition of MRSP in dogs admitted to an ICU, and to report the antimicrobial resistance profiles and genetic relatedness of MRSP isolates. Sterile swabs from the nostril, axilla, and rectum were collected daily during the hospitalization of 54 dogs. Samples were subjected to Mannitol Salt Agar, and colonies were identified by MALDI-ToF, polymerase chain reaction (PCR), and sequencing of the rpoB gene. Antimicrobial susceptibility testing and PCR detection of mecA were performed. Staphylococcus spp. was isolated from 94% of the dogs, and the most frequently isolated species was S. pseudintermedius (88.2%). Carriage of multidrug resistant (MDR) staphylococci was observed in 64.4% of the dogs, and approximately 39% had methicillin-resistant Staphylococcus sp. (MRS), of which 21.6% had MRSP and 1.9% had methicillin-resistant S. aureus (MRSA). The acquisition of MRSP during ICU hospitalization was associated with sex (female), age (>7 years), and dogs that had previously been treated with antimicrobials. Animals colonized by MRSP resistant to ≥9 antimicrobial classes had longer hospital stays than those colonized by other MRS strains. Among the 13 MRSP isolates that were subjected to whole-genome sequencing, ten were classified as ST71. A single nucleotide polymorphism (SNP) analysis revealed three clones, including one that was detected in infected dogs outside the ICU. This study indicates novel risk factors associated with colonization by MRSP. The detection of the same MRSP clone causing HAI outside the ICU reinforces the need for improved infection prevention and control practices at veterinary hospitals in general and at the ICU in particular.

Efficacy of olanexidine gluconate in canine superficial pyoderma: a randomised, single-blinded controlled trial

BACKGROUND

Topical treatments can be beneficial for managing canine superficial pyoderma. A novel antiseptic agent, olanexidine gluconate, has become available recently for use in humans, and its efficacy for canine pyoderma as topical therapy is unknown.

OBJECTIVE

The antimicrobial effect of olanexidine was evaluated using minimal inhibitory concentration (MIC) towards Staphylococcus pseudintermedius. Furthermore, its clinical efficacy in canine superficial pyoderma was assessed in a randomized, single-blinded study.

ANIMALS

Twenty-eight client-owned dogs with atopic dermatitis and superficial pyoderma.

METHODS AND MATERIALS

The MIC of olanexidine was determined for S. pseudintermedius isolates (n=73) by serial dilution of 96-well broth microdilution method. Regarding the clinical trial, all recruited dogs were randomized into two groups; one treated with 1.5% olanexidine spray once daily and the other with a 3% chlorhexidine shampoo once a week for 2 times, respectively. Clinical assessment was performed at days 0 and 14 according to the guidelines of the Japanese Society of Antimicrobials for Animals.

RESULTS

The MIC values for methicillin-resistant S. pseudintermedius (MRSP) and methicillin-sensitive S. pseudintermedius (MSSP) were 0.23 μg/ml and 0.24 μg/ml (P =0.9), respectively. In clinical trial, olanexidine and chlorhexidine showed substantial improvement in clinical presentation compared to the baseline.

CONCLUSIONS AND CLINICAL IMPORTANCE

Olanexidine showed comparable efficacy to chlorhexidine (P=0.73). Moreover, the MIC against S. pseudintermedius indicated high bactericidal activity, which was supported by the topical effectiveness of olanexidine.

Implanted Port Catheter System Infection Caused by Methicillin-resistant Staphylococcus pseudintermedius ST71-SCCmec type III

Staphylococcus pseudintermedius is commonly associated with skin and soft tissue infections in dogs. However, infections caused by S. pseudintermedius are only rarely reported in humans, and this pathogen is frequently misidentified as S. aureus. We herein report a case of an implanted port catheter system infection caused by methicillin-resistant S. pseudintermedius (MRSP) in a patient with hepatocellular carcinoma. The patient was also a dog owner. S. pseudintermedius was first identified using the Vitek2 system (BioMérieux). Whole-genome sequencing revealed that this MRSP was a sequence type 71-carrying staphylococcal cassette chromosome mec type III (ST71-SCCmec III) isolate.

Specific staphylococcal cassette chromosome mec (SCCmec) types and clonal complexes are associated with low-level amoxicillin/clavulanic acid and cefalotin resistance in methicillin-resistant Staphylococcus pseudintermedius

Background

Staphylococcus pseudintermedius is a common pathogen in dogs and methicillin resistance has emerged over recent decades. According to the current guidelines, S. pseudintermedius displaying oxacillin resistance should be reported as resistant to all β-lactams.

Objectives

To identify possible associations between β-lactam resistance levels and clonal complexes (CCs) and/or staphylococcal cassette chromosome mec (SCCmec) types in methicillin-resistant S. pseudintermedius (MRSP).

Methods

MICs of oxacillin, penicillin, ampicillin, amoxicillin/clavulanic acid and cefalotin were determined by broth microdilution for 86 clinical canine MRSP isolates from Denmark and the Netherlands. PCR and sequencing were used for SCCmec typing and MLST.

Results

Isolates belonged to CC71 (n = 36), CC258 (n = 33), CC45 (n = 11), CC68 (n = 1) and five singleton STs. SCCmecII-III was exclusively found in CC71 and SCCmecIV was significantly associated with CC258. SCCmecV and non-typeable SCCmec types occurred in 4 and 14 isolates, respectively. SCCmecIV was associated with lower MICs of oxacillin (<2 mg/L), ampicillin (<8 mg/L) and amoxicillin/clavulanic acid (<4 mg/L) and with susceptibility to cefalotin (<4 mg/L). All isolates harbouring SCCmecV were susceptible to cefalotin as well.

Conclusions

SCCmec types were associated with different CCs and with either high- or low-level resistance to different β-lactams. The finding of amoxicillin/clavulanic acid (20%) and cefalotin (70%) in vitro susceptibility across all CCs might have clinical implications, since amoxicillin/clavulanic acid and first-generation cephalosporins are first-choice antibiotics for treatment of S. pseudintermedius infections. Pharmacokinetic/pharmacodynamic and clinical outcome studies are warranted to evaluate the in vivo efficacy of these β-lactams for treatment of MRSP infections.

Influence of hospital size on antimicrobial resistance and advantages of restricting antimicrobial use based on cumulative antibiograms in dogs with Staphylococcus pseudintermedius infections in Japan

Background

Antimicrobial resistance in Staphylococcuspseudintermedius (SP) and the prevalence of meticillin‐resistant SP (MRSP) is increasing in dogs worldwide.

Objectives

To evaluate the influence of hospital size on antimicrobial resistance of SP and whether restricted use of antimicrobials based on antibiograms could reduce the identification of antimicrobial resistance in SP from infected dogs.

Methods and materials

In Study 1, a total of 2,294 SP isolates from dogs with pyoderma (n = 1,858, 52 hospitals) or otitis externa (OE; n = 436, 44 hospitals) taken between 2017 and 2019 were analysed. Clinics were categorised into small, medium and large based on numbers of practicing veterinary surgeons. In Study 2, a cumulative antibiogram was constructed for 12 antimicrobials from one large veterinary clinic from 2017 to 2018. Referring to this antibiogram, the clinic introduced strict antimicrobial selection criteria to treat dogs with pyoderma and OE, starting in 2018.

Results

MRSP was identified in 981 dogs (42.8%). In large clinics, the isolation rate of MRSP was 51.1% (404 of 791), which was significantly higher (P < 0.01) than in small clinics with less than two veterinary practitioners (34.0%, 154 of 453). In the antibiogram study, the susceptibility rates of oxacillin (MPIPC, 61.5%), cefpodoxime (CPDX, 55.8%) and minocycline (MINO, 55.8%) were significantly higher in 2019 (n = 52) than in 2017 to 2018 (n = 54; MPIPC, 37.0%; CPDX, 33.3%; MINO, 20.4%; P < 0.05).

Conclusions and clinical relevance

Hospital size could affect the isolation rate of MRSP in dogs. Restricted use of antimicrobials for over a year based on cumulative antibiograms could reduce the resistance rate of multiple antimicrobials in SP isolated from dogs with pyoderma and OE.

Background – Antimicrobial resistance in Staphylococcuspseudintermedius (SP) and the prevalence of meticillin‐resistant SP (MRSP) is increasing in dogs worldwide. Objectives: To evaluate the influence of hospital size on antimicrobial resistance of SP and whether restricted use of antimicrobials based on antibiograms could reduce the identification of antimicrobial resistance in SP from infected dogs. Conclusions and clinical relevance – Hospital size could affect the isolation rate of MRSP in dogs. Restricted use of antimicrobials for over a year based on cumulative antibiograms could reduce the resistance rate of multiple antimicrobials in SP isolated from dogs with pyoderma and OE.

Antimicrobial Activity of Some Essential Oils against Methicillin-Susceptible and Methicillin-Resistant Staphylococcus pseudintermedius-Associated Pyoderma in Dogs

Simple Summary

Pyoderma is one of the most common diseases in dogs, and Staphylococcus pseudintermedius, a Gram-positive coagulase-positive bacterium, represents the most common infectious agent causing canine pyoderma. Since multidrug-resistant S. pseudintermedius strains have become a relevant threat in veterinary medicine, this study aimed to test the antimicrobial properties of some essential oils (EOs) against S. pseudintermedius strains isolated from dogs suffering from pyoderma. The obtained findings demonstrated a clear in vitro efficacy of some tested EOs against clinical methicillin-resistant and methicillin-sensible S. pseudintermedius strains. The applicability and efficacy of EOs in cases of canine pyoderma supported by S. pseudintermedius could be beneficial for both dogs and pet owners, who are inevitably exposed to this zoonotic bacterium.

Abstract

This study aimed to test in vitro the antimicrobial activity of 11 essential oils (EOs) against four methicillin-resistant Staphylococcus pseudintermedius (MRSP) and four methicillin-susceptible S. pseudintermedius (MSSP) clinical isolates. The obtained findings demonstrated a clear in vitro efficacy of some tested EOs against both MRSP and MSSP strains. Particularly, modal minimum inhibitory concentration (MIC) values ranging from 1:2048 v/v for Melissa officinalis against an MSSP strain to 1:256 v/v for Cymbopogoncitratus against all MRSP strains were observed. The best results, highlighting a modal MIC value of 1:1024 v/v for all tested isolates, was provided by Cinnamomum zeylanicum. Intriguingly, Cinnamomum zeylanicum showed, in many cases, a correspondence between minimum bactericidal concentration (MBC) and MIC values, indicating that the inhibiting dose is also often bactericidal. Moreover, a mild antibacterial and bactericidal activity against both MRSP and MSSP isolates was detected for the other tested EOs. Considering the zoonotic potential of S. pseudintermedius and the increased dissemination of multidrug-resistant strains, the employment of EOs could be useful for the treatment of canine pyoderma. Since antibiotic resistance has become the most urgent issue, from the perspective of the One Health initiative, alternative therapeutic approaches are desirable to limit the use of antibiotics or to improve the efficacy of conventional therapies.

Population genomics of Staphylococcus pseudintermedius in companion animals in the United States

Staphylococcus pseudintermedius is a commensal bacterium and a major opportunistic pathogen of dogs. The emergence of methicillin-resistant S. pseudintermedius (MRSP) is also becoming a serious concern. We carried out a population genomics study of 130 clinical S. pseudintermedius isolates from dogs and cats in the New England region of the United States. Results revealed the co-circulation of phylogenetically diverse lineages that have access to a large pool of accessory genes. Many MRSP and multidrug-resistant clones have emerged through multiple independent, horizontal acquisition of resistance determinants and frequent genetic exchange that disseminate DNA to the broader population. When compared to a Texas population, we found evidence of clonal expansion of MRSP lineages that have disseminated over large distances. These findings provide unprecedented insight into the diversification of a common cutaneous colonizer of man's oldest companion animal and the widespread circulation of multiple high-risk resistant clones.

Identification and molecular epidemiology of methicillin resistant Staphylococcus pseudintermedius strains isolated from canine clinical samples in Argentina

BACKGROUND

Staphylococcus pseudintermedius is the leading cause of pyoderma in dogs and the frequent use of antimicrobial treatment is associated to the development of resistance to nearly all classes of antibiotics. Despite S. pseudintermedius significance, our understanding of the molecular mechanism of β-lactam resistance and its genetic diversity remains limited. We aimed to: i) determine the phenotypic resistance profile of methicillin resistant Staphylococcus pseudintermedius (MRSP) isolated from infected dogs in three different veterinary hospitals in Buenos Aires, Argentina; ii) identify the SCCmec elements and resistance genes; and iii) analyze the clonal relationship between isolates and in regard of dominant lineages found in the world.

RESULTS

In addition to the differential levels of β-lactam resistance, MRSP isolates (n = 10) showed resistance to 5-6 families of antibiotics, and were therefore categorized as multidrug-resistant. All the isolates were variant of SCCmec V homologous to S. aureus; additional SCCmecFinder analysis classified five of the genomes as SCCmec type V (5C2&5) with mecA (encodes for PBP2a), mecRI and mecI and all the genes closely related to the reference SCCmec type V S. aureus TSGH17 strain. In the remaining five strains, mecA was present, although other genes associated with SCCmec V including mecR1 and mecI were missing. PBP2a was inducible in low level resistance strains (MRSP 8151), and constitutively expressed in MRSP 8150, suggesting different mecA regulatory mechanisms. MRSP isolates showed significant genetic diversity: eight PFGE clonal types and six multilocus-sequence typing (MLST) sequence types (STs) (339, 649, 919, 920, 921 and 922), including four new STs genetically distinct from STs reported in other geographic areas. Comparative genomics and phylogenetic analyses of the MRSP showed a correlation between the genetic content and the phenotypes, and established the genetic relationship between the isolates.

CONCLUSIONS

MRSP could be a threat to animal health due to it concerning level of antimicrobial resistance. Our study highlights genetic and epidemiological aspects of multidrug-resistant MRSP strains from Argentina showing high degree of correlation between the resistance genes and the phenotype of the isolates and, furthermore, they appeared evolutionary closer to major worldwide reported ST68 and ST71.

Development of a sprayable hydrogel formulation for the skin application of therapeutic antibodies

A formulation of an antibody with antibacterial properties for topical use on Staphylococcal skin infections was developed and characterized. The best formulation was obtained with 1.5% (w/v) sodium carboxymethylcellulose containing 10 mg/ml immunoglobulin. Spraying forces and rheological behavior were measured in order to characterize the hydrogel formulation. The percentage of antibody aggregates in gel as well as the antibody release, folding and target binding properties of the released antibody were analyzed to proof an acceptable shelf life and no significant changes in the activity of the antibody over time. No microbial contamination was observed in the chosen non-airless application container. Functional testing of the topical skin formulation was performed with an ex vivo biopsy culture model of dog skin. Histological analysis indicated efficacy in protection from Staphylococcus mediated skin damage and antibody delivery restricted to the epidermal surface. The results demonstrate that this hydrogel is suitable for cutaneous antibody applications in the medical field.

Diagnostic accuracy of phenotypic assays for determining antimicrobial resistance status in Staphylococcus pseudintermedius isolates from canine clinical cases

This study evaluated the diagnostic test accuracy of disc diffusion relative to broth-microdilution for clinical Staphylococcus pseudintermedius isolated from dogs in Australia (n = 614). Accuracy of disc diffusion and broth-microdilution for oxacillin relative to mecA real-time PCR was also assessed. Each isolate had paired minimum inhibitory concentration and zone diameter values for ten antimicrobial agents. Data was dichotomised using Clinical and Laboratory Standards Institute susceptible and resistant clinical breakpoints. Test accuracy was reported using relative diagnostic sensitivity (RSe), specificity (RSp), likelihood ratio pairs, diagnostic odds ratio, and area-under-the receiver-operating characteristic (ROC AUC) analysis. Disc diffusion was found to have high test accuracy for most antimicrobials (ROC AUC range: 0.96 - 0.99) except rifampicin (ROC AUC = 0.80). The RSp of disc diffusion was high for all antimicrobials (range, 97.1%-100%). However, RSe was considerably variable (range, 35.7%-98.8%), particularly for amoxicillin-clavulanic acid (51.5%, 95% CI, 38.9%, 64.0%), cefoxitin (35.7%, 95% CI, 12.8%, 64.9%), and cephalothin (43.6%, 95% CI, 27.8%, 60.4%). When disc diffusion and broth-microdilution were compared to mecA real-time PCR, the overall accuracy of both assays was similar (ROC AUC, 0.99 respectively). However, the RSe for broth-microdilution (96.1%, 95% CI, 88.9%, 99.2%) was significantly higher than for disc diffusion (86.8%, 95% CI, 77.1%, 93.5%) (McNemars mid-p value 0.01). Overall, these findings demonstrate that for most antimicrobials, disc diffusion performed according to CLSI guidelines can be used to differentiate clinical S. pseudintermedius isolates that might otherwise be assessed by broth-microdilution, provided consideration is given to the performance estimates reported here.

Residual antibacterial activity of canine hair treated with five mousse products against Staphylococcus pseudintermedius in vitro

BACKGROUND

Topical therapy alone can be effective in the treatment of canine pyoderma. Topical products are commercially available as shampoos, sprays, wipes and mousses. To date, no studies have evaluated the efficacy of commercially available mousse products in the treatment of canine pyoderma.

OBJECTIVE

To determine the residual antibacterial activity of canine hairs treated with mousse products containing different active ingredients.

ANIMALS

Fifteen client-owned dogs with no history of dermatological disease.

METHODS AND MATERIALS

Dogs were treated once with five mousse products [(i) 2% chlorhexidine and 1% ketoconazole, (ii) 2% chlorhexidine and 2% miconazole, (iii) 3% chlorhexidine and 0.5% climbazole, (iv) 2% salicylic acid 10% ethyl lactate and (v) phytosphingosine HCl 0.05%; control]. Hair samples were collected from each treatment area before application, one hour after application and on days 2, 4, 7, 10 and 14 post-treatment. Collected hairs were weighed and plated on Mueller-Hinton agar plates streaked with a Staphylococcus pseudintermedius isolate showing no antimicrobial resistance. Plates were incubated for 24 h and bacterial growth inhibition zones around the hairs were measured.

RESULTS

Mousses 1, 2 and 3 created significant inhibition zones up to Day 10 when compared to pre-treatment samples. On Day 14, only mousse 3 produced a significant zone of inhibition when compared to the pre-treatment sample. Mousses 4 and 5 showed no statistical difference between any of the samples.

CONCLUSIONS AND CLINICAL IMPORTANCE

These results suggest that three of the mousse products had residual activity in inhibiting S. pseudintermedius growth in vitro for at least 10 days.

Characterization of Staphylococcal Cassette Chromosome mec Elements from Methicillin-Resistant Staphylococcus pseudintermedius Infections in Australian Animals

Staphylococcus pseudintermedius is a significant veterinary pathogen and occasional cause of infections in humans. β-Lactams are an important group of antimicrobials used to treat staphylococcal infections in humans and animals. However, when staphylococci become methicillin resistant via the acquisition of a mobile genetic element called staphylococcal cassette chromosome mec (SCCmec), they become resistant to all β-lactams. This study detected a novel SCCmec element among a cluster of methicillin-resistant S. pseudintermedius isolates from animals in Australia. It also detected SCCmec elements in S. pseudintermedius that had high similarity to those identified in methicillin-resistant Staphylococcus aureus, demonstrating how human and animal pathogens can share the same resistance determinants.

We examined the oxacillin resistance phenotype and genomic structure of staphylococcal cassette chromosome mec (SCCmec) elements from 77 veterinary methicillin-resistant Staphylococcus pseudintermedius (MRSP) isolates. Isolates were characterized by oxacillin broth microdilution, whole-genome sequencing, and bioformatics analysis. Five previously described SCCmec elements, and a sixth novel element, were identified: SCCmec III (also known as II-III), ΨSCCmec₅₇₃₉₅, and SCCmec_NA45 (a SCCmec VII variant), all previously described in MRSP, and SCCmec IVg and SCCmec V_T, previously described in both methicillin-resistant Staphylococcus aureus (MRSA) and MRSP. The sixth element was novel and found among nine geographically clustered isolates. This novel pseudostaphylococcal cassette chromosome (ΨSCCmec_KW21) contained a class A mec gene complex but lacked ccr genes. It also harbored heavy metal (cadmium) resistance determinants. The median oxacillin MIC values among ΨSCCmec_KW21, SCCmec III, and SCCmec V_T isolates were significantly higher than those determined for the SCCmec_NA45 VII variant isolates and ΨSCCmec₅₇₃₉₅ and SCCmec IVg isolates. ΨSCCmec_KW21 was found exclusively in sequence type 497 (ST497), an MRSP clone that is locally successful in Victoria, Australia. Future studies are necessary to determine if this clone has disseminated further afield and if ΨSCCmec_KW21 has moved into other MRSP lineages or staphylococcal species.

IMPORTANCEStaphylococcus pseudintermedius is a significant veterinary pathogen and occasional cause of infections in humans. β-Lactams are an important group of antimicrobials used to treat staphylococcal infections in humans and animals. However, when staphylococci become methicillin resistant via the acquisition of a mobile genetic element called staphylococcal cassette chromosome mec (SCCmec), they become resistant to all β-lactams. This study detected a novel SCCmec element among a cluster of methicillin-resistant S. pseudintermedius isolates from animals in Australia. It also detected SCCmec elements in S. pseudintermedius that had high similarity to those identified in methicillin-resistant Staphylococcus aureus, demonstrating how human and animal pathogens can share the same resistance determinants.

Draft Genome Sequences of 12 Clinical and Environmental Methicillin-Resistant Staphylococcus pseudintermedius Strains Isolated from a Veterinary Teaching Hospital in Washington State

Methicillin-resistant Staphylococcus pseudintermedius (MRSP) is a globally emergent multidrug-resistant pathogen of dogs associated with nosocomial transmission in dogs and with potential zoonotic impacts. Here, we report the draft whole-genome sequences of 12 hospital-associated MRSP strains and their resistance genotypes and phenotypes.