Meticillin-resistant Staphylococcus Pseudintermedius Research Articles

In vitro efficacy of 0.2% and 0.4% sodium oxychlorosene against meticillin-resistant Staphylococcus pseudintermedius.

There is a need for alternative topical therapies as a consequence of the increased prevalence of meticillin-resistant Staphylococcus pseudintermedius (MRSP) skin infections in dogs. Sodium oxychlorosene has been used as a topical antibacterial agent in human medicine since 1955. To determine whether 0.2% and 0.4% sodium oxychlorosene solutions have a bactericidal effect (>3-log reduction) on MRSP strains isolated from canine skin infections. A genetically heterogeneous collection of MRSP isolates from dogs was assembled from laboratories across the United States. Time-kill assays were performed with 0.2% and 0.4% sodium oxychlorosene on a 0.5 McFarland standard [approximately 108 colony-forming units (cfu/ml)] suspension of each strain. The average bacterial counts (cfu/ml) of each MRSP strain then were determined at 5, 10, 20 and 60 s after exposure to sodium oxychlorosene; cfu/ml data were converted to log10 scale to calculate microbial reduction. The average bacterial counts following exposure to the 0.2% solution at 5, 10, 20 and 60 s were 6.94 × 104 , 5.63 × 103 , 2.96 × 102 and 1.48 × 102 cfu/ml, respectively. For the 0.4% solution, the average bacterial count at 5s was 2.12 × 103 cfu/ml. No bacterial growth was observed for any MRSP strain by 10s. The greatest reduction in cfu/ml occurred within 5s following exposure to each solution 3.4-log and 4.9-log reduction for 0.2% and 0.4%, respectively. 0.2% and 0.4% sodium oxychlorosene solutions have a bactericidal effect (>99.9% reduction) against MRSP in vitro. Further in vivo studies are necessary to determine whether it is an appropriate alternative therapy for canine pyoderma.

The nose is not enough: Multi-site sampling is best for MRSP detection in dogs and households.

Following recovery from meticillin-resistant Staphylococcus pseudintermedius (MRSP) infection of any type, dogs may continue to carry MRSP asymptomatically on skin and mucosae, contributing to the spread of this multidrug-resistant, veterinary hospital-associated pathogen with zoonotic potential to others and into the environment. This study determined which canine anatomic and household environmental sites are most sensitive for sampling to identify carriage and contamination. Fifty-one dogs and 22 households, MRSP-positive on at least one tested site, were sampled on 132 and 40 occasions over time, respectively. Dogs were swabbed at six sites (mouth, nose, conjunctiva, skin, prepuce/vulva, perianal area); household environments were sampled using contact plates (mannitol salt agar [MSA] and MSA +6mg/L oxacillin [MS+]) on five sites. MRSP was isolated after enrichment, grown on MSA/MS+ and was confirmed by PCR. Generalized estimating equations were used for calculation of sensitivity (95% confidence interval) for each site/combination. Each anatomical and environmental site yielded MRSP at least once. MRSP was isolated from only a single site in 27.3% of dogs, with the buccal mucosa showing the highest sensitivity (63.8%). Multi-site sampling of a minimum of four canine anatomical or four environmental sites, respectively, was needed to achieve >95% sensitivity. The canine buccal mucosa should be included in MRSP sampling protocols, ideally in addition to at least three other anatomical sites. Likewise, environment sampling should be of multiple household sites in cases where it is used as a part of clinical case management.

Effect of topical antimicrobial therapy and household cleaning on meticillin-resistant Staphylococcus pseudintermedius carriage in dogs.

Meticillin-resistant Staphylococcus pseudintermedius (MRSP) is a multidrug-resistant canine pathogen with a low zoonotic potential. This study investigated MRSP carriage and clearance through topical antimicrobial therapy and household cleaning in dogs recovered from MRSP infection. Dogs were swabbed for MRSP carriage; household contamination was assessed using contact plates. Carrier dogs were allocated randomly to receive topical fusidic acid and chlorhexidine/miconazole treatment combined with owners implementing a household hygiene protocol (H&T) or implementation of hygiene alone (H) over three weeks. Carriage-negative dogs were monitored monthly. The relatedness of isolates over time was investigated by pulsed-field gel electrophoresis (PFGE). At inclusion, MRSP carriage was confirmed in 31/46 (67.4%) index dogs and 16/24 (66.7%) contact dogs, and contamination was found in 18/40 (45%) environments. In dogs completing all cycles, interventions cleared carriage in 5/9 (55.6%) dogs in group H&T and 2/6 (33.3%) in group H. Environmental contamination was infrequent but associated with carrier dogs (p=0.047). Monthly monitoring of initially negative dogs showed intermittent carriage in 9/14 dogs. PFGE-concordance was found among all 34 MRSP isolated from eight index dogs over time. MRSP carriage was common in dogs after recovery from infection. Topical antimicrobial therapy temporarily eliminated carriage but recurrence was frequent. Management efforts must include the prevention of recurrent infections and hygiene.

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.

BackgroundAntimicrobial resistance in Staphylococcus pseudintermedius (SP) and the prevalence of meticillin‐resistant SP (MRSP) is increasing in dogs worldwide.ObjectivesTo 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 materialsIn 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.ResultsMRSP 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 relevanceHospital 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.

Efficacy of three disinfectant formulations and a hydrogen peroxide/silver fogging system on surfaces experimentally inoculated with meticillin-resistant Staphylococcus pseudintermedius.

Effective environmental disinfection is necessary to prevent nosocomial infections from meticillin-resistant Staphylococcus pseudintermedius (MRSP). However, there are currently no commercial disinfectant sprays or fogging systems with label claims against MRSP. To evaluate the efficacy of a quaternary ammonium product (QAC), an accelerated hydrogen peroxide product (AHP), a hydrogen peroxide and silver product (HAL), and a hydrogen peroxide and silver fogging system (FOG) against MRSP. Sterile plastic surfaces inoculated with MRSP were treated with 200µL of QAC, AHP or HAL for the recommended contact times. For FOG, inoculated samples were placed in eight positions within a sealed room before fogging for the recommended contact time. Post-treatment bacterial counts were compared to untreated positive controls. Sterile uninoculated surfaces served as negative controls. Least-squares mean reduction (log10 ) in colony forming units (cfu) was 3.55 log10 for QAC (P<0.0001), 3.60 log10 for AHP (P<0.0001), 1.66 log10 for HAL (P<0.0001) and 0.32 log10 for FOG (P=0.004). QAC, AHP and HAL reduced MRSP cfu by 99.97%, 99.98% and 97.81%, respectively. FOG reduced cfu by 52.14%. QAC and AHP effectively disinfected surfaces inoculated with MRSP. Although HAL provided lower MRSP reduction, it may be considered clinically acceptable. FOG as a sole means of MRSP disinfection was not supported yet may have utility as an adjunctive disinfectant in clinical areas with bacterial densities lower than our experimental inoculum.

Low prevalence of mupirocin resistance in Staphylococcus pseudintermedius isolates from canine pyoderma in Korea.

Mupirocin is a topical antibacterial drug used for the treatment of staphylococcal infections, including meticillin-resistant Staphylococcus pseudintermedius (MRSP). The recent emergence of resistance to mupirocin is a major concern in many countries. This study investigated the prevalence and genotype of mupirocin-resistant S.pseudintermedius isolated from pet dogs with pyoderma. A total of 110 clinical isolates of S.pseudintermedius were collected from dogs with pyoderma (n=110) between July 2010 and September 2016. All animals were client-owned dogs. Low- and high-level mupirocin resistance were evaluated with both the broth microdilution and disk diffusion tests. Mupirocin resistance in S.pseudintermedius isolates was confirmed by genetic analysis of the ileS-2 and naïve ileS genes. MRSP and meticillin-susceptible S.pseudintermedius were detected in 69 and 41 dogs, respectively. One MRSP strain was highly resistant to mupirocin and contained the high-level mupirocin resistance gene ileS-2. There were no low-level mupirocin-resistant isolates. Mupirocin is a useful topical antibacterial for MRSP, but a clinical MRSP isolate that had not previously been exposed to mupirocin exhibited the high-level mupirocin resistance in phenotype and genotype. Therefore, continuous monitoring for mupirocin resistance is important in small animal practice.

The in vitro antibacterial activity of incomplete iron salt of polyacrylic acid against Pseudomonas aeruginosa, meticillin-resistant Staphylococcus pseudintermedius and meticillin-resistant S. aureus.

The incomplete iron salt of polyacrylic acid (IIS-PAA) has been used for its haemostatic, wound healing and antibacterial properties in human patients. IIS-PAA is a water-soluble, acidic, hydrophilic polymer that is active at pH 2.9-4.0. To evaluate the antibacterial effect of IIS-PAA against Pseudomonas aeruginosa, meticillin-resistant Staphylococcus pseudintermedius (MRSP) and meticillin-resistant S. aureus (MRSA). This was a prospective, nonblinded in vitro study. Sixty canine isolates of P. aeruginosa, MRSP and MRSA were included. Minimum inhibitory concentrations (MICs) of IIS-PAA were determined by agar dilution on Mueller-Hinton agar using testing concentrations ranging from 0.0625-0.4% (raw material 100%) and based on Clinical and Laboratory Standards Institute guidelines. The median MIC for P. aeruginosa was 0.2% (range 0.2-0.3%), mean 0.2% and standard deviation (SD) of 0.018%. The median MIC for MRSP was 0.05% (0.025-0.1%), mean 0.058% and SD 0.022%, and the median MIC for MRSA was 0.1% (0.00625-0.4%), mean 0.126% and SD 0.080%. There were significant differences in MICs between the three bacteria types with MICs highest for Pseudomonas and lowest for MRSP (all P < 0.0001). IIS-PAA had in vitro antibacterial activity against three important bacterial pathogens. Further studies of IIS-PAA are indicated to assess the potential clinical benefit and in vitro studies to investigate the spectrum of anti-bacterial activity and mode of action.

In vitro bactericidal activity of blue light (465 nm) phototherapy on meticillin-susceptible and meticillin-resistant Staphylococcus pseudintermedius.

Staphylococcus pseudintermedius is the most common cause of bacterial skin infections in dogs. Meticillin-resistant infections have become more common and are challenging to treat. Blue light phototherapy may be an option for treating these infections. The objective of this study was to measure the in vitro bactericidal activity of 465 nm blue light on meticillin-susceptible Staphylococcus pseudintermedius (MSSP) and meticillin-resistant Staphylococcus pseudintermedius (MRSP). We hypothesized that irradiation with blue light would kill MSSP and MRSP in a dose-dependent fashion in vitro as previously reported for meticillin-resistant Staphylococcus aureus (MRSA). In six replicate experiments, each strain [MSSP, n = 1; MRSP ST-71 (KM1381) n = 1; and MRSA (BAA-1680) n = 1] were cultivated on semisolid media, irradiated using a 465 nm blue light phototherapeutic device at the cumulative doses of 56.25, 112.5 and 225 J/cm2 and incubated overnight at 35°C. Controls were not irradiated. Colony counts (CC) were performed manually. Descriptive statistics were performed and treatment effects assessed using the Wilcoxon-Mann-Whitney rank-sum test. Bonferroni-corrected rank-sum tests were performed for post hoc analysis when significant differences were identified. There was a significant decrease in CC with blue light irradiation at all doses for MRSA (P = 0.0006) but not for MSSP (P = 0.131) or MRSP (P = 0.589). Blue light phototherapy significantly reduced CC of MRSA, but not of MSSP or MRSP. The mechanism for the relative photosensitivity of the MRSA isolate is unknown, but is hypothesized to be due to an increased concentration of porphyrin in S. aureus relative to S. pseudintermedius, which would modulate blue light absorption.

Prior antibacterial drug exposure in dogs with meticillin-resistant Staphylococcus pseudintermedius (MRSP) pyoderma.

The emergence of meticillin-resistant Staphylococcus pseudintermedius (MRSP) has become a significant animal health problem. Recent studies have indicated that previous antibacterial drug exposure is a factor in acquisition of meticillin-resistant strains of staphylococci. The purpose of this study was to identify factors associated with prior antimicrobial drug use and MRSP pyoderma in dogs presented to a veterinary teaching hospital. Dogs diagnosed with pyoderma associated with MRSP (n = 53) or meticillin-sensitive S. pseudintermedius (MSSP; n = 45). The medical records of dogs diagnosed with pyoderma associated with isolation of S. pseudintermedius between January 2006 and November 2012 were reviewed. All cases with a complete twelve month to 3 yr drug history prior to the diagnosis were included. Fifty two of 53 (98%) MRSP cases and 42 of 45 (93%) MSSP cases had received at least one course of antibacterial drug prior to diagnosis. The total number of antibacterial drug prescriptions provided to pet owners and the variety of antibacterial drug classes represented were higher for cases with MRSP than for cases with MSSP (P < 0.0001 and P = 0.009, respectively). More cases with MRSP (98%) received beta-lactam drugs than those with MSSP (82%; P = 0.007) and the proportion of MRSP cases that had received concurrent immunomodulatory therapy was higher (62% versus 42%; P = 0.048). These results suggest that the total number of antibacterial drug prescriptions, exposure to multiple drug classes (beta-lactams in particular) and concurrent immunomodulatory therapy may be associated with increased risk for acquisition of MRSP.

Increasing antimicrobial resistance in clinical isolates of Staphylococcus intermedius group bacteria and emergence of MRSP in the UK

Frequencies of antimicrobial resistance were determined amongst 14,555 clinical Staphylococcus intermedius group (SIG) isolates from UK dogs and cats to estimate resistance trends and quantify the occurrence of meticillin-resistant Staphylococcus...

Characterization of meticillin-resistant and meticillin-susceptible isolates of Staphylococcus pseudintermedius from cases of canine pyoderma in Australia

Meticillin-resistant Staphylococcus pseudintermedius (MRSP) has recently emerged as a worldwide cause of canine pyoderma. In this study, we characterized 22 S. pseudintermedius isolates cultured from 19 dogs with pyoderma that attended a veterinary dermatology referral clinic in Australia in 2011 and 2012. Twelve isolates were identified as MRSP by mecA real-time PCR and phenotypic resistance to oxacillin. In addition to β-lactam resistance, MRSP isolates were resistant to erythromycin (91.6 %), gentamicin (83.3 %), ciprofloxacin (83.3 %), chloramphenicol (75 %), clindamycin (66 %), oxytetracycline (66 %) and tetracycline (50 %), as shown by disc-diffusion susceptibility testing. Meticillin-susceptible S. pseudintermedius isolates only showed resistance to penicillin/ampicillin (90 %) and tetracycline (10 %). PFGE using the SmaI restriction enzyme was unable to type nine of the 12 MRSP isolates. However the nine isolates provided the same PFGE pulsotype using the Cfr91 restriction enzyme. Application of the mec-associated direct repeat unit (dru) typing method identified the nine SmaI PFGE-untypable isolates as dt11cb, a dru type that has only previously been associated with MRSP sequence type (ST)45 isolates that possess a unique SCCmec element. The dt11cb isolates shared a similar multidrug-resistant antibiogram phenotype profile, whereas the other MRSP isolates, dt11a, dt11af (dt11a-associated) and dt10h, were resistant to fewer antibiotic classes and had distinct PFGE profiles. This is the first report of MRSP causing pyoderma in dogs from Australia. The rapid intercontinental emergence and spread of multidrug-resistant MRSP strains confirms the urgent need for new treatment modalities for recurrent canine pyoderma in veterinary practice.

An in vitro study to determine the minimal bactericidal concentration of sodium hypochlorite (bleach) required to inhibit meticillin‐resistant Staphylococcus pseudintermedius strains isolated from canine skin

Meticillin-resistant Staphylococcus pseudintermedius (MRSP) is becoming a more common pathogen in animals treated in veterinary hospitals, raising concerns for transmission and possible contamination of the hospital itself. The identification of effective agents for the decontamination of veterinary patients and hospitals is crucial. Sodium hypochlorite (6.15%) or 'bleach' is an inexpensive and frequently used decontamination agent in human and veterinary hospitals and an adjunctive treatment for human patients. There are no published data on the minimal bactericidal concentration (MBC) of sodium hypochlorite (6.15%) for MRSP. The objective of this study was to determine the MBC of sodium hypochlorite (6.15%) against MRSP strains isolated from canine skin. In this in vitro study, 12 canine skin isolates were obtained from the Antech Diagnostics microbiology department. Twofold serial dilutions of sodium hypochlorite (6.15%) were allowed to react with each of the MRSP strains for 15 min, followed by overnight incubation on agar plates. Colonies on each plate were counted. This process was repeated in triplicate. The overall MBC for the canine skin-isolated MRSP strains was 1:32, but most strains had an MBC between 1:64 and 1:128 dilution. This study shows that sodium hypochlorite (6.15%) is an effective agent for decontamination at easily achievable concentrations.

Meticillin‐resistantStaphylococcus pseudintermedius: clinical challenge and treatment options

Meticillin-resistant Staphylococcus pseudintermedius (MRSP) has emerged as a major therapeutic challenge for small animal veterinarians over the past 10 years and continues to spread worryingly in many countries. This review focuses on the clinical aspects of MRSP infections seen in patients with skin disease and on currently available treatment options. In addition, it discusses the implications for in-contact people, other animals and the environment, because infection control strategies are likely to have a significant impact on treatment success and prevention of spread. There is currently no indication that MRSP is more virulent than meticillin-susceptible S. pseudintermedius, and reported infections have mostly been treated successfully, although possibly with a longer time to resolution than infections with more susceptible S. pseudintermedius. However, in vitro testing of MRSP isolates indicates resistance to most or all antibacterial agents licensed for use in pets. Based on susceptibility results, the most useful systemic antimicrobials may include chloramphenicol, rifampicin, amikacin, clindamycin and/or minocycline. Adverse effects of some of these medications may limit their usefulness. While in vitro susceptibility to vancomycin and linezolid is reported by some laboratories, use of these drugs in animals is strongly discouraged because of ethical considerations. Aggressive topical therapy has been effective as the only treatment in certain cases. Awareness, continued research and comprehensive management of infections are required by veterinary practitioners not only to help treat infected animals but also to limit the spread and prevent the establishment of this highly drug-resistant and zoonotic pathogen in veterinary facilities and in the community.

In vitro antimicrobial activity of miconazole and polymyxin B against canine meticillin‐resistant Staphylococcus aureus and meticillin‐resistant Staphylococcus pseudintermedius isolates

Meticillin-resistant Staphylococcus aureus (MRSA) and meticillin-resistant Staphylococcus pseudintermedius (MRSP) infections are increasingly reported in dogs, and these bacteria may be isolated from ear infections. The main aim of the present study was to investigate the in vitro antimicrobial activity of miconazole, polymyxin B and a combination of both against 24 canine MRSA and 50 canine MRSP isolates. The minimal inhibitory concentration (MIC) values of 12 other antimicrobial agents were also determined. All MIC values were determined according to a broth microdilution assay. Acquired resistance was found to all tested agents, except for linezolid, miconazole and polymyxin B. The MIC values for miconazole and polymyxin B against MRSA were in the range of 4-8 and 8-64 μg/mL, respectively, while the MIC values for miconazole and polymyxin B against MRSP were in the range of 1-2 and 0.25-4 μg/mL, respectively. Using a combination of miconazole and polymyxin B, there was no evidence for enhanced in vitro activity of the combination (i.e. synergy) of both products. Nevertheless, MIC(90) values of the combination of these antimicrobial agents and of a commercial product containing both agents were at least 1000 times lower than the concentration present in the commercial product. These results indicate that the topical use of a combination of miconazole and polymyxin B in a 43.5:1 ratio may have potential for the treatment of MRSA-mediated and MRSP-associated otitis externa in dogs.

Prevalence of meticillin‐resistant Staphylococcus pseudintermedius (MRSP) from skin and carriage sites of dogs after treatment of their meticillin‐resistant or meticillin‐sensitive staphylococcal pyoderma

Meticillin-resistant staphylococci are significant pathogens in veterinary dermatology, yet longitudinal studies of the impact of routine antimicrobial therapy on emergence or resolution of resistance are lacking. To determine the prevalence of meticillin-resistant staphylococci on skin and carriage sites in dogs with bacterial pyoderma and evaluate the prevalence of meticillin-resistant Staphylococcus pseudintermedius (MRSP) colonization after successful treatment of pyoderma. One hundred and seventy-three dogs that presented to a dermatology referral service with pyoderma and 41 healthy control dogs. Skin, nasal and rectal swabs for bacterial culture were collected at the time of referral and after clinical resolution of the pyoderma. Meticillin resistance was confirmed by demonstration of penicillin binding protein 2a antigen. Initially, skin cultures yielded MRSP in 70 (40.5%) dogs, meticillin-resistant Staphylococcus aureus (MRSA) in three (1.7%) and meticillin-resistant Staphylococcus schleiferi ssp. coagulans (MRSScoag) in five (2.9%). Samples collected from the nose and rectum (carriage sites) yielded MRSP in 59 (34.1%) dogs, MRSA in 11 (6.4%) and MRSScoag in seven (4.0%). One hundred and two dogs were available for follow-up cultures after clinical cure. Of 42 dogs initially diagnosed with MRSP pyoderma, MRSP was isolated at follow-up from skin in 19 (45.2%) and carriage sites in 20 (47.6%). Of 60 dogs that did not have MRSP pyoderma initially, MRSP was isolated post-treatment from the skin in 17 (28.3%), and MRSP from carriage sites increased from 7.8% (initially) to 26.7% (P = 0.0022). Colonization by MRSP often persists after resolution of MRSP pyoderma. Acquisition of MRSP during treatment appears to be common.

Selection of antibiotics for meticillin‐resistantStaphylococcus pseudintermedius: time to revisit some old drugs?

The aim of this review is to consider systemic therapy options for meticillin-resistant Staphylococcus pseudintermedius (MRSP). Infections caused by MRSP in small animals--particularly dogs--have been frustrating veterinarians in recent years. After a susceptibility test is performed, veterinarians are left to select from drugs that have not been frequently encountered on a susceptibility report. Some of these are old drugs that have not been used regularly by veterinary dermatologists. As MRSP is, by definition, resistant to all β-lactam antibiotics, including cephalosporins, penicillins and amoxicillin-clavulanate combinations, the β-lactam drugs are not an option for systemic treatment. As most MRSPs are multidrug resistant, familiar drugs, such as trimethoprim-sulfonamides, fluoroquinolones, macrolides and lincosamides (clindamycin), are also not usually an option for treatment. Therefore, veterinarians are left with drugs such as rifampicin, chloramphenicol, tetracyclines, aminoglycosides and vancomycin to choose from on the basis of an in vitro susceptibility test. Some of these drugs were originally approved over 50 years ago and may not be familiar to some veterinarians. Each of these drugs possesses unique properties and has particular advantages and disadvantages. Veterinarians should be particularly aware of the adverse effects, limitations and precautions when using these drugs. New drugs also have been developed for meticillin-resistant Staphylococcus aureus in humans. These include linezolid, ceftaroline, daptomycin and tigecycline. Although these drugs are very infrequently--if ever--considered for veterinary use, the properties of these drugs should also be known to veterinary dermatologists.