Genetic resistance determinants to fusidic acid and chlorhexidine in variably susceptible staphylococci from dogs.

BACKGROUND: Concern exists that frequent use of topically-applied fusidic acid (FA) and chlorhexidine (CHX) for canine pyoderma is driving clinically relevant resistance, despite rare description of FA and CHX genetic resistance determinants in canine-derived staphylococci. This study aimed to determine minimum inhibitory concentrations (MICs) and investigate presence of putative resistance determinants for FA and CHX in canine-derived methicillin-resistant (MR) and -susceptible (MS) staphylococci. Plasmid-mediated resistance genes (fusB, fusC, fusD, qacA/B, smr; PCR) and MICs (agar dilution) of FA and CHX were investigated in 578 staphylococci (50 MR S. aureus [SA], 50 MSSA, 259 MR S. pseudintermedius [SP], 219 MSSP) from Finland, U.S.A., North (NUK) and South-East U.K. (SEUK) and Germany. In all isolates with FA MIC ≥64 mg/L (n = 27) fusA and fusE were amplified and sequenced. RESULTS: FA resistance determinants (fusA mutations n = 24, fusB n = 2, fusC n = 36) were found in isolates from all countries bar U.S.A. and correlated with higher MICs (≥1 mg/L), although 4 SP isolates had MICs of 0.06 mg/L despite carrying fusC. CHX MICs did not correlate with qacA/B (n = 2) and smr (n = 5), which were found in SEUK SA, and SP from NUK and U.S.A. CONCLUSIONS: Increased FA MICs were frequently associated with fusA mutations and fusC, and this is the first account of fusB in SP. Despite novel description of qacA/B in SP, gene presence did not correlate with CHX MIC. Selection pressure from clinical use might increase prevalence of these genetic determinants, but clinical significance remains uncertain in relation to high skin concentrations achieved by topical therapy.

What has changed in canine pyoderma? A narrative review.

Canine pyoderma is a common presentation in small animal practice and frequently leads to prescription of systemic antimicrobial agents. A good foundation of knowledge on pyoderma was established during the 1970s and 1980s, when treatment of infection provided relatively few challenges. However, the ability to treat canine pyoderma effectively is now limited substantially by the emergence of multidrug-resistant, methicillin-resistant staphylococci (MRS) and, in some countries, by restrictions on antimicrobial prescribing for pets. The threat from rising antimicrobial resistance and the zoonotic potential of MRS add a new dimension of public health implications to the management of canine pyoderma and necessitate a revisit and the search for new best management strategies. This narrative review focusses on the impact of MRS on how canine pyoderma is managed and how traditional treatment recommendations need to be updated in the interest of good antimicrobial stewardship. Background information on clinical characteristics, pathogens, and appropriate clinical and microbiological diagnostic techniques, are reviewed in so far as they can support early identification of multidrug-resistant pathogens. The potential of new approaches for the control and treatment of bacterial skin infections is examined and the role of owner education and hygiene is highlighted. Dogs with pyoderma offer opportunities for good antimicrobial stewardship by making use of the unique accessibility of the skin through cytology, bacterial culture and topical therapy. In order to achieve long term success and to limit the spread of multidrug resistance, there is a need to focus on identification and correction of underlying diseases that trigger pyoderma in order to avoid repeated treatment.

Low temperature and dust favour in vitro survival of Mycoplasma hyopneumoniae: time to revisit indirect transmission in pig housing.

Porcine enzootic pneumonia (EP) caused by Mycoplasma hyopneumoniae adversely affects pig welfare and is associated with major economic losses in the pig industry worldwide. Transmission is predominantly by direct contact, but the role of indirect transmission remains poorly understood. This study examined survival of six M. hyopneumoniae isolates dried onto five different surfaces encountered in pig units and exposed to temperatures of 4, 25 and 37°C for up to 12 days. Survival of the organisms was determined by recovering the organism from the surface material and culturing in Friis broth. Data were analysed by logistic regression to identify factors influencing survival of M. hyopneumoniae. Maximum survival was 8 days for all isolates on at least one surface (except stainless steel) at 4°C and was limited to 2 days at 25 and 37°C. Overall, dust and polypropylene copolymer supported M. hyopneumoniae survival the longest when compared with other surface materials. In conclusion, we have demonstrated that M. hyopneumoniae can survive outside the host for at least 8 days. SIGNIFICANCE AND IMPACT OF THE STUDY: Understanding the transmission of Mycoplasma hyopneumoniae and optimizing biosecurity practices are keys to reducing the use of antimicrobial agents to control this pathogen. Direct transmission of the pathogen between pigs is the main route of spread and its lack of cell wall may compromise its resilience outside the host. The results from our study show that M. hyopneumoniae can survive for up to several days on dry surfaces and therefore may have the potential to infect pigs by indirect transmission. Factors influencing the survival of M. hyopneumoniae outside the host are further elucidated.

Susceptibility in vitro of canine methicillin-resistant and -susceptible staphylococcal isolates to fusidic acid, chlorhexidine and miconazole: opportunities for topical therapy of canine superficial pyoderma.

OBJECTIVES: Increasing multidrug resistance amongst canine pathogenic staphylococci has renewed interest in topical antibacterial therapy for skin infections in the context of responsible veterinary prescribing. We therefore determined the activity in vitro of three clinically relevant topical agents and synergism between two of them against Staphylococcus pseudintermedius and Staphylococcus aureus. METHODS: The MICs of fusidic acid (n = 199), chlorhexidine (n = 198), miconazole (n = 198) and a 1:1 combination of miconazole/chlorhexidine (n = 198) were determined for canine isolates [50 MRSA and 49 methicillin-resistant S. pseudintermedius (MRSP), 50 MSSA and 50 methicillin-susceptible S. pseudintermedius (MSSP)] collected from the UK and Germany using an agar dilution method (CLSI VET01-A4). Fractional inhibitory concentration (FIC) indices were calculated to assess the interaction of miconazole with chlorhexidine. RESULTS: MICs of each drug/combination were significantly (P < 0.0005) higher for S. aureus when compared with S. pseudintermedius. Most strains (n = 172) had an MIC of fusidic acid of ≤0.03 mg/L (MIC ≥64 mg/L, n = 5 MRSA). All strains had MICs of chlorhexidine of 0.5-4 mg/L, except for one MRSA (MIC = 8 mg/L). All but four strains had MICs of miconazole of 1-4 mg/L (MIC = 16 mg/L, n = 3; MIC = 256 mg/L, n = 1). Miconazole/chlorhexidine (1:1 ratio) had a synergistic effect against 49/50 MRSA, 31/50 MSSA, 12/49 MRSP and 23/49 MSSP. CONCLUSIONS: Since the majority of these staphylococci, including methicillin-resistant isolates, had MICs that should be readily exceeded by topical skin application of these agents, their therapeutic efficacy for canine superficial pyoderma should be assessed. The synergistic interaction shown in vitro supports further clinical evaluation of miconazole/chlorhexidine combination therapy for staphylococcal infection.

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 pseudintermedius (MRSP). Reports from two diagnostic laboratories (13,313 general submissions, 1242 referral centre only submissions) were analysed retrospectively (2003/2006-2012). MRSP were defined by phenotypic resistance to meticillin and concurrent broad ß-lactam resistance; a subset was confirmed genetically (SIG-specific nuc and mecA). Trends were analysed by Cochran-Armitage test. Resistance remained below 10 per cent for cefalexin, amoxicillin-clavulanic acid and the fluoroquinolones. Increasing resistance trends were seen in both laboratories for ampicillin/amoxicillin (both P<0.001), cefovecin (both P<0.046) and enrofloxacin (both P<0.02). Resistance to cefalexin increased over time in referral hospital isolates (P<0.001) to clindamycin (P=0.01) and trimethoprim-sulfamethoxazole (P=0.001) amongst general laboratory submissions. Overall, 106 MRSP were isolated (0.7 per cent of submissions) including 32 (2.6 per cent of submissions, all genetically confirmed) from the referral centre population (inter-laboratory difference P<0.001). Against a background of widely susceptible SIG isolates, a new trend of increasing resistance to important antimicrobials was identified overtime and the emergence of MRSP from UK clinical cases was confirmed. Attention to responsible use of antibacterial therapy in small animal practice is urgently needed.

The birthrate drop in Iran.

The recent steep decline in Iran's birthrate poses methodological and interpretive challenges insofar as statistical information on demographic factors cannot satisfactorily establish causalities or delineate processes of change. Our research suggests that this decline rests on the interplay of socio-cultural "idea" variables that augment factors of the developmental paradigm commonly used in population studies. Especially modernist ideas labeled "progress" in Iran have influenced reproductive behavior. Aiming to demonstrate the usefulness of idea-oriented qualitative research for understanding demographic dynamics represented quantitatively in the literature, we contribute to an explanation of a particular case as well as to demographic research methods.

Development of a skin colonization model in gnotobiotic piglets for the study of the microbial ecology of meticillin-resistant Staphylococcus aureus ST398.

AIMS: Meticillin-resistant Staphylococcus aureus (MRSA) ST398 continues to spread amongst pigs and other domestic animals and man. This highlights the need for models to examine MRSA colonization and investigate control strategies. This study aimed to develop a gnotobiotic pig model and assess the potential of bacterial interference from selected coagulase-negative staphylococci (CNS) against MRSA ST398. METHODS AND RESULTS: Groups of 2-week-old piglets were atraumatically inoculated either with MRSA and/or CNS. Skin and mucosae were swabbed, and bacterial counts compared over a period of 21 days. Piglets developed healthily, and bacterial populations increased similarly for both MRSA and CNS until day 32. On day 37, MRSA counts in groups with CNS reduced significantly compared with MRSA alone (P = 0·03). CONCLUSIONS: The results showed that inoculation of piglet skin with MRSA resulted in spontaneous colonization and that MRSA ST398 has a low pathogenic potential in gnotobiotic piglets. Quantitative bacteriology indicated that initial MRSA colonization was unaffected by concurrent CNS colonization but that interference may occur over a longer period. SIGNIFICANCE AND IMPACT OF THE STUDY: Gnotobiotic piglets provide a reproducible model suitable for bacterial interference studies, which should be further explored as an alternative to antimicrobials in the control of MRSA.

What's happened to Staphylococcus intermedius? Taxonomic revision and emergence of multi-drug resistance.

Staphylococcus intermedius has been the predominant coagulase-positive Staphylococcus isolated from canine skin and mucosae and the most commonly reported staphylococcal pathogen in small animal practice for the last 35 years. Although microbiological tests have historically indicated variability in biochemical characteristics amongst S. intermedius isolates from animals, an acceptable level of diagnostic accuracy for clinical purposes was readily achievable with routine phenotypic testing. However, three recent developments have changed our understanding of the term "S. intermedius" and have challenged veterinary bacteriologists to ensure correct species identification of pathogenic staphylococci from small animals. First, the increasing recognition of meticillin-resistant Staphylococcus aureus in small animal practice and its human health implications demand accurate species identification. Secondly, the application of molecular techniques to analysis of staphylococcal isolates has led to a revised taxonomy and canine isolates of S. intermedius being re-named S. pseudintermedius. Thirdly, the recent, rapid emergence of meticillin- and multi-drug-resistant strains of Staphylococcus pseudintermedius (MRSP) has become a major therapeutic challenge in veterinary practice worldwide, including the UK. This article discusses the background of the recent taxonomic changes within the genus Staphylococcus and reviews the key features of MRSP and its implications for day-to-day laboratory diagnosis and small animal practice.

Comparison of a chlorhexidine and a benzoyl peroxide shampoo as sole treatment in canine superficial pyoderma.

The clinical and antibacterial efficacy of two shampoos used as a sole antibacterial treatment in dogs with superficial pyoderma were investigated and compared. In a randomised, partially blinded study, a 3 per cent chlorhexidine gluconate shampoo (Chlorhex 3; Leo Animal Health) was compared against a 2.5 per cent benzoyl peroxide shampoo (Paxcutol; Virbac) in 22 dogs with superficial pyoderma. Dogs were washed two to three times weekly with a 10-minute contact time over 21 days. Clinical scores and bacterial counts were assessed on days 1, 8 and 22 and compared within and between treatment groups; overall response was assessed at the end of the study. Twenty dogs completed the study; 15 (68.2 per cent) showed an overall clinical improvement and the clinical signs resolved in three chlorhexidine-treated dogs. In the chlorhexidine-treated group, scores for papules/pustules (P<0.001), investigator-assessed pruritus (P=0.003), total bacterial counts (P=0.003) and counts for coagulase-positive staphylococci (P=0.003) were reduced after three weeks. Scores and bacterial counts did not vary significantly in the benzoyl peroxide-treated group.

Prevalence of and risk factors for MRSA carriage in companion animals: a survey of dogs, cats and horses.

We investigated the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) carriage in a convenience sample of purposely selected populations of dogs, cats and horses in the Greater London area. Swabs from carriage sites were pooled, enriched and processed by standard bacteriological methods. The presence of nuc and mecA was confirmed for MRSA. Risk factors were investigated among veterinary treatment group animals using exact logistic regression analysis. Twenty-six (1.53%) MRSA carriers were identified in the 1692 animals (15/704 dogs, 8/540 cats, 3/152 horses). Animals presenting for veterinary treatment more frequently carried MRSA than healthy animals (OR 7.27, 95% CI 2.18-24.31, P<0.001). Concurrent carriage of non-MRSA coagulase-positive staphylococci was associated with MRSA carriage (OR 0.088, 95% CI 0.016-0.31, P<0.001); none of the other 13 putative risk factors was significant. MRSA carriage was rare in the selected companion animal populations. The absence of typical risk factors indicates that companion animals act as contaminated vectors rather than as true reservoirs.

Companion animals: a reservoir for methicillin-resistant Staphylococcus aureus in the community?

This article reviews the literature on the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in dogs, cats and horses. Over the past 10 years, MRSA has emerged as an important pathogen in veterinary medicine, especially in countries with a high MRSA burden in human hospitals. During the same period, community-associated MRSA (CA-MRSA) infections in humans without apparent links to healthcare facilities have increased dramatically. Although animal infections occur outside human hospitals, significant epidemiological, clinical and genetic differences exist between CA-MRSA in humans and the majority of MRSA infections in the different animal species. The recognition of MRSA in animals has raised concern over their role as potential reservoirs or vectors for human MRSA infection in the community. However, available data on MRSA transmission between humans and companion animals are limited and the public health impact of such transmission needs to be the subject of more detailed epidemiological studies.

Meticillin-resistant Staphylococcus aureus carriage in UK veterinary staff and owners of infected pets: new risk groups.

Meticillin-resistant Staphylococcus aureus (MRSA) nasal carriage on admission to hospital remains one of the most important risk factors for subsequent infection. Identification of high risk groups for MRSA carriage is vital for the success of infection control programmes. Veterinary staff may be one such risk group but little is known about pet owners and the role of contact with infected pets. As part of a UK-wide case-control study investigating risk factors for MRSA infection in dogs and cats between 2005 and 2008, 608 veterinary staff and pet owners in contact with 106 MRSA and 91 meticillin-susceptible S. aureus (MSSA)-infected pets were screened for S. aureus nasal carriage. Laboratory isolation and characterisation included salt broth enrichment, standard and automated microbiological tests, demonstration of the S. aureus-specific thermonuclease gene (nuc) and of mecA, and polymerase chain reaction-based lineage characterisation. MRSA carriage was 12.3% in veterinarians attending MRSA-infected animals and 7.5% in their owners. In the MSSA control group, MRSA carriage was 4.8% in veterinary staff and 0% in owners. Veterinary staff carried MRSA more frequently than owners (odds ratio: 2.33; 95% confidence interval: 1.10-4.93). All MRSA from humans and all but one animal MRSA were CC22 or CC30, typical for hospital MRSA in the UK. This study indicates for the first time an occupational risk for MRSA carriage in small animal general practitioners. Veterinary staff and owners of MRSA-infected pets are high risk groups for MRSA carriage despite not having direct hospital links. Strategies to break the cycle of MRSA infection must take these potential new reservoirs into account.

Lack of transmission of methicillin-resistant Staphylococcus aureus (MRSA) between apparently healthy dogs in a rescue kennel.

Although it is widely accepted that methicillin-resistant Staphylococcus aureus (MRSA) can be transmitted between humans and animals in both directions, little is known about the dynamics of animal-to-animal transfer. This study aimed to investigate aspects of dog-to-dog MRSA transfer in a rescue facility in the South-East of England during an MRSA outbreak. One hundred and twenty-nine apparently healthy dogs, mostly housed in pairs, were swabbed at nasal, oral, axillary and perianal sites. Swabs were enriched in selective broth and staphylococci identified using standard biological methods. MRSA isolates were confirmed by demonstration of the thermonuclease gene (nuc) and mecA. After initial swabbing, a dog excluded from the study design but housed at the same facility was discovered to have a wound infection due to MRSA. MRSA carriage was identified in 10/129 dogs (7.8%) and all isolates were of the same lineage as the one isolated from the infected dog. All carrier dogs lived in shared kennels and their 16 kennel partners sampled negative on two occasions. Concurrently with successful antimicrobial treatment of the infected patient, MRSA carriage resolved spontaneously in all dogs within two weeks. In conclusion, MRSA did not transmit readily between apparently healthy dogs, MRSA carriage was not supported for long periods in a regularly cleaned environment and exposure alone may not lead to MRSA acquisition by dogs without the presence of additional risk factors.

In vitro activity of fusidic acid and mupirocin against coagulase-positive staphylococci from pets.

OBJECTIVES: Methicillin-resistant Staphylococcus aureus (MRSA) and multiresistant Staphylococcus pseudintermedius (MRSP) have emerged as important pathogens in animal infections. Associated therapeutic problems and the zoonotic potential of staphylococci have renewed interest in topical antibiotics for treatment and carrier decolonization. Fusidic acid and mupirocin are used topically in humans and animals but resistant strains isolated from people are increasing. This study investigates the in vitro activity of fusidic acid and mupirocin against coagulase-positive staphylococci from pets. METHODS: A collection of 287 staphylococci was examined, comprising 102 MRSA, 102 methicillin-susceptible S. aureus, 71 S. pseudintermedius and 12 MRSP from canine and feline infections and carrier sites isolated in the UK and Germany. MICs were determined by the agar dilution method according to CLSI (formerly NCCLS) standards. RESULTS: The majority (89.7%) of all MICs were

Dietary trials with a commercial chicken hydrolysate diet in 63 pruritic dogs.

The owners of 63 pruritic dogs were instructed to feed them a chicken hydrolysate diet exclusively for six weeks as part of diagnostic investigations into non-seasonal pruritus. Ectoparasitism and microbial infections were eliminated during the dietary trial. The dogs' skin lesions, gastrointestinal signs and frequency of defecation were assessed and scores for pruritus were assigned before they started the diet and before and after they resumed their original diet. An adverse food reaction was diagnosed if the pruritus resolved while they were on the diet, but recurred when they resumed their original food regimen. Seventeen of the 63 dogs were withdrawn from the trial, including four which found the diet unpalatable; however, its palatability was reported to be good or excellent in 48 of the dogs. An adverse food reaction alone was diagnosed in nine (19.6 per cent) of the 46 dogs and another nine had an adverse food reaction and atopy. There were gastrointestinal signs in six of the nine dogs with an adverse food reaction, which resolved on the trial diet but recurred when they resumed their original diet.