The Staphylococcus intermedius group of bacterial pathogens: species re-classification, pathogenesis and the emergence of meticillin resistance

Pathogenic Potential of Coagulase-Positive Staphylococcus Strains Isolated from Aviary Capercaillies and Free-Living Birds in Southeastern Poland

The aim of the study was to determine the occurrence and characteristics of coagulase-positive Staphylococcus strains in the carcasses of wild birds and aviary capercaillies in Southeastern Poland. In total, samples taken from 333 birds were examined. The material consisted of swabs from the internal organs of dead birds (heart, liver, and spleen), the tarsal joints, and mucous membranes (conjunctiva and palatine fissure), as well as from unhatched embryos. The isolated Staphylococcus strains were tested for sensitivity to nine antimicrobial agents and the presence of selected virulence genes. An analysis of the similarity of isolates within species was performed using pulsed-field gel electrophoresis (PFGE). The result indicates that coagulase-positive strains accounted for 5.7% and belonged to the species: Staphylococcus aureus, Staphylococcus pseudintermedius, and Staphylococcus delphini. Among isolated strains, 15.8% were multidrug resistant. The most frequently detected virulence genes were hla in 58% of isolates and hlb and hld in 47.4% of isolates. The results of multiplex PCR showed the presence of genes responsible for the production of enterotoxins C, B, E, and J, in single isolates. It can be concluded that coagulase-positive Staphylococcus strains accounted for a small percentage of staphylococci isolated from free-living birds in the study area. The occurrence of multidrug-resistant coagulase-positive Staphylococcus strains in aviary capercaillies suggests that they play a role in the transmission and spread of resistant strains into the environment. Free-living birds may also be a reservoir of enterotoxigenic Staphylococcus strains.

An Uncommon Case of Prosthetic Elbow Joint Infection Caused by Staphylococcus intermedius

Staphylococcus intermedius is known to cause a wide variety of infectious processes in animals and is well described in the veterinary literature. However, the incidence of human infections from this organism has increased in recent years, which highlights the zoonotic potential of this pathogen. Here, we present a case of a S. intermedius prosthetic joint infection potentially resulting from exposure to a pet dog.

One Health Approach for Reporting Veterinary Carbapenem-Resistant Enterobacterales and Other Bacteria of Public Health Concern

A carbapenem-resistant Enterobacterales outbreak at a veterinary teaching hospital in the United States increased urgency for improved communication among diagnostic laboratories, public health authorities, veterinarians, and pet owners. Kansas State University, University of Missouri, Kansas Department of Health and Environment, and Veterinary Laboratory Investigation and Response Network created a surveillance, storage, and reporting protocol for veterinary antimicrobial-resistant bacteria; determined frequency of those bacteria in companion animals during 2018-2021; and created educational flyers for veterinarians and pet owners. We recommend a One Health strategy to create efficient surveillance programs to identify and report antimicrobial-resistant bacteria and educate veterinarians and pet owners about transmission risks.

Fluorescent Light Energy in the Management of Multi Drug Resistant Canine Pyoderma: A Prospective Exploratory Study

The increase in prevalence of staphylococcal antimicrobial resistance has been also associated with pyoderma in dogs, and prolonged antibiotic treatment, as often needed in severe cases of pyoderma, has been related to influencing possible development of multidrug resistance (MDR). Fluorescent light energy (FLE) has been indicated to improve pyoderma lesions as adjunct therapy to systemic antibiotics. In the present study, we evaluated the effect of FLE on clinical signs of MDR canine deep pyoderma (CDP) and interdigital furunculosis (CIF) when administered as solely management. Sixteen client-owned dogs affected by CIF (five dogs) and CDP (eleven dogs) were scored using a dedicated scoring system and received a single FLE applications twice weekly, until clinical resolution was achieved. Mean time to achieve complete resolution was 5.20 ± 3.56 weeks (median 3 weeks) for CIF cases and 4.18 ± 1.47 weeks (median 4 weeks) for CDP ones. FLE shows promise as an aid to managing clinical signs while reducing reliance on antibiotics for MDR CDP and CIF. In this study, FLE was responsible for the decrease in lesion scores and resolution of MDR pyoderma infection without any adjunct therapy, having a potential useful role to play in antibiotic stewardship programs, efficiently promoting complete clinical resolution of MDR lesions while optimizing the use of antibiotics.

Colonization of Dogs and Their Owners with Staphylococcus aureus and Staphylococcus pseudintermedius in Households, Veterinary Practices, and Healthcare Facilities

There are uncertainties with respect to the transmission of methicillin-susceptible and methicillin-resistant Staphylococcus aureus (MSSA and MRSA) and Staphylococcus pseudintermedius between dogs and humans. In this study, we investigated concomitant nasal colonization of dogs and humans in three cohorts. Cohort I, households owning dogs: In 42 of 84 households, 66 humans (36.9%) and 10 dogs (8.9%) carried S. aureus. MRSA, attributed to sequence type (ST) 22 and ST130, were detected in two (1.1%) of the humans but in none of the dogs. Typing by means of spa-typing and whole-genome sequencing (WGS) indicated eight transmissions of S. aureus between humans and dogs in 8 of 42 (19.0%) households with human S. aureus carriers, whereas in 11 of 38 (29.0%) households with ≥two persons and S. aureus colonization of humans, 15 human-to-human transmissions were observed (p = 0.43). S. pseudintermedius was isolated from 42 dogs (37.5%), but from only one human (0.6%). In this case, WGS-based typing indicated strong relatedness of this isolate with a canine isolate from the same household. Cohort II, dogs and their owners visiting a veterinary practice: Among 17 humans and 17 dogs attending a veterinary practice, MSSA was detected in three humans and two dogs, and S. pseudintermedius in only six dogs. Cohort III, dogs used for animal-assisted interventions in human healthcare facilities and their owners: MSSA was obtained in 1 of 59 dogs (1.7%) and in 17 of 60 (28.3%) of the dog owners, while S. pseudintermedius was isolated from seven (12%) dogs and one (1.7%) human owner. We conclude that the risk of exchanging S. aureus/MRSA between humans and dogs is higher than that for S. pseudintermedius.

Molecular Mechanisms of Staphylococcus and Pseudomonas Interactions in Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal recessive genetic disorder that is characterized by recurrent and chronic infections of the lung predominantly by the opportunistic pathogens, Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa. While S. aureus is the main colonizing bacteria of the CF lungs during infancy and early childhood, its incidence declines thereafter and infections by P. aeruginosa become more prominent with increasing age. The competitive and cooperative interactions exhibited by these two pathogens influence their survival, antibiotic susceptibility, persistence and, consequently the disease progression. For instance, P. aeruginosa secretes small respiratory inhibitors like hydrogen cyanide, pyocyanin and quinoline N-oxides that block the electron transport pathway and suppress the growth of S. aureus. However, S. aureus survives this respiratory attack by adapting to respiration-defective small colony variant (SCV) phenotype. SCVs cause persistent and recurrent infections and are also resistant to antibiotics, especially aminoglycosides, antifolate antibiotics, and to host antimicrobial peptides such as LL-37, human β-defensin (HBD) 2 and HBD3; and lactoferricin B. The interaction between P. aeruginosa and S. aureus is multifaceted. In mucoid P. aeruginosa strains, siderophores and rhamnolipids are downregulated thus enhancing the survival of S. aureus. Conversely, protein A from S. aureus inhibits P. aeruginosa biofilm formation while protecting both P. aeruginosa and S. aureus from phagocytosis by neutrophils. This review attempts to summarize the current understanding of the molecular mechanisms that drive the competitive and cooperative interactions between S. aureus and P. aeruginosa in the CF lungs that could influence the disease outcome.

Staphylococcus pseudintermedius: Is it a real threat to human health?

Staphylococcus Intermedius Group (SIG) staphylococci, especially Staphylococcus pseudintermedius (S. pseudintermedius), share many features with the common human Staphylococcus aureus. The similarities concern both the phenotypic characteristics and virulence of the bacteria. It is a cause of difficulties in identifying the species of isolated staphylococci. Until now, S. pseudintermedius was considered a typically animal species, of marginal importance for humans. However, it is likely that the incidence of this staphylococcus in humans is underestimated due to the misidentification of S. pseudintermedius strains as S. aureus. The cases of infections caused by S. pseudintermedius both in humans and animals described so far in the literature show that these bacteria have a similar pathogenic potential. S. pseudintermedius also produces virulence factors that favor colonization of various body regions and infections, and may affect the species composition of the natural microbiota and the host’s immune response mechanisms. Also, S. pseudintermedius may show the ability to grow in the form of a biofilm, which significantly impedes effective antibiotic therapy in clinical practice. Due to its zoonotic potential, S. pseudintermedius deserves the attention of physicians and animal owners.

Effectiveness of liposomal ozonized oil in reducing ocular microbial flora in patients undergoing cataract surgery

PURPOSE

To evaluate the antimicrobial effectiveness of a liposomal ozonized oil solution used as a home therapy in patients undergoing cataract surgery. Antimicrobial efficacy was evaluated as the reduction in the bacterial load of the most common bacteria isolated from cases with endophthalmitis.

SETTING

20 Italian experimental centers of the Effectiveness of Liposomal Ozonized oil on Ocular Microbial flora before cataract surgery study group.

DESIGN

Interventional, nonrandomized, paired-eye designed, phase 4 clinical study.

METHODS

A total of 174 patients undergoing cataract surgery were divided into 2 groups: the study group (174 eyes) underwent surgery and received an isotonic ophthalmic solution of 0.5% ozonized oil in liposomes plus hypromellose treatment (2 drops 4 times/d), and the control group (174 contralateral eyes) was treated with saline solution. The treatment lasted for 3 days. Subconjunctival swabs were taken from both eyes of each patient at T0 (the day before starting the treatment and 4 days preoperatively) and at T4 (after 3 days of treatment and 10 min preoperatively) and sent to the laboratory within 24 hours of collection for microbiological analysis.

RESULTS

30% of 696 swabs taken at T0 were sterile. Contaminated swabs had a high prevalence of coagulase-negative staphylococci, including Staphylococcus epidermidis, and more than 60 different bacterial species were isolated. A significant reduction in microbial load was observed after treatment (>90% of the samples). The microbial load in the control group remained unchanged.

CONCLUSIONS

Liposomal ozonized oil reduced the microbial burden after topical administration in a large study population.

Identification of Staphylococcus pseudintermedius Isolates from Wound Cultures by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry Improves Accuracy of Susceptibility Reporting at an Increase in Cost

Staphylococcus pseudintermedius can easily be mistaken for Staphylococcus aureus using phenotypic and rapid biochemical methods. We began confirming the identification of all coagulase-positive staphylococci isolated from human wound cultures at our centralized laboratory, servicing both community and inpatients, with matrix-assisted laser desorption ionization-time of flight mass spectrometry instead of using phenotypic and rapid biochemical tests, and determined the prevalence of S. pseudintermedius since the change in identification procedure and at what cost. A retrospective review was performed on all wound swab cultures from which coagulase-positive staphylococci were isolated 7 months before and after the change in identification procedure. A total of 49 S. intermedius/pseudintermedius (SIP) isolates were identified, including 7 isolates from 14,401 wound cultures in the before period and 42 isolates from 14,147 wound cultures in the after period. The number of SIP isolates as a proportion of isolated coagulase-positive staphylococci increased significantly from the before, 7/6,351 (0.1%), to the after, 42/5,435 (0.7%), period (difference, 0.6% [95% confidence interval, 0.037 to 0.83%, P < 0.0001]). Antibiotic susceptibility testing was performed in 42 isolates; none had an oxacillin MIC of 1.0 to 2.0 μg/ml, the range in which, if the isolate was misidentified as S. aureus, a very major error in susceptibility interpretation would occur. The increase in cost of the change in identification procedure was Can$17,558 per year in our laboratory, performing microbiology testing for community and acute-care patients in a zone servicing nearly 1.7 million people. While we will only continue to learn more about this emerging pathogen if we make attempts to properly identify it in clinical cultures, the additional time and cost involved may be unacceptably high in some laboratories.  .

Outbreak of a novel disease caused by Staphylococcus pseudintermedius in raccoon dogs (Nyctereutes procyonoides)

This study reports outbreak of a new disease caused by Staphylococcus pseudintermedius (S. pseudintermedius) in raccoon dogs. The disease occurred in a breeding farm of raccoon dogs in Guan County of Shandong Province in China in August of 2019. 47% (425/896) of the raccoon dogs showed some abnormal symptoms; 17.6% (75/425) of which had severe skin and soft tissue infections (SSTIs), dyspnoea and severe pathological lesions in lungs, livers, etc; and 4.2% (18/425) of which died within 4 weeks. The pathogen of the disease was identified as S. pseudintermedius by mass spectrometer detection, animal pathogenicity tests, microscopic examination and biochemical reaction tests. Its nucleotide homology of 16S rRNA gene was 100% with that of other published strains, and its genotype was between the American and Brazilian strains from other animals. The isolated S. pseudintermedius strain from the diseased raccoon dogs could cause ulceration and suppuration in the skins and severe pathological lesions not only in raccoon dogs, but also in mice; and it is confirmed as a methicillin-resistant S. pseudintermedius (MRSP) strain by the amplification of mecA gene; and 12 sensitive drugs were screened by drug sensitivity tests. Full attention should be paid to the great economic loss and the potential zoonotic risk caused by the S. pseudintermedius in raccoon dogs, and this study can provide a reference for the clinical diagnosis and treatment of this new disease.

Genomic and in vitro pharmacodynamic analysis of rifampicin resistance in multidrug-resistant canine Staphylococcus pseudintermedius isolates

BACKGROUND

Antimicrobial resistance is a growing concern in canine Staphylococcus pseudintermedius dermatitis. Treatment with rifampicin (RFP) is considered only in meticillin-resistant and multidrug-resistant S. pseudintermedius (MDR-MRSP).

HYPOTHESIS/OBJECTIVES

To determine an optimal RFP dosing for MDR-MRSP treatment without induction of RFP resistance and identify causal mutations for antimicrobial resistance.

METHODS AND MATERIALS

Time-kill assays were performed in a control isolate and three MDR-MRSP isolates at six clinically relevant concentrations [32 to 1,024 × MIC (the minimum inhibitory concentration)]. Whole-genome resequencing and bioinformatic analysis were performed in the resistant strains developed in this assay.

RESULTS

The genomic analysis identified nine antimicrobial resistance genes (ARGs) in MDR-MRSP isolates, which are responsible for resistance to seven classes of antibiotics. RFP activity against all four isolates was consistent with a time-dependent and bacteriostatic response. RFP resistance was observed in six of the 28 time-kill assays, including concentrations 64 × MIC in MDR-MRSP1 isolates at 24 h, 32 × MIC in MDR-MRSP2 at 48 h, 32 × MIC in MDR-MRSP3 at 48 h and 256 × MIC in MDR-MRSP3 at 24 h. Genome-wide mutation analyses in these RFP-resistant strains discovered the causal mutations in the coding region of the rpoB gene.

CONCLUSIONS AND CLINICAL RELEVANCE

A study has shown that 6 mg/kg per os results in plasma concentrations of 600-1,000 × MIC of S. pseudintermedius. Based on our data, this dose should achieve the minimum MIC (×512) to prevent RFP resistance development; therefore, we recommend a minimum daily dose of 6 mg/kg for MDR-MRSP pyoderma treatment when limited antibiotic options are available.

Diversity and Risk Factors Associated with Multidrug and Methicillin-Resistant Staphylococci Isolated from Cats Admitted to a Veterinary Clinic in Eastern Province, Saudi Arabia

Understanding the distribution, antimicrobial resistance (AMR), and risk factors associated with multidrug-resistant (MDR) and methicillin-resistant staphylococci (MRS) isolated from cats admitted to veterinary clinics may decrease the risk of MDR and MRS transmission to humans and other cats. As such, the objectives of this study were to investigate the diversity in Staphylococcus spp. recovered from different anatomical locations in healthy and diseased cats and to determine the occurrence of MDR and MRS spp. as well as possible risk factors associated with colonization in these cats. Five swabs were collected from the anus, skin, ear canal, conjunctival sac, and nares of each cat (209 healthy and 191 diseased) admitted to a veterinary clinic in Eastern Province, Saudi Arabia, between January and December 2018. Prior to sample collection, cat owners completed a questionnaire collecting information on cat demographics, health status, management, and antimicrobial usage. In total, 179 Staphylococcus isolates were recovered from healthy (n = 71) and diseased (n = 108) cats, including 94 (52.5%) coagulase-positive staphylococci (CoPS), and 85 (47.5%) coagulase-negative staphylococci (CoNS). Five Staphylococcus spp. were identified, namely, Staphylococcus aureus, Staphylococcus pseudintermedius, Staphylococcus felis, Staphylococcus capitis, and Staphylococcus saprophyticus. Staphylococcus isolates were most commonly resistant to penicillin (56.4%) and ciprofloxacin (25.7%); however, no isolate was resistant to clindamycin. Thirty (16.8%) Staphylococcus spp. (24 S. aureus and 6 S. pseudintermedius) isolates were MDR, with resistance to up to six different antibiotic classes. Only 17 (9.5%) Staphylococcus spp. (15 methicillin-resistant S. aureus and 2 methicillin-resistant S. pseudintermedius) harbored the mecA gene. Risk factor analysis showed that cats with a history of antibiotic therapy, those raised mainly indoors with a child, and those who visit a veterinary clinic for treatment were at higher risk of MDR and MRS colonization. In conclusion, MDR and MRS were common in healthy and diseased cats in Saudi Arabia. Thus, an effective antimicrobial stewardship program and further studies using a One Health approach are required to investigate the role of cats as vectors for AMR transmission to humans.

Methicillin-resistant Staphylococcus pseudintermedius synthesizes deoxyadenosine to cause persistent infection

Methicillin-resistant Staphylococcus pseudintermedius (MRSP) is an emerging zoonotic pathogen of canine origin that causes an array of fatal diseases, including bacteremia and endocarditis. Despite large-scale genome sequencing projects have gained substantial insights into the genomic landscape of MRSP, current knowledge on virulence determinants that contribute to S. pseudintermedius pathogenesis during human or canine infection is very limited. Using a panel of genetically engineered MRSP variants and a mouse abscess model, we here identified the major secreted nuclease of S. pseudintermedius designated NucB and adenosine synthase A (AdsA) as two synergistically acting enzymes required for MRSP pathogenesis. Similar to Staphylococcus aureus, S. pseudintermedius requires nuclease secretion along with the activity of AdsA to degrade mammalian DNA for subsequent biosynthesis of cytotoxic deoxyadenosine. In this manner, S. pseudintermedius selectively kills macrophages during abscess formation thereby antagonizing crucial host immune cell responses. Ultimately, bioinformatics analyses revealed that NucB and AdsA are widespread in the global S. pseudintermedius population. Together, these data suggest that S. pseudintermedius deploys the canonical Nuc/AdsA pathway to persist during invasive disease and may aid in the development of new therapeutic strategies to combat infections caused by MRSP.

Virulence factors in coagulase-positive staphylococci of veterinary interest other than Staphylococcus aureus

Coagulase-positive Staphylococci (CoPS) can exist as commensals in humans, companion and food-producing animals, but can cause severe or even lethal diseases. Exchange of these bacteria between humans and animals has been described. Special attention has been focused on Methicillin-Resistant Staphylococcus aureus, but other CoPS can also represent an important threat. In addition to significant antimicrobial resistance, these bacteria may carry a plethora of virulence factors - molecules that allow bacteria to establish on or within a host and increase their ability to cause disease. These virulence factors have been widely described in S. aureus but information about other species of CoPS is scarce. The aim of this paper is to review the recent literature about the virulence factors of non-aureus CoPS of animal origin. Their possible effects on human health are also described. The role and prevalence of different virulence factors including leukocidins, hemolysins, adhesins, enterotoxins, exfoliative and toxic shock syndrome toxins as well as superantigen-like proteins are addressed. The effect of these virulence factors on human health is also described. The possibility of misdiagnosis of species of CoPS has been demonstrated in human clinical samples. Prevalence of zoonotic infections could be higher than thought and medical laboratories should be aware of these other staphylococcal species. In keeping with the ‘One Health’ approach to animal and human disease, medical professionals, veterinarians and health workers should be aware of the risks derived from exposure to these bacteria in people in close contact with animals, including pet owners, farmers and veterinarians themselves.

Whole genome sequencing of coagulase positive staphylococci from a dog-and-owner screening survey

BACKGROUND

Staphylococcus aureus and S. pseudintermedius are the two most common coagulase positive staphylococci (CPS). S. aureus is more prevalent among humans, whereas S. pseudintermedius is more commonly isolated from dogs, however, both can cause various community and hospital acquired diseases in humans.

METHODS

In the current study we screened 102 dogs and 84 owners in Hungary. We tested the antibiotic susceptibility of the strains and in order to get a better picture of the clonal relationship of the strains, we used pulsed-field gel electrophoresis. In addition, three pairs of isolates with identical PFGE patterns were whole genome sequenced, MLST and spa types were established.

RESULTS

Carriage rate of S. aureus was 23.8% in humans and 4.9% in dogs and two cases of co-carriage were found among dogs and owners. S. pseudintermedius carriage rate was 2.4% and 34.3%, respectively, with only one co-carriage. The isolates were generally rather susceptible to the tested antibiotics, but high tetracycline resistance of S. pseudintermedius strains was noted. The co-carried isolates shared almost the same resistance genes (including tet(K), bla(Z), norA, mepR, lmrS, fosB) and virulence gene pattern. Apart from the common staphylococcal enzymes and cytotoxins, we found enterotoxins and exfoliative toxins as well. The two S. aureus pairs belonged to ST45-t630, ST45-t671 and ST15-t084, ST15-t084, respectively. The co-carried S. pseudintermedius isolates shared the same housekeeping gene alleles determining a novel sequence type ST1685.

CONCLUSIONS

Based on the genomic data, dog-owner co-carried strains displayed only insignificant differences therefore provided evidence for potential human-to-dog and dog-to-human transmission.

Antimicrobial Prodrug Activation by the Staphylococcal Glyoxalase GloB

With the rising prevalence of multidrug resistance, there is an urgent need to develop novel antibiotics. Many putative antibiotics demonstrate promising in vitro potency but fail in vivo due to poor drug-like qualities (e.g., serum half-life, oral absorption, solubility, and toxicity). These drug-like properties can be modified through the addition of chemical protecting groups, creating "prodrugs" that are activated prior to target inhibition. Lipophilic prodrugging techniques, including the attachment of a pivaloyloxymethyl group, have garnered attention for their ability to increase cellular permeability by masking charged residues and the relative ease of the chemical prodrugging process. Unfortunately, pivaloyloxymethyl prodrugs are rapidly activated by human sera, rendering any membrane permeability qualities absent during clinical treatment. Identification of the bacterial prodrug activation pathway(s) will allow for the development of host-stable and microbe-targeted prodrug therapies. Here, we use two zoonotic staphylococcal species, Staphylococcus schleiferi and S. pseudintermedius, to establish the mechanism of carboxy ester prodrug activation. Using a forward genetic screen, we identify a conserved locus in both species encoding the enzyme hydroxyacylglutathione hydrolase (GloB), whose loss-of-function confers resistance to carboxy ester prodrugs. We enzymatically characterize GloB and demonstrate that it is a functional glyoxalase II enzyme, which has the capacity to activate carboxy ester prodrugs. As GloB homologues are both widespread and diverse in sequence, our findings suggest that GloB may be a useful mechanism for developing species- or genus-level prodrug targeting strategies.

Staphylococcal Protein A (spa) Locus Is a Hot Spot for Recombination and Horizontal Gene Transfer in Staphylococcus pseudintermedius

Staphylococcus pseudintermedius is a major canine pathogen but can also occasionally infect humans. Identification of genetic factors contributing to the virulence and clonal success of multidrug-resistant S. pseudintermedius clones is critical for the development of therapeutics against this pathogen. Here, we characterized the genome sequences of a global collection of 622 S. pseudintermedius isolates. We show that all major clones, besides carrying core virulence genes, which are present in all strains, carry one or more lineage-specific genes. Many of these genes have been acquired from other bacterial species through a horizontal gene transfer mechanism. Importantly, we have discovered that the staphylococcal protein A gene (spa), a widely used marker for molecular typing of S. pseudintermedius strains and a potential vaccine candidate antigen, is deleted in 62% of strains. Furthermore, the spa locus in S. pseudintermedius acts as a reservoir to accumulate lineage-associated genes with adaptive functions.

Staphylococcus pseudintermedius is a major canine pathogen but also occasionally colonizes and infects humans. Multidrug-resistant methicillin-resistant S. pseudintermedius (MDR MRSP) strains have emerged globally, making treatment and control of this pathogen challenging. Sequence type 71 (ST71), ST68, and ST45 are the most widespread and successful MDR MRSP clones. The potential genetic factors underlying the clonal success of these and other predominant clones remain unknown. Characterization of the pangenome, lineage-associated accessory genes, and genes acquired through horizontal gene transfer from other bacteria is important for identifying such factors. Here, we analyzed genome sequence data from 622 S. pseudintermedius isolates to investigate the evolution of pathogenicity across lineages. We show that the predominant clones carry one or more lineage-associated virulence genes. The gene encoding staphylococcal protein A (SpA), a key virulence factor involved in immune evasion and a potential vaccine antigen, is deleted in 62% of isolates. Most importantly, we have discovered that the spa locus is a hot spot for recombination and horizontal gene transfer in S. pseudintermedius, where genes related to restriction modification, prophage immunity, mercury resistance, and nucleotide and carbohydrate metabolism have been acquired in different lineages. Our study also establishes that ST45 is composed of two distinct sublineages that differ in their accessory gene content and virulence potential. Collectively, this study reports several previously undetected lineage-associated genetic factors that may have a role in the clonal success of the major MDR MRSP clones. These data provide a framework for future experimental studies on S. pseudintermedius pathogenesis and for developing novel therapeutics against this pathogen.

IMPORTANCEStaphylococcus pseudintermedius is a major canine pathogen but can also occasionally infect humans. Identification of genetic factors contributing to the virulence and clonal success of multidrug-resistant S. pseudintermedius clones is critical for the development of therapeutics against this pathogen. Here, we characterized the genome sequences of a global collection of 622 S. pseudintermedius isolates. We show that all major clones, besides carrying core virulence genes, which are present in all strains, carry one or more lineage-specific genes. Many of these genes have been acquired from other bacterial species through a horizontal gene transfer mechanism. Importantly, we have discovered that the staphylococcal protein A gene (spa), a widely used marker for molecular typing of S. pseudintermedius strains and a potential vaccine candidate antigen, is deleted in 62% of strains. Furthermore, the spa locus in S. pseudintermedius acts as a reservoir to accumulate lineage-associated genes with adaptive functions.

Antibacterial and Antivirulence Activity of Manuka Honey against Genetically Diverse Staphylococcus pseudintermedius Strains

Staphylococcus pseudintermedius is an important member of the skin microbial community in animals and can cause opportunistic infections in both pets and their owners. The high incidence of antimicrobial resistance in S. pseudintermedius highlights that this opportunistic zoonotic pathogen can cause infections which require prolonged and intensive treatment to resolve. Manuka honey has proven efficacy against many bacterial pathogens and is an accepted topical treatment for infections in both veterinary and clinical practice, and so it is a particularly appropriate antimicrobial for use with zoonotic pathogens such as S. pseudintermedius. Here, we demonstrate that not only is manuka honey highly potent against novel multidrug-resistant S. pseudintermedius isolates, it also acts synergistically with clinically relevant antibiotics. In addition, manuka honey modulates S. pseudintermedius virulence activity, even at subinhibitory concentrations. In a clinical setting, these attributes may assist in controlling infection, allowing a more rapid resolution and reducing antibiotic use.

Staphylococcus pseudintermedius causes opportunistic infections in dogs. It also has significant zoonotic potential, with the emergence of multidrug resistance leading to difficulty treating both animal and human infections. Manuka honey has previously been reported to inhibit many bacterial pathogens, including methicillin-resistant Staphylococcus aureus, and is successfully utilized in both clinical and veterinary practice. Here, we evaluated the ability of manuka honey to inhibit strains of S. pseudintermedius grown alone and in combination with antibiotics, as well as its capacity to modulate virulence within multiple S. pseudintermedius isolates. All 18 of the genetically diverse S. pseudintermedius strains sequenced and tested were inhibited by ≤12% (wt/vol) medical-grade manuka honey, although tolerance to five clinically relevant antibiotics was observed. The susceptibility of the isolates to four of these antibiotics was significantly increased (P ≤ 0.05) when combined with sublethal concentrations of honey, although sensitivity to oxacillin was decreased. Virulence factor (DNase, protease, and hemolysin) activity was also significantly reduced (P ≤ 0.05) in over half of isolates when cultured with sublethal concentrations of honey (13, 9, and 10 isolates, respectively). These findings highlight the potential for manuka honey to be utilized against S. pseudintermedius infections.

IMPORTANCEStaphylococcus pseudintermedius is an important member of the skin microbial community in animals and can cause opportunistic infections in both pets and their owners. The high incidence of antimicrobial resistance in S. pseudintermedius highlights that this opportunistic zoonotic pathogen can cause infections which require prolonged and intensive treatment to resolve. Manuka honey has proven efficacy against many bacterial pathogens and is an accepted topical treatment for infections in both veterinary and clinical practice, and so it is a particularly appropriate antimicrobial for use with zoonotic pathogens such as S. pseudintermedius. Here, we demonstrate that not only is manuka honey highly potent against novel multidrug-resistant S. pseudintermedius isolates, it also acts synergistically with clinically relevant antibiotics. In addition, manuka honey modulates S. pseudintermedius virulence activity, even at subinhibitory concentrations. In a clinical setting, these attributes may assist in controlling infection, allowing a more rapid resolution and reducing antibiotic use.

Potent, specific MEPicides for treatment of zoonotic staphylococci

Coagulase-positive staphylococci, which frequently colonize the mucosal surfaces of animals, also cause a spectrum of opportunistic infections including skin and soft tissue infections, urinary tract infections, pneumonia, and bacteremia. However, recent advances in bacterial identification have revealed that these common veterinary pathogens are in fact zoonoses that cause serious infections in human patients. The global spread of multidrug-resistant zoonotic staphylococci, in particular the emergence of methicillin-resistant organisms, is now a serious threat to both animal and human welfare. Accordingly, new therapeutic targets that can be exploited to combat staphylococcal infections are urgently needed. Enzymes of the methylerythritol phosphate pathway (MEP) of isoprenoid biosynthesis represent potential targets for treating zoonotic staphylococci. Here we demonstrate that fosmidomycin (FSM) inhibits the first step of the isoprenoid biosynthetic pathway catalyzed by deoxyxylulose phosphate reductoisomerase (DXR) in staphylococci. In addition, we have both enzymatically and structurally determined the mechanism by which FSM elicits its effect. Using a forward genetic screen, the glycerol-3-phosphate transporter GlpT that facilitates FSM uptake was identified in two zoonotic staphylococci, Staphylococcus schleiferi and Staphylococcus pseudintermedius. A series of lipophilic ester prodrugs (termed MEPicides) structurally related to FSM were synthesized, and data indicate that the presence of the prodrug moiety not only substantially increased potency of the inhibitors against staphylococci but also bypassed the need for GlpT-mediated cellular transport. Collectively, our data indicate that the prodrug MEPicides selectively and robustly inhibit DXR in zoonotic staphylococci, and further, that DXR represents a promising, druggable target for future development.

Staphylococcus pseudintermedius 5'-nucleotidase suppresses canine phagocytic activity

Staphylococcus pseudintermedius is a major opportunistic bacterial pathogen and the leading cause of pyoderma in dogs. In canines it is also often associated with infections of the urinary system and wounds and occasionally infects people. Widespread antimicrobial resistance has made the development of alternative treatments a high priority. The development of a staphylococcal vaccine, however, has proven challenging. Identification of virulence factors that inhibit phagocytosis and avoid innate immunity may play a significant role in preventing or treating infection with S. pseudintermedius. In this study, we identified a putative 5'-nucleotidase provisionally named SpAdsA, a S. pseudintermedius cell- wall protein encoded by SpAdsA. SpAdsA shares approximately 52% identity with the orthologous protein of Staphylococcus aureus and 14.8% identity with that of Streptococcus suis type2. It catalyzes the dephosphorylation of adenosine triphosphate and attenuation of this enzyme with critical amino acid substitutions nearly eliminated its hydrolytic activity. Exogenous adenosine inhibited phagocytosis of S. pseudintermedius by canine neutrophils and monocytes. Conversely, the addition of SpAdsA inhibitor or A_2A adenosine receptor antagonist impaired the capacity of S. pseudintermedius to escape from killing by phagocytic cells. The neutralizing ability of canine antibody produced against SpAdsA-M was determined. Taken together, these results suggest that SpAdsA likely plays an important role in S. pseudintermedius virulence and that attenuated SpAdsA may be a good candidate for inclusion in a vaccine against S. pseudintermedius.

Draft Genome Sequence of Staphylococcus pseudintermedius Strain 13-13613, Isolated from a Case of Canine Pyoderma

Here, we report the draft genome sequence of Staphylococcus pseudintermedius strain 13-13613, isolated from a case of canine pyoderma. The draft genome contains 2,533,486 bp in 570 contigs.

Underrated Staphylococcus species and their role in antimicrobial resistance spreading

The increasing threat of antimicrobial resistance has shed light on the interconnection between humans, animals, the environment, and their roles in the exchange and spreading of resistance genes. In this review, we present evidences that show that Staphylococcus species, usually referred to as harmless or opportunistic pathogens, represent a threat to human and animal health for acting as reservoirs of antimicrobial resistance genes. The capacity of genetic exchange between isolates of different sources and species of the Staphylococcus genus is discussed with emphasis on mobile genetic elements, the contribution of biofilm formation, and evidences obtained either experimentally or through genome analyses. We also discuss the involvement of CRISPR-Cas systems in the limitation of horizontal gene transfer and its suitability as a molecular clock to describe the history of genetic exchange between staphylococci.

Characterization of Staphylococcus intermedius Group Isolates Associated with Animals from Antarctica and Emended Description of Staphylococcus delphini

Members of the genus Staphylococcus are widespread in nature and occupy a variety of niches, however, staphylococcal colonization of animals in the Antarctic environment has not been adequately studied. Here, we describe the first isolation and characterization of two Staphylococcus intermedius group (SIG) members, Staphylococcus delphini and Staphylococcus pseudintermedius, in Antarctic wildlife. Staphylococcus delphini were found exclusively in Adélie penguins. The report of S. pseudintermedius from Weddell seals confirmed its occurrence in all families of the suborder Caniformia. Partial RNA polymerase beta-subunit (rpoB) gene sequencing, repetitive PCR fingerprinting with the (GTG)₅ primer, and matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry gave consistent identification results and proved to be suitable for identifying SIG members. Comparative genomics of S. delphini isolates revealed variable genomic elements, including new prophages, a novel phage-inducible chromosomal island, and numerous putative virulence factors. Surface and extracellular protein distribution were compared between genomes and showed strain-specific profiles. The pathogenic potential of S. delphini was enhanced by a novel type of exfoliative toxin, trypsin-like serine protease cluster, and enterotoxin C. Detailed analysis of phenotypic characteristics performed on six Antarctic isolates of S. delphini and eight reference strains from different animal sources enabled us to emend the species description of S. delphini.

Hybrid Assembly from a Pathogenic Methicillin- and Multidrug-Resistant Staphylococcus pseudintermedius Strain Isolated from a Case of Canine Otitis in Spain

Here we report the genome assembly, using a hybrid approach with Illumina and Nanopore sequencing, of a pathogenic Staphylococcus pseudintermedius strain isolated from a case of canine otitis. Genome assembly confirmed the antimicrobial resistance profile (disk diffusion testing) with specific genes and mutations.

Influence of administration of antimicrobial medications after tibial plateau leveling osteotomy on surgical site infections: A retrospective study of 308 dogs

OBJECTIVE

To determine the influence of prophylactic administration of oral antimicrobial medications after tibial plateau leveling osteotomy (TPLO) on surgical site infections (SSI) and antimicrobial-resistant infections.

STUDY DESIGN

Retrospective study.

SAMPLE POPULATION

Dogs treated with unilateral TPLO (n = 308) between January 2013 and December 2015.

METHODS

Medical records were reviewed for signalment, surgically treated limb, duration of surgery and anesthesia, postoperative administration of antimicrobial medications, antibiotic agent, surgeon, and development of SSI. Statistical analyses included descriptive statistics, simple linear regression, analysis of variance, Fisher's protected least significant difference, and χ² testing.

RESULTS

Data were collected from records of 31 dogs that did not receive antimicrobial medications and 277 dogs that did receive oral antimicrobial medications for 14 days after TPLO. Superficial incisional SSI was detected in two of 31 dogs that did not receive antimicrobial medications and in 48 of 277 dogs that did receive antimicrobial medications (P = .1194). Deep incisional SSI occurred in two of 31 dogs that did not receive antimicrobial medications and in 27 of 277 dogs that did receive antimicrobial medications (P = .5513). Antibiotic-resistant deep incisional SSI occurred in two of 31 dogs that did not receive antimicrobial medications and in 18 of 277 dogs that did receive antimicrobial medications (P = .9920). Body weight correlated with deep incisional SSI and resistant infections. Prolonged duration of surgery and anesthesia were associated with superficial incisional SSI, deep incisional SSI, and antibiotic resistance. Surgeons influenced deep incisional SSI.

CONCLUSION

Previously reported predisposing factors for infection were confirmed, but postoperative administration of antimicrobial medications was not protective against SSI nor did it predispose to antibiotic resistance in our clinical setting.

CLINICAL SIGNIFICANCE

This study does not provide evidence to support administration of prophylactic oral antimicrobial medications after unilateral TPLO.

Preoperative topical liposomal ozone dispersion to reduce bacterial colonization in conjunctival sac and periocular skin: Preliminary study in dogs

Prophylaxis represents a keystone to reduce periocular skin and ocular conjunctiva bacterial load before surgical procedures. Despite many prophylactic agents are available the preferred perioperative ocular surface antimicrobial is still unknown. The purpose of this study was to assess the effectiveness of preoperative liposomal ozone dispersion in reducing bacterial colonization from the conjunctival sac and periocular skin in dogs, in comparison with povidone-iodine and fluoroquinolone. Twenty-two owned dogs consisting with 44 eyes in total scheduled for ophthalmic surgical procedure were enrolled for the study and divided in four groups receiving either ozone dispersion or povidone iodine in eyelid and conjunctiva, fluoroquinolone or placebo. A swab was taken before and after the antisepsis protocol evaluating total microbial count, coagulase positive and negative staphylococci. Statistical analysis revealed a significant decrease in colony forming units (CFU) for total microbial count, coagulase positive and negative staphylococci both for liposomal ozone dispersion and povidone iodine. No statistical differences were detected in median CFU for both one-day placebo and fluoroquinolone preoperative prophylactic topical therapy. The results of this preliminary study demonstrate that liposomal ozone-dispersion is as effective as povidone iodine to reduce preoperative bacterial load in ocular surface.

Identification, cloning and characterization of SpEX exotoxin produced by Staphylococcus pseudintermedius

Staphylococci have evolved numerous strategies to evade their hosts’ immune systems. Some staphylococcal toxins target essential components of host innate immunity, one of the two main branches of the immune system. Analysis of the Staphylococcus pseudintermedius secretome using liquid chromatography mass spectrometry guided by genomic data, was used to identify an S. pseudintermedius exotoxin provisionally named SpEX. This exoprotein has low overall amino acid identity with the Staphylococcus aureus group of proteins named staphylococcal superantigen like proteins (SSLs) and staphylococcal enterotoxin- like toxin X (SEIX), but predictive modeling showed that it shares similar folds and domain architecture to these important virulence factors. In this study, we found SpEX binds to complement component C5, prevents complement mediated lysis of sensitized bovine red blood cells, kills polymorphonuclear leukocytes and monocytes and inhibits neutrophil migration at sub-lethal concentrations. A mutant version of SpEX, produced through amino acid substitution at selected positions, had diminished cytotoxicity. Anti-SpEX produced in dogs reduced the inhibitory effect of native SpEX on canine neutrophil migration and protected immune cells from the toxic effects of the native recombinant protein. These results suggest that SpEX likely plays an important role in S. pseudintermedius virulence and that attenuated SpEX may be an important candidate for inclusion in a vaccine against S. pseudintermedius infections.

Genome Sequences of Six Prophages Isolated from Staphylococcus pseudintermedius Strains Recovered from Human and Animal Clinical Specimens

Staphylococcus pseudintermedius is a common bacterial pathogen in companion animal medicine and has demonstrated zoonotic potential. Here, we report six new Staphylococcus pseudintermedius prophage genomes of the Siphoviridae family, identified in isolates recovered from human and canine clinical specimens.

Staphylococcus pseudintermedius is a common bacterial pathogen in companion animal medicine and has demonstrated zoonotic potential. Here, we report six new Staphylococcus pseudintermedius prophage genomes of the Siphoviridae family, identified in isolates recovered from human and canine clinical specimens.

A new host cell internalisation pathway for SadA-expressing staphylococci triggered by excreted neurochemicals

Staphylococcus aureus is a facultative intracellular pathogen that invades a wide range of professional and nonprofessional phagocytes by triggering internalisation by interaction of surface‐bound adhesins with corresponding host cell receptors. Here, we identified a new concept of host cell internalisation in animal‐pathogenic staphylococcal species. This new mechanism exemplified by Staphylococcus pseudintermedius ED99 is not based on surface‐bound adhesins but is due to excreted small neurochemical compounds, such as trace amines (TAs), dopamine (DOP), and serotonin (SER), that render host cells competent for bacterial internalisation. The neurochemicals are produced by only one enzyme, the staphylococcal aromatic amino acid decarboxylase (SadA). Here, we unravelled the mechanism of how neurochemicals trigger internalisation into the human colon cell line HT‐29. We found that TAs and DOP are agonists of the α2‐adrenergic receptor, which, when activated, induces a cascade of reactions involving a decrease in the cytoplasmic cAMP level and an increase in F‐actin formation. The signalling cascade of SER follows a different pathway. SER interacts with 5HT receptors that trigger F‐actin formation without decreasing the cytoplasmic cAMP level. The neurochemical‐induced internalisation in host cells is independent of the fibronectin‐binding protein pathway and has an additive effect. In a sadA deletion mutant, ED99ΔsadA, internalisation was decreased approximately threefold compared with that of the parent strain, and treating S. aureus USA300 with TAs increased internalisation by approximately threefold.

Molecular characterisation of methicillin-resistant Staphylococcus pseudintermedius from dogs and the description of their SCCmec elements

In recent years an increasing number of methicillin-resistant S. pseudintermedius (MRSP) has been observed in both, healthy and clinically infected dogs. The aim of the study was the characterisation of MRSP isolates from clinical routine diagnostics of a German laboratory in order to assess the abundancy of resistance genes and SCCmec elements. 97 isolates from 96 dogs were analysed using microarrays detecting resistance genes and SCCmec-associated markers. All isolates harboured mecA and blaZ. Other abundant resistance markers (in >80% of isolates) included aacA-aphD, aphA3 and sat as well as erm(B). Tetracycline resistance genes (tet(K), tet(M)) and cat also were common (in >20%). The vast majority (n = 59) of isolates carried SCCmec III elements. SCCmec IV and V elements were identified in 21 and 15 isolates, respectively. Irregular or pseudo-SCCmec elements were found in 2 isolates. The high degree of uniformity of hybridisation patterns of tested strains suggest that the majority of MRSP infections was caused by one single strain and comparison to previously published reports and sequences suggest that this was the ST71-SCCmec III strain that also predominates elsewhere in Western Europe.

Improved Performance of a Rapid Immunochromatographic Assay for Detection of PBP2a in Non-Staphylococcus aureus Staphylococcal Species

Non-Staphylococcus aureus staphylococcal species (non-SASS) are important pathogens in both animal and human populations. The development of β-lactam resistance in non-SASS through acquisition and expression of penicillin-binding protein 2a (PBP2a) represents a significant clinical and public health threat. Here, we evaluated the diagnostic performance of two versions of a PBP2a immunochromatographic assay with non-SASS. Our data show that the revised version of the assay, the PBP2a SA culture colony test, has superior diagnostic sensitivity compared to the previous version of the assay, the PBP2a culture colony test, 100% (95% confidence interval [CI], 93.3 to 100%) versus 67.9% (95% CI, 53.7 to 80.1%), respectively, while both assays display a specificity of 100% (95% CI, 92.5 to 100%). Therefore, the PBP2a SA culture colony test offers a rapid, accurate, and relatively inexpensive method for detecting PBP2a-mediated β-lactam resistance in clinically relevant non-SASS for the management of infections due to these organisms and for antimicrobial stewardship.

First reported human isolation of Staphylococcus delphini

The Staphylococcus intermedius group is a collection of coagulase-positive staphylococci composed of 5 members, including Staphylococcus pseudintermedius, a zoonotic pathogen often associated with exposure to dogs, and Staphylococcus delphini, which has not previously been recovered from humans. Here, we describe the first human case of S. delphini infection.

Synthesis of a leopolic acid-inspired tetramic acid with antimicrobial activity against multidrug-resistant bacteria

The increasing emergence of multidrug-resistant pathogens is one of the biggest threats to human health and food security. The discovery of new antibacterials, and in particular the finding of new scaffolds, is an imperative goal to stay ahead of the evolution of antibiotic resistance. Herein we report the synthesis of a 3-decyltetramic acid analogue of the ureido dipeptide natural antibiotic leopolic acid A. The key step in the synthetic strategy is an intramolecular Lacey–Dieckmann cyclization reaction of a linear precursor to obtain the desired 3-alkyl-substituted tetramic acid core. The synthesized analogue is more effective than the parent leopolic acid A against Gram-positive (Staphylococcus pseudintermedius) and Gram-negative (E. coli) bacteria (MIC 8 µg/mL and 64 µg/mL, respectively). Interestingly, the compound shows a significant activity against Staphylococcus pseudintermedius strains expressing a multidrug-resistant phenotype (average MIC 32 µg/mL on 30 strains tested). These results suggest that this molecule can be considered a promising starting point for the development of a novel class of antibacterial agents active also against resistant strains.

Correct species identification (reclassification in CNCTC) of strains of Staphylococcus intermedius-group can improve an insight into their evolutionary history

A group of 59 putative strains of Staphylococcus intermedius/Staphylococcus pseudintermedius deposited in the Czech National Collection of Type Cultures (CNCTC, National Institute for Public Health, Prague, Czech Republic) and the National Reference Laboratory for Staphylococci (NRL for Staphylococci, National Institute for Public Health, Prague, Czech Republic) was reclassified using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). There the biggest human collection of S. pseudintermedius in Europe was analysed; 44 samples (75%) were of human origin. Twenty-two percent (n = 13) of the strains were isolated from animals, and two staphylococci were of unknown origin. This study revealed the prevalence of Staphylococcus pseudintermedius (94%, n = 53) vs. Staphylococcus intermedius (6%, n = 6) in the collection of human and veterinary staphylococci after reclassification. Results of PCR-RFLP analysis were verified by comparison with a repetitive element sequence-based polymerase chain reaction (Rep-PCR) analysis on 26 (44%) randomly selected strains. Due to a low-resolution ability of PCR-RFLP to separate Staphylococcus intermedius from Staphylococcus delphini, four isolates of Staphylococcus intermedius were biochemically verified further to exclude the presence of Staphylococcus delphini in the collection. Our results indicate that S. intermedius and S. pseudintermedius have occurred independently over an age-long period of their co-evolution.

Diversity of Staphylococcus pseudintermedius in carriage sites and skin lesions of dogs with superficial bacterial folliculitis: potential implications for diagnostic testing and therapy

BACKGROUND

Staphylococcus pseudintermedius is genotypically diverse within the canine population and multiple strains may colonize individual dogs at any given time. If multiple strains with distinct antimicrobial resistance profiles are present in superficial bacterial folliculitis (SBF), sampling a single skin lesion for culture and antimicrobial susceptibility testing (AST) might be inadequate to select effective therapy.

HYPOTHESIS/OBJECTIVES

To investigate S. pseudintermedius diversity in carriage sites and lesions of dogs with SBF.

ANIMALS

Fourteen dogs with SBF.

METHODS

Staphylococcus pseudintermedius isolates obtained from perineum, gingiva and four to six skin lesions per dog were subjected to pulsed-field gel electrophoresis (PFGE) and AST to assess diversity between lesions. For two dogs, 14-16 isolates per lesion were included in the analysis to assess diversity within lesions.

RESULTS

Analysis of one isolate per lesion revealed one to four strains displaying unique PFGE profiles, and up to three unique antimicrobial resistance (AMR) profiles for each dog. Multiple pustules from the same dog always harboured the same strain, whereas papules, crusts and collarettes did not. Up to four strains with distinct AMR profiles were isolated from the same lesion in two dogs. In 12 dogs, at least one carriage site strain also was represented in lesions.

CONCLUSIONS AND CLINICAL IMPORTANCE

Lesions of SBF may harbour multiple S. pseudintermedius strains with distinct antimicrobial resistance profiles. Pustules are the best target for bacterial culture. It remains unclear whether isolation of different strains from other lesion types is a consequence of contamination or co-infection by multiple strains.

Expression and function of protein A in Staphylococcus pseudintermedius

Staphylococcus pseudintermedius is an opportunistic pathogen in dogs and the most frequent cause of canine pyoderma. Protein A, a potent virulence factor in S. aureus is encoded by the spa gene. S. pseudintermedius possesses genes seemingly analogous to spa, but the expression and the characteristics of their products have not been directly determined. The purpose of this study was to test isolates from major clonal groups for the presence of spa gene orthologs, quantitate their expression levels, and to characterize protein A in S. pseudintermedius.  From the data, it was observed that S. pseudintermedius isolates express genes analogous to spa in S. aureus. Isolates representing major clonal populations in the United States and Europe, ST68 and ST71 respectively, bound significantly higher amounts of canine IgG than isolates with other genetic backgrounds, suggesting that these isolates have a higher density of protein A on their surface. Also, canine IgG bound to protein A on S. pseudintermedius via its Fc region similar to protein A from S. aureus. The mRNA profile differed based on the bacterial sequence types and correlated to the density of protein A on the bacterial surface. Protein A was also found to be secreted during the exponential growth phase. Phagocytosis experiments with S. pseudintermedius show that blocking of protein A enhanced phagocytosis in whole blood, neutrophils and in DH82 canine macrophage-like cell line. Taken together, the results demonstrate that S. pseudintermedius produces protein A that shares S. aureus protein A's ability to bind the Fc region of immunoglobulins and may serve as a potential virulence factor by evading the host immune system.

Outcome following removal of TPLO implants with surgical site infection

Objective To evaluate the outcome of surgical site infection (SSI) associated with tibial plateau levelling osteotomy (TPLO) implants following treatment by medical management alone or implant removal with or without the administration of antibiotic medication.

Animals Ninety dogs (104 TPLO surgical procedures).

Methods Records of dogs that had undergone TPLO implant removal due to SSI were reviewed. Outcome following treatment with antibiotic medications without implant removal, and treatment with implant removal with and without the administration of antibiotic medications was evaluated.

Results Treatment of SSI with antibiotic medication alone failed in 88.9% (64/72) of the dogs. The clinical signs of SSI resolved in 94.9% (74/78) of the dogs treated with implant removal (with and without the administration of antibiotic medication postimplant removal). The effect of administration of antibiotic medication on outcome of treatment of the SSI by implant removal was not significant. The rate of SSI associated with the Synthes implant was higher than with the Slocum implant, but not the New Generation implant.

Conclusion Implant removal with or without the administration of antibiotic medication post-implant removal for treatment of TPLO SSI provided superior outcome compared to treatment with antibiotic medications without implant removal.

Clinical significance Implant removal should be considered for TPLO SSI that have not responded to appropriate medical management. Further investigation of the various TPLO implants and their effects on postoperative infection rate is warranted.

Recommendations for approaches to meticillin-resistant staphylococcal infections of small animals: diagnosis, therapeutic considerations and preventative measures.: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology

BACKGROUND

Multiple drug resistance (MDR) in staphylococci, including resistance to the semi-synthetic penicillinase-resistant penicillins such as meticillin, is a problem of global proportions that presents serious challenges to the successful treatment of staphylococcal infections of companion animals.

OBJECTIVES

The objective of this document is to provide harmonized recommendations for the diagnosis, prevention and treatment of meticillin-resistant staphylococcal infections in dogs and cats.

METHODS

The authors served as a Guideline Panel (GP) and reviewed the literature available prior to September 2016. The GP prepared a detailed literature review and made recommendations on selected topics. The World Association of Veterinary Dermatology (WAVD) provided guidance and oversight for this process. A draft of the document was presented at the 8th World Congress of Veterinary Dermatology (May 2016) and was then made available via the World Wide Web to the member organizations of the WAVD for a period of three months. Comments were solicited and posted to the GP electronically. Responses were incorporated by the GP into the final document.

CONCLUSIONS

Adherence to guidelines for the diagnosis, laboratory reporting, judicious therapy (including restriction of use policies for certain antimicrobial drugs), personal hygiene, and environmental cleaning and disinfection may help to mitigate the progressive development and dissemination of MDR staphylococci.

Antimicrobial resistance in Staphylococcus pseudintermedius and the molecular epidemiology of methicillin-resistant S. pseudintermedius in small animals in Finland

Objectives

To investigate antimicrobial susceptibility in Staphylococcus pseudintermedius and the occurrence of methicillin-resistant S. pseudintermedius (MRSP), to explore the molecular structure of the MRSP population and to analyse risk factors for MRSP.

Methods

Susceptibility data for clinical S. pseudintermedius isolates in 2011-15 were analysed using WHONET. All MRSP isolates in 2010-14 ( n  =   362) were typed using PFGE. Representative isolates ( n  =   87) of clusters were analysed using MLST and staphylococcal cassette chromosome mec (SCC mec ) typing. Risk factors were analysed using logistic regression.

Results

Of the clinical S. pseudintermedius ( n  =   1958; 98% from dogs), 14% were MRSP. Resistance to other antimicrobials varied between 12% and 39%. No trends were observed over time. Among clinical specimens (from infection sites) and screening specimens (from potential carriers), respectively, 2.5% (267/10 813) and 9% (211/2434) revealed MRSP. MLST revealed 42 different STs, including 19 new ones. Clonal complexes 71, 45 and 258 were the most common, but the MRSP population diversified over the years. A clinical S. pseudintermedius isolate was more likely to be MRSP if the patient was on antimicrobials at the time of sampling or was male. The presence of MRSP in screening specimens was more likely if the patient was on multiple antimicrobials at the time of sampling. Specimens from private clinics (versus the Veterinary Teaching Hospital of the University of Helsinki) had a higher likelihood of MRSP in both analyses.

Conclusions

Resistance to antimicrobials among S. pseudintermedius in Finland is high, emphasizing the importance of infection control measures and susceptibility testing prior to therapy. The diverse MRSP population indicates non-clonal spread.

Skin infection caused by a novel strain of Staphylococcus pseudintermedius in a Siberian husky dog owner

Introduction.Staphylococcus pseudintermedius, an opportunistic pathogen of dogs and cats, is rarely reported to cause infection in humans. Here, we describe a case of severe skin infection caused by S. pseudintermedius, in a 47-year-old male, a dog owner; to the best of our knowledge, this is the first such case reported from Scotland.

Case presentation. The patient presented with a short history of a severe ecthyma-like lesion on his forehead, with smaller lesions on his abdomen and legs. Bacterial culture revealed Clostridium perfringens, thought to be colonizing the wound, and a Staphylococcus species, identified as S. pseudintermedius by matrix-assisted laser desorption/ionization-time of flight MS and confirmed by molecular methods using a PCR-RFLP approach. The patient was treated with flucloxacillin, penicillin V and Fucibet cream, and recovered fully. Zoonotic infection was considered likely; however, screening swabs from his dogs grew S. pseudintermedius of a different clonal type. Both patient and dog strains carried Staphylococcus intermedius exfoliative toxin and leucocidin I, closely related to Panton–Valentine leucocidin, possibly contributing to the severity of the infection. S pseudintermedius, although coagulase positive, is normally negative by rapid slide clumping and latex agglutination tests routinely used to identify Staphylococcus aureus. Hence, S. pseudintermedius may easily be misidentified as a coagulase-negative staphylococcus and considered insignificant.

Conclusion. This is, to the best of our knowledge, the first reported case of a human S. pseudintermedius infection in Scotland. Zoonotic transmission of S. pseudintermedius between pets and owners has been shown. However, in this case zoonosis could not be confirmed.

Characterization of Staphylococcus pseudintermedius isolated from diseased dogs in Lithuania

The aim of this study was to characterize Staphylococcus pseudintermedius for its antimicrobial resistance and virulence factors with a special focus on methicillin-resistant (MRSP) strains isolated from sick dogs in Lithuania. Clinically sick adult dogs suffering from infections (n=214) and bitches with reproductive disorders (n=36) from kennels were selected for the study. Samples (n=192) from the 250 tested (76.8%) dogs were positive for Staphylococcus spp. Molecular profiling using the species-specific nuc gene identified 51 isolates as S. pseudintermedius (26.6% from a total number of isolated staphylococci) of which 15 isolates were identified as MRSP. Ten MRSP isolates were isolated from bitches with reproductive disorders from two large breeding kennels. Data on susceptibility of S. pseudintermedius to different antimicrobials revealed that all isolates were susceptible to vancomycin, daptomycin and linezolid. Two isolates (3.9%) were resistant to rifampicin. A high resistance was seen towards penicillin G (94.1%), tetracycline (64.7%) and macrolides (68.7%). Resistance to fluoroquinolones ranged from 25.5% (gatifloxacin) to 31.4% (ciprofloxacin). The most prevalent genes encoding resistance included blaZ, aac(6')-Ie-aph(2'')-Ia, mecA, and tet(M). The Luk-I gene encoding a leukotoxin was detected in 29% of the isolates, whereas the siet gene encoding exfoliative toxin was detected in 69% of the S. pseudintermedius isolates. This report of MRSP in companion animals represents a major challenge for veterinarians in terms of antibiotic therapy and is a concern for both animal and public health.

Human infections due to Staphylococcus pseudintermedius, an emerging zoonosis of canine origin: report of 24 cases

BACKGROUND

Staphylococcus pseudintermedius has been recently identified as a novel species within the genus Staphylococcus, and is commonly associated with infections in dogs. Currently, there are few reports of human infections due to this bacterium.

OBJECTIVE

To use a population-based approach to describe the characteristics of human S. pseudintermedius infections in a large Canadian healthcare region.

METHODS

All adult cases aged ≥18 years identified at a large regional laboratory from April 1, 2013 to April 1, 2015 who had at least one positive culture for S. pseudintermedius were retrospectively reviewed. A combination of phenotypic methods, mass spectrometry (i.e., MALDI-TOF), and cpn60 sequencing were used to identify S. pseudintermedius. Chart review was conducted, and cases were analysed descriptively.

RESULTS

Twenty-seven isolates of S. pseudintermedius from 24 human cases were included for analysis. 58.3% were male with median age of 61 years (IQR 55-70.5). Most patients [22 (92.1%)] had confirmed contact with dogs at time of infection. S. pseudintermedius was isolated in 18 cases (75.0%) of skin and soft tissue infections (SSTI), and 2 invasive cases (8.3%) including a prosthetic joint and bloodstream infection. The other 4 patients were considered to be colonized (skin - 3; lung - 1). Methicillin resistance was identified in 3 cases with 6 total isolates (22.2%); multi-drug resistance was also demonstrated commonly.

CONCLUSION

S. pseudintermedius is most commonly associated with SSTIs in humans. Transmission probably occurs from a pet dog. Species-level identification of S. pseudintermedius is important due to the high prevalence of antibiotic resistance, particularly to methicillin.

Crystal structure of FhuD at 1.6 Å resolution: a ferrichrome-binding protein from the animal and human pathogen Staphylococcus pseudintermedius

Staphylococcus pseudintermedius is a leading cause of disease in dogs, and zoonosis causes human infections. Methicillin-resistant S. pseudintermedius strains are emerging, resembling the global health threat of S. aureus. Therefore, it is increasingly important to characterize potential targets for intervention against S. pseudintermedius. Here, FhuD, an S. pseudintermedius surface lipoprotein implicated in iron uptake, was characterized. It was found that FhuD bound ferrichrome in an iron-dependent manner, which increased the thermostability of FhuD by >15 °C. The crystal structure of ferrichrome-free FhuD was determined via molecular replacement at 1.6 Å resolution. FhuD exhibits the class III solute-binding protein (SBP) fold, with a ligand-binding cavity between the N- and C-terminal lobes, which is here occupied by a PEG molecule. The two lobes of FhuD were oriented in a closed conformation. These results provide the first detailed structural characterization of FhuD, a potential therapeutic target of S. pseudintermedius.

Evaluation of an Immunochromatographic Assay for Rapid Detection of Penicillin-Binding Protein 2a in Human and Animal Staphylococcus intermedius Group, Staphylococcus lugdunensis, and Staphylococcus schleiferi Clinical Isolates

The performance of a rapid penicillin-binding protein 2a (PBP2a) detection assay, the Alere PBP2a culture colony test, was evaluated for identification of PBP2a-mediated beta-lactam resistance in human and animal clinical isolates of Staphylococcus intermedius group, Staphylococcus lugdunensis, and Staphylococcus schleiferi. The assay was sensitive and specific, with all PBP2a-negative and PBP2a-positive strains testing negative and positive, respectively.

Genotypic relatedness and characterization of Staphylococcus pseudintermedius associated with post-operative surgical infections in dogs

Staphylococcus pseudintermedius is a commensal organism of dogs that can also be implicated in surgical site infections (SSIs) in dogs. Particularly with the recent emergence and spread of the ST71-t02-SCCmecII-III multidrug-resistant S. pseudintermedius clonal lineage (MDRSP), it is important to understand the clonal diversity of S. pseudintermedius in SSIs in dogs. The study reported here investigated the genotypic relatedness of 124 S. pseudintermedius isolates from the surgical wounds of 90 dogs admitted to a referral practice in the UK. This study also aimed to understand whether MDRSP is better adapted to survival and persistence in different environments compared with other S. pseudintermedius. Whilst no individual S. pseudintermedius clonal type was primarily responsible for S. pseudintermedius-associated SSIs in dogs, we found that MDRSP was the most represented clonal type among the isolates studied. However, we observed no difference in the level of biofilm production, susceptibility to biocides or carriage of specific virulence determinants between MDRSP and other S. pseudintermedius isolates studied. Interestingly, in the competitive fitness study, MDRSP did not outcompete any member of the other S. pseudintermedius isolates studied in each environment. Our data suggest that the determinants that promote S. pseudintermedius-associated SSIs in dogs are distributed among S. pseudintermedius as a species and are not restricted to a few clonal types. They also provide evidence to support the suggestion that MDRSP is not better adapted to survival or persistence in different environments and is no more virulent than other S. pseudintermedius isolates.