Twenty-two methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from various infected locations in domestic cats and dogs between June 2008 and September 2014 were analyzed for their genotype, genetic fingerprint, virulence and antibiotic resistance profile. Eighteen strains belonged to the clonal complex (CC) 22 [ST22(MLST)-A(PFGE)-t032(spa)-IV(SCCmec) and ST22-A-t1214-IV], 2 strains to the livestock associated MRSA ST398-t011-IV and two were individual strains of ST5-t002-II and ST1-t001-IV. They contained virulence factors such as γ-hemolysins, β-hemolysin converting phage genes, leukocidins and enterotoxins. Most widespread resistances were observed against β-lactams, trimethoprim and fluoroquinolones, but single strains also exhibited resistance to macrolides, lincosamides, aminoglycosides, tetracycline, chloramphenicol and/or mupirocin. The predominant presence of CC22 MRSA strongly indicates clonal spread of a human associated lineage in Swiss companion animals. It is therefore of public health importance to maintain a low level of MRSA infections in animals to avoid uncontrolled dissemination of MRSA clones in humans and animals.

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Bovine mastitis, an inflammatory disease of the mammary gland, is one of the most costly diseases affecting the dairy industry. The treatment and prevention of this disease is linked heavily to the use of antibiotics in agriculture and early detection of the primary pathogen is essential to control the disease. Milk samples (n = 67) from cows suffering from mastitis were analyzed for the presence of pathogens using PCR electrosprayionization mass spectrometry (PCR/ESI-MS) and were compared with standard culture diagnostic methods. Concurrent identification of the primary mastitis pathogens was obtained for 64% of the tested milk samples, whereas divergent results were obtained for 27% of the samples. The PCR/ESI-MS failed to identify some of the primary pathogens in 18% of the samples, but identified other pathogens as well as microorganisms in samples that were negative by culture. The PCR/ ESI-MS identified bacteria to the species level as well as yeasts and molds in samples that contained a mixed bacterial culture (9%). The sensitivity of the PCR/ESI-MS for the most common pathogens ranged from 57.1 to 100% and the specificity ranged from 69.8 to 100% using culture as gold standard. The PCR/ESI-MS also revealed the presence of the methicillin-resistant gene mecA in 16.2% of the milk samples, which correlated with the simultaneous detection of staphylococci including Staphylococcus aureus. We demonstrated that PCR/ESI-MS, a more rapid diagnostic platform compared with bacterial culture, has the significant potential to serve as an important screening method in the diagnosis of bovine clinical mastitis and has the capacity to be used in infection control programs for both subclinical and clinical disease.

Genome alignment of a macrolide, lincosamide, and streptogramin B (MLS B )-resistant Staphylococcus fleurettii strain with an MLS B -susceptible S. fleurettii strain revealed a novel 11,513-bp genomic island carrying the new erythromycin resistance methylase gene erm(45). This gene was shown to confer inducible MLS B resistance when cloned into Staphylococcus aureus. The erm(45)-containing island was integrated into the housekeeping gene guaA in S. fleurettii and was able to form a circular intermediate but was not transmissible to S. aureus. Staphylococcus fleurettii is a commensal bacterium of various animal species and an occasional cause of bovine mastitis (1-3). It naturally contains the methicillin resistance gene mecA within its chromosome and is therefore suspected to have been the source of the mecA gene found in staphylococcal cassette chromosome mec (SCCmec) of methicillin-resistant staphylococci, including methicillin-resistant Staphylococcus aureus (MRSA) (4).Due to this intrinsic resistance to ␤-lactams, other antibiotic classes such as macrolides or lincosamides are being used for the treatment of mastitis caused by S. fleurettii (5, 6).S. fleurettii strain JW205, recently isolated from bovine milk in Switzerland, exhibited resistance to erythromycin and inducible resistance to clindamycin (3). This suggested the presence of a macrolide, lincosamide, and streptogramin B (MLS B ) resistance methylase (Erm) (7). However, none of the erm genes commonly occurring in staphylococci were detected by microarray analysis (8, 9). We therefore examined S. fleurettii strain JW205 for a novel MLS B resistance mechanism by genome comparison with MLS Bsusceptible S. fleurettii strain JW404 (Table 1).Detection and characterization of erm(45). Genomes of strain JW205 and JW404 were sequenced using Ion Torrent (Life Technologies, Grand Island, NY) at the UZH/ETH Functional Genomics Center (Zurich, Switzerland) and Illumina MiSeq (Illumina, San Diego, CA) at the Department of Clinical Microbiology at Hvidovre Hospital (Hvidovre, Denmark), respectively. Contigs of the sequenced strains were aligned using the progressive Mauve algorithm (10). This revealed an 11,513-bp integrated genomic island in JW205, which was absent in strain JW404. The island contained 18 open reading frames (ORFs) (Fig. 1), which were identified by the Prokaryotic Dynamic Programming Genefinding Algorithm (Prodigal) (11) and compared to protein sequences and conserved domains in the BLASTp program (http: //blast.ncbi.nlm.nih.gov/Blast.cgi) and the Swiss Institute of Bioinformatics PROSITE database (http://prosite.expasy.org/). The rightmost ORF of the island encoded a 245-amino-acid (aa) protein, which contained the rRNA adenine dimethylase PROSITE signature PS01131, which is present in nearly all Erm 23S rRNA methylases (12). Of all 36 currently described Erm determinants, this methylase exhibited the highest similarity to Erm(B), with 64% aa and 67% nucleotide (nt) identity (Fig. 2).The novel gene was assigned the name erm(45) according to th...

No abstract

The murine bacterial pathogen Chlamydia muridarum (Cm) has been used to study human Chlamydia infections in various mouse models. CD4+ T-cells, natural killer cells, and interferon-gamma (IFN-γ)–mediated immunity are important to control experimentally induced Cm infections. Despite its experimental use, natural infection by Cm has not been documented in laboratory mice since the 1940s. In 2022, the authors reported the discovery of natural Cm infections in numerous academic institutional laboratory mouse colonies around the globe. To evaluate the impact of Cm infection in severely immunocompromised mice, 19 NOD.Cg- Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice were cohoused with Cm shedding, naturally infected immunocompetent mice and/or their soiled bedding for 4 weeks and subsequently euthanized. Clinical disease, characterized by lethargy, dyspnea, and weight loss, was observed in 11/19 NSG mice, and 16/18 NSG mice had neutrophilia. All mice exhibited multifocal to coalescing histiocytic and neutrophilic bronchointerstitial pneumonia (17/19) or bronchiolitis (2/19) with intraepithelial chlamydial inclusions (CIs). Immunofluorescence showed CIs were often associated with bronchiolar epithelium. CIs were frequently detected by immunohistochemistry in tracheal and bronchiolar epithelium (19/19), as well as throughout the small and large intestinal epithelium without lesions (19/19). In a subset of cases, Cm colonized the surface epithelium in the nasopharynx (16/19), nasal cavity (7/19), and middle ear canal (5/19). Endometritis and salpingitis with intraepithelial CI were identified in a single mouse. These findings demonstrate that Cm infection acquired through direct contact or soiled bedding causes significant pulmonary pathology and widespread intestinal colonization in NSG mice.

Clostridioides difficile is an enteric pathogen that can cause significant clinical disease in both humans and animals. However, clinical disease arises most commonly after treatment with broad-spectrum antibiotics. The organism's ability to cause naturally occurring disease in mice is rare, and little is known about its clinical significance in highly immunocompromised mice. We report on 2 outbreaks of diarrhea associated with C. difficile in mice. In outbreak 1, 182 of approximately 2, 400 NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) and related strains of mice became clinically ill after cessation of a 14-d course of 0.12% amoxicillin feed to control an increase in clinical signs associated with Corynebacterium bovis infection. Most mice had been engrafted with human tumors; the remainder were experimentally naïve. Affected animals exhibited 1 of 3 clinical syndromes: 1) peracute death; 2) severe diarrhea leading to euthanasia or death; or 3) mild to moderate diarrhea followed by recovery. A given cage could contain both affected and unaffected mice. Outbreak 2 involved a small breeding colony (approximately 50 mice) of NOD. CB17-Prkdcscid/NCrCrl (NOD-scid) mice that had not received antibiotics or experimental manipulations. In both outbreaks, C. difficile was isolated, and toxins A and B were detected in intestinal content or feces. Histopathologic lesions highly suggestive of C. difficile enterotoxemia included fibrinonecrotizing and neutrophilic typhlocolitis with characteristic 'volcano' erosions or pseudomembrane formation. Genomic analysis of 4 isolates (3 from outbreak 1 and 1 from outbreak 2) revealed that these isolates were closely related to a pathogenic human isolate, CD 196. To our knowledge, this report is the first to describe naturally occurring outbreaks of C. difficile-associated typhlocolitis with significant morbidity and mortality in highly immunocompromised strains of mice.

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.