Non-aureus staphylococci and mammaliicocci (NASM) are the most frequently isolated bacterial group from bovine milk samples. Most studies focus on subclinical mastitis caused by NASM, however NASM can cause clinical mastitis (CM) as well. We evaluated retrospective data from 6 years (2017-2022) to determine the species and frequency of NASM isolated from quarter bovine CM. The data comprised of microbiological results from quarter CM samples routinely submitted to Quality Milk Production Services (QMPS), Cornell University, NY, US, for microbial identification by MALDI-TOF MS. A total of 9,909 microbiological results from 410 dairy herds were evaluated. Our results showed that 29 distinct NASM species were identified, with the 8 most prevalent NASM species being Staphylococcus chromogenes, S. haemolyticus, S. simulans, S. epidermidis, S. sciuri (now Mammaliicoccus sciuri), S. agnetis/S. hyicus, S. borealis, and S. xylosus. The NASM distribution remained similar among seasons, but the frequency of NASM CM cases was higher during the summer. Our results showed different patterns of variations in the isolation frequency over time, depending on the bacterial species: increasing or decreasing trends, cyclic fluctuations, and except for S. borealis, a significant seasonality effect for our study's most prevalent NASM was observed. This study showed that S. chromogenes remains the most frequent (43%) NASM species identified from bovine CM, followed by S. haemolyticus (18%), and S. simulans (12%).

pdf/frequency-of-non-aureus-staphylococci-and-mammaliicocci-1u18zt248m.pdf

Frequency of non-aureus staphylococci and mammaliicocci species isolated from quarter clinical mastitis: a six-year retrospective study.

Methicillin resistance, mediated by the mecA gene in staphylococci and mammaliicocci, has caused tremendous setbacks in the use of antibiotics in human and veterinary medicine due to its high potential of presenting the multidrug resistance (MDR) phenotype. Three other mec analogs exist, of which the mecC has evolutionary been associated with methicillin-resistant Staphylococcus aureus (MRSA) in wild animals, thus loosely referred to as the wild MRSA. In this study, we present an epidemiological review and genomic analysis of non-aureus staphylococci and mammaliicocci that carry the mecC-mediated methicillin resistance trait and determine whether this trait has any relevant link with the One Health niches. All previous studies (2007 till 2023) that described the mecC gene in non-aureus staphylococci and mammaliicocci were obtained from bibliometric databases, reviewed, and systematically analyzed to obtain the antimicrobial resistance (AMR) and virulence determinants, mobilome, and other genetic contents. Moreover, core genome single-nucleotide polymorphism analysis was used to assess the relatedness of these strains. Of the 533 articles analyzed, only 16 studies (on livestock, environmental samples, milk bulk tanks, and wild animals) were eligible for inclusion, of which 17 genomes from 6 studies were used for various in silico genetic analyses. Findings from this systematic review show that all mecC-carrying non-aureus staphylococci were resistant to only beta-lactam antibiotics and associated with the classical SCCmec XI of S. aureus LGA251. Similarly, two studies on wild animals reported mecC-carrying Mammaliicoccus stepanovicii associated with SCCmec XI. Nevertheless, most of the mecC-carrying Mammaliicoccus species presented an MDR phenotype (including linezolid) and carried the SCCmec-mecC hybrid associated with mecA. The phylogenetic analysis of the 17 genomes revealed close relatedness (<20 SNPs) and potential transmission of M. sciuri and M. lentus strains in livestock farms in Algeria, Tunisia, and Brazil. Furthermore, closely related M. sciuri strains from Austria, Brazil, and Tunisia (<40 SNPs) were identified. This systematic review enhances our comprehension of the epidemiology and genetic organization of mecC within the non-aureus staphylococci and mammaliicocci. It could be hypothesized that the mecC-carrying non-aureus staphylococci are evolutionarily related to the wild MRSA-mecC. The potential implications of clonal development of a lineage of mecA/mecC carrying strains across multiple dairy farms in a vast geographical region with the dissemination of MDR phenotype is envisaged. It was observed that most mecC-carrying non-aureus staphylococci and mammaliicocci were reported in mastitis cases. Therefore, veterinarians and veterinary microbiology laboratories must remain vigilant regarding the potential existence of mecA/mecC strains originating from mastitis as a potential niche for this resistance trait.

Beyond the Wild MRSA: Genetic Features and Phylogenomic Review of mecC-Mediated Methicillin Resistance in Non-aureus Staphylococci and Mammaliicocci

The antimicrobial resistance (AMR) genes of 268 non-duplicated coagulase-negative staphylococci (CoNS) previously obtained from nasotracheal cavities of nestling storks were characterized. They included S. sciuri isolates (n=191), and non-sciuri-CoNS isolates (NSc-CoNS, n= 77). All S. sciuri carried the intrinsic salA gene (for clindamycin-resistance) and so, clindamycin was not considered for general analysis in this species. About 71.7%/41.6% of the S. sciuri/NSc-CoNS were susceptible to all antibiotics tested; moreover, 14.1%/16.9% and 3.1%/20.8% of S. sciuri/NSc-CoNS showed single antibiotic resistance and multidrug resistance (MDR) phenotype, respectively. Of the ten mecA-positive CoNS isolates, six were associated with SCCmec types-III, -IV or -V elements. Remarkably was the detection of one MDR-S. lentus isolate carrying both mecA and mecC genes, as well as the SCCmec type-IX element. MDR-CoNS was relatively higher in nestlings of parent storks foraging in landfills (21.3%) than those in natural areas (9.7%) (χ2 = 3.421, df=1, p= 0.064). AMR phenotypes (and genes detected) include penicillin (blaZ, blaARL), erythromycin-clindamycin-constitutive (ermA, ermC, ermT), clindamycin (lnuA, salA, vgaA), erythromycin (msrA, mphC), tetracycline (tetK, tetL, tetM), tobramycin (ant4’), tobramycin-gentamicin (aac6’-aph2”), sulfamethoxazole-trimethoprim (dfrA, dfrG, dfrK), chloramphenicol (fexA, fexB, catPC221), and mupirocin (mupA). Interestingly, one S. epidermidis isolate carried the ermT gene. About 29.9% of nestlings harboured ≥1 non-duplicated CoNS (with varied 2-5 AMR profiles). This study demonstrated that most of the CoNS isolates were susceptible to all the antibiotics tested (63.1%). However, AMR genes of public health importance were found, including the mecC-mediated methicillin resistance trait. 

Antimicrobial resistome of coagulase-negative staphylococci from nasotracheal cavities of nestlings of Ciconia ciconia in Southern Spain: Detection of mecC-SCCmec type-XI-carrying S. lentus.

Role of Programmed Cell Death Receptor-1 and Cytotoxic T Lymphocyte-Associated Antigen 4 in Bovine Leukemia Virus Infection

Mammaliicoccus sciuri’s Pan-Immune System and the Dynamics of Horizontal Gene Transfer Among Staphylococcaceae: a One-Health CRISPR Tale

Emergence of livestock-associated Mammaliicoccus sciuri ST71 co-harbouring mecA and mecC genes in Brazil.

Bovine leukemia virus (BLV) is caused by a deltaretrovirus and has been associated with immunosuppression as well as comorbidities such as bovine mastitis, the costliest disease in the dairy sector. However, no previous study has explored at the synergistic immunosuppressive effect of the peripartum period with an immunosuppressive viral disease such as BLV. Thus, our study explored the effect of BLV infection in the periparturient period on the expression of PD-1 and CTLA-4 in blood T lymphocytes, and the impact of BLV infection on the rate of new intramammary infections during the early lactation. Here, we found that BLV-infected dairy cows always had a statistically significant higher expression of CTLA-4 and PD-1 in blood T cells. Furthermore, our findings indicated that BLV infection prolongs immunosuppression in dairy cows during the periparturient period by sustaining higher expression of immunological checkpoints in T cells. In addition, BLV-infected dairy cows have a higher rate of new intramammary infections during early lactation. Thus, our study provides new insights of the immunosuppressive effect of BLV on the most critical period of the cows' life with marked detrimental effect on protective T-cell immunity and comorbidities, such as bovine mastitis. 

The bovine leukemia virus infection prolongs immunosuppression in dairy cows during the periparturient period by sustaining higher expression of immunological checkpoints in T cells.

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Emergence of livestock-associated Mammaliicoccus sciuri ST71 co-harbouring mecA and mecC genes in Brazil.

The bovine leukemia virus infection prolongs immunosuppression in dairy cows during the periparturient period by sustaining higher expression of immunological checkpoints in T cells.