Characterization of Livestock-Associated Methicillin-Resistant Staphylococcus aureus CC398 and mecC-positive CC130 from Zoo Animals in the United Kingdom

Presence of Methicillin Resistant Staphylococcus aureus (MRSA) in Feces of the Small Indian Mongooses (Urva auropunctata) on Saint Kitts and Nevis, West Indies

Although, historically, Methicillin-Resistant Staphylococcus aureus (MRSA) was restricted to humans, since 2005 these strains emerged in livestock and wildlife. Therefore, a One Health approach was applied to analyze the diversity and characteristics of S. aureus strains isolated from the invasive species of mongoose (Urva auropunctata) in St. Kitts. Fecal samples collected from these animals (n = 81) were cultured on selective agar. The isolated S. aureus strains were identified using MALDI-TOF and further characterized by whole genome sequence analysis. The fecal microbiome study identified the presence of S. aureus in 5 animals. Both MSSA (n = 3) and MRSA (n = 2) strains were identified. The two MRSA isolated were nearly identical ST5 SCCmec IVa (2B) strains. The two MSSA isolated were a new ST7434, pertaining to clonal complex 30, and the other belonged to ST5, but unrelated to the MRSA ST5. The SCCmec IVa (2B) is, however, the main SCCmec in human MRSA of different STs identified in St Kitts, indicating potential horizontal transmission events. In conclusion, a new type of MSSA, ST7434, was found and MRSA ST5 t002 SCCmec IVa (2B) found its way into wildlife on a small Caribbean Island. Further One Health studies are necessary to determine the role of MRSA in wildlife.

Prevalence and Diversity of Staphylococcus aureus and Staphylococcal Enterotoxins in Raw Milk From Northern Portugal

Staphylococcus aureus and staphylococcal enterotoxins are a serious public health concern associated with hospital and community-acquired illnesses. Dairy animals frequently shed S. aureus into the milk supply which can lead to food poisoning in humans. This study aims to investigate the prevalence and genetic diversity of S. aureus and staphylococcal enterotoxins in raw milk from the main dairy region of mainland Portugal. S. aureus was found in 53.0% (95% CI: 40.6-65.4%) of 100 raw cow's milk samples collected from bulk cooling tanks. The highest contamination level was 3.4 log10 CFU.mL-1, and in some samples more than one S. aureus strain was identified. Staphylococcal enterotoxins (SEA-SEE) were detected in one sample. Spa typing revealed 62 distinct S. aureus isolates, being t529 (17.7%, 95% CI: 8.2-27.3%) and t1403 (16.1%, 95% CI: 7.0-25.3%) the predominant types, commonly associated with livestock infection or carriage. The antimicrobial susceptibility test showed that 35.5% of the S. aureus isolates were resistant to at least one antimicrobial agent, with resistance to penicillin being the highest (32.3%, 95% CI: 20.6-43.9%) followed by tetracycline (24.2%, 95% CI: 13.5-34.9%), ciprofloxacin (16.1%, 95% CI: 7.0-25.3%) and chloramphenicol (16.1%, 95% CI: 7.0-25.3%). Moreover, five isolates (8.1%, 95% CI: 1.3-14.8%) were identified as methicillin-resistant S. aureus (MRSA, cefoxitin resistant). Regarding virulence/resistance genes, 46,8% (95% CI: 34.4-59.2%) isolates harbored at least one enterotoxin-encoding gene, and the seg gene was the most frequently detected (41.9%, 95% CI: 29.7-54.2%) followed by the sei (40.3%, 95% CI: 28.1-52.5%), sec (6.5%, 95% CI: 0.3-12.6%), seh (4.8%, 95% CI: 0.0-10.2%), and sea (1.6%, 95% CI: 0.0-4.7%) genes. Five (8.1%, 95% CI: 1.3-14.8%) non-enterotoxigenic isolates carried the mecA gene (corresponding to isolates phenotypically classified as MRSA), and 4.8% (95% CI: 0.0-10.2%) enterotoxigenic strains also had the tsst-1 gene. Our study confirm that raw milk can be a zoonotic source of S. aureus, including enterotoxigenic and MRSA strains. Furthermore, the majority of enterotoxigenic isolates were found to contain genes encoding SEs (SEG, SEH and SEI) not routinely screened. This shows the need for a broader SE screening in food safety control, as well as the relevance of risk mitigation measures to control S. aureus transmission along the food chain in Portugal.

Low prevalence of livestock-associated methicillin-resistant Staphylococcus aureus clonal complex 398 and mecC MRSA among human isolates in North-West England

AIMS

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is an important public health problem in many countries. Despite reports of such isolates being found in both animals and humans in the United Kingdom few data are available on the prevalence in humans of such isolates. A prevalence study was therefore undertaken in the north-west of England.

METHODS AND RESULTS

One thousand two hundred and forty-two human MRSA isolates collected during 2015 were screened by PCR to detect two of the major forms of LA-MRSA: clonal complex (CC)398 and mecC MRSA. Isolates identified were further characterized by antimicrobial susceptibility testing and whole-genome sequencing using HiSeq technology. A single mecC MRSA isolate and three CC398 LA-MRSA were identified among the isolates screened. All four isolates were from MRSA screening. A phylogenetic analysis, including previously sequenced isolates from the United Kingdom, provided strong evidence for the genomic and epidemiological linkage between a pair of animal and human isolates of CC398 LA-MRSA in England. These data are indicative of animal and humans isolates of CC398 LA-MRSA being involved in the same transmission network and is the first demonstration of such closely linked animal and human isolates of this lineage in the UK.

CONCLUSIONS

The study indicates there is a low prevalence of CC398 LA-MRSA and mecC MRSA among MRSA isolates in the sampled population.

SIGNIFICANCE AND IMPACT OF THE STUDY

While the study demonstrates that LA-MRSA were rare among human MRSA isolates in the sampled population, the data provide a baseline for the future surveillance of what is a significant public health challenge in some regions. The demonstration of linked human and animal isolates of CC398 LA-MRSA, supported by genomic and epidemiological data, reinforces the need for such surveillance and for continued awareness of the risks that LA-MRSA may pose in the UK.

Livestock-Associated Methicillin-Resistant Staphylococcus aureus in Patients Admitted to Kuwait Hospitals in 2016-2017

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has been reported to colonize and cause infections in animals as well as in humans. LA-MRSA isolates have only recently been identified in patients admitted to Kuwait hospitals. This study was conducted to characterize LA-MRSA isolates obtained from patients admitted to Kuwait hospitals. A total of 202 (7.1%) of 2,823 MRSA isolates obtained from clinical samples in 2016 and 2017 in 11 public Kuwait hospitals were assigned to lineages previously known to be associated with livestock. They were characterized using antibiogram, spa typing, and DNA microarray for the assignment of clonal complexes (CCs) and detection of antibiotic resistance and virulence determinants. Identification as putative LA-MRSA clones was based on the molecular definition inferred from DNA microarray. The LA-MRSA isolates consisted of CC96 (N = 31), CC97 (N = 169), and CC398 (N = 2). Isolates belonging to CC96 and CC398 were resistant to erythromycin and clindamycin mediated by erm(A) and erm(C). CC97 isolates were multiresistant to gentamicin, kanamycin, erythromycin, clindamycin, tetracycline, chloramphenicol, fusidic acid, trimethoprim, and ciprofloxacin and harbored aacA-aphD, erm(A), erm(C), msr(A), tet(K), cat, fusC, and dfrS1. In total, 35 spa types were identified among the isolates. CC398 isolates consisted of t899 and t034. Ten spa types were identified among CC96 with t11822 (N = 13) as the most prevalent. CC97 consisted of 26 spa types with most belonging to t267 (N = 73) followed by t359 (N = 39). CC398 was composed of CC398-MRSA-IV and CC398-MRSA-V (PVL+). CC96 belonged to CC96-MRSA-IV and CC96-MRSA-IV (PVL+) Central Asian caMRSA/WA MRSA-119. CC97 consisted of six strains including CC97-MRSA-V (fusC +), CC97-MRSA-IV WA MRSA-54/63, CC97-MRSA-V, CC97-MRSA-(V+fus), CC97-MRSA-(mec VI+fus), and CC97-MRSA (mecV/VT+fus+ccrAB2). Whereas CC96 and CC97 isolates were identified in 2016 and 2017, CC398 isolates were detected only in 2016. This study identified four LA-MRSA clones among MRSA isolated from patients in Kuwait hospitals in 2016-2017 with CC97-MRSA-V (fusC +) as the dominant clone. The presence of LA-MRSA with different genetic backgrounds suggests its independent acquisition from different sources.

Isolation and Molecular Identification of Virulence, Antimicrobial and Heavy Metal Resistance Genes in Livestock-Associated Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus is one of the most important pathogens of humans and animals. Livestock production contributes a significant proportion to the South African Gross Domestic Product. Consequently, the aim of this study was to determine for the first time the prevalence, virulence, antibiotic and heavy metal resistance in livestock-associated S. aureus isolated from South African livestock production systems. Microbial phenotypic methods were used to detect the presence of antibiotic and heavy metal resistance. Furthermore, molecular DNA based methods were used to genetically determine virulence as well as antibiotic and heavy metal resistance determinants. Polymerase chain reaction (PCR) confirmed 217 out of 403 (53.8%) isolates to be S. aureus. Kirby-Bauer disc diffusion method was conducted to evaluate antibiotic resistance and 90.8% of S. aureus isolates were found to be resistant to at least three antibiotics, and therefore, classified as multidrug resistant. Of the antibiotics tested, 98% of the isolates demonstrated resistance towards penicillin G. High resistance was shown against different heavy metals, with 90% (196/217), 88% (192/217), 86% (188/217) and 84% (183/217) of the isolates resistant to 1500 µg/mL concentration of Cadmium (Cd), Zinc (Zn), Lead (Pb) and Copper (Cu) respectively. A total of 10 antimicrobial resistance and virulence genetic determinants were screened for all livestock associated S. aureus isolates. Methicillin-resistant S. aureus (MRSA) isolates were identified, by the presence of mecC, in 27% of the isolates with a significant relationship (p < 0.001)) with the host animal. This is the first report of mecC positive LA-MRSA in South Africa and the African continent. The gene for tetracycline resistance (tetK) was the most frequently detected of the screened genes with an overall prevalence of 35% and the highest prevalence percentage was observed for goats (56.76%) followed by avian species (chicken, duck and wild birds) (42.5%). Virulence-associated genes were observed across all animal host species. The study reports the presence of luks/pv, a gene encoding the PVL toxin previously described to be a marker for community acquired-MRSA, suggesting the crossing of species between human and livestock. The high prevalence of S. aureus from the livestock indicates a major food security and healthcare threat. This threat is further compounded by the virulence of the pathogen, which causes numerous clinical manifestations. The phenomenon of co-selection is observed in this study as isolates exhibited resistance to both antibiotics and heavy metals. Further, all the screened antibiotic and heavy metal resistance genes did not correspond with the phenotypic resistance.

Patterns of cross-resistance and collateral sensitivity between clinical antibiotics and natural antimicrobials

Bacteria interact with a multitude of other organisms, many of which produce antimicrobials. Selection for resistance to these antimicrobials has the potential to result in resistance to clinical antibiotics when active compounds target the same bacterial pathways. The possibility of such cross-resistance between natural antimicrobials and antibiotics has to our knowledge received very little attention. The antimicrobial activity of extracts from seaweeds, known to be prolific producers of antimicrobials, is here tested against Staphylococcus aureus isolates with varied clinical antibiotic resistance profiles. An overall effect consistent with cross-resistance is demonstrated, with multidrug-resistant S. aureus strains being on average more resistant to seaweed extracts. This pattern could potentially indicate that evolution of resistance to antimicrobials in the natural environment could lead to resistance against clinical antibiotics. However, patterns of antimicrobial activity of individual seaweed extracts vary considerably and include collateral sensitivity, where increased resistance to a particular antibiotic is associated with decreased resistance to a particular seaweed extract. Our correlation-based methods allow the identification of antimicrobial extracts bearing most promise for downstream active compound identification and pharmacological testing.

Death Associated to Methicillin Resistant Staphylococcus aureus ST8 Infection in Two Dolphins Maintained Under Human Care, Italy

The present study describes the isolation of Methicillin-resistant Staphylococcus aureus (MRSA) from respiratory tract of 2 dolphins of different origin, a stranded juvenile Risso's dolphin (Grampus griseus) and a captive born common bottlenose dolphin (Tursiops truncatus) calf, which died in the same institution at 1-month distance from the other. A complete microbiological and genetic investigation confirmed the presence of MRSA clone-complex 8, sequence type (ST) 8, spa-type t008 in both individuals. This strain differs from the one previously reported in walruses and dolphins and has never been described in dolphins before, but it is randomly isolated from Italian human patients. Vertical transmission of the infection may also occurs in other species and considering the description and location of the pathological lesions, this seems to be the most likely route of transmission implied in the young bottlenose dolphin. Staphylococcus aureus is known as an opportunistic agent, usually secondary to other pathogens, but its multiple antibiotic resistance and its zoonotic implications suggest a thorough and strict application of animal management hygiene protocols.