Livestock-associated Methicillin-resistant Staphylococcus Aureus Research Articles

Antimicrobial Resistance and Molecular Characterization of Methicillin-Resistant Staphylococcus aureus from Two Pig Farms: Longitudinal Study of LA-MRSA.

Pigs were identified as the most important reservoir of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA), mostly belonging to the emergent zoonotic clonal complex (CC) 398. Here, we investigated the presence of MRSA in sows and piglets over a period of several months in two pig farms (intensive farm A and family-run farm B). Isolates underwent antimicrobial susceptibility testing, PCR characterization and spa typing. We collected 280 samples, namely 206 nasal swabs from pigs and 74 environmental samples from pig housings at 12 consecutive time points. A total of 120/161 (74.5%) and 75/119 (63.0%) samples were MRSA-positive in farms A and B, respectively. All isolates harbored mecA but lacked mecC and PVL-encoding genes. The identified spa types (t571, t034, t1250 and t898 in farm A, t1451 and t011 in farm B) were indicative of CC398. Antimicrobial resistance patterns (all multidrug resistant in farm A, 57.2% in farm B) depended on the farm, suggesting the impact of farm size and management practices on the prevalence and characteristics of MRSA. Due to the intermittent colonization of pigs and the high contamination of their immediate environment, MRSA status should be determined at the farm level when considering preventive measures or animal trade between farms.

Cfr and fexA genes in methicillin-resistant Staphylococcus aureus from humans and livestock in the Netherlands

BackgroundAlthough the Netherlands is a country with a low endemic level of methicillin-resistant Staphylococcus aureus (MRSA), a national MRSA surveillance has been in place since 1989. In 2003 livestock emerged as a major reservoir of MRSA and currently livestock-associated MRSA (clonal complex CC398) make up 25% of all surveillance isolates. To assess possible transfer of resistant strains or resistance genes, MRSA obtained from humans and animals were characterized in detail.MethodsThe sequenced genomes of 6327 MRSA surveillance isolates from humans and from 332 CC398 isolates from livestock-related samples were analyzed and resistance genes were identified. Several isolates were subjected to long-read sequencing to reconstruct chromosomes and plasmids.ResultsHere we show the presence of the multi-resistance gene cfr in seven CC398 isolates obtained from humans and in one CC398 isolate from a pig-farm dust sample. Cfr induces resistance against five antibiotic classes, which is true for all but two isolates. The isolates are genetically unrelated, and in seven of the isolates cfr are located on distinct plasmids. The fexA gene is found in 3.9% surveillance isolates and in 7.5% of the samples from livestock. There is considerable sequence variation of fexA and geographic origin of the fexA alleles.ConclusionsThe rare cfr and fexA resistance genes are found in MRSA from humans and animals in the Netherlands, but there is no evidence for spread of resistant strains or resistance plasmids. The proportion of cfr-positive MRSA is low, but its presence is worrying and should be closely monitored.

Metabolic Characteristics of Porcine LA-MRSA CC398 and CC9 Isolates from Germany and China via Biolog Phenotype MicroArrayTM.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is an important zoonotic pathogen, often multi-resistant to antimicrobial agents. Among swine, LA-MRSA of clonal complex (CC) 398 dominates in Europe, Australia and the Americas, while LA-MRSA-CC9 is the main epidemic lineage in Asia. Here, we comparatively investigated the metabolic properties of rare and widespread porcine LA-MRSA isolates from Germany and China using Biolog Phenotype MicroArray technology to evaluate if metabolic variations could have played a role in the development of two different epidemic LA-MRSA clones in swine. Overall, we were able to characterize the isolates' metabolic profiles and show their tolerance to varying environmental conditions. Sparse partial least squares discriminant analysis (sPLS-DA) supported the detection of the most informative substrates and/or conditions that revealed metabolic differences between the LA-MRSA lineages. The Chinese LA-MRSA-CC9 isolates displayed unique characteristics, such as a consistently delayed onset of cellular respiration, and increased, reduced or absent usage of several nutrients. These possibly unfavorable metabolic properties might promote the ongoing gradual replacement of the current epidemic LA-MRSA-CC9 clone in China with the emerging LA-MRSA-CC398 lineage through livestock trade and occupational exposure. Due to the enhanced pathogenicity of the LA-MRSA-CC398 clone, the public health risk posed by LA-MRSA from swine might increase further.

Emergence of Cfr-Mediated Linezolid Resistance among Livestock-Associated Methicillin-Resistant Staphylococcus aureus (LA-MRSA) from Healthy Pigs in Portugal.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) ST398 is mainly found in Europe and North America, colonizing the nasal cavity of pigs. This study characterized the MRSA isolates recovered from pig nasal swabs (n = 171) by evaluating the antimicrobial susceptibility profile by broth microdilution and characterizing the genetic lineages by spa-typing. Three linezolid-resistant isolates were subjected to Whole-Genome Sequencing (WGS). All strains harbored the mecA gene and were resistant to tetracycline and susceptible to vancomycin. A high frequency of multidrug resistance (97.6%) was evidenced, with 55 different multidrug resistance profiles identified. The MRSA strains were found to belong to 17 spa-types, three being novel. The linezolid-resistant strains appeared to belong to the ST398 type, spa-type t011, and SCCmec_type_Vc and to harbor the cfr, fexA, blaZ, mecA, tetM, and tetK genes. The cfr gene was predicted to be carried in the plasmid, flanked by ISSau9 and the transposon TnpR. MRSA from Portuguese fattening pigs present a high diversity of genetic lineages. The presence of cfr-positive LA-MRSA may represent a risk of transmission to humans, mainly to those in contact with livestock.

MRSA in Humans, Pets and Livestock in Portugal: Where We Came from and Where We Are Going.

Over the years, molecular typing of methicillin-resistant S. aureus (MRSA) has allowed for the identification of endemic MRSA strains and pathogenic strains. After reaching a peak of predominance in a given geographic region, MRSA strains are usually replaced by a new strain. This process is called clonal replacement and is observed worldwide. The worldwide spread of hospital-associated MRSA (HA-MRSA), community-associated MRSA (CA-MRSA) and livestock-associated MRSA (LA-MRSA) clones over the last few decades has allowed this microorganism to be currently considered a pandemic. In Portugal, most HA-MRSA infections are associated with EMRSA-15 (S22-IV), New York/Japan (ST5-II) and Iberian (ST247-I) clones. Regarding the strains found in the community, many of them are frequently associated with the hospital environment, namely the Pediatric, Brazilian and Iberian clones. On the other hand, a strain that is typically found in animals, MRSA clonal complex (CC) 398, has been described in humans as colonizing and causing infections. The ST398 clone is found across all animal species, particularly in farm animals where the economic impact of LA-MRSA infections can have disastrous consequences for industries. In contrast, the EMRSA-15 clone seems to be more related to companion animals. The objective of this review is to better understand the MRSA epidemiology because it is, undoubtedly, an important public health concern that requires more attention, in order to achieve an effective response in all sectors.

Bioinformatics study of expression from genomes of epidemiologically related MRSA CC398 isolates from human and wild animal samples

One of the most important livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) genetic lineages is the clonal complex (CC) 398, which can cause typical S. aureus-associated infections in people. In this work, whole-genome sequencing, RNA-sequencing, and gel-based comparative proteomics were applied to study the genetic characteristics of three MRSA CC398 isolates recovered from humans (strains C5621 and C9017), and from an animal (strain OR418). Of the three strains, C9017 presented the broadest resistance genotype, including resistance to fluroquinolone, clindamycin, tiamulin, macrolide and aminoglycoside antimicrobial classes. The scn, sak, and chp genes of the immune evasion cluster system were solely detected in OR418. Pangenome analysis showed a total of 288 strain-specific genes, most of which are hypothetical or phage-related proteins. OR418 had the most pronounced genetic differences. RNAIII (δ-hemolysin) gene was clearly the most expressed gene in OR418 and C5621, but it was not detected in C9017. Significant differences in the proteome profiles were found between strains. For example, the immunoglobulin-binding protein Sbi was more abundant in OR418. Considering that Sbi is a multifunctional immune evasion factor in S. aureus, the results point to OR418 strain having high zoonotic potential. Overall, multiomics biomarker signatures can assume an important role to advance precision medicine in the years to come. SignificanceMRSA is one of the most representative drug-resistant pathogens and its dissemination is increasing due to MRSA capability of establishing new reservoirs. LA-MRSA is considered an emerging problem worldwide and CC398 is one of the most important genetic lineages. In this study, three MRSA CC398 isolates recovered from humans and from a wild animal were analyzed through whole-genome sequencing, RNA-sequencing, and gel-based comparative proteomics in order to gather systems-wide omics data and better understand the genetic characteristics of this lineage to identify distinctive markers and genomic features of relevance to public health.

A review of horses as a source of spreading livestock-associated methicillin-resistant Staphylococcus aureus to human health.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) was first discovered in horses in 1989. Since then, LA-MRSA has begun to be considered an important strain of pathogenic bacteria in horses, which can cause LA-MRSA infection and colonization in humans with public health impacts. The anterior nares are the primary site of LA-MRSA colonization in horses, although LA-MRSA colonization may also occur in the gastrointestinal tract in horses. LA-MRSA-infected horses typically exhibit clinical infection or may not exhibit clinical infection. There are two potential risks associated with LA-MRSA colonization in horses: The possibility of disease development in horses infected with LA-MRSA and the possibility of LA-MRSA transfer to humans and other horses. The diagnosis of LA-MRSA in horses can be made by conducting in vitro sensitivity testing for oxacillin and cefoxitin, and then followed by a molecular test using polymerase chain reaction. LA-MRSA transmission in animal hospitals and on farms is most likely due to contact with horses infected or colonized by LA-MRSA. The history of prior antibiotic administration, history of prior LA-MRSA colonization, and length of equine hospitalization were described as risk factors in cases of infection and colonization of LA-MRSA in horses. Nebulized antibiotics may be a viable alternative to use in horses, but nebulized antibiotics are only used in horses that are persistently colonized with LA-MRSA. Controlling the spread of LA-MRSA in horses can be done by regularly washing horses, eradicating vectors in horse stalls such as rats, and maintaining the cleanliness of the stable and animal hospital environment. Meanwhile, cleaning hands, using gloves, and donning protective clothes are ways that humans can prevent the transmission of LA-MRSA when handling horses. This review will explain the definition of LA-MRSA in general, LA-MRSA in horses, the epi­demiology of LA-MRSA in horses, the diagnosis of LA-MRSA in horses, the transmission of LA-MRSA in horses, risk factors for spreading LA-MRSA in horses, public health impact, treatment of LA-MRSA infection in horses, and control of the spread of LA-MRSA in horses.

Stable antibiotic resistance and rapid human adaptation in livestock-associated MRSA.

Mobile genetic elements (MGEs) are agents of horizontal gene transfer in bacteria, but can also be vertically inherited by daughter cells. Establishing the dynamics that led to contemporary patterns of MGEs in bacterial genomes is central to predicting the emergence and evolution of novel and resistant pathogens. Methicillin-resistant Staphylococcus aureus (MRSA) clonal-complex (CC) 398 is the dominant MRSA in European livestock and a growing cause of human infections. Previous studies have identified three categories of MGEs whose presence or absence distinguishes livestock-associated CC398 from a closely related and less antibiotic-resistant human-associated population. Here, we fully characterise the evolutionary dynamics of these MGEs using a collection of 1180 CC398 genomes, sampled from livestock and humans, over 27 years. We find that the emergence of livestock-associated CC398 coincided with the acquisition of a Tn916 transposon carrying a tetracycline resistance gene, which has been stably inherited for 57 years. This was followed by the acquisition of a type V SCCmec that carries methicillin, tetracycline, and heavy metal resistance genes, which has been maintained for 35 years, with occasional truncations and replacements with type IV SCCmec. In contrast, a class of prophages that carry a human immune evasion gene cluster and that are largely absent from livestock-associated CC398 have been repeatedly gained and lost in both human- and livestock-associated CC398. These contrasting dynamics mean that when livestock-associated MRSA is transmitted to humans, adaptation to the human host outpaces loss of antibiotic resistance. In addition, the stable inheritance of resistance-associated MGEs suggests that the impact of ongoing reductions in antibiotic and zinc oxide use in European farms on livestock-associated MRSA will be slow to be realised.

Prevalence of Livestock-Associated MRSA ST398 in a Swine Slaughterhouse in Guangzhou, China.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is an important zoonotic microorganism that is increasingly causing public health concern worldwide. The objective of this study was to determine the transmission and occurrence of MRSA in a slaughterhouse environment and evaluate its antimicrobial resistance and genetic characterization. In this study, we conducted a comprehensive epidemiological survey of S. aureus by spa typing and whole-genome sequencing (WGS) of samples obtained from the pork production chain, the environment, and community residents. To clarify the evolutionary relationships of MRSA sequence type (ST) 398 in this study and global isolates, 197 published whole-genome sequences data of MRSA ST398 strains were downloaded from the GenBank database and included in the phylogenetic analysis. A total of 585 porcine samples (snout and carcass swabs), 78 human nasal samples, and 136 environmental samples were collected. The MRSA isolates were detected at higher frequencies in samples from swine (15.0%) than carcasses (10.0%), slaughterhouse workers (8.0%), community residents (0%), and environment samples (5.9%). The spa typing results showed that t571 accounted for a higher proportion than other spa types. Closely related isolates from the samples of swine, slaughterhouse workers, carcasses, carrier vehicle, and surrounding fishpond water indicate that MRSA ST398 strains may spread among swine, humans, and the environment. MRSA ST398-t571 isolates were genetically different from global strains, except for two Korean isolates, which showed genetic closeness with it. In addition, a MRSA ST398 isolate recovered from an infected patient in Europe differed by only 31 SNPs from the airborne dust-associated strain isolated in this study, thereby suggesting potential transmission among different countries. Antimicrobial susceptibility testing results demonstrated that 99.0% (96/97) of MRSA and 95.1% (231/243) of methicillin-sensitive S. aureus (MSSA) showed multidrug-resistant (MDR) phenotypes. According to WGS analysis, the poxtA-carrying segment (IS431mec-optrA-IS1216-fexB-IS431mec) was reported in MRSA ST398 isolates for the first time. The coexistence of cfr and optrA in a plasmid was first detected in MRSA ST398. The potential transmission of MRSA among humans, animals, and the environment is a cause for concern. The emergence and transmission of LA-MRSA ST398 with high levels of resistance profiles highlight the urgent need for LA-MRSA surveillance.

Livestock-associated methicillin-resistant Staphylococcus aureus in inpatients: a snapshot from an Italian hospital

ObjectivesThis study aimed to characterize livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) strains isolated from patients admitted to Policlinico San Matteo in Pavia, located in an Italian region with high livestock density. MethodsThe starting dataset was composed by 353 MRSA strains isolated from blood cultures between 2011 and 2019 and in 954 MRSA isolated from nasal swabs, wound swabs, skin swabs, ulcer swabs, conjunctival swabs, urine and respiratory samples collected between 2018 and 2019. LA-MRSA was identified based on being MRSA resistant to tetracycline and negative for the PCR amplification of scn locus. Whole genome sequencing of the selected strains was performed, and virulence and resistance genes searched. ResultsFive out of 353 MRSA isolates from blood cultures (1.4%) and nine out of 904 MRSA isolates obtained from other materials (1%) were resistant to tetracycline and negative for the scn locus. The 14 strains were also negative for the lukS-pv, tsst, eta and etb loci. Nine of the 14 strains belonged to ST398, the most common ST of LA-MRSA in Europe. ST398 isolates belonged to four spa-types, of which the prevalent was t899. Eight genomes had the cassette SCCmec type V, five genomes had SCCmec type IV and one genome lacked SCCmec, mecA and mecC. ConclusionThe frequency of LA-MRSA in the patients of this study (1.4% in blood cultures, 1% in other samples) is low but relatively constant over time prevalence and comparable to that found in the few studies performed on patients to date.

Novel macrolide-lincosamide-streptogramin B resistance gene erm(54) in MRSA ST398 from Germany.

Macrolides are important broad-spectrum antimicrobial agents in human and veterinary medicine. Macrolide resistance genes are often located on mobile genetic elements (MGEs) in staphylococci, which can be horizontally transferred across strain, species or genus boundaries.1 The erm genes encode 23S rRNA methylases, which confer combined resistance to macrolide, lincosamide and streptogramin B (MLS) compounds by adding one or two methyl groups to the adenine A2058 in the 23S rRNA.1,2 Livestock-associated MRSA (LA-MRSA) are often multiresistant and mainly associated with ST398 in many parts of the world.3 They have their main reservoir in food-producing animals and, therefore, represent a considerable health risk for humans, especially for those having frequent contact with livestock.3 Macrolides are commonly used to treat bacterial infections in livestock and, consequently, different erm genes, including erm(A), erm(B), erm(C) and erm(T), have so far been detected on MGEs among LA-MRSA ST398.1,4,5 LA-MRSA ST398 isolate 3860 was obtained from the nasal swab of a pig suffering from respiratory disease in the German National Resistance Monitoring programme GERM-Vet in 2007. WGS on Illumina MiSeq and PacBio Sequel II platforms, followed by hybrid assembly and consecutive sequence analysis, revealed the presence of a novel erm gene, designated erm(54) by the Nomenclature Center for MLS Resistance Genes (https://faculty.washington.edu/marilynr), on the non-conjugative 36 929 bp plasmid pHKS3860 (GenBank accession number OM362497) (Figure 1a). Upstream of the erm(54) gene, a regulatory region, known as translational attenuator, was identified. This regulatory region was more complex compared with the corresponding regions of other known staphylococcal erm genes.1,6,7 Besides an open reading frame for a 30 amino acid (aa) regulatory peptide, seven pairs of inverted repeats (IRs), IR1a,b to IR7a,b, were detected. A putative stable mRNA secondary structure formed by the IR sequences was identified, in which the IR7b sequence, which covered in part the erm(54)-associated ribosome binding site and the start of the erm(54) gene, was freely accessible to ribosomes and thereby allowed the translation of the erm(54) transcript.6 Screening for inducible macrolide/lincosamide resistance by agar disc diffusion8 using erythromycin (15 μg), clindamycin (2 μg) and pirlimycin (2 μg) discs confirmed the constitutive expression of erm(54).

The synergistic inhibition and mechanism of epicatechin gallate and Chitosan against Methicillin-resistant Staphylococcus aureus and the application in pork preservation

Livestock-associated -Methicillin-resistant S. aureus (LA-MRSA) contamination on pork has emerged as one of the major concerns worldwide. Combinations of natural plant extracts (NPEs) and food preservatives were tested for their anti-MRSA activities. The most effective combination was evaluated using texture profile, physicochemical analysis and sensory quality. The synergistic antibacterial mechanisms were examined using transcriptomic sequencing and electron microscope. Results showed that 1/8 minimal inhibitory concentration (MIC) (−)-epicatechin gallate (ECG) + 1/16 MIC chitosan had the optimum inhibition on the growth of MRSA with FIC of 0.19. The combination extended the shelf life of pork from 5 to 7 d at 4 °C and from 36 h to 48 h at 25 °C based on MRSA challenge test. The combination effectively maintained the hardness, elasticity, cohesion, recovery, and chewiness of pork and delayed the process of spoilage, lipid oxidation, accumulation of free amino acid, and Met Mb of pork contaminated by MRSA. Synergistic antibacterial mechanisms may be associated with improved cell deformation (stickiness and slight shrinkage). Six differentially expressed genes, lrgB and LytM, clfA, icaB, and icaA and blaI were confirmed to be responsible for the synergistic antibacterial mechanisms. Combining ECG with chitosan may be useful food preservatives in the pork industry.

Livestock-associated methicillin-resistant Staphylococcus aureus in Czech retailed ready-to-eat meat products

This study was aimed on the detection of methicillin resistant Staphylococcus aureus (MRSA) in different categories of retailed ready-to-eat (RTE) meat products from the Czech producers and determination of their genetic properties, antimicrobial resistance and virulence. In RTE meat products, 2% (4/181) of examined samples were MRSA positive. MRSA strains were detected only in durable fermented meat products made exclusively from pork meat. Detection of livestock-associated MRSA (LA-MRSA) clonal lineages (ST398 and ST4999), SCCmec cassette type V and tetracycline resistance indicate a source of contamination from raw pork. The study confirms the ability of these strains to survive the technological process rather than contamination of meat products from the food processing environment. MRSA strains did not carry any of the tested genes encoding staphylococcal enterotoxins or virulence genes (for Panton-Valentine leukocidin, exfoliative toxins A, B and toxic shock syndrome). Our results point out the spread of LA-MRSA through the meat processing chain.

Multilocus sequence type-dependent activity of human and animal cathelicidins against community-, hospital-, and livestock-associated methicillin-resistant Staphylococcus aureus isolates.

Sequence type (ST) 5 methicillin-resistant Staphylococcus aureus (MRSA) with staphylococcal cassette chromosome mec (SCCmec) type II (ST5-MRSA-II) and ST72-MRSA-IV represent the most significant genotypes for healthcare- (HA) and community-associated (CA) MRSA in Korea, respectively. In addition to the human-type MRSA strains, the prevalence of livestock-associated (LA) MRSA clonal lineages, such as ST541 and ST398 LA-MRSA-V in pigs and ST692 LA-MRSA-V and ST188 LA-MRSA-IV in chickens, has recently been found. In this study, clonotype-specific resistance profiles to cathelicidins derived from humans (LL-37), pigs (PMAP-36), and chickens (CATH-2) were examined using six different ST groups of MRSA strains: ST5 HA-MRSA-II, ST72 CA-MRSA-IV, ST398 LA-MRSA-V, ST541 LA-MRSA-V, ST188 LA-MRSA-IV, and ST692 LA-MRSA-V. Phenotypic characteristics often involved in cathelicidin resistance, such as net surface positive charge, carotenoid production, and hydrogen peroxide susceptibility were also determined in the MRSA strains. Human- and animal-type MRSA strains exhibited clonotype-specific resistance profiles to LL-37, PMAP-36, or CATH-2, indicating the potential role of cathelicidin resistance in the adaptation and colonization of human and animal hosts. The ST5 HA-MRSA isolates showed enhanced resistance to all three cathelicidins and hydrogen peroxide than ST72 CA-MRSA isolates by implementing increased surface positive charge and carotenoid production. In contrast, LA-MRSA strains employed mechanisms independent of surface charge regulation and carotenoid production for cathelicidin resistance. These results suggest that human- and livestock-derived MRSA strains use different strategies to counteract the bactericidal action of cathelicidins during the colonization of their respective host species.

Genomic characterisation of CC398 MRSA causing severe disease in Australia

Clonal complex 398 (CC398) livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has been reported worldwide in a variety of food-animal species. Although CC398 is synonymous with LA-MRSA, community-associated MRSA (CA-MRSA) variants have emerged, including the Panton-Valentine leukocidin (PVL)-positive ST398-V and ST398 single-locus variant ST1232-V, and the PVL-negative ST398-V clones. Using comparative genomic analysis, we determined whether ten CC398 MRSA bacteraemia episodes recently identified in Australia were due to LA-MRSA or CA-MRSA CC398. Isolates were sourced from the Australian Group on Antimicrobial Resistance S. aureus surveillance programme and episodes occurred across Australia. Whole-genome sequencing (WGS) and phylogenetic comparison of the ten CC398 bacteraemia isolates with previously published CC398 MRSA whole-genome sequences identified that the Australian CC398 isolates were closely related to the human-associated II-GOI clade and the livestock-associated IIa clade. The identified CC398 MRSA clones were: PVL-positive ST1232-V (5C2&5), PVL-negative community-associated ST398-V (5C2&5) and livestock-associated ST398-V (5C2&5). Our findings demonstrate the importance of using WGS and comparing the sequences with international sequences to distinguish between CC398 CA-MRSA and LA-MRSA and to determine the isolates' origin. Furthermore, our findings suggest that CC398 CA-MRSA has become established in the Australian community and that ST398-V (5C2&5) LA-MRSA is now widespread in Australian piggeries. Our study emphasises the need for national One Health antimicrobial resistance surveillance programmes to assist in monitoring the ongoing epidemiology of MRSA and other clinically significant antimicrobial-resistant organisms.

Beyond CC398: Characterisation of Other Tetracycline and Methicillin-Resistant Staphylococcus aureus Genetic Lineages Circulating in Spanish Hospitals.

Tetracycline resistance (TetR) has been evidenced as a good phenotypic marker for detection of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) isolates of the clonal complex CC398. The aim of this study was to characterise a collection of 95 TetR-MRSA isolates, not belonging to the lineage CC398, that were obtained in a previous multicentre study, to detect other MRSA clonal complexes that could be associated with this phenotypic TetR marker. The TetR-MRSA isolates were recovered from 20 Spanish hospitals during 2016 and they were characterised to determine their antimicrobial resistance and virulence phenotypes/genotypes as well as the presence of the immune evasion cluster (IEC). A high proportion of isolates belonging to the CC1 lineage (46%) were observed, as well as to the CC5, CC8 and CC45 lineages (11% each one). Thirty-two different spa-types were identified, being predominantly CC1-t127 (40%) and CC45-t1081 (11%). The IEC system (with the gene scn as marker) was present in 73% of isolates and 16% produced the Panton Valentine leucocidin (PVL). A high proportion of MRSA-CC1 isolates were scn-negative (38.6%) and 52.9% of them were blaZ-negative. A multidrug resistance (MDR) phenotype was identified in 86% of MRSA isolates. The knowledge of other TetR-MRSA genetic lineages, in addition to CC398, is highly relevant, since most of them were MDR and some of them presented important virulence factors. Strains potentially associated with livestock (as the subpopulation CC1-t127-scn-negative) or with humans (as the CC45 lineage or the subpopulation CC1-scn-positive) have been found in this study. The use of tetracycline-resistance for detection, not only of CC398 but also of other LA-MRSA lineages should be tracked in the future.

Modelling environmentally mediated spread of livestock-associated methicillin-resistant Staphylococcus aureus in a pig herd

Infectious disease models are a useful tool to support within-herd disease control strategies. This study presents a stochastic compartment model with environmentally mediated transmission to represent the spread of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in a farrow-to-finish pig herd. The aims of the study were to (1) construct a model of the spread of LA-MRSA that included spread of LA-MRSA through the environment; (2) parameterise the model to fit previously published observational data in order to obtain realistic LA-MRSA transmission rates; (3) and to investigate how changes in the mixing of animals in the farrowing and finishing units may affect the prevalence of LA-MRSA in a herd. The results showed that indirect transmission allowed LA-MRSA to persist in the herd without the assumption of persistently shedding individuals. Reducing the mixing of pigs upon entry to the finishing unit was also shown to lower the LA-MRSA prevalence in the unit if the initial LA-MRSA level in the unit was low, but at high prevalence, no effect of mixing was identified. In the farrowing unit, changing the proportion of piglets that were cross-fostered did not affect the within-herd LA-MRSA prevalence. The study demonstrates that there are several important knowledge gaps regarding the shedding and transmission of LA-MRSA in different animal age groups and further experimental studies are needed. This work also provides a new, robust and flexible model framework for the investigation of control and mitigation strategies for LA-MRSA and other infections in a pig herd.

The emergence and molecular study of methicillin-resistant Staphylococcus aureus ST239, ST59, ST9, and ST630 in food animals, Chongqing, China

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) in animals is an increasing concern for the agriculture and public health. A four-years (2016) successional study was conducted to investigate the antimicrobial resistant profiles and molecular characterizations of the livestock-associated MRSA (LA-MRSA) from animal farms or slaughterhouses in Chongqing, China. A total of 1667 samples were collected from 2013 to 2016 in different animal farms and hog markets. LA-MRSA were isolated and subjected to antimicrobial susceptibility testing and whole genome sequencing (WGS). S. aureus was detected at a ratio of 3.7% (n = 62), in which 18 isolates were identified as MRSA. All the S. aureus isolates were multidrug-resistant (MDR) with the resistance to at least four drugs; however, none of those isolates was resistant to linezolid, vancomycin, or nitrofurantoin. The resistance was more obvious in the pig-associated S. aureus isolates than the strains associated with chickens or cows. The majority of multilocus sequence typing (MLST) types of the MRSA isolates were ST239, subsequently ST59, ST9, and ST630. Among these isolates, 18 MRSA possessed SCCmec type Ⅲ (n = 10), Ⅳa (n = 4), Ⅻ (n = 3) and Ⅴ(n = 1). Multiple spa types were also detected in the isolates, such as 899, 437, 30, 421, 969, 37, and 4549. This study indicates that MRSA could be transferred between humans and animals, and highlights the necessity of continuous surveillance of MRSA.

First isolation of ST398 methicillin-resistant Staphylococcus aureus carrying staphylococcal cassette chromosome mec type IVd from pig ears in Japan.

The emergence and increasing prevalence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) are a global concern. To investigate the prevalence and characteristics of sequence type 398 (ST398) MRSA in pig ears, 102 pig’s ears were collected from 102 animals shipped from 51 farms at an abattoir. Eight ST398 MRSA isolates were isolated from the ears of eight pigs shipped from seven farms. Of the eight ST398 isolates, seven had the staphylococcal cassette chromosome mec (SCCmec) type IVd and these were obtained from seven pigs shipped from six farms. Single nucleotide polymorphisms ranging from 13 to 26 were observed in the core-genome regions in the seven SCCmec type IVd isolates. We believe that this is the first report on the isolation of ST398 MRSA SCCmec type IVd in Japan.

An outbreak of livestock-associated meticillin-resistant Staphylococcus aureus (LA-MRSA) clonal complex 398 in a regional burns centre

Meticillin-resistant Staphylococcus aureus (MRSA) outbreaks have been reported previously in burns centres with resulting mortality and morbidity. This article describes the first human-associated outbreak in the UK caused by a strain of mupirocin-resistant (MuR) livestock-associated MRSA clonal complex 398 (LA-MRSA CC398) in an adult burns centre. The centre historically had a very low prevalence of MRSA infections. To describe the clinical and epidemiological context of how the outbreak was identified and contained using a range of infection prevention and control (IPC) measures guided by both traditional and genetic methods. A cluster of MuR-MRSA led to an outbreak investigation. Cases were detected via retrospective search and real-time laboratory surveillance. Isolates were sent continuously for whole-genome sequencing (WGS). A live timeline of cases and interventions was produced throughout the period. The outbreak consisted of 12 cases (seven males and five females) aged between 22 and 70 years. Patients were identified between May and October 2020. All patients were colonized rather than infected. The strain acquired the plasmid bearing MupA while colonizing the index case before dissemination. The index case was found to be a chicken farmer. This outbreak was eventually controlled using IPC measures, audits, and blind staff decolonization guided by insight from WGS. It was not possible to determine how the strain entered the centre, or if a staff carrier was involved. The outbreak demonstrated the potential for continued transmissions for months despite active surveillance and stringent control measures.