Transmission of MRSA between humans and animals on duck and turkey farms.

OBJECTIVES: The objectives of this study were to estimate the prevalence of MRSA on duck and turkey farms, identify risk factors for human carriage and study transmission between animals and humans. METHODS: On 10 duck and 10 turkey farms, samples were taken from animals, poultry houses, home residences and humans and cultured using pre-enrichment and selective enrichment. MRSA isolates were typed by spa typing and multiple-locus variable number tandem repeat analysis (MLVA) typing. A subset of isolates from animals and humans was investigated using whole-genome mapping. RESULTS: MRSA was found on one duck farm and three turkey farms. On duck farms, all humans were MRSA negative. On turkey farms, 5 of 11 farmers, 2 of 32 family members and 15 of 49 samples from the home residences were MRSA positive. Individuals with daily contact with turkeys were significantly more often MRSA positive than individuals without daily contact. All MRSA isolates belonged to livestock-associated MLVA complex 398, belonged to spa type t011, were negative for Panton-Valentine leucocidin, were mecC negative and were mecA positive. Whole-genome mapping proved a valuable tool to study the transmission of livestock-associated MRSA and showed that on two turkey farms the isolates from the animals and humans were indistinguishable or closely related, indicating transmission. CONCLUSIONS: MRSA carriage in individuals in daily contact with turkeys was significantly higher than that in individuals only living on the farms or than in the general Dutch population. Therefore, persons with a high degree of contact with turkeys have an increased risk of MRSA carriage, and we propose that they should be screened prior to hospitalization in order to decrease the risk of nosocomial transmission.

Transmission and persistence of livestock-associated methicillin-resistant Staphylococcus aureus among veterinarians and their household members.

After the first isolation of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in 2003, this MRSA variant quickly became the predominant MRSA obtained from humans as part of the Dutch national MRSA surveillance. Previous studies have suggested that human-to-human transmission of LA-MRSA, compared to that of other MRSA lineages, rarely occurs. However, these reports describe the transmission of LA-MRSA based on epidemiology and limited molecular characterization of isolates, making it difficult to assess whether transmission actually occurred. In this study, we used whole-genome maps (WGMs) to identify possible transmission of LA-MRSA between humans. For this, we used LA-MRSA isolates originating from a 2-year prospective longitudinal cohort study in which livestock veterinarians and their household members were repeatedly sampled for the presence of S. aureus. A considerable degree of genotypic variation among LA-MRSA strains was observed. However, there was very limited variability between the maps of the isolates originating from the same veterinarian, indicating that each of the veterinarians persistently carried or had reacquired the same LA-MRSA strain. Comparison of WGMs revealed that LA-MRSA transmission had likely occurred within virtually every veterinarian household. Yet only a single LA-MRSA strain per household appeared to be involved in transmission. The results corroborate our previous finding that LA-MRSA is genetically diverse. Furthermore, this study shows that transmission of LA-MRSA between humans occurs and that carriage of LA-MRSA can be persistent, thus posing a potential risk for spread of this highly resistant pathogen in the community.

Molecular characteristics of carbapenemase-producing Enterobacterales in the Netherlands; results of the 2014-2018 national laboratory surveillance.

OBJECTIVES: Carbapenem resistance mediated by mobile genetic elements has emerged worldwide and has become a major public health threat. To gain insight into the molecular epidemiology of carbapenem resistance in The Netherlands, Dutch medical microbiology laboratories are requested to submit suspected carbapenemase-producing Enterobacterales (CPE) to the National Institute for Public Health and the Environment as part of a national surveillance system. METHODS: Meropenem MICs and species identification were confirmed by E-test and MALDI-TOF and carbapenemase production was assessed by the Carbapenem Inactivation Method. Of all submitted CPE, one species/carbapenemase gene combination per person per year was subjected to next-generation sequencing (NGS). RESULTS: In total, 1838 unique isolates were received between 2014 and 2018, of which 892 were unique CPE isolates with NGS data available. The predominant CPE species were Klebsiella pneumoniae (n = 388, 43%), Escherichia coli (n = 264, 30%) and Enterobacter cloacae complex (n = 116, 13%). Various carbapenemase alleles of the same carbapenemase gene resulted in different susceptibilities to meropenem and this effect varied between species. Analyses of NGS data showed variation of prevalence of carbapenemase alleles over time with blaOXA-48 being predominant (38%, 336/892), followed by blaNDM-1 (16%, 145/892). For the first time in the Netherlands, blaOXA-181, blaOXA-232 and blaVIM-4 were detected. The genetic background of K. pneumoniae and E. coli isolates was highly diverse. CONCLUSIONS: The CPE population in the Netherlands is diverse, suggesting multiple introductions. The predominant carbapenemase alleles are blaOXA-48 and blaNDM-1. There was a clear association between species, carbapenemase allele and susceptibility to meropenem.