Carmen Espinosa-Gongora

Carriage frequency, diversity and methicillin resistance of Staphylococcus aureus in Danish small ruminants.

The ecology of Staphylococcus aureus in animals has recently gained attention by the research community due to the emergence of livestock-associated methicillin-resistant strains (MRSA). We investigated carriage frequency and clonal diversity of S. aureus in 179 sheep and 17 goats in Denmark using spa typing and MLST. S. aureus was detected in 74 sheep (41%) and 11 goats (64%). The isolates belonged to 26 spa types (including six novel spa types) and 12 STs (including three novel STs). The most common lineage was ST133, which was found in 65% sheep and 55% goats. MRSA was found in three animals and two of them harboured mecC and corresponded to the same lineage (ST130, t843) previously reported in mecC-associated human MRSA infections in Denmark. The remaining MRSA isolate belonged to ST398 but its recovery in sheep could be a consequence of cross contamination due to contact with pigs. This study provides novel data about the occurrence of S. aureus in small ruminants, revealing high carriage frequency and diversity in these animals. The finding of mecC in ovine ST130 isolates suggests that sheep may be a reservoir of this new emerging MRSA clone of suspected animal origin. Inclusion of sheep in national MRSA surveillance programmes in animals is advisable in view of this finding.

Longitudinal study on transmission of MRSA CC398 within pig herds

BackgroundSince the detection of MRSA CC398 in pigs in 2004, it has emerged in livestock worldwide. MRSA CC398 has been found in people in contact with livestock and thus has become a public health issue. Data from a large-scale longitudinal study in two Danish and four Dutch pig herds were used to quantify MRSA CC398 transmission rates within pig herds and to identify factors affecting transmission between pigs.ResultsSows and their offspring were sampled at varying intervals during a production cycle. Overall MRSA prevalence of sows increased from 33% before farrowing to 77% before weaning. Overall MRSA prevalence of piglets was > 60% during the entire study period. The recurrent finding of MRSA in the majority of individuals indicates true colonization or might be the result of contamination. Transmission rates were estimated using a Susceptible-Infectious-Susceptible (SIS-)model, which resulted in values of the reproduction ratio (R0) varying from 0.24 to 8.08. Transmission rates were higher in pigs treated with tetracyclins and β-lactams compared to untreated pigs implying a selective advantage of MRSA CC398 when these antimicrobials are used. Furthermore, transmission rates were higher in pre-weaning pigs compared to post-weaning pigs which might be explained by an age-related susceptibility or the presence of the sow as a primary source of MRSA CC398. Finally, transmission rates increased with the relative increase of the infection pressure within the pen compared to the total infection pressure, implying that within-pen transmission is a more important route compared to between-pen transmission and transmission through environmental exposure.ConclusionOur results indicate that MRSA CC398 is able to spread and persist in pig herds, resulting in an endemic situation. Transmission rates are affected by the use of selective antimicrobials and by the age of pigs.

Human health risks associated with antimicrobial-resistant enterococci and Staphylococcus aureus on poultry meat

Enterococci and staphylococci are frequent contaminants on poultry meat. Enterococcus faecalis, Enterococcus faecium and Staphylococcus aureus are also well-known aetiological agents of a wide variety of infections resulting in major healthcare costs. This review provides an overview of the human health risks associated with the occurrence of these opportunistic human pathogens on poultry meat with particular focus on the risk of food-borne transmission of antimicrobial resistance. In the absence of conclusive evidence of transmission, this risk was inferred using data from scientific articles and national reports on prevalence, bacterial load, antimicrobial resistance and clonal distribution of these three species on poultry meat. The risks associated with ingestion of antimicrobial-resistant enterococci of poultry origin comprise horizontal transfer of resistance genes and transmission of multidrug-resistant E. faecalis lineages such as sequence type ST16. Enterococcus faecium lineages occurring in poultry meat products are distantly related to those causing hospital-acquired infections but may act as donors of quinupristin/dalfopristin resistance and other resistance determinants of clinical interest to the human gut microbiota. Ingestion of poultry meat contaminated with S. aureus may lead to food poisoning. However, antimicrobial resistance in the toxin-producing strains does not have clinical implications because food poisoning is not managed by antimicrobial therapy. Recently methicillin-resistant S. aureus of livestock origin has been reported on poultry meat. In theory handling or ingestion of contaminated meat is a potential risk factor for colonization by methicillin-resistant S. aureus. However, this risk is presently regarded as negligible by public health authorities.

Efficacy of 65% permethrin applied to dogs as a spot-on against Phlebotomus perniciosus

Leishmania infantum is a protozoan parasite causing leishmaniosis, a visceral disease transmitted by the bites of sand flies. As the main reservoir of the parasite, dogs are the principal targets of control measures against this disease, which affects both humans and dogs. Several studies have revealed the usefulness of topical insecticide treatment (collars, spot-ons and sprays) in reducing the incidence and prevalence of L. infantum. The present study was designed to test the efficacy of 65% permethrin applied to dogs as a spot-on against the sand fly vector Phlebotomus perniciosus. The duration of the desired effects was also estimated to help design an optimal treatment regimen. Twelve dogs assigned to treatment (n=6) and control (n=6) groups were exposed to sand flies once a week over a seven-week period. Repellent and insecticidal efficacies were estimated and compared amongst the groups. Our findings indicate satisfactory repellent, or anti-feeding, effects lasting 3 weeks and short-term insecticidal effects lasting 2 weeks after initial application. Accordingly, we recommend the use of this product every 2-3 weeks during the active phlebotomine sand fly period to protect dogs against the bites of P. perniciosus.

Mustelidae are natural hosts of Staphylococcus delphini group A

According to the current taxonomy, the Staphylococcus intermedius group (SIG) comprises of at least three distinct species. While S. intermedius and S. pseudintermedius are associated with specific hosts (pigeons and dogs, respectively), the natural host of S. delphini remains unclear. We analysed 158 SIG isolates from less studied animal species belonging to the order Carnivora, including mink (n=118), fox (n=33), badger (n=6) and ferret (n=1). Species identification was performed by nuc PCR in combination with sodA sequence analysis and pta PCR restriction fragment length polymorphism (RFLP). The results showed a consistent association between host and bacterial species. All isolates from minks, ferret and badgers belonged to S. delphini group A, whereas all fox isolates except one were identified as S. pseudintermedius. The remaining fox isolate belonged to S. delphini group A. The results indicate that Mustelidae such as minks, ferrets and badgers are natural hosts of S. delphini group A. This is in contrast with Canidae, which are primarily colonized and infected with S. pseudintermedius. These findings suggest that coagulase-positive staphylococcal species may have evolved and diverged through host adaptation.

Transmission of MRSA CC398 strains between pig farms related by trade of animals

Meticillin-resistant Staphylococcus aureus (MRSA) clonal complex (CC) 398 is a genetic lineage associated with livestock, especially pigs. The authors investigated the role of pig trade in the transmission of MRSA CC398 between farms using pulsed-field gel electrophoresis (PFGE), a highly discriminatory method for strain typing. PFGE analysis of 58 MRSA isolates from a retrospective study in the Netherlands and a prospective study in Denmark provided molecular evidence that the strains present in five of the eight recipient farms were indistinguishable from those occurring in the corresponding supplying farm. The molecular typing data confirm the findings of a previous risk-analysis study indicating that trading of colonised pigs is a vehicle for transmission of MRSA CC398.

Occurrence and distribution of Staphylococcus aureus lineages among zoo animals

Abstract The current knowledge of the occurrence and diversity of Staphylococcus aureus in animals is largely biased in favor MRSA and domestic animals. In order to generate novel information on the ecology and population structure of this bacterial species in the animal kingdom, we investigated the occurrence and genotypic diversity of S. aureus in a range of animal species kept at the Copenhagen Zoo. We sampled 146 animals belonging to 25 mammalian species and 21 reptiles belonging to six species. A total of 59 S. aureus isolates were found in 10 of the 25 mammalian species tested. All isolates were MSSA belonging to fourteen spa types, including three novel spa types. MLST revealed the occurrence of seven STs. The study of the ecology of commensal S. aureus in captive wild animals revealed that ST133 has a broader host range than previously thought.

MRSA carrying mecC in captive mara

Objectives To characterize the staphylococcal cassette chromosome mec (SCCmec), virulence and antimicrobial susceptibility of Staphylococcus aureus ST130 isolated from mara (Dolichotis patagonum), a large rodent species native to South America and kept in captivity at Copenhagen Zoo. Methods The presence of mecC was confirmed by PCR in 15 S. aureus ST130 isolated from mara during a previous study. WGS was performed on two randomly selected isolates to characterize their genomes with respect to SCCmec, virulence and resistance gene content. Antimicrobial susceptibility was tested using commercial broth microdilution tests. Results All the isolates belonged to spa type t528 ST130 and carried mecC. Based on WGS, mecC was 100% identical to the prototype sequence of S. aureus strain LGA251. The sequence of SCCmec type XI in the mara isolates had 23 SNPs compared with the one described in LGA251. The two sequenced strains harboured a set of virulence factors and other genomic features previously observed in ST130. Both strains carried norA as the only putative antimicrobial resistance gene in addition to mecC. Conclusions Our findings support the notion that a genetically conserved mecC-carrying MRSA ST130 clone is widespread in a variety of unrelated hosts in Denmark. Since the mara at Copenhagen Zoo have limited contact with humans and other animal species, it remains unclear whether mara are natural hosts of ST130 or acquired this lineage from unknown sources. The broad host range of MRSA ST130 supports its designation as a generalist lineage.

Comparative host specificity of human- and pig- associated Staphylococcus aureus clonal lineages.

Bacterial adhesion is a crucial step in colonization of the skin. In this study, we investigated the differential adherence to human and pig corneocytes of six Staphylococcus aureus strains belonging to three human-associated [ST8 (CC8), ST22 (CC22) and ST36(CC30)] and two pig-associated [ST398 (CC398) and ST433(CC30)] clonal lineages, and their colonization potential in the pig host was assessed by in vivo competition experiments. Corneocytes were collected from 11 humans and 21 pigs using D-squame® adhesive discs, and bacterial adherence to corneocytes was quantified by a standardized light microscopy assay. A previously described porcine colonization model was used to assess the potential of the six strains to colonize the pig host. Three pregnant, S. aureus-free sows were inoculated intravaginally shortly before farrowing with different strain mixes [mix 1) human and porcine ST398; mix 2) human ST36 and porcine ST433; and mix 3) human ST8, ST22, ST36 and porcine ST398] and the ability of individual strains to colonize the nasal cavity of newborn piglets was evaluated for 28 days after birth by strain-specific antibiotic selective culture. In the corneocyte assay, the pig-associated ST433 strain and the human-associated ST22 and ST36 strains showed significantly greater adhesion to porcine and human corneocytes, respectively (p<0.0001). In contrast, ST8 and ST398 did not display preferential host binding patterns. In the in vivo competition experiment, ST8 was a better colonizer compared to ST22, ST36, and ST433 prevailed over ST36 in colonizing the newborn piglets. These results are partly in agreement with previous genetic and epidemiological studies indicating the host specificity of ST22, ST36 and ST433 and the broad-host range of ST398. However, our in vitro and in vivo experiments revealed an unexpected ability of ST8 to adhere to porcine corneocytes and persist in the nasal cavity of pigs.

Phenotypes and genotypes of old and contemporary porcine strains indicate a temporal change in the S. aureus population structure in pigs

Introduction Staphylococcus aureus sequence type ST398 has recently gained attention due to the spread of methicillin-resistant strains among people exposed to livestock. The aim of this study was to explore temporal changes in the population structure of S. aureus in pigs over the last 40 years with particular reference to the occurrence of ST398. Methods We analysed a unique collection of 91 porcine strains isolated in six countries between 1973 and 2009 using a biotyping scheme described in the 1970s in combination with spa typing and multi-locus sequence typing (MLST). The collection comprised 32 historical isolates from 1973–1974 (n = 19) and from 1991–2003 (n = 13), and 59 contemporary isolates from 2004–2009. The latter isolates represented the most common MLST types (ST1, ST9, ST97 and ST433) and spa types isolated from pigs in Europe. Results and Discussion S. aureus sequence type ST398 was not found among old isolates from the 1970s or from 1991–2003, suggesting that this lineage was absent or present at low frequencies in pigs in the past. This hypothesis is supported by the observed association of ST398 with the ovine ecovar, which was not described in pigs by studies carried out in the 1970s. In addition, various phenotypic and genotypic differences were observed between old and contemporary isolates. Some biotypes commonly reported in pigs in the 1970s were either absent (human ecovar) or rare (biotype A) among contemporary isolates. Nine clonal lineages found among old porcine isolates are occasionally reported in pigs today (ST8, ST30, ST97, ST387, ST1092, ST2468) or have never been described in this animal host (ST12, ST133, ST1343). These results indicate that the population structure of porcine S. aureus has changed over the last 40 years and confirm the current theory that S. aureus ST398 does not originate from pigs.