Browsing by Author "Moreno Grúa, Elena"

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have been a growing problem in human medicine since the 1960s, and more recently in veterinary medicine with the appearance of livestock-associated MRSA (LA-MRSA). Nevertheless, information about the presence of MRSA in rabbits is quite scarce since only one LA-MRSA identification has been previously reported. The present study aimed to determine genotypic characterization by verifying the presence of resistance determinants, virulence, and toxin genes of different S. aureus strains that cause lesions in rabbits, and their phenotypic traits based on the antimicrobial susceptibility profile. The analysis of 240 S. aureus isolates obtained from different lesion types collected from 89 Spanish and Portuguese rabbit commercial farms in the last 4 years (2014–2017) was performed. The methicillin-resistant gene mecA was found in 11.25% of the studied isolates (27 of 240) from 19 farms (13 Spanish and 6 Portuguese). Staphylococcal cassette chromosome mec (SCCmec) typing predominantly revealed type III (n = 15). Additionally, three MRSA isolates carrying the mecC gen were detected in samples from three different farms (two Spanish and one Portuguese). None of the 30 MRSA isolates was PVL-positive or tst-positive. After the multilocus sequence typing (MLST) procedure, 16 belonged to ST2855, 6 to ST146, 6 to ST398, and 2 ST4774. No ST121 isolate was mec-positive. ST398 and ST4774 isolates lacked the immuneevasion-cluster (IEC) genes. ST2855 strains were associated with the presence only of the sak gene, and ST146 isolates were ascribed to IEC type E. Therefore, this is the first description of LA-MRSA from rabbits belonging to ST2855. Interestingly, one ST2855 and two ST4774 isolates were mecC-positive, which could act as a mecCMRSA reservoir. More studies are needed to further characterize these isolates and their relationship with humans and other animal species.

En este trabajo, se ha estudiado el patógeno Staphylococcus aureus con especial atención a las cepas resistentes a meticilina. Para ello, se ha evaluado la presencia de S. aureus en granjas de conejos y en conejos silvestres. A continuación, se ha evaluado un hospedador frecuente de este patógeno, el conejo (Oryctolagus cuniculus). En primer lugar, se encontró una cantidad inesperada de cepas de MRSA de lesiones poco frecuentes conejos de granjas. Además, es la primera vez que se han descrito cepas mecC-MRSA aisladas de granjas de conejos. En segundo lugar, se detectó un alto porcentaje de portadores de S. aureus en conejos y liebres silvestres, siendo la oreja el principal nicho ecológico. Tras la secuenciación del elemento genético móvil SCCmec, dos tipos no descritos anteriormente fueron encontrados: uno que contiene el gen mecC y otro que contiene simultáneamente los genes mecA y mecC. Dos de estas cepas tenían además el SCCmec escindido del genoma. Finalmente, se observó que la selección genética por ganancia diaria promedio no afectó la capacidad de las hembras de conejos de generar una respuesta inmune y además favoreció la capacidad de respuesta del sistema inmunológico cuando éste se enfrenta a un desafío infeccioso con S. aureus.

Staphylococcal mastitis is a major health problem in humans and livestock that leads to economic loss running in millions. This process is currently one of the main reasons for culling adult rabbit does. Surprisingly, the two most prevalent S. aureus lineages isolated from non-differentiable natural clinical mastitis in rabbits (ST121 and ST96) generate different immune responses. This study aimed to genetically compare both types of strains to search for possible dissimilarities to explain differences in immune response, and to check whether they showed similar virulence in in vitro tests as in experimental intramammary in vivo infection. The main differences were observed in the enterotoxin gene cluster (egc) and the immune-evasion-cluster (IEC) genes. While isolate ST121 harboured all six egc cluster members (seg, sei, selm, seln, selo, selu), isolate ST96 lacked the egc cluster. Strain ST96 carried a phage integrase Sa3 (Sa3int), compatible with a phage integrated into the hlb gene (β-haemolysin-converting bacteriophages) with IEC type F, while isolate ST121 lacked IEC genes and the hlb gene was intact. Moreover, the in vitro tests confirmed a different virulence capacity between strains as ST121 showed greater cytotoxicity for erythrocytes, polymorphonuclear leukocytes and macrophages than strain ST96. Differences were also found 7 days after experimental intramammary infection with 100 colony-forming units. The animals inoculated with strain ST121 developed more severe gross and histological mastitis, higher counts of macrophages in tissue and of all the cell populations in peripheral blood, and a significantly larger total number of bacteria than those infected by strain ST96.

In recent decades, concern about rabbit welfare and sustainability has increased. The housing system is a very important factor for animal welfare. However, information about how different available housing types for female rabbits affect their health status is scarce, but this is an important factor for their welfare. Hence, the objective of this study was to evaluate the health status of female rabbits in five common housing systems: three different single-housing systems with distinct available surfaces and heights; a single-housing system with a platform; a collective system. Female rabbits in the collective and platform cages had greater cortisol concentrations in hair than those in the single-housing system with no platform. Haptoglobin concentrations and kit mortality rates during lactation were greater for the collective-cage female rabbits. The collective group had more culled females and more lesions than in the other groups. The main reasons for culling in all the groups were reproduction problems and presence of abscesses, and the collective group of females was the most affected. In conclusion, it appears that keeping females together in collective systems negatively affects their health status and welfare, while single-housing systems imply lower kit mortality rates during lactation and cortisol concentrations, and fewer lesions in female rabbits.

The aim of the work was to evaluate if genetic selection for daily gain may affect the immune system. Two experiments were performed. The first one involved 80 rabbit females and their first two litters to explore the effect of selection on the ability of animals to maintain immune competence. Two generations from a line selected for average daily gain (ADG) were evaluated (VR19 generation 19th, n = 43; VR37 generation 37th, n = 37). In females, the effect of selection and its interaction with physiological state were not significant for any trait. In litters, the selection criterion increased the granulocyte to lymphocyte ratio. The second experiment involved 73 19-week-old females (VR19, n = 39; VR37, n = 34) to explore the effect of genetic selection on immune response after S. aureus infection. The VR37 rabbit females had lower counts for total lymphocytes, CD5+, CD4+, CD8+, CD25+, monocytes, the CD4+/CD8+ ratio and platelets than those of VR19 (-14, -21, -25, -15, -33, -18, -11 and -11%, respectively; P < 0.05). VR37 had less erythema (-8.4 percentage points; P < 0.05), fewer nodules (-6.5 percentage points; P < 0.05) and a smaller nodule size (-0.65 cm3 on 7 day post-inoculation; P < 0.05) compared to VR19. Our study suggests that genetic selection for average daily gain does not negatively affect the maintenance of a competent immune system or the ability to establish immune response. It seems that such selection may improve the response to S. aureus infections.

The appearance of methicillin-resistant strains of Staphylococcus aureus (MRSA) in several animal species (including rabbits) has set o alarms for their capacity to act as reservoirs for this bacterium. This is especially important in wild animals given its epidemiological implications. The objectives of this study were to identify and characterize S. aureus, specifically MRSA, strains in wild lagomorph high-density areas. Ten hares and 353 wild rabbits from 14 towns with a high rabbit density in the Valencian region (eastern Spanish coast) were sampled. Swabs from the nasal cavity, ears, perineum and lesions (when present) were taken for microbiological studies. The detection of di erent genes and antibiotic susceptibility studies were also carried out. Of all the animals, 41.3% were positive for S. aureus, of which 63.3% were MRSA. Ears were the anatomical location with more S. aureus and MRSA strains. The more frequently identified MLST type was ST1945 (97.1%, 136/140). The mecA gene was found only in one sample. The rest (n = 139) carried the mecC gene and were included in CC130, except one. Penicillin resistance was detected in 28 mec-negative isolates and, in one case, bacitracin resistance. mecA isolate presented resistance to enrofloxacin and tetracycline, and 10 mecC isolates also showed bacitracin resistance. No MRSA isolate was positive for genes chp, sea, tst and PVL. Two ST1945 isolates contained IEC type E (comprising genes scn and sak). mecA-isolate was positive for blaZ. Of the 28 MSSA strains showing resistance to penicillin, 22 carried the blaZ gene. These surprising results highlight the marked presence of MRSA strains in wild rabbits in high-density areas.

Despite the enormous efforts made to achieve effective tools that fight against Staphylococcus aureus, the results have not been successful. This failure may be due to the absence of truly representative experimental models. To overcome this deficiency, the present work describes and immunologically characterizes the infection for 28 days, in an experimental low-dose (300 colony-forming units) intradermal model of infection in rabbits, which reproduces the characteristic staphylococcal abscess. Surprisingly, when mutant strains in the genes involved in virulence (JΔagr, JΔcoaΔvwb, JΔhla, and JΔpsmα) were inoculated, no strong effect on the severity of lesions was observed, unlike other models that use high doses of bacteria. The inoculation of a human rabbitized (FdltBr) strain demonstrated its capacity to generate a similar inflammatory response to a wild-type rabbit strain and, therefore, validated this model for conducting these experimental studies with human strains. To conclude, this model proved reproducible and may be an option of choice to check both wild-type and mutant strains of different origins.