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- Insights into the dynamics of methicillin-resistant staphylococci in animals : a focus on Staphylococcus pseudintermedius in dogsPublication . Couto, Natacha; Pomba, Maria Constança Matias Ferreira; Coelho, Ana Maria de Jesus Bispo VarelaStaphylococci are a group of bacteria with clinical, agricultural, and economic importance because of their wide range of virulence factors and ability to become resistant to antimicrobials. This thesis has pursued three main objectives: I. Determine the frequency of methicillin-resistant S. aureus (MRSA) strains in several animal species, identify the characteristics of strains present in animals and comparison with human strains MRSA nasal screening was performed in 71 horses and 307 calves, and the observed frequencies were 3% and 2%, respectively. Seventy-four MRSA isolated from 2001 to 2014 were characterized: fourteen spa types, three SCCmec types and three clonal complexes (CC) 5, CC22 and CC398, were found. Most isolates were multidrug-resistant. Fourteen MRSA CC398 strains had qac genes (13 qacG and 1 qacJ), while 4 isolates (three CC5 and one CC22) had insertions in the norA promoter gene. MRSA linages from pets (CC5 and CC22) harboured specific sets of virulence genes and a lower number of resistance genes than CC398 from livestock-animals. II. Reveal antimicrobial/biocide susceptibility patterns/trends and resistance genes in methicillin-resistant staphylococci (MRS) Several antimicrobial resistance patterns and genes were found in MRS from horses. Minimum bactericidal concentrations of biocides chlorhexidine acetate, benzalkonium chloride, triclosan and glutaraldehyde were lower than the recommended in-use concentrations for veterinary medicine, although two MRS carried plasmid-borne qacA and sh-fabI or qacB and qacH-like genes. An investigation on the evolution of resistance to 38 antimicrobials, corresponding mechanisms and molecular characteristics of 644 clinical Staphylococcus spp. isolates obtained from companion animals between 1999-2014 revealed resistance to the majority of antimicrobials and the number of mecA-positive strains increased significantly over time. Considering S. pseudintermedius, the methicillin-susceptible (MSSP) were genetically more diverse than methicillin-resistant (MRSP). All MRSP and two MSSP strains were multidrug- resistant, with several antimicrobial resistance genes identified. One MSSP isolate harbored a qacA and another a qacB gene. Three biocide products had high bactericidal activity (Otodine®, Clorexyderm Spot Gel®, Dermocanis Piocure-M®), while Skingel® failed to achieve a five log reduction in the bacterial counting. III. Study of the pathogenesis of S. pseudintermedius in dogs The agr type III predominated in MRSP. Five virulence genes were found in all strains and only spsO gene was significantly associated with MSSP. MSSP produced more biofilm on BHIB and BHIB+1% glucose than MRSP isolates. Several virulence genes encoding surface proteins and toxins were highly expressed in the MRSP strain (compared to MSSP). By whole proteome characterization of S. pseudintermedius through 2DE MALDI-TOF/TOF MS approach we were able to identify 367 unique proteins, of which 39 were surface proteins. By subsequent use of the serological proteome analysis (SERPA) approach we identified 4 antigenic proteins with promising features for vaccine development. These results indicate that MRS were widely disseminated in the studied animal population, the environment and people in contact with these animals. The resistant trends and mechanisms detected in MRS strains are worrying and make animals a reservoir of important MRS clones and genes. Biocides are still a good therapeutic choice, even in the presence of efflux genes. Higher expression of virulence genes may play a role in the rapid and widespread of MRSP clones. Dogs are able to mount an IgG-response against S. pseudintermedius and the proteins identified by the immune system can in the future be used as vaccine candidates.
- Nasal carriage of methicillin-resistant coagulase-positive staphylococci among cats and dogs hospitalized in the Veterinary Teaching Hospital of the Faculty of Veterinary Medicine – Technical University of Lisbon, PortugalPublication . Couto, Natacha; Pomba, Maria Constança Matias Ferreira; Guardabassi, LucaMethicillin-resistant coagulase-positive staphylococci (MRCPS) colonization in companion animals is an emerging and significant problem in public and animal health. During one year, nasal swabs were obtained from 40 cats and 146 dogs admitted to the Teaching Hospital of the Faculty of Veterinary Medicine - Technical University of Lisbon. MRCPS colonization was screened by plating enrichment cultures on a selective medium, Chrom MRSA ID. Bacterial species and mecA were confirmed by PCR. Clonality of the isolates was assessed by pulsed-field gel electrophoresis (PFGE). All isolates were subjected to spa and SCCmec typing. They were also tested by PCR for the lukF/lukS genes encoding Panton-Valentine leukocidin (PVL) in Staphylococcus aureus and Luk-I and Staphylococcus intermedius exfoliative toxin (SIET) in Staphylococcus pseudintermedius. Methicillin-resistant S. aureus (MRSA) was found in two cats (5 %) and one dog (0.6 %). Isolates were spa type t032, SCCmec IV and shared identical PFGE profiles. These were similar to the EMRSA-15 human clone. Strains were PVL-negative. Nine dogs carried methicillin-resistant S. pseudintermedius (MRSP) (6 %), whereas none of the cats was positive. The PFGE type A strain (n=1) showed identical characteristics as the American MRSP clone strains (CC68-MRSP-V), while PFGE cluster B grouped European MRSP isolates (CC71-MRSP-III) (n=8). All isolates were SIETnegative. The 8 European MRSP isolates were positive for the lukF/lukS genes and the American MRSP isolate was negative for both genes. Strains were multidrug-resistant, which represents a major challenge for veterinarians in terms of antibiotic therapy.
- Commonality of multidrug-resistant klebsiella pneumoniae ST348 isolates in horses and humans in PortugalPublication . Trigo Da Roza, Filipa; Couto, Natacha; Carneiro, Carla; Cunha, Eva; Rosa, Teresa; Magalhães, Mariana; Tavares, Luis; Novais, Ângela; Peixe, Luísa; Lamas, Luís P.; Oliveira, ManuelaABSTRACT - Multidrug-resistant (MDR) Klebsiella pneumoniae is considered a major global concern by the World Health Organization. Evidence is growing on the importance of circulation of MDR bacterial populations between animals and humans. Horses have been shown to carry commensal isolates of this bacterial species and can act as human MDR bacteria reservoirs. In this study, we characterized an extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae sequence type (ST) 348 isolate from a horse, an ST reported for the first time in an animal, using next-generation sequencing. We compared it with six other MDR K. pneumoniae ST348 human isolates previously identified in health-care facilities in Portugal using a core genome multi-locus sequence typing approach to evaluate a possible genetic link. The horse isolate was resistant to most of the antimicrobials tested, including 3rd generation cephalosporins, fluoroquinolones, and aminoglycosides, and presented several antimicrobial resistance genes, including blaESBL. Twenty-one allele differences were found between the horse isolate and the most similar human isolate, suggesting a recent common ancestor. Other similarities were observed regarding the content on antimicrobial resistance genes, plasmid incompatibility groups, and capsular and somatic antigens. This study illustrates the relevance of the dissemination of MDR strains, and enhances that identification of these types of bacterial strains in both human and veterinary settings is of significant relevance in order to understand and implement combined control strategies for MDR bacteria in animals and humans.