Borderline oxacillin-resistant Staphylococcus aureus (BORSA) represents a quite poorly understood and inadequately defined phenotype of methicillin resistance. BORSA strains show low, borderline resistance to penicillinase-resistant penicillins (PRPs), with oxacillin MICs typically equal to 1-8 µg ml, and in contrast to methicillin-resistant S. aureus (MRSA), do not have an altered penicillin-binding protein, PBP2a, encoded by the mecA or mecC gene. Their resistance is typically associated with hyperproduction of beta-lactamases or, in some cases, point mutations in PBP genes. BORSA cannot be classified as either truly methicillin-resistant or truly methicillin-susceptible strains. However, they are frequently misidentified, which poses an obvious epidemiological and therapeutic threat. BORSA strains are commonly isolated from humans and animals, and are found both in hospitals and in a community setting. The epidemiology and clinical presentation of BORSA infections seem to be similar to those for MRSA; these infections are usually more severe than those caused by methicillin-sensitive S. aureus (MSSA). Treatment of severe infections caused by BORSA may be ineffective, even with larger doses of oxacillin. The available evidence suggests that BORSA represent a frequently neglected problem, and their emergence in new environments implies that they need to be monitored and accurately distinguished from MSSA and MRSA.
The aim of this study was to compare the spread of multidrug-resistant (MDR) and methicillin-resistant (MR) staphylococci in healthy dogs and in dogs with evident symptoms of infection. The samples from 172 healthy and 197 infected dogs were examined. The staphylococci were identified with conventional methods and by means of the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method (MboI). Susceptibility to 15 antibiotics from 10 different antimicrobial classes was tested. Resistance to methicillin was confirmed by the presence of Staphylococcus aureus mecA and S. sciuri mecA genes. Multidrug resistance was defined as resistance to three or more antimicrobial classes. The oral mucosa to be the most frequent site of staphylococcal colonization (55.8 %), followed by nasal cavity (44.2 %), and anus (32.6 %). The prevalence of MDR staphylococci in infected dogs was significantly higher than in the healthy animals (74/137 vs. 34/95, P = 0.006). The MR strains of S. pseudintermedius (2.9 %) originated solely from infected dogs. In contrast, the MR coagulase-negative strains (7.4 %) were isolated solely from healthy dogs. S. aureus strains originated from nasal swabs, MRSA strains were not isolated. MDR staphylococci and MR S. pseudintermedius are more common among infected dogs, but coagulase-negative staphylococci (mostly S. sciuri) seem to be a reservoir of methicillin resistance in healthy dogs.
BackgroundThe aim of this study was to assess the relatedness of molecular types of Staphylococcus aureus isolates colonizing cystic fibrosis (CF) patients with their antimicrobial resistance and prevalence of toxin genes.MethodsA total of 215 isolates from the airways of 107 patients with CF were tested for spa and SCCmec type, antimicrobial resistance and carriage of toxin genes.Resultst015, t084, t091, t700 and t002 were the largest group (approximately 25%) among all 69 identified spa types. Five new spa types, t14286, t14287, t14288, t14289 and t14290, were identified and registered. Isolates from CF patients were clustered into 11 multi-locus sequence typing clonal complexes, with CC30, CC22, CC97, CC45, CC15 and CC5 being the most frequent ones. Twelve (5.6%) methicillin-resistant S. aureus (MRSA) isolates and 102 (47.7%) multidrug-resistant isolates were identified, along with three SCCmec types (I, III and V). All isolates (both MRSA and methicillin-sensitive S. aureus) were Panton–Valentine leucocidin-negative, and 56.7% harbored egc genes. This was the first study documenting the presence of ST398-V-t571 livestock-associated MRSA in a European patient with CF.ConclusionThese findings imply that individuals with CF can also be colonized with animal-related ST398 MRSA, and justify constant monitoring of staphylococcal colonization and identification of epidemic S. aureus clones in this group.
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