A working scheme developed in our laboratory for identification (by species group and species) of coagulasenegative staphylococci (CNS) was evaluated with 201 consecutive isolates and then validated by using the reference method of Kloos and Schleifer (W. E. Kloos and K. H. Schleifer, J. Clin. Microbiol. 1: [82][83][84][85][86][87][88] 1975). This five-test simple scheme (referred to here as the simple scheme) combines the novobiocin susceptibility test with tests for urease, pyrrolidonyl arylamidase, ornithine decarboxylase, and aerobic acid from mannose. The addition of one or two tests within a particular species group could then positively identify the isolate. Two commercial systems, Staph-Zym (Rosco) and API-Staph (bioMérieux), along with results obtained by using Rosco diagnostic tablets (nongrowth tests), were also compared with the reference method. One isolate could not be identified even by the reference method. Of the remaining 200 strains, 191 (95.5%) strains were correctly identified with Staph-Zym and 171 strains (85.5%) were correctly identified with API-Staph. The most frequent clinical CNS species isolated were Staphylococcus epidermidis (50.5%), S. haemolyticus (18.5%), S. saprophyticus subsp. saprophyticus (16.0%), S. lugdunensis (6.0%), and S. warneri (2.5%). The simple scheme validated with the reference method has demonstrated an excellent correlation in the identification of the three most frequent species isolated: S. epidermidis, S. haemolyticus, and S. saprophyticus subsp. saprophyticus. With the simple scheme, identification of CNS was possible within 24 h after the enzymatic tests were used, whereas up to 72 h is necessary for the growth tests. This methodology would be very useful in any clinical microbiology laboratory for the presumptive identification of CNS species groups and species.Many studies have been initiated since 1958 as a result of the growing recognition that coagulase-negative staphylococci (CNS) are clinically important (28) in an attempt to classify these organisms (1, 21). In the 1970s, W. E. Kloos and K. H. Schleifer determined the natural relationships of CNS based on systematic studies that allowed these researchers to resolve and characterize different CNS species (14). Species were identified based on an ensemble of morphological, physiological, and biochemical characteristics, antibiotic susceptibility patterns, and cell wall composition.In the last decade, molecular studies contributed to a notable progress in the classification of staphylococci and in the development of methods for identifying them at the genus, species, subspecies, and strain levels (5). Although Staphylococcus epidermidis accounts for most CNS infections, many other species have been identified in association with human infections (3, 27, 29). The importance of CNS as major nosocomial pathogens is mainly associated with prosthetic and indwelling devices such as prosthetic joints, heart valves, pacemaker implants, ventricular-peritoneal shunts, and peritoneal dialysis catheters and with s...
Background Staphylococcus pseudintermedius is the leading cause of pyoderma in dogs and the frequent use of antimicrobial treatment is associated to the development of resistance to nearly all classes of antibiotics. Despite S. pseudintermedius significance, our understanding of the molecular mechanism of β-lactam resistance and its genetic diversity remains limited. We aimed to: i ) determine the phenotypic resistance profile of methicillin resistant Staphylococcus pseudintermedius (MRSP) isolated from infected dogs in three different veterinary hospitals in Buenos Aires, Argentina; ii ) identify the SCC mec elements and resistance genes; and iii ) analyze the clonal relationship between isolates and in regard of dominant lineages found in the world. Results In addition to the differential levels of β-lactam resistance, MRSP isolates ( n = 10) showed resistance to 5–6 families of antibiotics, and were therefore categorized as multidrug-resistant. All the isolates were variant of SCC mec V homologous to S. aureus ; additional SCC mec Finder analysis classified five of the genomes as SCC mec type V (5C2&5) with mecA (encodes for PBP2a) , mecRI and mecI and all the genes closely related to the reference SCC mec type V S. aureus TSGH17 strain. In the remaining five strains, mecA was present, although other genes associated with SCC mec V including mecR1 and mecI were missing. PBP2a was inducible in low level resistance strains (MRSP 8151), and constitutively expressed in MRSP 8150, suggesting different mecA regulatory mechanisms. MRSP isolates showed significant genetic diversity: eight PFGE clonal types and six multilocus-sequence typing (MLST) sequence types (STs) (339, 649, 919, 920, 921 and 922), including four new STs genetically distinct from STs reported in other geographic areas. Comparative genomics and phylogenetic analyses of the MRSP showed a correlation between the genetic content and the phenotypes, and established the genetic relationship between the isolates. Conclusions MRSP could be a threat to animal health due to it concerning level of antimicrobial resistance. Our study highlights genetic and epidemiological aspects of multidrug-resistant MRSP strains from Argentina showing high degree of correlation between the resistance genes and the phenotype of the isolates and, furthermore, they appeared evolutionary closer to major worldwide reported ST68 and...
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