Five-Test Simple Scheme for Species-Level Identification of Clinically Significant Coagulase-Negative Staphylococci

Abstract

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...

Prevalence and antimicrobial susceptibility pattern of Coagulase-negative Staphylococcus

“…In another study among catheter related blood stream infections -96% were S. epidermidis [21] . Similarly in another study, of the isolated CoNS strains, 51% were S.epidermidis , 18% S.haemolyticus , 16% S. saprophyticus [22] . The results obtained in our study were similar coinciding with the fact that the most frequently isolated CoNS strain was S.epidermidis followed by S.haemolyticus .…”

Core genome conservation of Staphylococcus haemolyticus limits sequence based population structure analysis

“…Misidentification, or failure of identification of S. haemolyticus by conventional biochemical methods has been reported (De Paulis et al, 2003). This observation might result from structural rearrangements in the chromosome due to the presence of IS elements (Watanabe et al, 2007).…”

Comparison phenotypic and genotypic identification of Staphylococcus species isolated from bovine mastitis

“…The importance of identifying the species of CoNS in the clinical laboratories, for the determination of their physiopathological and epidemiological characteristics has been increasing. However, it is not an easy task, since phe- notypic tests can present similar results, hindering the obtaining of a result, as well as a great expense of time in the identification of the species (Bannerman 2003, De Paulis et al 2003.…”

“…The significance of S. aureus was well recognized not only to to animal health as well to human health. It is also imperative to point out the relevance of those other species to public health in view of the fact that S. epidermidis frequency among human isolates ranged from 43% to 92%, depending on the geographical region where the study was conducted (Ieven et al 1995, Couto et al 2001, Vuong & Otto 2002, De Paulis et al 2003, Spanu et al 2003, Cunha et al 2004, Caierão et al 2006. Among hospitalized Brazilian patients Pereira (2014) studying 300 CoNS isolated by blood cultures from verified that S. epidermidis was the most frequent identified specie (74.3%) and followed by S. haemolyticus 27 (9.0%), S. hominis 22 (7.3%), S. warneri 14 (4.7%), S. lugdunensis 9 (3.0%) e S. capitis 5 (1.7%).…”