Both Staphylococcus epidermidis and Staphylococcus aureus are important causes of infections associated with catheters and other medical devices. It has recently been shown that not only S. epidermidis but also S. aureus can produce slime and carries the ica operon responsible for slime production. In the operon, coexpression of icaA and icaD is required for full slime synthesis. In this study, the presence of icaA and icaD was determined in a collection of 91 staphylococcal (68 S. epidermidis and 23 S. aureus) strains from intravenous catheterassociated infections, in 10 strains from the skin and mucosa of healthy volunteers, and in two reference strains by a PCR method. Slime-forming ability was tested on Congo red agar plates; 49% of S. epidermidis strains from catheters and, surprisingly, 61% of S. aureus strains were icaA and icaD positive and slime forming. All the saprophytic strains turned out to be negative for both icaA and icaD and also non-slime forming. Two S. aureus and one S. epidermidis strain from catheters, detected as icaA and icaD positive by PCR analysis and as slime forming (black colonies) at 24 h on Congo red agar, at 48 h exhibited tiny red spikes at the center of black colonies. The onset of these variants could not be ascribed to a mutagenic potential of Congo red, which, in the Ames test, was devoid of mutagenicity. PCR analysis showed that these red variants were negative for both icaA and icaD and even lacking the entire icaADBC operon. The data reported indicate an important role of ica genes as a virulence marker in staphylococcal infections from intravenous catheters.Staphylococcus epidermidis is a saprophyte which is part of the normal mucosa and skin microflora. In recent years, however, S. epidermidis emerged, together with Staphylococcus aureus, as a frequent etiologic agent of infections associated with catheters and other indwelling medical devices. As they possess little intrinsic pathogenic power, staphylococci are usually regarded as opportunistic agents (16,18). Over the last few years, several studies have been done to elucidate the structures and pathogenetic mechanisms by which staphylococci are able to cause severe and irreducible infections associated with biomaterials (4, 13, 22). As far as S. epidermidis is concerned, polysaccharide slime (also called biofilm) seems to be the most important factor by which it adheres to and colonizes artificial materials (31). As for S. aureus, it was well known, until now, for its ability to express molecules which recognize host matrix proteins (8,10,23,32). It has recently been shown that S. aureus as well as S. epidermidis is capable of forming slime (2, 5, 9, 21, 23).Recently, the genetic control of slime production has begun to be elucidated (17), first in S. epidermidis and then in S. aureus (9, 21). Synthesis of the capsular polysaccharide is mediated by the ica operon. Upon activation of this operon, a polysaccharide intercellular adhesin is synthesized. This supports cell-to-cell bacterial contacts by means of a multila...

A collection of Enterococcus faecalis strains from clinical isolates, healthy individuals and the environment was screened for the presence of virulence factor genes, such as those for collagenbinding protein (ace), endocarditis antigen (efaA), haemolysin activator (cylA), gelatinase (gelE), aggregation substances (asa1 and asa373), a surface protein (esp) and two novel putative surface antigens (EF0591 and EF3314). Apart from some genes that were present in all strains (ace, efaA and EF3314), the gelE gene was the most common factor, although its presence did not correlate with its expression. The genes that encode Esp and CylA were never detected in endocarditis isolates, whereas an association was noted between the esp gene and isolates from urinary tract infection (UTI) and bacteraemia. An aggregation substance gene was always present in commensal strains. As for gelatinase, the presence of the cylA and asa genes did not correlate completely with their phenotypic expression. Generally, isolates from endocarditis, biliary stents and the environment were equipped with fewer virulence factors than isolates from other sources. UTI strains possessed the highest number of factors.

Group B streptococci (GBS) comprising three different sets of isolates (31 invasive, 36 noninvasive, and 24 colonizing isolates) were collected in Italy during the years 2002 to 2005. Clonal groups were established by pulsed-field gel electrophoresis (PFGE), and selected isolates were studied by multilocus sequence typing (MLST). GBS isolates were also characterized by classical and molecular techniques for serotyping and protein gene and antibiotic resistance profiling. Some serotypes were significantly associated with a particular isolate population: serotype Ia more frequently corresponded to invasive strains than other strains, serotype V was more frequently encountered among noninvasive strains, and nontypeable strains were more common among isolates from carriers. Four major clonal groups accounted for 52.7% of all isolates: PFGE type 1/clonal complex 1 (CC1) comprised mainly serotype V isolates carrying the alp3 gene, PFGE type 2/CC23 encompassed serotype Ia isolates with the alp1 or alpha gene, PFGE type 3/CC17 comprised serotype III isolates carrying the rib gene, and PFGE type 4/CC19 consisted mainly of serotype II isolates possessing the rib gene. The same serotypes were shared by isolates of different clonal groups, and conversely, isolates belonging to the same clonal groups were found to be of different serotypes, presumably due to capsular switching by the horizontal transfer of capsular genes. Erythromycin resistance (prevalence, 16.5%; 15 resistant isolates of 91) was restricted to strains isolated from patients with noninvasive infections and carriers, while tetracycline resistance was evenly distributed (prevalence, 68.1%; 62 resistant isolates of 91). Most erythromycin-resistant GBS strains were of serotype V, were erm(B) positive, and belonged to the PFGE type 1/CC1 group, suggesting that macrolide resistance may have arisen both by clonal dissemination and by the horizontal transfer of resistance genes.Streptococcus agalactiae (group B streptococcus [GBS]) is one of the leading causes of neonatal sepsis and meningitis (2,20,32). The colonization of the female genital tract with GBS is significantly associated with infections in neonates, and it should be carefully monitored. Moreover, GBS has also been recently recognized as an important pathogen in immunocompromised patients (12, 14, 37). The first-line agent against GBS infection is penicillin, and penicillin resistance among GBS strains has not been reported so far (5). However, for patients allergic to penicillin, macrolides (e.g., erythromycin) and lincosamides (e.g., clindamycin) are the alternative choices for the treatment of GBS infections. In the United States, the frequencies of resistance to erythromycin and clindamycin among GBS isolates have been reported to be approximately 37 and 17%, respectively (16).Two main mechanisms of erythromycin resistance in GBS isolates have been described previously (17,25). One mechanism is macrolide-specific efflux encoded by the mef(A)/mef(E) gene ( Capsular serotyping is the classic method fo...

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Enterococcus faecalis is among the predominant causes of nosocomial infections. Surface molecules like D-alanine lipoteichoic acid (LTA) perform several functions in gram-positive bacteria, such as maintenance of cationic homeostasis and modulation of autolytic activities. The aim of the present study was to evaluate the effect of D-alanine esters of teichoic acids on biofilm production and adhesion, autolysis, antimicrobial peptide sensitivity, and opsonic killing. A deletion mutant of the dltA gene was created in a clinical E. faecalis isolate. The absence of D-alanine in the LTA of the dltA deletion mutant was confirmed by nuclear magnetic resonance spectroscopy. The wild-type strain and the deletion mutant did not show any significant differences in growth curve, morphology, or autolysis. However, the mutant produced significantly less biofilm when grown in the presence of 1% glucose (51.1% compared to that of the wild type); adhesion to eukaryotic cells was diminished. The mutant absorbed 71.1% of the opsonic antibodies, while absorption with the wild type resulted in a 93.2% reduction in killing. Sensitivity to several cationic antimicrobial peptides (polymyxin B, colistin, and nisin) was considerably increased in the mutant strain, confirming similar results from other studies of gram-positive bacteria. Our data suggest that the absence of D-alanine in LTA plays a role in environmental interactions, probably by modulating the net negative charge of the bacterial cell surface, and therefore it may be involved in the pathogenesis of this organism.