Synergistic hemolysis associated with coagulase-negative staphylococci isolated from bovine mammary glands.

A total of 353 coagulase-negative staphylococcus (CNS) isolates from infected bovine mammary glands were tested for cytolysin production by using the synergistic hemolysin assay (SHA). Overall, 34.6% of CNS isolates were SHA positive. Human-associated, coagulase-negative staphylococcal species contained the greatest number of SHA-positive strains. Milk leukocyte levels expressed as somatic cell counts (SCC) were elevated with SHA-positive Staphylococcus epidermidis, Staphylococcus hominis, and Staphylococcus warneri strains. Elevated SCC levels were associated with strains of Staphylococcus hyicus and Staphylococcus chromogenes. However, no difference in SCC levels was observed between SHA-positive and SHA-negative strains. Results indicated that the SHA was a sensitive test for the detection of cytolysin-producing CNS.     

Evaluation of the Staph-Zym system with staphylococci isolated from bovine intramammary infections

A total of 148 staphylococci isolated from bovine intramammary infections were used to evaluate the Staph-Zym system (ROSCO, Taastrup, Denmark). The overall accuracy of the system was 91.9%. The system correctly identified all strains of Staphylococcus aureus, Staphylococcus simulans, and Staphylococcus xylosus and 95% of Staphylococcus intermedius strains. Of 33 Staphylococcus hyicus strains, 31 (93.9%) were classified correctly by the Staph-Zym system, as well as 8 (80%) of 10 Staphylococcus chromogenes strains. All 11 Staphylococcus epidermidis strains and the 1 Staphylococcus haemolyticus strain included in the study were identified, but the Staph-Zym system had difficulty distinguishing strains of Staphylococcus warneri and Staphylococcus hominis from other species in the S. epidermidis group. The Staph-Zym system correctly identified all six S. xylosus strains and two of three Staphyloccus sciuri strains. The Staph-Zym system was considered an acceptable alternative to conventional methods for identification of bovine mammary gland isolates.     

Bovine lactoferrin binding to six species of coagulase-negative staphylococci isolated from bovine intramammary infections.

Bovine lactoferrin (BLf), an acute-phase iron-binding secretory protein present in secretions of the bovine udder, was demonstrated to bind to the following staphylococcal species associated with bovine intramammary infections: S. epidermidis, S. warneri, S. hominis, S. xylosus, S. hyicus, and S. chromogenes. The degree of 125I-labeled BLf uptake significantly varied among the blood agar-grown cells of all six species of coagulase-negative staphylococci tested. Isolates identified as S. xylosus demonstrated the highest (mean, 35.1 x 10(6) +/- 13.3 x 10(6) nmol) and S. hyicus the lowest (mean, 10.7 x 10(6) +/- 5.9 x 10(6) nmol) binding to 125I-BLf. BLf binding was optimum at an acidic pH, with time-dependent binding saturation ranging from 70 min for S. warneri to 240 min for S. hominis. The BLf-binding mechanism was specific, with affinity constants (Ka values) ranging between 0.96 x 10(6) and 11.90 x 10(6) liters/mol. The numbers of BLf-binding sites per cell, as determined by using Scatchard analysis, were as follows: S. epidermidis, 3,600; S. warneri, 1,900; S. hominis, 4,100; S. xylosus, 4,400; S. hyicus, 6,100; and S. chromogenes, 4,700. 125I-BLf binding to all species was inhibited by unlabled BLf and unlabeled human lactoferrin, whereas none of the various plasma, connective tissue, or mucosal secretory proteins or carbohydrates tested caused significant interference. BLf-binding receptors of the six coagulase-negative staphylococcal species demonstrated marked differences in patterns of susceptibility to proteolytic or glycolytic enzyme digestion and to heat or periodate treatment. These data suggest that the BLf-binding components in S. epidermidis and S. warneri are proteins containing glycosidyl residues. In the remaining four species, the proteinaceous nature of the BLf-binding component was evident, but the involvement of glycosidyl residues was not clear. Results of this study establish the presence of specific binding components for BLf on coagulase-negative staphylococci isolated from bovine intramammary infections.     

Detection of ica genes and slime production in a collection of Staphylococcus epidermidis strains from catheter-related infections in neutropenic patients

Slime production, principal virulence factor of Staphylococcus epidermidis associated with catheter-related infections is mediated by icaADBC operon wich expression is subject to phase variation. Reversible transposition of IS256 element into this operon is one of the most important mechanisms of biofilm phenotypic variation. Our study compared 28 S. epidermidis strains from catheter-related infection to 28 strains from nasal carriage concerning slime production on Congo red agar plate and ica genes and IS256 presence by PCR. ica operon was present among all slime-producing strains, and was absent among slime-negative strains. Only 79% of ica-positive strains were slime producers and no insertion of IS256 element was detected inside ica genes. A significative difference was found between catheter-related infections strains and commensal ones in terms of oxacillin (67,8 versus 35,7%) and ofloxacin resistance (75 versus 35,7%), slime production (64,2 versus 28,5%), phase variability (46,4 versus 7,1%) and ica genes presence (82,1 versus 35,7%). Our study demonstrates the role of ica genes, of phenotypic variability of slime production and antibiotic multiresistance as virulence factors of S. epidermidis associated with catheter-related infections; it confirms also the complexity and the diversity of regulation mechanisms implicated in biofilm formation.     

Slime production by bovine milk Staphylococcus aureus and identification of coagulase-negative staphylococcal isolates.

Staphylococcus aureus isolates from bovine milk were assessed for capsule or slime production. When pure S. aureus cultures in milk were inoculated directly into serum-soft agar constituted with a modified staphylococcus 110 medium, 100% of the isolates grew with diffuse colony morphology. Diffuse colony morphology was rapidly lost on subculture and was more rapidly lost in brain heart infusion-serum-soft agar. No evidence was seen for encapsulation in India ink preparations or by the clumping factor test. It was concluded that freshly isolated S. aureus strains produce slime, not true capsules. During examination of the 84 milk samples that grew staphylococci in addition to S. aureus (27.4%), a significant number of coagulase-negative staphylococcal species were encountered and identified by conventional tests as S. simulans (41.7%), S. xylosus (11.9%), S. epidermidis (3.6%), S. saprophyticus (3.6%), S. hyicus (2.9%), S. cohnii (1.2%), S. haemolyticus (1.2%), and S. warneri (1.2%). Five isolates (6.0%) were not identified. Attempts were also made to identify the isolates by the API Staph-Ident system, which gave an overall accuracy of 45.2%. The susceptibilities of the isolates to a variety of antibiotics were determined, and they appeared to be less resistant than human clinical isolates.     

Presence of icaA and icaD genes and slime production in a collection of staphylococcal strains from catheter-associated infections

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 catheter-associated 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.     

Collagen mediates adhesion of Streptococcus mutans to human dentin.

Some strains of Streptococcus mutans were found to recognize and bind collagen type I. Binding of 125I-labeled collagen type I was specific in that collagen types I and II, but not unrelated proteins, were able to inhibit binding of the labeled ligand to bacteria. Collagen binding to S. mutans was partially reversible and involved a limited number of bacterial binding sites per cell. S. mutans UA 140 cells bound collagen type I with high affinity (Kd = 8 x 10(-8) M). The number of binding sites per cell was 4 x 10(4). Collagen-binding strains of S. mutans were found to adhere to collagen-coated surfaces as well as to pulverized root tissue. S. mutans strains that did not bind the soluble ligand were unable to adhere to these substrata. Adherence to collagen-coated surfaces could be inhibited with collagen or clostridial collagenase-derived collagen peptides. Adherence of S. mutans to dentin was enhanced by collagen types I and II but inhibited by collagen peptides. S. mutans UA 140 bound significantly less 125I-collagen type I following treatment with peptidoglycan-degrading enzymes. These enzymes released a collagen-binding protein (collagen receptor) with a relative molecular size of 16 kDa. The results of this study suggest that collagen mediates adhesion of S. mutans to dentin. This interaction may target collagen-binding strains of S. mutans to dentin in the oral cavity and may play a role in the pathogenesis of root surface caries.     

Effect of milk on fibronectin and collagen type I binding to Staphylococcus aureus and coagulase-negative staphylococci isolated from bovine mastitis.

Tryptic soy broth (TSB)-grown cells of Staphylococcus aureus isolated from acute and chronic bovine mastitis bound mainly 125I-fibronectin (Fn) [corrected], whereas strains of nine species of coagulase-negative staphylococci showed a predominant interaction with 125I-collagen (Cn) [corrected] type I. A particle agglutination assay (PAA) was used to examine the interaction of coagulase-negative staphylococci with 125I-Fn and 125I-Cn immobilized on latex. All 368 coagulase-negative staphylococci demonstrated high 125I-Cn and moderate to low 125I-Fn interactions in the PAA. Cn-PAA reactivity was high among strains of Staphylococcus xylosus (84.2%), Staphylococcus simulans (77.8%), Staphylococcus epidermidis (76.7%), and Staphylococcus hyicus (74.3%), whereas all six Staphylococcus capitis strains clumped Cn-PAA reagent. Incubating TSB-grown cells in 10% skim milk for 1 h decreased the 125I-Fn- and 125I-Cn-binding affinity in most of the S. aureus and coagulase-negative staphylococci, while growth in 10% skim milk for 18 h resulted in more than 90% decrease or complete loss of interaction with these proteins. Decreased 125I-Fn binding in the presence of milk was correlated with protease production but not with 125I-Cn binding.     

Attachment of staphylococci to silicone catheters in vitro

The adherence of radiolabeled staphylococci to silicone catheters was investigated in vitro. Staphylococcus aureus and Staphylococcus epidermidis strains bound to the same extent to the catheters. Also, S. epidermidis strains isolated from patients with plastic-related infections showed binding similar to that of other S. epidermidis strains. By preincubation of catheters the influence of purified staphylococcal cell surface components on the binding was evaluated. The most potent inhibitors of the binding of S. aureus were the two surface proteins, clumping factor and protein A, and the cytoplasmic membrane. Surface proteins and the cell membrane of S. epidermidis also blocked the binding. Only protein-containing surface proteins inhibited the binding. The production of slime correlated with the degree of S. epidermidis binding. Human plasma and serum, as well as purified albumin and IgG, inhibited the binding of both staphylococcal species. Fibrinogen, and to a certain extent fibronectin, inhibited the binding of S. epidermidis, while both these purified plasma proteins enhanced the binding of S. aureus.     

Binding of fibronectin, fibrinogen and type II collagen to streptococci isolated from bovine mastitis

Binding of 125I-labelled fibronectin, fibrinogen and type II collagen to group B (S. agalactiae), group C (S. dysgalactiae and S zooepidemicus), group E (S. uberis) and nontypable streptococci isolated from bovine mastitis was studied. S. agalactiae and S. uberis were found to bind low levels of all three proteins, while S. zooepidemicus bound high levels. Binding of the proteins to S. dysgalactiae varied, i.e. fibronectin was high, fibrinogen moderate and collagen low. Nontypable strains showed moderate or low binding of all proteins. Both hydrophobic and hydrophilic strains were found to bind fibronectin. For S. dysgalactiae the specific fibronectin binding ranged from 70% to 10% and for S. zooepidemicus it was more than 80% and this binding was sensitive to papain treatment. The binding of 29K-fibronectin fragment to one S. dysgalactiae strain showed an affinity of KD = 2.6 x 10(-8) M and the number of binding sites per colony forming unit (CFU) was calculated at 11,000.     

A rapid PCR method for the detection of slime-producing strains of Staphylococcus epidermidis and S. aureus in periprosthesis infections.

In periprosthesis tissues, Staphylococcus epidermidis produces extracellular polysaccharide slime. Recently it has been shown that S. aureus also produces slime and that both S. epidermidis and S. aureus contain the ica operon responsible for slime production. In the operon, icaA encodes for N-acetylglutaminyltransferase, the enzyme for polysaccharide synthesis. However, co-expression of icaA and icaD is required for full slime synthesis. The slime-producing strains of both S. epidermidis and S. aureus are more virulent and are responsible for severe postsurgical or periprosthesis infections. The authors describe a simple, rapid, and reliable polymerase chain reaction method to detect icaA and icaD. The method was applied to the detection of ica genes on two reference strains, 15 strains each of S. epidermidis and S. aureus from periprosthesis infections and 10 strains from the skin and mucosa of healthy volunteers. icaA and icaD were detectable only in slime-producing strains (tested for slime production on Congo Red agar), and never in nonslime-producing ones. This method is a straightforward way of detecting the slime-producing ability by S. epidermidis and S. aureus. In clinical specimens this polymerase chain reaction method enables rapid diagnosis of virulent slime-producing strains with respect to the traditional culture method on Congo Red agar, which requires much more time. Rapid identification of the virulent properties of the bacterial strain responsible for a staphylococcal infection is crucial for deciding treatment.     

Regulation of slime production in Staphylococcus epidermidis by iron limitation.

Slime production by most strains of Staphylococcus epidermidis was enhanced by conditions of iron limitation produced by the addition of ethylenediamine-di-o-hydroxyphenol acetic acid to the growth medium. The density of the biofilm which formed on the base of microtiter plates was dependent on the degree of iron limitation, the stage of the growth cycle, and the nutritional state of the initial inoculum. One repeatedly slime-negative S. epidermidis strain, passaged in tryptic soya broth containing ethylenediamine-di-o-hydroxyphenol acetic acid, expressed high levels of slime after two passages. These observations suggest that iron limitation is one factor that regulates slime production by S. epidermidis. These findings could explain inconsistencies between the in vivo observation that biofilms invariably form on implanted catheters and the in vitro finding that some isolates from catheter-associated infection fail to produce slime.     

In catheter infections by Staphylococcus epidermidis the intercellular adhesion (ica) locus is a molecular marker of the virulent slime-producing strains.

Recently, it has been shown that S. epidermidis includes the ica operon responsible for slime production. In the operon, coexpression of icaA and icaD genes is required for full slime synthesis. In this study, the presence of icaA and icaD genes was searched for in a collection of 100 Staphylococcus epidermidis strains from catheter-associated infections by an original PCR method. Another 51 strains of S. epidermidis isolated from the skin or mucosa of healthy volunteers (26 of which derived from the hospital staff) were also investigated. Slime-forming ability was phenotypically tested on Congo red agar plates. Sixty-one percent of the strains isolated from catheters were icaA- icaD-positive and produced slime. The results indicate that detection of ica genes by a PCR method is a useful tool for prompt identification of S. epidermidis slime-forming strains isolated from catheter-related infections. Also, three saprophytic strains from the hospital staff were positive for slime synthesis and presence of ica genes, suggesting a potential diffusion of slime-forming strains in hospital personnel.     

Characteristic bacteriolytic activities of Staphylococcus hyicus.

Staphylococcus hyicus demonstrated characteristic bacteriolytic activities towards a Micrococcus luteus reference strain. This lytic activity was demonstrated on medium containing M. luteus cells as large zones of transparency around the culture streak. Smaller zones of transparency were observed with Staphylococcus intermedius, Staphylococcus chromogenes, and some strains of Staphylococcus aureus but not with other coagulase-negative staphylococcal species. The distribution and extent of the bacteriolytic activity could be useful as additional criteria for differentiation of S. hyicus.     

Adherence of slime-producing strains of Staphylococcus epidermidis to smooth surfaces.

Slime production is not a generally recognized feature of Staphylococcus epidermidis. In a recent outbreak of S. epidermidis intravascular catheter-associated sepsis, we noted that 63% of clinically implicated strains grew as a slimy film coating the culture tube walls when propagated in tryptic soy broth. Only 37% of randomly collected blood culture contaminants and skin isolates demonstrated a similar phenomenon (p less than 0.05). Transmission electron micrographs of these coating bacteria showed them to be encased in an extracellular matrix that stained with alcian blue. Slime production was most evident in autoclaved media containing Casamino Acids and glucose supplementation (0.25% wt/vol). There were strain and media preparation variability of slime production in the presence of other carbohydrates. Some strains were not able to produce slime under any of the tested conditions. The production or nonproduction of slime did not influence growth rate. When grown in vitro, slime producers accumulated on the surface of intravascular catheters as macrocolonies, whereas non-slime, producers did not. Transmission and scanning electron micrographs showed slime producers to be encased in an adhesive layer on the catheter surface, whereas nonproducers were not encased. These results suggest that slime-mediated adherence may be a critical factor in the pathogenesis of S. epidermidis infections of medical devices.     

Invasion of dentinal tubules by oral streptococci is associated with collagen recognition mediated by the antigen I/II family of polypeptides.

Cell surface proteins SspA and SspB in Streptococcus gordonii and SpaP in Streptococcus mutans are members of the antigen I/II family of polypeptides produced by oral streptococci. These proteins are adhesins and mediate species-specific binding of cells to a variety of host and bacterial receptors. Here we show that antigen I/II polypeptides are involved in the attachment of oral streptococci to collagen and that they also determine the ability of these bacteria to invade human root dentinal tubules. Wild-type S. gordonii DL1 (Challis) cells showed heavy invasion of tubules to a depth of approximately 200 microm, whereas the abilities of cells of isogenic mutant strains OB220 (sspA) and OB219 (sspA sspB) to invade were 50 and >90% reduced, respectively. Likewise, wild-type S. mutans NG8 cells invaded dentinal tubules, whereas cells of isogenic mutant strain 834 (spaP) did not. The invasive abilities of strains OB220 and OB219 were restored by heterologous expression of S. mutans SpaP polypeptide in these strains. The extents of tubule invasion by various wild-type and mutant strains correlated with their levels of adhesion to type I collagen, a major component of dentin. Furthermore, S. gordonii DL1 cells exhibited a growth response to collagen by forming long chains. This was not shown by ssp mutants but was restored by the expression of SpaP in these cells. The production of SspA polypeptide by S. gordonii DL1, but not production of SspB polypeptide by strain OB220 (sspA), was enhanced in the presence of collagen. These results are the first to demonstrate that antigen I/II family polypeptides bind collagen and mediate a morphological growth response of streptococci to collagen. These antigen I/II polypeptide activities are critical for intratubular growth of streptococci and thus for establishment of endodontic infections.     

Binding of von Willebrand factor by coagulase-negative staphylococci

Coagulase-negative staphylococci (CNS) are the most common infectious micro-organisms isolated from prosthetic devices. To determine whether von Willebrand factor (vWF) acts as an adhesin in bacterial recognition, bacterial binding of recombinant vWF (rvWF) was studied. Eleven CNS strains, belonging to S. epidermidis, S. haemolyticus and S. hominis species, bound soluble rvWF, but to a lesser extent than S. aureus. S. epidermidis strain H2-W bound 125I-labelled rvWF in a dose-dependent manner. The binding could be inhibited by unlabelled rvWF and thrombospondin, but not by fibrinogen, vitronectin or the carbohydrates N-acetylgalactoseamine, D-galactose, D-glucose, and D-fucose. Pre-incubation of rvWF with type I collagen and Arg-Gly-Asp-Ser (RGDS) peptides did not inhibit binding, whereas pre-incubation of rvWF with heparin decreased binding significantly. The interaction between CNS and rvWF was sensitive to proteinase treatment of bacterial cells. CNS strains bound to immobilised rvWF an extent greater or equal to the positive control strain S. aureus Cowan I. rvWF binding structures from bacterial cell wall were detected by immunoblot. Cowan I strain had 140-, 90- and 38-kDa binding molecules. S. haemolyticus strain SM131 and S. epidermidis strain H2-W had two (120 and 60 kDa) and five (120, 90, 60, 52 and 38 kDa) binding molecules, respectively. Similar binding structures were formed when cell wall extracts from these strains were incubated with thrombospondin. These results indicate that specific ligand-receptor interaction between CNS and rvWF may contribute to bacterial adhesion and colonisation on biomaterial surfaces. Heparin-binding domains of rvWF might be the crucial regions for bacterial attachment. rvWF and thrombospondin may recognise similar molecules in staphylococcal cell wall extracts.     

Identification of an antigenic marker of slime production for Staphylococcus epidermidis.

The pathogenic Staphylococcus epidermidis strain RP62A (ATCC 35984) adheres to smooth surfaces by forming a tenacious bacterial film known as slime. The mechanism of slime production is not known; however, workers in the laboratory of G. Pier (Harvard Medical School, Boston, Mass.) have isolated from RP62A a galactose-rich capsular polysaccharide adhesin (CPA) which mediates the attachment of the organism to smooth surfaces. We have obtained two daughter strains from RP62A that no longer produce slime. One daughter strain, H4A, was obtained by selection for a spontaneous variant; the other strain, HAM892, was obtained by treating growing cultures of RP62A with acriflavin. Using an antiserum generated against whole cells of RP62A, we have examined lysozyme-lysostaphin digests of RP62A, H4A, and HAM892 by double immunodiffusion. The two strains that no longer produced slime no longer produced a particular antigen, which we refer to as the slime-associated antigen (SAA). SAA was also produced by unrelated strains of slime-producing S. epidermidis. SAA was heat and protease stable, had a molecular weight of greater than 50,000, and could be partially purified by chromatographing trypsin-digested material over a Sephadex G-200 column. Chemical analysis of partially purified SAA by gas-liquid chromatography found SAA to be glucose rich (59%) and galactose poor (1.4%). This analysis chemically distinguished SAA from CPA. When tested together by double immunodiffusion with anti-RP62A and anti-CPA antisera, partially purified SAA did not cross-react with CPA. Kinetic studies suggested that SAA is a marker for surface accumulation whereas CPA mediates initial adherence.     

Correlation of penicillin minimum inhibitory concentrations and penicillin zone edge appearance with staphylococcal beta-lactamase production.

Production of staphylococcal beta-lactamase was shown to be correlated with penicillin G minimum inhibitory concentrations (MICs) of greater than 0.05 microgram/ml for 97% of the Staphylococcus aureus and 99% of the Staphylococcus epidermidis strains tested. However, it is important to note that of the isolates for which MICs were equal to or less than 0.05 micro/ml, a significant percentage (16% of S. aureus and 5% of S. epidermidis) were beta-lactamase producers. Thus, lack of beta-lactamase production, which implies susceptibility to penicillin, cannot be presumed solely on the basis of low MICs. Beta-lactamase production can be easily predicted from disk diffusion susceptibility tests by observing the appearance of the penicillin inhibition zone edge. A sharply demarcated edge was correlated with beta-lactamase production for 100% of the S. aureus and 93% of the S. epidermidis strains tested. The presence of this type of zone edge when a penicillin zone measures in the intermediate or susceptible range indicates that the isolate should be checked for beta-lactamase production.     

Bacterial components inhibit fibroblast proliferation in vitro

Perigraft fluid from Staphylococcus epidermidis infected grafts in a mouse model significantly inhibits fibroblast proliferation (60-98% at 7 and 28 days), compared with perigraft fluid from sterile grafts. The fibroblast inhibitor was trypsin-heat resistant and dependent primarily upon the bacteria, not the host proinflammatory mediators or the vascular graft biomaterial. We tested the inhibitory properties of S. epidermidis strains RP62A (slime producer) and RP62NA (nonslime producer) and Staphylococcus aureus strain 502a, using an in vitro tritiated thymidine murine fibroblast (ATCC CCL-12) proliferation assay. Whole killed bacteria, disrupted bacteria (live and killed), bacterial supernatants, and purified cell wall products (peptidoglycan, teichoic acid, and lipoteichoic acid from disrupted bacteria) were studied. Significant fibroblast inhibition occurred for all three bacterial strains with disrupted bacteria (live or killed) and cell free bacteria derived supernatants. The fibroblast inhibitor from disrupted slime producing S. epidermidis was trypsin-heat resistant. The fibroblast inhibitor from disrupted S. aureus and supernatants for all three bacterial strains at 1 x 10(7) were trypsin-heat sensitive. Fibroblast inhibition was not dependent upon bacterial viability and not mediated by bacterial cell wall products. In conclusion, components of slime and nonslime producing S. epidermidis and S. aureus inhibit fibroblast proliferation.