Slime-producing Coagulase-negative Staphylococci Research Articles

Bottle Contamination

Bottle Contamination

Isolation and Characterization of a Novel 20-kDa Sulfated Polysaccharide from the Extracellular Slime Layer of Staphylococcus epidermidis

Slime-producing coagulase-negative staphylococci have emerged as important pathogens especially in immunocompromised hosts and patients with implanted devices. Although the extracellular slime layer is considered an important virulence factor, the chemical composition of the slime polysaccharide(s) remains unknown. The crude slime product derived from two reference Staphylococcus epidermidis strains (ATCC 35983 and 35984) and two clinical isolates was found to contain protein (11-20.5%), hexosamines (8-19%), neutral sugars (12.2-14%), phosphates (4-9.5%), uronic acids (1-13%), and small amounts of sulfates (0.5-3%). Preparative anion-exchange chromatography separated a main carbohydrate component which was isolated by combined chromatographies on DEAE-Sephacel and Sepharose CL-6B. HPLC and electrophoreses on polyacrylamide gel and cellulose acetate membrane revealed the presence of one species of low-sulfated polysaccharide with a relative molecular mass of 20-kDa. Chemical analyses of the polysaccharide showed that it is rich in glucosamine (46%) and neutral sugars (30-34%) with small amounts of sulfates (5.7-6.5%) and glucuronic acid (2.9-3.4%). Ten percent of the glucosamine is sulfated at the amino group. The neutral monosaccharides present are glucose, fucose, and xylose with glucose as the predominant one. It is estimated that the polysaccharide consists of 61-65 molecules of glucosamine (6-7 of which are N-sulfated), 30-35 neutral monosaccharides, 3-4 molecules of glucuronic acid, and 1-3 of fucose and xylose. Isolation and characterization of such a polysaccharide from the extracellular slime layer of S. epidermidis has not been previously reported. Its role to pathogenicity remains to be elucidated.

Antibiotic Susceptibility of Coagulase-negative Staphylococcal Blood Isolates with Special Reference to Adherent, Slime-producing Staphylococcus epidermidis Strains

The epidemiologic relationship between slime-producing coagulase-negative staphylococci and antibiotic resistance was evaluated by analyzing the in vitro susceptibility of 278 blood isolates to 10 different antimicrobial agents. The strain collection consisted of 60 coagulase-negative staphylococcal septicemia isolates, recovered from at least 2 successive blood cultures from 59 septicemia patients and 218 single blood isolates defined as insignificant. When the slime-producing Staphylococcus epidermidis isolates were compared with all non-slime-producing S. epidermidis isolates, the slime-producing isolates exhibited higher MIC50 and/or MIC90 values than the non-slime-producing isolates, and were also more commonly resistant against many of the antimicrobials tested. The association between slime production and resistance against tobramycin, gentamicin and rifampicin was statistically significant (p less than 0.05). A similar finding was observed among the S. epidermidis septicemia isolates when they were analyzed separately from the single (suspected blood contaminant) S. epidermidis isolates. Further characterization of the septicemia isolates revealed that the positive correlation between slime production and antibiotic resistance reflected, to some extent, multiresistance of 1 epidemic slime-producing S. epidermidis strain. No difference in resistance was observed between the slime-producing and non-slime-producing single S. epidermidis blood isolates.

Association of coagulase-negative staphylococcal slime production and adherence with the development and outcome of adult septicemias

The relationship of coagulase-negative staphylococcal slime production and adherence with the development and outcome of bloodstream infections in two Finnish hospitals was evaluated. Analysis of 64 strains from 62 adult septicemias disclosed 34 (53%) adherent slime producers. In comparison, only 142 (29%) of 489 single blood culture isolates were adherent slime producers. Although tube adherence test-positive strains were significantly (P less than 0.001) more common among the septicemia strains than among clinically insignificant isolates, almost half of the septicemia cases were caused by tube test-negative strains. Thus, regarding any single patient isolate, a cautious posture to the clinical impact of positivity in the tube adherence test seems warranted. Moreover, adherence and slime production, as such, apparently played no role in the clinical outcome of these infections. The epidemiologic findings revealed that slime-producing coagulase-negative staphylococci were common in the hospital environment and suggested that epidemic spread of such strains was influenced by antimicrobial therapy. Collectively, these results indicate that, at least in these two hospitals, positivity in the tube was of minor importance in guiding clinical decisions in treating adult septicemias.

Sequential analysis of staphylococcal colonization of body surfaces of patients undergoing vascular surgery

Slime-producing coagulase-negative staphylococci are pathogens in vascular surgery by virtue of their ability to adhere to and persist on prosthetic graft material. Inguinal and abdominal skin sites were cultured in 41 patients upon hospitalization, and slime production and antimicrobial susceptibility were assessed in all recovered staphylococcal isolates. Twenty-one patients eventually underwent lower-extremity revascularization. In the operative population, cultures were also obtained on the day of surgery and fifth postoperative day. All 21 patients received perioperative cefazolin. Of 327 coagulase-negative staphylococci recovered, Staphylococcus epidermidis (47%), S. haemolyticus (21%), and S. hominis (10%) were the predominant isolates. Slime-producing coagulase-negative staphylococci were recovered from 17 of 21 patients at admission but only from 8 of 21 patients on day 5 postoperation (P less than 0.05). S. epidermidis isolates demonstrated increasing multiple resistance from admission to 5 days postoperation to methicillin, gentamicin, clindamycin, erythromycin, and trimethoprim-sulfamethoxazole (P less than 0.05). All coagulase-negative staphylococcal isolates were susceptible to ciprofloxacin and vancomycin. Slime-producing capability was not associated with increased methicillin resistance for the recovered isolates. The data demonstrate that patients enter the hospital colonized with slime-producing strains of coagulase-negative staphylococci and that during hospitalization the staphylococcal skin burden shifts from a predominately susceptible to a resistant microbial population, which may enhance the importance of slime production as a risk factor in lower-extremity revascularization.

Staphylococcus epidermidis Extracted Slime Inhibits the Antimicrobial Action of Glycopeptide Antibiotics

Certain strains of Staphylococcus epidermidis produce a mucoid slime that appears to be an important virulence factor. After crude slime was isolated from selected strains of S. epidermidis, phenol and chloroform were used to remove proteins and lipids. The remaining extract contained a polysaccharide that was seen on SDS gels stained with Stains-all. This extract was an inhibitor of the antimicrobial action of vancomycin, raising the minimum inhibitory concentration (MIC) to vancomycin in all 18 isolates of S. epidermidis. A dose-response curve was seen between the amount of extract added and the degree of resistance, as measured by both MIC and growth curves. A similar effect was noted with MICs of organisms to teicoplanin. Addition of the extract did not change the MIC to LY146032, although a modest effect on growth rate was observed. The extract did not raise the MIC to clindamycin, rifampin, and cefazolin. The extract reversed the synergism seen between vancomycin and gentamicin in the 5 strains tested in time-kill studies. The interference by slime of the antimicrobial effect of vancomycin and teicoplanin may explain why these antibiotics are sometimes ineffective in eradicating foreign body infections due to slime-producing coagulase-negative staphylococci.

Absence of factors associated with significant urinary tract infections caused by coagulase-negative staphylococci.

Coagulase-negative staphylococci, excluding Staphylococcus saprophyticus, have recently been implicated as pathogens in urinary tract infections, especially in catheterized patients. In order to evaluate any laboratory markers for significant isolates of coagulase-negative staphylococci, we prospectively studied 72 patients with significant, indeterminant, or contaminant urine isolates of coagulase-negative staphylococci. Patients in the three categories did not differ by age, sex, presence of a urinary catheter, or other instrumentation or likelihood of nosocomial acquisition. The isolates from these three groups of patients were similar in antibiotic susceptibility and ability to produce slime. Overall, slime-producing coagulase-negative staphylococci were more likely to be S. epidermidis than any other species, but slime production was not associated with presence of pyuria, symptomatic urinary tract infection, instrumentation, nosocomial acquisition, or multiple antibiotic resistance. In this prospective study, no demographic characteristics or laboratory markers of coagulase-negative staphylococci were associated with clinical significance, as defined by symptoms or the presence of pyuria.