Nosocomial and community-acquired spontaneous bacterial peritonitis: comparative microbiology and therapeutic implications.

In order to compare the microbiological characteristics of nosocomial and community-acquired episodes of bacterial peritonitis, 95 consecutive, spontaneous episodes were reviewed. Seventy of these episodes were bacteriologically documented. Fifty-three (55.8%) episodes were nosocomial and 42 (44.2%) were community acquired. A total of 78 pathogens were isolated, including 40 gram-positive cocci (34 streptococci, 6 Staphylococcus aureus), 35 gram-negative bacilli (including 23 Escherichia coli), 2 gram-positive bacilli and 1 yeast. Streptococci were found more frequently in community-acquired episodes (53.8%) than in nosocomial episodes (33.3%). Gram-negative bacilli were significantly more frequent in nosocomial episodes than in community-acquired episodes (56.4% vs. 33.3%, P<0.05). Nosocomial isolates were significantly more resistant to amoxicillin-clavulanic acid (48.7% vs. 18.4%, P<0.01) and cefotaxime (33.3% vs. 13.2%, P<0.05) than community-acquired isolates, but no difference was detected regarding resistance to ciprofloxacin. The results indicate that the empirical treatment of spontaneous bacterial peritonitis should differ for nosocomial and community-acquired cases.

Association between nasal carriage of Staphylococcus aureus and infection in liver transplant recipients.

We reviewed the records of 87 patients who underwent liver transplantation and who were screened by use of nasal swabs on the day before surgery. Twenty-four patients harbored methicillin-susceptible Staphylococcus aureus (MSSA), and 8 harbored methicillin-resistant S. aureus (MRSA). MSSA infection occurred in 3 (12.5%) of 24 MSSA carriers and in 2 (3.2%) of 63 noncarriers (nonsignificant). In contrast, MRSA infection occurred more frequently in MRSA carriers (7 [87.5%] of 8) than in MRSA noncarriers (8 [10.1%] of 79; P<.001). Nasal carriage of MRSA is associated with a very high risk of MRSA infection in liver transplant recipients.

Screening for Staphylococcus epidermidis markers discriminating between skin-flora strains and those responsible for infections of joint prostheses.

Fifty-four Staphylococcus epidermidis strains responsible for infections of joint prostheses and 23 strains isolated from skin flora were studied for markers of virulence, to discriminate invasive strains from normal flora. They were screened for binding to polystyrene and matrix proteins and for the presence of staphylococcal genes involved in adhesion. The ica operon involved in biofilm formation was the only marker discriminating between these 2 categories of strains.

Phenotypic and molecular typing of nosocomial methicillin-resistant Staphylococcus aureus strains susceptible to gentamicin isolated in france from 1995 to 1997.

Methicillin-resistant strains susceptible to gentamicin (Gm(s) MRSA) have emerged since 1993 in several French hospitals. To study whether particular clones have spread in various French cities and whether some clones are related to gentamicin-resistant (Gm(r)) MRSA strains, various methods (antibiotyping, phage typing, determination of SmaI macrorestriction patterns before and after hybridization with IS256 transposase and aacA-aphD probes) were used to compare 62 Gm(s) MRSA strains isolated from 1995 to 1997 in nine cities and 15 Gm(r) MRSA strains. Eighteen major SmaI genotypes were identified, of which 11 included only Gm(s) MRSA strains and 5 included only Gm(r) MRSA strains. Each of the Gm(r) MRSA strains contained 6 to 13 SmaI fragments hybridizing with the insertion sequence IS256, of which a single band also hybridized with the aacA-aphD gene. No such hybridizing sequences were detected in 60 of the 62 Gm(s) MRSA strains. Thus, the divergence between Gm(r) and Gm(s) MRSA strains is revealed, not only by their distributions in distinct SmaI genotypes but also by the differences in hybridization patterns. Two of the 62 Gm(s) MRSA strains had the uncommon feature of carrying several SmaI bands hybridizing with IS256, suggesting that they are possibly related to the Gm(r) MRSA strains grouped in the same SmaI genotype. Five of the 11 SmaI genotypes including only Gm(s) MRSA strains contained strains from diverse cities, isolated during different years and with different antibiograms, suggesting that some clones have spread beyond their cities of origin and persisted.

TEM-24 extended-spectrum beta-lactamase-producing Enterobacter aerogenes: long-term clonal dissemination in French hospitals.

OBJECTIVE: To investigate interstrain relatedness of TEM-24-producing Enterobacter aerogenes clinical strains isolated between 1993 and 1998 in 10 French hospitals from nine areas by pulsed-field gel electrophoresis (PFGE) and plasmid patterns. METHODS: Fifteen TEM-24-producing strains and a set of 16 control strains having various other antibiotic resistance phenotypes were genotyped by PFGE. Plasmid DNA from TEM-24-producing strains and transconjugants was analyzed. RESULTS: Analysis of XbaI macrorestriction patterns revealed only minor variations, and showed that all 15 TEM-24-producing strains were closely related. Some isolates originating from distant areas had indistinguishable patterns. According to their clustering correlation coefficients, they were also genomically distant from the control strains. Two plasmid patterns were observed in TEM-24-producing strains, one of them in 13 of the strains. Large plasmids of 85 kb encoding TEM-24 beta-lactamase were present in all isolates and, in all except one strain, could be transferred with high frequency by conjugation. CONCLUSIONS: These results confirm that the spread of the TEM-24 extended-spectrum beta-lactamase in France was essentially due to the dissemination of a single clone.

Phenotypic and genomic variation among Staphylococcus epidermidis strains infecting joint prostheses.

We studied the SmaI and SstII macrorestriction patterns of 54 Staphylococcus epidermidis strains isolated from 14 patients infected following the implantation of joint prostheses. Multiple strains from pus and infected tissue specimens of each patient were selected on the basis of different colony morphologies and drug resistance patterns. The same criteria were used to select 23 S. epidermidis strains from hand swabs of eight healthy individuals. For 10 of the 14 patients, all the intrapatient strains appeared to be closely or possibly related, whereas related strains were detected in the skin flora of only one of the eight healthy individuals. This observation suggests that, in most cases, the patients were infected by a single S. epidermidis clone which subsequently underwent rearrangements that yielded derivatives with divergent phenotypes and, occasionally, divergent macrorestriction patterns. The four patients whose specimens contained unrelated S. epidermidis strains were probably infected with several polyclonal strains.

Elution of six antibiotics bonded to polyethylene vascular grafts sealed with three proteins.

The elution of six antistaphylococcal antibiotics from vascular polyethylene grafts sealed with albumin, gelatin, or collagen were studied in an in vitro system. The antibiotics tested were pefloxacin, vancomycin, teicoplanin, fusidic acid, pristinamycin, and rifampicin. The grafts were impregnated by simple soaking in antibiotic (1 mg/ml). The data were fitted to an exponential model and antibiotic half-lives (t1/2) were calculated from the regression lines. All the antibiotics tested were bound to the protein sealants. Antibiotic release varied with the type of antibiotic and the sealant. Rifampicin was eluted most slowly, particularly with albumin- and gelatin-sealed grafts, with t1/2 at 4-5.5 hr and antibiotic activity was still found at 48 hr. The glycopeptides were also eluted more slowly from albumin or gelatin sealant than from collagen. Although large quantities of glycopeptides were initially bound, they were quickly eluted (t1/2 = 30-44 min) and there was no residual antibiotic activity at 24 hr. Pefloxacin, pristinamycin, and fusidic acid bound to collagen or gelatin sealants were the most rapidly eluted, with t1/2 of 3-14 min, but they were eluted more slowly from albumin-sealed grafts, with t1/2 of 22-90 min. In vitro studies can be useful for evaluating the binding of antibiotics to protein-sealed grafts before animal experiments or human testing.