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Interpretive reading analyses the complete resistance profiles of bacteria to multiple antibiotics and infers the resistance mechanisms present; it aids therapeutic choice and enhances surveillance data. We evaluated the Advanced Expert System (AES), which interprets MICs generated by the VITEK 2. Ten European laboratories tested 42 reference strains and 76-106 of their own strains, representing important resistance genotypes. Interpretive reading by the VITEK 2 AES achieved full agreement with genotype data for 88-89% of strains, with the correct mechanism identified as one of two possibilities for a further 5-6%. Mechanisms inferred with 90% agreement with reference data included methicillin resistance in staphylococci, glycopeptide resistance in enterococci, quinolone resistance in staphylococci and Enterobacteriaceae, AAC(6')-APH(2")-mediated aminoglycoside resistance in Gram-positive cocci, erm-mediated macrolide resistance in pneumococci, extended-spectrum beta-lactamases (ESBLs) in Enterobacteriaceae and Pseudomonas aeruginosa, and acquired penicillinases in Enterobacteriaceae. VanA, VanB and VanC phenotypes of enterococci were distinguished reliably, and ESBL production was accurately inferred in AmpC-inducible species as well as Escherichia coli and Klebsiella spp. Mechanisms identified, but only as possibilities among several, included IRT-type beta-lactamases and individual aminoglycoside-modifying enzymes in Enterobacteriaceae. Most disagreements with reference data concerned pneumococci found to have high-level penicillin resistance by the VITEK 2 AES but previously determined, phenotypically, to have intermediate resistance. When ESBL production was inferred in E. coli and klebsiellae, the VITEK 2 AES edited susceptible results for cephalosporins (except cefoxitin) to resistant; when an acquired penicillinase was inferred in Enterobacteriaceae, piperacillin results were edited to resistant; and when staphylococci were found methicillin resistant, resistance was reported for all beta-lactams. Further editing may be desirable (e.g. of cephalosporin results for salmonellas inferred to have ESBLs). [ABSTRACT FROM AUTHOR]

OBJECTIVES: To investigate the presence of extended-spectrum beta-lactamases (ESBLs) among Pseudomonas aeruginosa clinical isolates referred to two Belgian reference laboratories. METHODS: Antibiograms were analysed for P. aeruginosa isolates referred between 2004 and 2008. Isolates resistant to ceftazidime (MIC > 8 mg/L) and with a positive double-disc synergy test between ceftazidime and clavulanate were serotyped and screened for the presence of ESBL-encoding genes. Genes encoding metallo-beta-lactamases (bla(MBL)) were sought by PCR in ESBL-producing isolates with positive imipenem/EDTA synergy tests. PFGE of SpeI-digested genomic DNA was used to compare isolates and selected strains were characterized by multilocus sequence typing. RESULTS: Forty-eight (2.2%) of 2150 P. aeruginosa isolates were confirmed as class A ESBL-producing isolates by molecular testing. bla(BEL) and bla(PER) alleles were detected, respectively, in 39 and 10 P. aeruginosa isolates originating from 16 hospitals (two isolates were simultaneously positive for BEL and PER). Fifteen of the isolates were found to co-produce ESBLs and VIM carbapenemases. These strains were pan-resistant and remained susceptible only to colistin (MICs

Objectives: To investigate the presence of extended-spectrum β-lactamases (ESBLs) among Pseudomonas aeruginosa clinical isolates referred to two Belgian reference laboratories. Methods: Antibiograms were analysed for P. aeruginosa isolates referred between 2004 and 2008. Isolates resistant to ceftazidime (MIC.8 mg/L) and with a positive double-disc synergy test between ceftazidime and clavulanate were serotyped and screened for the presence of ESBL-encoding genes. Genes encoding metallo-b-lactamases (blaMBL) were sought by PCR in ESBL-producing isolates with positive imipenem/EDTA synergy tests. PFGE of SpeI-digested genomic DNA was used to compare isolates and selected strains were characterized by multilocus sequence typing. Results: Forty-eight (2.2%) of 2150 P. aeruginosa isolates were confirmed as class A ESBL-producing isolates by molecular testing. blaBEL and blaPER alleles were detected, respectively, in 39 and 10 P. aeruginosa isolates originating from 16 hospitals (two isolates were simultaneously positive for BEL and PER). Fifteen of the isolates were found to co-produce ESBLs and VIM carbapenemases. These strains were pan-resistant and remained susceptible only to colistin (MICs≤2 mg/L). The majority of the ESBL-producing isolates belonged to the same PFGE clone and were identified as ST235; serotype O11. Conclusions: BEL enzymes were produced by 80% of P. aeruginosa isolates with phenotypic evidence of ESBL production. BEL or PER ESBLs co-existed with VIM carbapenemases in 15 isolates and caused outbreaks in four hospitals. Our data further highlight the epidemic potential of the international clone ST235, which may have acquired blaBEL-1 gene cassettes from a yet unidentified local gene reservoir. [ABSTRACT FROM AUTHOR]

Objectives: To determine susceptibility rates and patterns in Pseudomonas aeruginosa strains isolated from nosocomial infections.Methods: Seven hundred and sixteen P. aeruginosa isolates from 40 different hospitals in Belgium and the Grand Duchy of Luxembourg were collected in 1999.Results: Resistance rates varied significantly between hospitals. Of the fluoroquinolones, ciprofloxacin showed least resistance (24%), levofloxacin showed 27.5% resistance and ofloxacin 37.5%. Of the aminoglycosides, amikacin was the most potent antibiotic (10.5% resistance), followed by isepamicin (12%), tobramycin (19.5%) and gentamicin (23.5%). Of the beta-lactam antibiotics, meropenem was the most active (9.5% resistance); piperacillin and piperacillin/tazobactam had, respectively, 24% and 17.5% resistance, ceftazidime 28.5%, cefepime 29.5%, ticarcillin/clavulanic acid 37% and aztreonam 55.5%. MIC distribution curves show the presence of significant subpopulations, with MICs just below breakpoint for many antibiotics.Conclusion: Resistance of P. aeruginosa to penicillins, cephalosporins, fluoroquinolones and aminoglycosides varies between hospitals, but is increasing. [ABSTRACT FROM AUTHOR]

We have investigated the influence of subinhibitory concentrations of erythromycin on the interaction between Streptococcus pneumoniae and human respiratory epithelial cells. Confluent in vitro cell cultures were inoculated with erythromycin-resistant S. pneumoniae and incubated for 24 h. Erythromycin significantly reduced adherence of the pneumococci after 4 h and 24 h: 4.0% ± 0.7% (mean ± s.e.m.) of the pneumococci adhered to the epithelial cells in medium with erythromycin, compared with 7.7% ± 0.8% in medium without erythromycin (P = 0.002) after 4 h, and the corresponding values after 24 h were 24.2% ± 5.3% and 38.4% ± 5.0%, respectively (P = 0.038). Disruption of epithelial integrity by S. pneumoniae, measured as the decrease in transepithelial electrical resistance, was delayed in the presence of erythromycin. Neither addition of erythromycin to the culture medium nor infection of the cell cultures with pneumococci significantly affected secretion of interleukin-8 by the epithelial cells. Addition of erythromycin to a pneumococcal suspension in cell culture medium without respiratory epithelial cells almost completely prevented the release of pneumolysin. We conclude that erythromycin at subinhibitory concentrations reduces the adherence to and disruption of respiratory epithelial cells by S. pneumoniae, possibly by interfering with pneumolysin release. [ABSTRACT FROM PUBLISHER]

A subcutaneous catheter model in the rat was developed that allowed the study of prevention and treatment strategies for foreign body infection. In contrast to earlier models, the foreign body was inoculated with a low inoculum of Staphylococcus epidermidis just before implantation, thus mimicking intraoperative contamination with skin flora. Reproducible infection of all catheters followed if no prophylaxis was given. However, foreign body infection could be prevented or treated with antibiotics such as teicoplanin, which was marginally effective, and rifampicin, which proved very effective. [ABSTRACT FROM AUTHOR]

The genetic basis of macrolide resistance was characterized in 59 Streptococcus pneumoniae isolates. All isolates were collected in 1995 and 1997 and were from invasive infections. The majority of the isolates (54 of 59 isolates) were erythromycin and clindamycin resistant (MLS(B)-phenotype) and carried the ermAM gene. Five isolates were erythromycin resistant but clindamycin susceptible (M-phenotype). Using PCR the mefE gene was detected in these five isolates. Contrary to the situation found in Canada and the USA, mefE-mediated erythromycin resistance in S. pneumoniae is uncommon in Belgium. [ABSTRACT FROM AUTHOR]