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Bacterial spread between patients may contribute to the high prevalence of antibiotic-resistant pathogens within ICUs. The aim of this study was to evaluate the fate of Pseudomonas aeruginosa during the different antibiotic regimens. Susceptibility patterns and genotyping were performed to determine whether there was a predominant clone and to track the spread of resistant strains within the unit. Twenty-eight different ribotypes were found among 82 Pseudomonas isolates. Four ribotypes accounted for 42 (51%) isolates and were designated the ‘major clones’ occurring throughout multiple cycles. The ribotypes with multiple occurrences were more resistant to antibiotics than ribotypes that appeared only once. The correlation of antibiotic use with antibiotic resistance and the finding of a large number of ribotypes suggested that de novo development of antibiotic resistance is a likely event in P. aeruginosa. In addition, ribotypes associated with antibiotic resistance appeared to have a survival advantage and can become frequent colonizers in the ICU. [Copyright &y& Elsevier]

The target enzymes GyrA and ParC and two efflux pump regulatory genes mexR and nfxB were analysed to determine changes associated with fluoroquinolone resistance in Pseudomonas aeruginosa. Both low- and high-level ciprofloxacin resistance was associated with a Thr-83Ile substitution in GyrA. A ParC Ser-80Leu substitution was found in highly resistant isolates in tandem with the Thr-83Ile substitution in GyrA. Mutations in the efflux regulatory genes were associated with resistance only when in tandem with a mutation in GyrA or ParC. These data show that the main mechanism of fluoroquinolone resistance in P. aeruginosa is mediated primarily through mutations in GyrA, and that mutations in ParC and the efflux regulatory genes are secondary. [Copyright &y& Elsevier]

Antibiotic resistance is a major and well-known problem in intensive care units (ICUs) world-wide and previously susceptible isolates become resistant through the acquisition of resistance determinants from other bacteria or the development of mutations, as is the case in beta-lactam resistance. We evaluated the presence of resistance determinants involved in beta-lactam resistance and multi-resistance in order to establish the contribution of horizontal gene transfer to the spread of resistance in a surgical ICU during an antibiotic rotation study. Pseudomonas aeruginosa and Enterobacteriaceae isolates were selected and iso-electric focusing (IEF), DNA-typing methods such as specific beta-lactamase and specific integron PCRs were performed to determine the presence of beta-lactamases. The PCRs specific for IMP-1, OXA-1, and VIM-type beta-lactamases performed on the selected P. aeruginosa and Enterobacteriaceae isolates with MICs for cephalosporins >1 mg/l did not demonstrate any of these beta-lactamases. IEF for 14 pseudomonads, representing 7 genotypes from 9 patients, showed a beta-lactamase with a pI larger than 8.5 in 13 of the isolates. The integrase PCR was positive for only five isolates from three patients and conserved segment PCR showed integrons of variable sizes (700, 900, 1,400 and 1,500 bp). Each patient had its own integron types. It can be concluded that integrons and associated resistance determinants played only a minor role in the surgical ICU and beta-lactam resistance among P. aeruginosa isolates was most likely due to the derepression of its AmpC gene.

The objective of this study was to determine the activity of daptomycin, a novel lipopeptide, against European Gram-positive isolates (n = 1539). The MIC(90)-values of daptomycin against Staphylococcus aureus isolates was 0.25 mg/L, against Enterococcus faecalis 4 mg/L, against Enterococcus faecium 8 mg/L, 0.25 mg/L against Staphylococcus epidermidis, and 0.25mg/L against Streptococcus pneumoniae. Daptomycin was equally potent against antibiotic-susceptible and resistant strains within a particular species. Based on a breakpoint of 1 mg/L for S. aureus and group A streptococci, all isolates tested were susceptible to daptomycin. Based on a breakpoint of 4 mg/L for vancomcyin-susceptible E. faecalis 99.7% of these isolates were susceptible to daptomycin.

An increase in Haemophilus influenzae resistance has been documented around the world during the last 30 years. Resistance is due to the production of beta-lactamases, and/or changes to penicillin-binding protein (PBP) targets. The resistance problem has led to the need for new therapeutic strategies aimed at maintaining effective management of both upper respiratory tract infections (URTIs) and lower respiratory tract infections (LRTIs). Among antimicrobial agents tested, third-generation cephalosporins have been shown to possess excellent in vitro activity against beta-lactamase-positive and -negative isolates, corresponding with proven clinical efficacy in a wide range of RTIs. The role of H. influenzae in RTIs is outlined, changing trends in epidemiological surveillance studies monitored and implications for therapy, based upon results of clinical trials discussed.

The susceptibility of nasopharyngeal Streptococcus pneumoniae to eight antibiotics was studied in 482 children under 5 years of age with community-acquired pneumonia and in 429 healthy pneumococci carriers in Fortaleza, Brazil. Serotyping of strains with pooled and type-specific antisera was also performed. Overall, S. pneumoniae was isolated from 499/911 (55%) children. The carriage rate in children attending day-care centres was higher (72%) than in children with pneumonia (50%) (P<0.001). MIC determination in 441 strains revealed 45% to be intermediate penicillin-resistant and 4% high penicillin-resistant strains. Resistance rates to co-trimoxazole and erythromycin were 42 and 23%, respectively. Serotyping of 211 penicillin-resistant and 58 randomly selected penicillin-susceptible isolates showed that 78% of the strains belonged to paediatric serogroups 6, 14, 19 and 23 (86% of the penicillin-resistant and 51% of the penicillin-susceptible strains, P=0.001). Resistance rates of S. pneumoniae to penicillin and co-trimoxazole in Fortaleza were higher than previously reported in Brazil and associated with paediatric serogroups 6, 14, 19 and 23.

Global antibacterial resistance is becoming an increasing public health problem. Bacteria resistant to almost all of the available antibacterials have been identified. The pharmaceutical industry and fledgling biotechnology companies are responding to the threat of antibiotic resistance with renewed efforts to discover novel antibacterials in attempts to overcome bacterial resistance. Both short term and long term strategies are being vigorously pursued. Short-term efforts are focused on developing novel antibacterial agents with a narrow spectrum of action to combat the problem of gram-positive resistant bacteria. Long-term approaches include the use of microbial genomic sequencing techniques to discover novel agents active against potentially new bacterial targets. Better use of existing agents using pharmacodynamic data to optimise antibiotic regimens is increasingly being addressed and the hope is that such measures will prevail until the newer agents are available.

The objective of the study was to evaluate a rapid screening technique for the presence of mutations in the viral reverse transcriptase gene of HIV following prolonged therapy with zidovudine in patients with AIDS. Peripheral blood mononuclear cells (PBMCs) of 14 HIV-infected patients were analyzed by micro-titer point mutation assay (PMA) before therapy with zidovudine and after at least 10 months of treatment. In addition, five of these were analyzed longitudinally. Three nontreated HIV-seropositive individuals were tested as controls. To confirm the validity of the PMA, patients' material was also analyzed with the single strand conformational polymorphism (SSCP) assay. After 10-55 months of treatment, at codons 41, 70, and 215 a shift from predominantly wild type strains to a mixture of wild type and mutant strains (21%-100% mutant sequences) appeared in the majority of patients' PBMCs. At codons 67 and 219, the wild type strain persisted after therapy in all but 3 patients. Most mutations were detected by SSCP as well as by PMA, except for one mutation at codon 41 and one at codon 70. However, when the two mutations were both present, SSCP and PMA were both able to detect these mutations. In conclusion, both PMA and SSCP are rapid and simple methods for screening for mutations causing drug resistance in zidovudine-treated HIV-infected patients. Although PMA is more labor-extensive than SSCP, the advantage of PMA over SSCP is that it permits the quantitative detection of point mutations coding for zidovudine resistance. The application of these assays may improve procedures of monitoring and modifying antiretroviral therapy on an individual basis.

Cross-protection by anti-lipid A antibodies may be mediated by contribution to host defence mechanisms such as enhancement of bactericidal activity and phagocytosis. The lipid A-specific murine monoclonal antibody (mAb) E5 was evaluated in vitro for its ability to enhance antibacterial effects in concert with antibiotics in order to investigate underlying mechanisms for the proposed in vivo efficacy. The effect of antibiotic exposure of several E. coli strains on binding by mAb E5 was examined in solid phase enzyme-linked immunoassay (ELISA) and in complement activation and phagocytosis assays. MAb E5 binds scarcely to live E. coli, both encapsulated and unencapsulated, but exposure to subinhibitory concentrations of aztreonam and ceftriaxone led to enhanced binding of mAb E5 compared to mock treated strains. Enhanced binding of mAb E5 to aztreonam-treated E. coli O111:B4 or O7K1 resulted in a modest increase in complement consumption but complement-mediated phagocytosis by human polymorphonuclear leukocytes (PMN) of these complexes was not affected. It was concluded that exposure of E. coli to antibiotics induced specific alterations in the bacteria, resulting in accessbility of epitopes recognized by mAb E5. Enhanced binding was found to support complement-mediated host defense mechanisms and might contribute to better protection in a joint action of antibiotics and antibodies.