Derepressed beta-lactamase production as a mediator of high-level beta-lactam resistance in Pseudomonas cepacia

Clinical and in vitro evidence for the antimicrobial therapy in Burkholderia cepacia complex infections

Treatment of infections caused by Burkholderia cepacia complex (Bcc) in cystic fibrosis (CF) patients poses a complex problem. Bcc is multidrug-resistant due to innate and acquired mechanisms of resistance. As CF patients receive multiple courses of antibiotics, susceptibility patterns of strains from CF patients may differ from those noted in strains from non-CF patients. Thus, there was a need for assessing in vitro and clinical data to guide antimicrobial therapy in these patients. A systematic search of literature, followed by extraction and analysis of available information from human and in vitro studies was done. The results of the analysis are used to address various aspects like use of antimicrobials for pulmonary and non-pulmonary infections, use of combination versus monotherapy, early eradication, duration of therapy, route of administration, management of biofilms, development of resistance during therapy, pharmacokinetics-pharmacodynamics correlations, therapy in post-transplant patients and newer drugs in Bcc-infected CF patients.

Bugs, biofilms, and resistance in cystic fibrosis

Bacteria infect the respiratory tract early in the course of cystic fibrosis disease, often fail to be eradicated, and together with an aggressive host inflammatory response, are thought to be key players in the irreversible airway damage from which most patients ultimately die. Although incompletely understood, certain aspects of the cystic fibrosis airway itself appear to favor the development of chronic modes of survival, in particular biofilm formation; this and the development of antibiotic resistance following exposure to multiple antibiotic courses lead to chronic, persistent infection. In addition to the common cystic fibrosis pathogens, such as Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa, several newer species are becoming more common. Furthermore, new molecular techniques have led to the identification of multiple different organisms within respiratory secretions, many of which are not cultured with conventional tools. Future work should aim to develop clinically applicable methods to identify these and to determine which have the potential to impact pulmonary health. We outline the basic tenets of infection control and treatment.

Outer membrane permeability in Pseudomonas cepacia: diminished porin content in a beta-lactam-resistant mutant and in resistant cystic fibrosis isolates

Since beta-lactam resistance is a feature of Pseudomonas cepacia isolates causing pulmonary infections in cystic fibrosis (CF), this study was undertaken to determine whether alterations in beta-lactam permeability mediate drug resistance in this species. A beta-lactam-susceptible non-CF isolate (strain 75-26), a resistant mutant derived from 75-26 by selection for cross-resistance to ciprofloxacin and ceftazidime, and two resistant CF isolates of P. cepacia were used. Permeability constants were calculated from the rate of nitrocefin hydrolysis in intact bacterial cells. Qualitative changes in outer membrane proteins were determined electrophoretically. The permeability constants of the mutant and the resistant CF isolates were lower than the value for the reference strain, 75-26. Whereas the lipopolysaccharide side chains were present in the test and reference strains, the resistant mutant and the CF isolates contained reduced amounts of the 36-kilodalton (kDa) outer membrane protein and failed to express the 27-kDa outer membrane protein. These observations suggest that the 27-kDa outer membrane protein may be a major porin or a major protein component of the porin complex in P. cepacia and that decreased expression of the 36-kDa outer membrane and loss of the 27-kDa porin are associated with high-level beta-lactam resistance in some CF isolates of P. cepacia.