Bacteria possess a repertoire of distinct regulatory systems promoting survival in disparate environments. Under in vitro conditions it was demonstrated for the human pathogen Staphylococcus aureus that the expression of most virulence factors is coordinated by the global regulator agr. To monitor bacterial gene regulation in the host, we developed a method for direct transcript analysis from clinical specimens. Quantification of specific transcripts was performed by competitive reverse transcription-PCR, and results were normalized against the constitutively expressed gene for gyrase (gyr). Using sputum from cystic fibrosis (CF) patients infected with S. aureus we examined the transcription of the effector molecule RNAIII of agr, of spa (protein A), generally repressed by agr, and of hla (alpha-toxin), generally activated by agr. In the CF lung RNAIII was expressed poorly, indicating an inactive agr in vivo. Despite the low level of RNAIII expression, spa was detectable only in minute amounts and an irregular transcription of hla was observed in all sputum samples. After subculturing of patient strains agr-deficient isolates and isolates with unusual expression profiles, i.e., not consistent with those obtained from prototypic strains, were observed. In conclusion, the agr activity seems to be nonessential in CF, and from the described expression pattern of spa and hla, other regulatory circuits aside from agr are postulated in vivo.Over time, bacteria have evolved sophisticated regulatory circuits to modulate their gene expression in response to disparate environments (25). Our understanding of such adaptation processes during infection is limited by our ability to recreate host conditions in an experimental setting. Therefore, the sequential gene expression essential for host colonization, evasion of the immune system, tissue invasion, and maintenance in different organs remains to be determined for most bacterial infections. In recent years new approaches have been developed to identify bacterial genes which are induced during infection (15,23). While these methods are very useful for screening new candidate genes involved in pathogenesis, until now no method has been available to discern the transcription pattern of characterized virulence genes directly during infection.Staphylococcus aureus causes a variety of local and systemic infections in humans and is one of the most important community-acquired and nosocomially acquired pathogens. S. aureus infections are probably established via the coordinated synthesis of extracellular and cell-bound virulence factors (32). The expression of most virulence factors is controlled by the global regulator agr, which is thought to be a prime pathogenesis factor in S. aureus. The agr locus is composed of two divergent transcriptional units (RNAII and RNAIII). The RNA molecule RNAIII is the effector of the operon, which exhibits negative and positive regulatory functions (17, 29), activating extracellular proteins such as the hemolysins but repressing others, for exampl...

In cystic fibrosis (CF) patients early antibiotic treatment of lung infection has been shown to lead to Pseudomonas aeruginosa eradication. The present study determined: 1) the time period from eradication to new P. aeruginosa acquisition; 2) P. aeruginosa re-growth and new acquisition; and 3) the impact of eradication therapy on lung function, antimicrobial resistance, emergence of other pathogens and treatment costs.Ciprofloxacin and colistin were used to eradicate P. aeruginosa in 47 CF patients. Bacterial pathogens, lung function decline, P. aeruginosa antimicrobial resistance and anti-pseudomonal serum antibodies were assessed quarterly and compared with an age-matched CF control group. Additionally, costs of antibiotic therapy in both groups were assessed.Early antibiotic therapy leads to a P. aeruginosa free-period of a median (range) of 18 (4-80) months. New acquisition with different P. aeruginosa genotypes occurs in 73% of episodes. It also delays the decline of lung function compared with chronically infected patients, prevents the occurrence of antibiotic resistant P. aeruginosa strains, does not lead to emergence of other pathogens, and significantly reduces treatment costs. The treatment substantially lowers P. aeruginosa prevalence in CF.In conclusion, early antibiotic therapy exerts beneficial effects on the patient's clinical status and is cost-effective compared with conventional antibiotic therapy for chronically infected cystic fibrosis patients.

Background Pseudomonas aeruginosa chronic pulmonary infection is an unfavourable event in cystic fibrosis. Bacterial clearance is possible with an early antibiotic treatment upon pathogen isolation. Currently, no best practice exists for early treatment. The efficacy of two different regimens against initial P aeruginosa infection was assessed. Methods In a randomised, open-label, parallel-group study involving 13 centres, the superiority of inhaled tobramycin/oral ciprofloxacin compared with inhaled colistin/oral ciprofloxacin (reference treatment) over 28 days was evaluated. Patients were eligible if they were older than 1 year with first or new P aeruginosa isolation. Treatments were assigned equally by centralised balanced randomisation, stratified by age and forced expiratory volume in 1 s values. The participants and those giving the intervention were not masked to arm assignments. The primary endpoint was P aeruginosa eradication, defined as three successive negative cultures in 6 months. Analysis was by intention to treat. This trial was registered with EudraCT, number 2008-006502-42. Results 105 patients were assigned to inhaled colistin/ oral ciprofloxacin (arm A) and 118 to inhaled tobramycin/ oral ciprofloxacin (arm B). All patients were analysed. P aeruginosa was eradicated in 66 (62.8%) patients in arm A and in 77 (65.2%) in arm B (OR 0.90, 95% CI 0.52 to 1.55, p¼0.81). Following treatment, an increase in Stenotrophomonas maltophilia was noted (OR 3.97, 95% CI 2.27 to 6.94, p¼0.001) with no differences between the two arms (OR 0.89, 95% CI 0.44 to 1.78, p¼0.88). Conclusions No superiority of treatment under study was demonstrated in comparison to the reference treatment. Early eradication treatment was associated with an increase in S maltophilia.

The taxonomic position of members of the Mycobacterium abscessus complex has been the subject of intensive investigation and, in some aspects confusion, in recent years as a result of varying approaches to genetic data interpretation. Currently, the former species Mycobacterium massiliense and Mycobacterium bolletii are grouped together as Mycobacterium abscessus subsp. bolletii. They differ greatly, however, as the former M. bolletii has a functional erm(41) gene that confers inducible resistance to macrolides, the primary therapeutic antimicrobials for M. abscessus, while in the former M. massiliense the erm(41) gene is non-functional. Furthermore, previous whole genome studies of the M. abscessus group support the separation of M. bolletii and M. massiliense. To shed further light on the population structure of Mycobacterium abscessus, 43 strains and three genomes retrieved from GenBank were subjected to pairwise comparisons using three computational approaches: verage ucleotide dentity, enome to enome istance and single nucleotide polymorphism analysis. The three methods produced overlapping results, each demonstrating three clusters of strains corresponding to the same number of taxonomic entities. The distances were insufficient to warrant distinction at the species level, but met the criteria for differentiation at the subspecies level. Based on prior erm(41)-related phenotypic data and current genomic data, we conclude that the species M. abscessus encompasses, in adjunct to the presently recognized subspecies M. abscessus subsp. abscessus and M. abscessus subsp. bolletii, a third subspecies for which we suggest the name M. abscessus subsp. massiliense comb. nov. (type strain CCUG 48898T=CIP 108297T=DSM 45103T=KCTC 19086T).