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This work aimed to evaluate the predatory activity of Bdellovibrio bacteriovorus 109J on clinical isolates of Pseudomonas aeruginosa selected from well-characterized collections of cystic fibrosis (CF) lung colonization (n = 30) and bloodstream infections (BSI) (n = 48) including strains selected by genetic lineage (frequent and rare sequence types), antibiotic resistance phenotype (susceptible and multidrug-resistant isolates), and colony phenotype (mucoid and non-mucoid isolates). The intraspecies predation range (I-PR) was defined as the proportion of susceptible strains within the entire collection. In contrast, the predation efficiency (PE) is the ratio of viable prey cells remaining after predation compared to the initial inoculum. I-PR was significantly higher for CF (67%) than for BSI P. aeruginosa isolates (35%) probably related to an environmental origin of CF strains whereas invasive strains are more adapted to humans. I-PR correlation with bacterial features such as mucoid morphotype, genetic background, or antibiotic susceptibility profile was not detected. To test the possibility of increasing I-PR of BSI isolates, a polyhydroxyalkanoate depolymerase deficient B. bacteriovorus bd2637 mutant was used. Global median I-PR and PE values remained constant for both predators, but 31.2% of 109J-resistant isolates were susceptible to the mutant, and 22.9% of 109J-susceptible isolates showed resistance to predation by the mutant, pointing to a predator-prey specificity process. The potential use of predators in the clinical setting should be based on the determination of the I-PR for each species, and the PE of each particular target strain., (© 2022. The Author(s).)

Cystic fibrosis (CF) lung microbiota composition has recently been redefined by the application of next-generation sequencing (NGS) tools, identifying, among others, previously undescribed anaerobic and uncultivable bacteria. In the present study, we monitored the fluctuations of this ecosystem in 15 CF patients during a 1-year follow-up period, describing for the first time, as far as we know, the presence of predator bacteria in the CF lung microbiome. In addition, a new computational model was developed to ascertain the hypothetical ecological repercussions of a prey-predator interaction in CF lung microbial communities. Fifteen adult CF patients, stratified according to their pulmonary function into mild ( n = 5), moderate ( n = 9), and severe ( n = 1) disease, were recruited at the CF unit of the Ramón y Cajal University Hospital (Madrid, Spain). Each patient contributed three or four induced sputum samples during a 1-year follow-up period. Lung microbiota composition was determined by both cultivation and NGS techniques and was compared with the patients' clinical variables. Results revealed a particular microbiota composition for each patient that was maintained during the study period, although some fluctuations were detected without any clinical correlation. For the first time, Bdellovibrio and Vampirovibrio predator bacteria were shown in CF lung microbiota and reduced-genome bacterial parasites of the phylum Parcubacteria were also consistently detected. The newly designed computational model allows us to hypothesize that inoculation of predators into the pulmonary microbiome might contribute to the control of chronic colonization by CF pathogens in early colonization stages. IMPORTANCE The application of NGS to sequential samples of CF patients demonstrated the complexity of the organisms present in the lung (156 species) and the constancy of basic individual colonization patterns, although some differences between samples from the same patient were observed, probably related to sampling bias. Bdellovibrio and Vampirovibrio predator bacteria were found for the first time by NGS as part of the CF lung microbiota, although their ecological significance needs to be clarified. The newly designed computational model allows us to hypothesize that inoculation of predators into the lung microbiome can eradicate CF pathogens in early stages of the process. Our data strongly suggest that lower respiratory microbiome fluctuations are not necessarily related to the patient's clinical status., (Copyright © 2017 de Dios Caballero et al.)

Methicillin-resistant Staphylococcus aureus (MRSA) causes chronic pulmonary infections in patients with cystic fibrosis (CF). This study tracks the 13-year evolution (1996-2009) of a single MRSA clone in a male patient with CF, evaluating both the host immunogenic response and the microbial variations. Whole-genome sequencing was performed for the initial (CF-96) and evolved (CF-09) isolates. The immunogenicity of CF-96 and CF-09 was evaluated by incubation with innate immune cells from healthy volunteers. We also studied the patient's innate immune response profile, cytokine production, expression of triggering receptor expressed on myeloid cells-1 (TREM-1), and phagocytosis. A total of 30 MRSA ST247-SCCmecI-pvl(-) isolates were collected, which evidenced a genome size reduction from the CF-96 ancestor to the evolved CF-09 strain. Up to six changes in the spa-type were observed over the course of the 13-year evolution. Cytokine production, TREM-1 expression, and phagocytosis were significantly lower for the healthy volunteer monocytes exposed to CF-09, compared with those exposed to CF-96. Patient monocytes exhibited a reduced inflammatory response when challenged with CF-09. Genetic changes in MRSA, leading to reduced immunogenicity and entry into the refractory state, may contribute to the attenuation of virulence and efficient persistence of the bacteria in the CF lung.

Background: Although scientific knowledge about the benefits of probiotic use in cystis fibrosis (CF) is scarce, their expectative is promising. The aim of this work was to analyze the effect of a Lactobacillus reuteri probiotic preparation versus placebo in CF patients., Methods: A prospective, double blind, crossover and with placebo study was carried out in 30 CF patients from two Spanish hospitals. Patients were randomized in Group A (6 months of probiotic followed by 6 months of placebo) and Group B (6 months of placebo followed by 6 months of probiotic). GIQLI (gastrointestinal) and SF-12 (general) health tests were performed after probiotic and placebo intakes. Fat absorption coefficient, calprotectin, and inflammatory interleukin quantification were determined in fecal samples. Total fecal DNA was obtained and metagenomic 454-pyrosequencing was applied to analyze the microbiome composition. STATA v12 MP software was used for statistical analyses., Results: Statistically significant improvement in the gastrointestinal health and decrease of the calprotectin levels were demonstrated in patients after probiotic exposure, in comparison with placebo. All CF subjects reported good tolerance to L. reuteri without secondary effects. Metagenomic analysis showed an important dysbiosis in CF gut microbiota associated with a high concentration of Proteobacteria. Probiotic intake was followed by a reduction in the total bacterial density, mostly due to a considerable reduction in the γ-Proteobacteria phylum; and an important increase of the microbial diversity with a higher representation of Firmicutes., Conclusions: Probiotics might ameliorate the dysbiosis of CF gut microbiota, characterized by a high density of Proteobacterial organisms. L. reuteri significantly decrease intestinal inflammation and increase digestive comfort., (Copyright © 2014 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

The ability of antibiotics used in bronchopulmonary infections in cystic fibrosis (CF) patients to prevent Pseudomonas aeruginosa early biofilm formation was studied using a biofilm microtitre assay with 57 non-mucoid P. aeruginosa isolates (44 first colonisers and 13 recovered during the initial intermittent colonisation stage) obtained from 35 CF patients. Minimum biofilm inhibitory concentrations (BICs) of levofloxacin, ciprofloxacin, imipenem, ceftazidime, tobramycin, colistin and azithromycin were determined by placing a peg lid with a formed biofilm onto microplates containing antibiotics. A modification of this protocol consisting of antibiotic challenge during biofilm formation was implemented in order to determine the biofilm prevention concentration (BPC), i.e. the minimum concentration able to prevent biofilm formation. The lowest BPCs were for fluoroquinolones, tobramycin and colistin and the highest for ceftazidime and imipenem. The former antibiotics had BPCs identical to or only slightly higher than their minimum inhibitory concentrations (MICs) determined by standard Clinical and Laboratory Standards Institute (CLSI) microdilution and were also active on formed biofilms as reflected by their low BIC values. In contrast, ceftazidime and imipenem were less effective for prevention of biofilm formation and on formed biofilms. In conclusion, the new BPC parameter determined in non-mucoid P. aeruginosa isolates recovered during early colonisation stages in CF patients supports early aggressive antimicrobial treatment guidelines in first P. aeruginosa-colonised CF patients., (Copyright © 2012 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.)

Bacterial biofilms play an important role in the persistent colonization of the respiratory tract in cystic fibrosis (CF) patients. The trade-offs among planktonic or sessile modes of growth, mutation frequency, antibiotic susceptibility and mutant prevention concentrations (MPCs) were studied in a well-defined collection of 42 CF Pseudomonas aeruginosa isolates. MICs of ciprofloxacin, tobramycin, imipenem and ceftazidime increased in the biofilm mode of growth, but not the MPCs of the same drugs. The mutation frequency median was significantly higher in planktonic conditions (1.1 × 10(-8)) than in biofilm (9.9 × 10(-9)) (p 0.015). Isolates categorized as hypomutable increased their mutation frequency from 3.6 × 10(-9) in the planktonic mode to 6 × 10(-8) in biofilm, whereas normomutators (from 9.4 × 10(-8) to 5.3 × 10(-8)) and hypermutators (from 1.6 × 10(-6) to 7.7 × 10(-7)) decreased their mutation frequencies in biofilm. High and low mutation frequencies in planktonic growth converge into the normomutable category in the biofilm mode of growth of CF P. aeruginosa, leading to stabilization of MPCs. This result suggests that once the biofilm mode of growth has been established, the propensity of CF P. aeruginosa populations to evolve towards resistance is not necessarily increased., (© 2010 The Authors. Clinical Microbiology and Infection © 2010 European Society of Clinical Microbiology and Infectious Diseases.)

Objectives: Although methicillin-resistant Staphylococcus aureus (MRSA) is increasingly recognized in cystic fibrosis (CF) patients, it has not been sufficiently studied in large series. We analysed all MRSA isolates recovered from respiratory secretions of patients attending our CF unit (1994-2006)., Methods: Antibiotic susceptibilities were determined using both planktonic and sessile bacteria as inocula. Genetic relationships were determined by PFGE and multilocus sequence typing (MLST). SCCmec type and the presence of the pvl gene were also investigated., Results: A total of 93 MRSA isolates (1-20 isolates per patient) were recovered from 18 of 77 CF patients with positive staphylococcal culture. Mean prevalence (4.4%) increased (P < 0.001) over time. All isolates were susceptible to linezolid, quinupristin/dalfopristin and co-trimoxazole but presented high resistance rates to amikacin (90%), gentamicin (85%), levofloxacin (81%) and erythromycin (69%). Except for macrolides and gentamicin, isolates were less susceptible growing in biofilms than in planktonic cultures. Fifteen different PFGE patterns were found, one of them consistently recovered for 6 years in the same patient. Identical clones were detected in several unrelated patients. MLST demonstrated that the international ST228 was the most frequent (67%) clone. The pvl gene was negative in all isolates and the SCCmec corresponded to types I (97%) and IV (3%). Strong mutators were not detected, but a considerable number were considered weak mutators., Conclusions: Distinct microbiological and molecular features were detected among CF-MRSA isolates, probably due to adaptation to specific conditions in CF patients. Prevalence of MRSA increased among these patients, most of them colonized with a multiresistant biofilm-forming clone belonging to ST228-SSCmecI, suggesting cross-transmission or a common source.

Objectives: To compare the capability of biofilm development between Streptococcus pneumoniae isolates from cystic fibrosis (CF) respiratory samples and those from non-CF blood cultures. Antibiotic susceptibility of biofilm-forming isolates, as well as differences between antibiotic susceptibility of sessile cells [minimum biofilm inhibitory concentration (MBIC)] and their planktonic counterparts (conventional MIC), were also assessed., Methods: Biofilm formation was performed using a microtitre method in 20 CF and 22 non-CF blood culture S. pneumoniae isolates., Results and Conclusions: Biofilm formation occurs more frequently among S. pneumoniae isolates from CF (80%) than among non-CF blood culture isolates (50%) (P = 0.04). Moreover MBICs were significantly higher than conventional planktonic MICs among CF but not among non-CF blood isolates, suggesting a high adaptability of CF strains to form biofilms in adverse conditions.

Pseudomonas aeruginosa colonisation has a negative effect on pulmonary function in cystic fibrosis patients. The organism can only be eradicated in the early stage of colonisation, while reduction of bacterial density is desirable during chronic colonisation or exacerbations. Monthly, or at least 3-monthly, microbiological culture is advisable for patients without previous evidence of P. aeruginosa colonisation. Cultures should be performed at least every 2-3 months in patients with well-established colonisation, and always during exacerbations or hospitalisations. Treatment of patients following the first isolation of P. aeruginosa, but with no clinical signs of colonisation, should be with oral ciprofloxacin (15-20 mg/kg twice-daily for 3-4 weeks) plus inhaled tobramycin or colistin (intravenous treatment with or without inhaled treatment can be used as an alternative), while patients with acute infection should be treated for 14-21 days with high doses of two intravenous antimicrobial agents, with or without an inhaled treatment during or at the end of the intravenous treatment. Maintenance treatment after development of chronic P. aeruginosa infection/colonisation (pathogenic colonisation) in stable patients (aged>6 years) should be with inhaled tobramycin (300 mg twice-daily) in 28-day cycles (on-off) or, as an alternative, colistin (1-3 million units twice-daily). Colistin is also a possible choice for patients aged<6 years. Treatment can be completed with oral ciprofloxacin (3-4 weeks every 3-4 months) for patients with mild pulmonary symptoms, or intravenously (every 3-4 months) for those with severe symptoms or isolates with ciprofloxacin resistance. Moderate and serious exacerbations can be treated with intravenous ceftazidime (50-70 mg/kg three-times-daily) or cefepime (50 mg/kg three-times-daily) plus tobramycin (5-10 mg/kg every 24 h) or amikacin (20-30 mg/kg every 24 h) for 2-3 weeks. Oral ciprofloxacin is recommended for patients with mild pulmonary disease. If multiresistant P. aeruginosa is isolated, antimicrobial agents that retain activity are recommended and epidemiological control measures should be established.

Inhaled administration of tobramycin assures high concentrations in cystic fibrotic lungs, improving the therapeutic ratio over that of parenteral tobramycin levels, particularly against Pseudomonas aeruginosa. Conventional Clinical and Laboratory Standards Institute (CLSI; formerly National Committee for Clinical Laboratory Standards) breakpoints only consider parenteral levels and do not take into account these high antimicrobial concentrations. The Spanish Antibiogram Committee (The MENSURA Group) has tentatively defined specific breakpoint values for inhaled tobramycin when testing P. aeruginosa isolates from cystic fibrosis (CF) patients (susceptible, < or =64 microg/ml; resistant, > or =128 microg/ml). The antimicrobial susceptibilities of 206 prospectively collected CF P. aeruginosa isolates were determined by the reference agar dilution method. For tobramycin, the performance of high range tobramycin Etest strips (AB Biodisk, Solna, Sweden) and conventional tobramycin disks were assessed with the same collection. Applying MENSURA proposed breakpoints, 95.1% of the strains were categorized as susceptible to tobramycin, either using agar dilution or Etest high-range strips (99% categorical agreement between both methods). With CLSI breakpoints, susceptibility rates decreased to 79.1 and 81.1% for agar dilution and Etest strips, respectively (83.5% categorical agreement). Minor, major, and very major errors for Etest strips (CLSI criteria) were 13.6, 1.2, and 14.8%, respectively. Upon applying the new proposed criteria for inhaled tobramycin, only one major and one very major error were observed with Etest strips. Whenever inhaled tobramycin is considered for therapy, we suggest that P. aeruginosa strains from CF patients categorized as intermediate or resistant to tobramycin according to the CLSI criteria should be retested with high-range Etest strips and recategorized using MENSURA interpretive criteria. CLSI breakpoints should still be followed when intravenous tobramycin is used in CF patients, particularly during the course of exacerbations.

Forty-eight Streptococcus pneumoniae isolates recovered from sputum samples from 26 cystic fibrosis (CF) patients attending our CF unit (1995 to 2003) were studied. Mean yearly incidence of isolation was 5.5%, and all were strains recovered from young patients (< or = 12 years). The isolation was linked to clinical exacerbation in 35% of the cases, but only 27% of these were not accompanied by other CF pathogens. Fifty percent of the patients presented with two to four isolates over the studied period. Pulsed-field gel electrophoresis-SmaI digestion revealed a high heterogeneity (32 pulsotypes among 48 isolates) and the persistence over a 6-month period of a single clone (clone A) in two patients. This clone, presenting a varied multiresistance phenotype, was identified as the Spain23F-1 clone and was also recognized in six other patients, including two out of nine patients from the CF unit of Sant Joan de Deu Hospital, Barcelona, Spain. In our isolates, 16 different serotypes were recognized, the most frequent being 23F (33.3%), 19F (18.8%), 6A (6.2%), and 6B (6.2%). High overall resistance rates were observed: to penicillin, 73%; to cefotaxime, 33%; to erythromycin, 42%; to tetracycline, 58%; to chloramphenicol, 48%; and to trimethoprim-sulfamethoxazole, 67%. Resistance to fluoroquinolones was not detected. Multiresistance was a common feature (60%). The percentage of S. pneumoniae strains with increased frequencies of mutation to rifampin resistance (> or = 7.5 x 10(-8)) was significantly higher (P = 0.02) in CF (60%) than among non-CF (37%) isolates in the same institution (M. I. Morosini et al., Antimicrob. Agents Chemother. 47:1464-1467, 2003). Even though a clear association with acute exacerbations could not be observed, long-term clonal persistence and variability, high frequency of antibiotic resistance, and hypermutability indicate the plasticity for adaptation of S. pneumoniae to the CF lung environment.

The persistence and variability of 188 Haemophilus influenzae isolates in respiratory tract of 30 cystic fibrosis (CF) patients over the course of 7 years was studied. Antibiotic susceptibility testing, DNA fingerprinting, and analysis of outer membrane protein profiles were performed on all isolates. A total of 115 distinct pulsed-field gel electrophoresis profiles were identified. Ninety percent of patients were cocolonized with two or more clones over the studied period. A third of the patients were cross-colonized with one or two H. influenzae strains; 11% of the clones persisted for 3 or more months. Biotype, outer membrane protein profiles, and resistance profiles showed variation along the studied period, even in persisting clones. Four isolates (2.1%) recovered from 3 patients were type f capsulate, with three of them belonging to the same clone. beta-Lactamase production was detected in 23.9% of isolates while 7% of the beta-lactamase-negative isolates presented diminished susceptibility to ampicillin (beta-lactamase-negative ampicillin resistance phenotype). Remarkably, 21.3% of the H. influenzae isolates presented decreased susceptibility to ciprofloxacin, which was mainly observed in persisting clones. Of the H. influenzae isolates from CF patients, 18 (14.5%) were found to be hypermutable in comparison with 1 (1.4%) from non-CF patients (P < 0.0001). Ten patients (33.3%) were colonized by hypermutable strains over the study period. A multiresistance phenotype and long-term clonal persistence were significantly associated in some cases for up to 7 years. These results suggest that H. influenzae bronchial colonization in CF patients is a dynamic process, but better-adapted clones can persist for long periods of time.

Multiresistance in Stenotrophomonas maltophilia limits the effectiveness of antimicrobial therapy for infections due to this organism. It can be of special concern in cystic fibrosis (CF) patients due to frequent antimicrobial administration. The in vitro activity of 41 antimicrobial agents against 76 epidemiologically defined CF S. maltophilia isolates by pulsed-field-gel electrophoresis (PFGE) technique under XbaI and SpeI restriction was compared with that obtained with 51 non-CF strains recovered from respiratory sources. Minimal inhibitory concentrations (MICs) were determined with the standard National Committee for Clinical Laboratory Standards agar dilution technique, but with 24-hr incubation. Forty-seven different PFGE profiles were observed within 76 S. maltophilia CF isolates. Minocycline (resistance rate, 0%; MIC(90), 1 microg/ml), doxycycline (6.4%; 8 microg/ml), trovafloxacin (4.2%; 2 microg/ml), moxifloxacin (6.3%; 2 microg/ml), clinafloxacin (6.3%; 2 g/ml), and moxalactam (17.0%; 64 g/ml) displayed low resistance rates. On the contrary, resistance rates were higher with ceftazidime (70.0%; 256 microg/ml), cefepime (83.0%; 128 microg/ml), piperacillin (87.2%; >1,024 microg/ml), ticarcillin (87.2%; >512 microg/ml), and aztreonam (95.7%; >1,024 microg/ml). Clavulanate reverted resistance to ticarcillin and aztreonam in 40.4% and 31.7% of strains, respectively. Aminoglycosides displayed reduced activities with susceptibility rates lower than 20% and MIC(90) higher than 128 microg/ml. With the exception of trimethoprim-sulfamethoxazole (25.4 vs. 31.3%), CF isolates were more resistant than non-CF isolates. Remarkably, resistance was enhanced in S. maltophilia isolates persistently recovered in chronically colonized patients. Susceptibility analysis demonstrated higher resistance rates among CF S. maltophilia isolates when compared with respiratory isolates from non-CF patients. Moreover, persistently recovered CF S. maltophilia isolates were more resistant than sporadic non-CF isolates., (Copyright 2003 Wiley-Liss, Inc.)

The prevalence and clinical implications of colonization with nontuberculous mycobacteria were prospectively studied in 37 patients who had cystic fibrosis. Sputum samples were cultured on Coletsos and Löwenstein-Jensen selective media after decontamination with sodium hydroxide and oxalic acid. Oxalic acid-decontaminated fractions were also cultured in selective liquid medium. Nontuberculous mycobacteria were isolated from 6 patients (16.1%). Mycobacterium chelonae and Mycobacterium avium-intracellulare complex were the most common species. Three patients with positive results of culture had at least 1 positive result by acid-fast smear. Oxalic acid decontamination and culture in liquid medium had the lowest contamination rate (6.7%). Colonization with nontuberculous mycobacteria was associated with humoral response to mycobacteria (immunoglobulin G titers against antigen A60) in patients with samples that tested positive by acid-fast smear. An improvement in pulmonary function was observed in 2 patients after they received a course of antimycobacterial therapy. Screening for nontuberculous mycobacteria in patients with cystic fibrosis will contribute to understanding the relevance of these pathogens with regard to deterioration of pulmonary function in patients with cystic fibrosis.

During 1991 to 1998 at least one Stenotrophomonas maltophilia pulmonary infection was observed in 25 (24%) of 104 cystic fibrosis patients at the same unit of our hospital in Spain. Ribotyping and pulse-field gel electrophoresis (PFGE) characterization of 76 S. maltophilia isolates from these patients indicated an overall clonal incidence of 47.1%, reflecting new strains in 44% of patients with repeated positive cultures for S. maltophilia. Six patients with repeated episodes were persistently colonized (> or = 6 months) with the same strain. S. maltophilia bacterial counts were higher (geometric mean, 2.9 x 10(8) cfu/mL) in patients with repeated episodes than in those with a single episode (8.4 x 10(4) cfu/mL, p < 0.01). Single episodes of S. maltophilia occurred in patients < 10 years of age (43% [6/14]), whereas chronic colonization occurred more frequently in older patients (> 16 years of age).

The lungs of cystic fibrosis (CF) patients are chronically infected for years by one or a few lineages of Pseudomonas aeruginosa. These bacterial populations adapt to the highly compartmentalized and anatomically deteriorating lung environment of CF patients, as well as to the challenges of the immune defenses and antibiotic therapy. These selective conditions are precisely those that recent theoretical studies predict for the evolution of mechanisms that augment the rate of variation. Determination of spontaneous mutation rates in 128 P. aeruginosa isolates from 30 CF patients revealed that 36% of the patients were colonized by a hypermutable (mutator) strain that persisted for years in most patients. Mutator strains were not found in 75 non-CF patients acutely infected with P. aeruginosa. This investigation also reveals a link between high mutation rates in vivo and the evolution of antibiotic resistance.

The antimicrobial susceptibility profile of 77 oropharyngeal viridans streptococci isolates from 34 cystic fibrosis (CF) patients and 58 isolates from 43 healthy non-CF patients were studied by the E-test and the standard disk diffusion methods. Overall penicillin and cefotaxime resistances (intermediate plus resistant isolates) were significantly higher (p < 0.05) among CF isolates (72.7% and 45.5%, respectively) than among non-CF isolates (51.7% and 15.5%, respectively). No significant difference was observed in overall (intermediate plus resistant) erythromycin resistance rates, although high-level erythromycin resistance (> or =32 microg/mL) was more frequently found in CF isolates (24.6%) than in non-CF isolates (12.1%). An unexpected high percentage of isolates showed low level erythromycin resistance (MIC range, 0.5-15 microg/mL): 41.5% in cystic fibrosis and 46.5% in non-CF isolates. No significant differences were observed regarding the percentage of colonized patients with at least one penicillin-resistant isolate. On the contrary, colonization with cefotaxime (p < 0.001) or erythromycin (p = 0.014) resistant isolates were significantly more prevalent in CF patients. Similar tetracycline and chloramphenicol resistance rates were observed for both groups. Viridans isolates resistant to a single antibiotic were more prevalent among non-CF patients and multiple resistance was higher among CF patients. Prior antibiotic exposure could result in differences in beta-lactam resistance and colonization rates with resistant isolates between both groups. None of the non-CF patients was previously treated with antimicrobials for a period of three months before sampling. In contrast, 94.1% of CF patients were treated with antimicrobials within the same period; 65.6% with beta-lactam antibiotics. Patients with CF disease, frequently exposed to antimicrobials, may be a reservoir of viridans streptococci isolates with resistance determinants, particularly to beta-lactam antibiotics.

Ciprofloxacin has been a major advance in the treatment of chronic respiratory infections. Three patients with cystic fibrosis and colonized by 5 nontypeable Haemophilus influenzae strains exhibiting low- (MIC, 2 microg/mL) and high-level ciprofloxacin resistance (MICs, 16-32 microg/mL) are described. The patients had received several courses of ciprofloxacin. These MICs represent a decrease in ciprofloxacin susceptibility of 200-3200 times. Molecular epidemiologic methods demonstrated that 2 patients were chronically colonized by their own ciprofloxacin-resistant strains for > or = 15-17 months. Three strains showed simultaneous resistance to ampicillin and chloramphenicol by enzyme inactivation, and 2 had ampicillin resistance without beta-lactamase activity. These data suggest that the emergence and long-term persistence of ciprofloxacin-resistant H. influenzae in patients with cystic fibrosis can be a consequence of antibiotic treatment.

The evolution of imipenem resistance was evaluated in Pseudomonas aeruginosa sequentially isolated from 42 patients with cystic fibrosis. Susceptibility was determined using a commercial microdilution system and imipenem resistance was confirmed by the agar dilution technique. Resistance to imipenem increased during the years from 1988 to 1992. A total of 12 patients (28.5%) carried resistant strains (11.6% of the total P. aeruginosa isolates) but only two of them were treated with the carbapenem. The other patient under imipenem treatment did not harbour resistant isolates. Sixty-four per cent of the imipenem resistant isolates were also meropenem resistant and showed low susceptibility to the other beta-lactams and tobramycin and amikacin. Twenty-one strains were selected for biochemical study. Imipenem susceptible strains showed normal OprD in two strains and diminished OprD in two more. Five strains with MIC of imipenem of 4-8 mg/L lacked OprD while another two had a band with decreased density. All strains with MIC higher than 8 completely lacked this band in western-blot analysis. Imipenem MICs of 0.5-2 mg/L only slightly increased to 1-4 mg/L when a pattern of beta-lactamase derepression was observed. While those with imipenem MICs between 8-16 mg/L increased the imipenem MIC to 16-64 mg/L in the population with a beta-lactamase derepression phenotype.

Background: A 5-year study in patients with cystic fibrosis was carried out in order to gain a better understanding of the microbiological factors influencing clinical status and evolution., Methods: Fifty-two patients were evaluated (mean age 16.6 years, range 0-36) during a 5 years-period (July 1988- July 1992). The clinical score of Shwachman and pulmonary function were evaluated at the beginning and at the end of the study period. Quantitative bacterial cultures were performed every 3 weeks recording the different colonical morphotypes of Pseudomonas aeruginosa., Results: Beside the expected results regarding the prevalence of P. aeruginosa (80.7%) and Staphylococcus aureus (65.5%), a low rate of chronic infection with Burkholderia cepacia (1.9%) and high with S. maltophilia (9.6%) was found and it is worth noting the presence of Salmonella spp. in 3 patients. Microbial colonization followed the classical age-related sequence with 53.8% of patients older than 10 colonized with mucoid strains of P. aeruginosa. Colonization with mucoid Pseudomonas, increase in sputum bacterial counts and high diversity in colonizing morphotypes were parameters related with reduced clinical scores., Conclusions: The sequential study of the bacterial colonization in cystic fibrosis is important to follow the prognosis and evolution of the disease, and therefore, to choose the most effective therapy.