The epidemiology of Pseudomonas cepacia in patients with cystic fibrosis

Burkholderia cepacia complex in cystic fibrosis in the post-epidemic period: multilocus sequence typing-based approach

Cystic fibrosis (CF) patients in the Czech Republic suffered in the late 1990s from an epidemic with ST32 strain of Burkholderia cepacia complex (Bcc). Cohort segregation of Bcc and of ST32 positive patients was introduced in 1999 and 2002, respectively. We performed a study to evaluate the molecular epidemiology of Bcc infection after implementation of these infection control measures. Patients attending the Prague CF adult Centre from 2000 to 2015 were included in the present study. Demographic data and microbial statuses were collected from patient records. All Bcc isolates were analyzed using multilocus sequence typing (MLST). The prevalences of epidemic strain ST32 and of other Bcc strains were calculated. Ninety out of 227 CF patients were infected with Bcc during the study period. The prevalence of ST32 cases significantly decreased from 46.5% in 2000-2001 to 10.4% in 2014-2015 (P < 0.001) due to occurrence of only one new case in 2003, as well as to the death of 72% of ST32-infected patients. Conversely, there was a significant increase in prevalence of other Bcc strains, which rose from 0 to 14.9% (P = 0.015) and of transient infections. A micro-epidemic of infection with ST630 strain was observed in 2014 in lung transplant patients hospitalized in intensive care unit. The prevalence of epidemic strain ST32 decreased, whereas that of non-clonal strains of Bcc increased. Routine use of MLST allowed early detection of new and potentially epidemic strains.

Microorganisms resistant to free-living amoebae

Free-living amoebae feed on bacteria, fungi, and algae. However, some microorganisms have evolved to become resistant to these protists. These amoeba-resistant microorganisms include established pathogens, such as Cryptococcus neoformans, Legionella spp., Chlamydophila pneumoniae, Mycobacterium avium, Listeria monocytogenes, Pseudomonas aeruginosa, and Francisella tularensis, and emerging pathogens, such as Bosea spp., Simkania negevensis, Parachlamydia acanthamoebae, and Legionella-like amoebal pathogens. Some of these amoeba-resistant bacteria (ARB) are lytic for their amoebal host, while others are considered endosymbionts, since a stable host-parasite ratio is maintained. Free-living amoebae represent an important reservoir of ARB and may, while encysted, protect the internalized bacteria from chlorine and other biocides. Free-living amoebae may act as a Trojan horse, bringing hidden ARB within the human "Troy," and may produce vesicles filled with ARB, increasing their transmission potential. Free-living amoebae may also play a role in the selection of virulence traits and in adaptation to survival in macrophages. Thus, intra-amoebal growth was found to enhance virulence, and similar mechanisms seem to be implicated in the survival of ARB in response to both amoebae and macrophages. Moreover, free-living amoebae represent a useful tool for the culture of some intracellular bacteria and new bacterial species that might be potential emerging pathogens.

Risk factors for Burkholderia cepacia complex colonization and infection among patients with cystic fibrosis

OBJECTIVES

To determine risk factors for acquiring Burkholderia cepacia complex among patients with cystic fibrosis (CF).

STUDY DESIGN

A case-control study was conducted with active surveillance for B cepacia complex colonization/infection among patients at 21 CF centers from April 1986 to March 1989 (study period). A case-patient was defined as any CF patient with B cepacia complex colonization for the first time during the study period. Control patients were patients with CF not B cepacia complex colonized during the study period. For each patient, a questionnaire was completed semiannually.

RESULTS

In multivariate analyses, hospitalization for pulmonary exacerbations, living with a B cepacia complex-positive person, attending a CF summer camp, and direct contact with a B cepacia complex-colonized CF person outside of camp and home were associated with B cepacia complex acquisition. Receiving antimicrobial aerosol therapy or cleaning and drying a home-used nebulizer between uses were associated with a decrease in B cepacia complex acquisition.

CONCLUSIONS

Numerous factors inside and outside the health care setting are associated with person-to-person transmission of B cepacia complex among patients with CF. Prevention programs should reduce direct or indirect contact between noncolonized and B cepacia complex-colonized/infected patients with CF.

Detecting Stenotrophomonas maltophilia does not reduce survival of patients with cystic fibrosis

Stenotrophomonas maltophilia is a gram-negative bacterium that has been cultured with increasing prevalence from the sputum of patients with cystic fibrosis (CF). We conducted a cohort study, using the Cystic Fibrosis Foundation Registry, to assess the effect of S. maltophilia on survival. We studied all patients in this registry from 1991 to 1997 who were older than 6 years of age, were S. maltophilia negative in the first year of enrollment, and had their CF diagnosed before the age of 45 years (n = 19,255 in the study). We compared patients who acquired S. maltophilia with those who did not, using survival analysis. A total of 1,673 (8.7%) had at least one sputum sample positive for S. maltophilia. Compared with patients without S. maltophilia, those patients positive for S. maltophilia had the following baseline characteristics before detection: lower FEV(1) % pred (p < 0.001); older (p = 0.001); more likely to be female (p = 0.003); and more pulmonary exacerbations (p < 0.001), outpatient visits (p < 0.002), and total hospitalizations (p < 0.001). After controlling for differences in severity of disease and coinfection with Pseudomonas aeruginosa, the hazard ratio associated with S. maltophilia detection was 0.89 (95% confidence interval, 0.75-1.05). Although patients with CF who acquire S. maltophilia have more advanced disease than those who do not acquire this organism, detection does not independently affect short-term survival (3 years).

Burkholderia cepacia complex: a contraindication to lung transplantation in cystic fibrosis?

Previous studies have indicated that pulmonary infection with Burkholderia cepacia is associated with poor clinical outcome after lung transplantation in cystic fibrosis (CF). Many treatment centers consider B. cepacia infection an absolute contraindication to lung transplantation. However, the B. cepacia complex actually consists of several closely related bacterial species. Although each of these has been isolated from CF sputum culture, certain species are much more frequently recovered than others, and it is not yet clear whether all species have the same potential for virulence in CF. Additional study is needed to better define the relative risks associated with each species of the B. cepacia complex.

Genotypic analysis of Burkholderia cepacia isolates from 13 French cystic fibrosis centers

Burkholderia cepacia has been involved in outbreaks of pulmonary infection among patients with cystic fibrosis (CF), and the spread of a highly transmissible clone has been reported throughout the United Kingdom and Canada. These data prompted a DNA-based typing study of the strains recovered in French CF centers. Ninety-five isolates recovered from 71 patients attending 13 CF centers in 9 regions of France were characterized by randomly amplified polymorphic DNA (RAPD) analysis and pulsed-field gel electrophoresis (PFGE). Twenty-one genotypes were identified among the 95 isolates, and the results of RAPD and PFGE were concordant for 89 isolates (94%). Cross-colonization was demonstrated in 7 of the 13 CF centers. The investigation of serial isolates showed that most chronically colonized patients harbored a single B. cepacia strain. A geographically clustered distribution of B. cepacia genotypes was observed, except for one genotype, which was detected in four regions but was proven to be different from the genotype of the British-Canadian highly transmissible strain. The present study confirms the ability of B. cepacia to spread among CF communities in France and the importance of epidemiological surveys in the institution of prevention policies.

Burkholderia cepacia respiratory tract acquisition: epidemiology and molecular characterization of a large nosocomial outbreak

In 1994 we investigated a large outbreak of Burkholderia (formerly Pseudomonas) cepacia respiratory tract acquisition. A case patient was defined as any patient with at least one sputum culture from which B. cepacia was isolated from 1 January to 31 December 1994. Seventy cases were identified. Most (40 [61%]) occurred between 1 February and 31 March 1994; of these, 35 (86%) were mechanically ventilated patients, 30 of whom were in an intensive-care unit (ICU) when B. cepacia was first isolated. Compared with control patients who were mechanically ventilated in an ICU, these 30 case-patients were significantly more likely to have been ventilated for 2 or more days (30/30 v. 15/30; P < 0.001) or to have been intubated more than once (12/30 v. 2/30; OR = 9.3, 95% CI 1.6-68.8; P = 0.002) before the first isolation of B. cepacia. By multivariate analysis, the 35 mechanically ventilated case-patients were significantly more likely to have received a nebulized medication (OR = 11.9, 95% CI = 1.6-553.1; P < 0.001) and a cephalosporin antimicrobial (OR = 11.9, 95% CI = 1.6-553.1) in the 10 days before the first isolation of B. cepacia, compared with B. cepacia-negative control-patients matched by date and duration of most recent mechanical ventilation. Although B. cepacia was not cultured from medications or the hospital environment, all outbreak strains tested had an identical DNA restriction endonuclease digestion pattern by pulsed-field gel electrophoresis. Review of respiratory therapy procedures revealed opportunities for contamination of nebulizer reservoirs. This investigation suggests that careful adherence to standard procedures for administration of nebulized medications is essential to prevent nosocomial respiratory infections.

Is Burkholderia (Pseudomonas) cepacia disseminated from cystic fibrosis patients during physiotherapy?

Burkholderia cepacia is well recognized as a potential respiratory pathogen in cystic fibrosis (CF) patients and there is increasing concern about nosocomial acquisition. Environmental contamination with B. cepacia before, during and after physiotherapy was studied in eight adult CF patients. Air was sampled using a surface air sampler, and horizontal surfaces and pillows were sampled with moistened swabs and contact plates, respectively. Thirty-nine (40%) of 97 air samples were positive and counts ranged from 1-63 cfu/m3. Forty-four percent of samples taken after physiotherapy were positive. B. cepacia was not recovered from sinks or horizontal surfaces but the pillows of three patients were positive. B. cepacia is disseminated into the immediate environment by adult CF patients receiving physiotherapy. The potential risk of person-to-person transmission during hospitalization justifies the recommendation that B. cepacia-positive patients should be segregated from other CF patients.

Airborne dissemination of Burkholderia (Pseudomonas) cepacia from adult patients with cystic fibrosis

BACKGROUND

Burkholderia (Pseudomonas) cepacia is an increasingly important pathogen in patients with cystic fibrosis but it is unclear how it spreads from patient to patient. A study was undertaken to determine whether B cepacia could be recovered from room air occupied by colonised adult patients with cystic fibrosis.

METHODS

Air samples were obtained consecutively from an enclosed room or isolation cubicle before, during, and after occupation by six patients on nine occasions using a surface air sampler incorporating contact plates with selective medium. Settle plates were also used and sputum from five patients was cultured.

RESULTS

B cepacia was recovered from room air during occupation by five of six patients, the number of bacteria ranging from 1 to 158 cfu/m3 (mean 32 cfu/m3). The number of bacteria isolated was greater when patients were coughing. B cepacia persisted in room air on four occasions after the patient left the room, on one occasion for up to 45 minutes.

CONCLUSIONS

The isolation of B cepacia from the air of rooms occupied by colonised patients suggests that dissemination might occur by aerosol as well as by direct physical contact with patients or contaminated environmental sites.

Acquisition of Pseudomonas cepacia at summer camps for patients with cystic fibrosis. Summer Camp Study Group

To assess the risk of acquisition of Pseudomonas cepacia by person-to-person transmission at cystic fibrosis summer camps, we conducted in 1990 a study at three camps attended by patients with cystic fibrosis who had P. cepacia infection and patients without P. cepacia infection but who were considered susceptible to infection. We obtained sputum or throat cultures from campers on their arrival at, weekly during, at the end of, and 14 to 30 days after camp. We compared the incidence of sputum conversion of patients at camp with that of patients outside camp by culturing specimens from noncamper control subjects with cystic fibrosis who were known not to be infected < or = 2 weeks before and 4 to 6 weeks after camp. We also determined the risk factors for P. cepacia acquisition by determining the relative risk of acquisition between campers who were exposed versus campers who were not exposed to campers known to be infected or to potential environmental sources of P. cepacia at camp. The ribotype of P. cepacia isolates from campers with sputum conversion was compared with that of isolates from other campers and from an environmental source. The cumulative incidence of sputum conversion during the study period was 6.1% (11/181) among campers compared with no incidence (0/92) among noncampers (p = 0.02, Fisher Exact Test). The incidence of sputum conversion at camp varied according to the prevalence of campers with known infection (p < 0.001, chi-square test for trend). The rate of sputum conversion was higher in the camp with longer duration (relative risk = 12.0; 95% confidence interval = 2.7 to 53.5). Ribotyping showed that P. cepacia isolates from all 11 campers with sputum conversion were identical or similar (1 to 2 band difference) to isolates of other P. cepacia-infected campers including co-converters. These results suggest that P. cepacia can be acquired by patients with cystic fibrosis who are attending summer camp for such patients, possibly through person-to-person transmission, and that the risk increases with the prevalence of P. cepacia-infected campers and the duration of camp.

Isoenzyme analysis of Pseudomonas cepacia as an epidemiologic tool

Multilocus enzyme electrophoresis has successfully been used to establish basic marker systems for the epidemiologic analysis of a variety of bacterial pathogens. This study was done to determine the efficacy of this technique for characterizing Pseudomonas cepacia, using 31 known-related strains isolated during an outbreak of infections involving intrinsically contaminated povidone-iodine solution, and five outbreak-unrelated strains used in serotyping of P. cepacia. Crude cell extracts were analyzed by starch gel electrophoresis for electrophoretic variants using 13 enzyme substrates; esterase bands were detected using an additional four substrates. The 31 outbreak strains had identical isoenzyme patterns for all enzymes examined. Five electrophoretic types were obtained for the serotyping strains; electrophoretic mobilities of one of the five strains corresponded to the patterns obtained for the outbreak strains. These results suggest that enzyme electrophoretic typing may be a useful adjunct to other typing methods used in epidemiologic analyses of P. cepacia infections.

Pseudomonas cepacia: a new pathogen in patients with cystic fibrosis referred to a large centre in the United Kingdom

Pseudomonas cepacia infection has become increasingly common among patients with cystic fibrosis in North America. In a large cystic fibrosis centre in the United Kingdom 11 cases have been identified during the last six years, with a maximum prevalence of 7% in 1988. Three patients have died, two of whom deteriorated rapidly shortly after acquisition of the organism despite intensive treatment with appropriate antibiotics. Analysis of possible causes of the increase in P cepacia infection suggested that neither patient to patient transmission nor the use of nebulised antibiotics was associated with an increased risk of infection.

The epidemiology of nosocomial epidemic Pseudomonas cepacia infections

Pseudomonas cepacia has occasionally been identified as an epidemic and endemic nosocomial pathogen. In outbreaks, usually one clinical site predominates but many may be involved. Detailed investigations have usually implicated a contaminated liquid reservoir or moist environmental surface as the source. Liquid sources have included a number of different classes of antiseptics and disinfectants such as quaternary ammonium chlorides, biguanides, hexachlorophene, and iodophors. Environmental and patient isolates have had multiply resistant antimicrobial susceptibility patterns. The clinical distinction between colonization and infection may be difficult and may challenge the skills of the clinician. Expenditure of resources needed to solve epidemics is justified in view of the potential virulence of this organism and the high likelihood that an unrecognized but easily eliminated liquid environmental reservoir may be the source.