Risk factors for acquisition of methicillin-resistant Staphylococcus aureus (MRSA) by patients with cystic fibrosis

The role of Staphylococcus aureus in cystic fibrosis pathogenesis and clinico-microbiological interactions

Cystic fibrosis (CF) is a progressive and inherited disease that affects approximately 70000 individuals all over the world annually. A mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene serves as its defining feature. Bacterial infections have a significant impact on the occurrence and development of CF. In this manuscript, we discuss the role and virulence factors of Staphylococcus aureus as an important human pathogen with the ability to induce respiratory tract infections. Recent studies have reported S. aureus as the first isolated bacteria in CF patients. Methicillin-resistant Staphylococcus aureus (MRSA) pathogens are approximately resistant to all β-lactams. CF patients are colonized by MRSA expressing various virulence factors including toxins, and Staphylococcal Cassette Chromosome mec (SCCmec) types, and have the potential for biofilm formation. Therefore, variations in clinical outcomes will be manifested. SCCmec type II has been reported in CF patients more than in other SCCmec types from different countries. The small-colony variants (SCVs) as specific morphologic subtypes of S. aureus with slow growth and unusual properties can also contribute to persistent and difficult-to-treat infections in CF patients. The pathophysiology of SCVs is complicated and not fully understood. Patients with cystic fibrosis should be aware of the intrinsic risk factors for complex S. aureus infections, including recurring infections, physiological issues, or coinfection with P. aeruginosa.

Role of RND Efflux Pumps in Drug Resistance of Cystic Fibrosis Pathogens

Drug resistance represents a great concern among people with cystic fibrosis (CF), due to the recurrent and prolonged antibiotic therapy they should often undergo. Among Multi Drug Resistance (MDR) determinants, Resistance-Nodulation-cell Division (RND) efflux pumps have been reported as the main contributors, due to their ability to extrude a wide variety of molecules out of the bacterial cell. In this review, we summarize the principal RND efflux pump families described in CF pathogens, focusing on the main Gram-negative bacterial species (Pseudomonas aeruginosa, Burkholderia cenocepacia, Achromobacter xylosoxidans, Stenotrophomonas maltophilia) for which a predominant role of RND pumps has been associated to MDR phenotypes.

Risk factors and clinical course of children with cystic fibrosis colonized with Staphylococcus aureus

BACKGROUND

The literature is limited on staphylococcal infection in children with cystic fibrosis (CF) from tropical countries. We aimed to study the risk factors and clinical course of children with CF infected with Staphylococcus aureus.

METHODS

In this chart review we compared demographic, clinical and spirometry characteristics in CF children with S. aureus alone (group A), both S. aureus and Pseudomonas aeruginosa (group B) and P. aeruginosa alone (group C) colonization.

RESULTS

We included 79 cases (group A, 22; group B, 19; group C, 38). There was no difference in age of onset of symptoms, age of diagnosis, age of first isolation and spirometry parameters before colonization between the groups. The median duration of follow-up was shorter in group A. After colonization, children in group A and group B had significantly lower mean Shwachman and Kulczycki (SK) scores (44.7±5.4 and 40.8±5.8, respectively) compared with group C (49.9±6.8). Pulmonary exacerbations and hospitalizations were significantly greater in the combined group. After colonization, group A had a significant deterioration in SK score and forced vital capacity (FVC).

CONCLUSIONS

S. aureus colonization, especially in combination with P. aeruginosa, in children with CF was associated with worsening of FVC and clinical severity score and increased pulmonary exacerbations.

Area Deprivation as a Risk Factor for Methicillin-resistant Staphylococcus aureus Infection in Pediatric Cystic Fibrosis

BACKGROUND

In US cystic fibrosis (CF) patients, methicillin-resistant Staphylococcus aureus (MRSA) rates have tripled in the past 2 decades. Known clinical risk factors include exposure to a healthcare setting, Pseudomonas aeruginosa and CF-related diabetes. Area-level socio-environmental exposures have not been evaluated. We explored the association of area-level deprivation with MRSA prevalence in a pediatric CF Center in the Southeastern United States.

METHODS

Patients' residential addresses were geocoded and linked to a composite Area Deprivation Index and Rural-Urban Commuting Area scores. The association of MRSA with Area Deprivation Index and Rural-Urban Commuting Area scores was evaluated using logistic regression with robust standard errors adjusted for sociodemographic covariates (age, sex, race, mother's and father's education and household income), clinical risk factors (P. aeruginosa, CF-related diabetes, hospitalizations and number of clinic visits) and clustering.

RESULTS

The study included all pediatric patients (N = 231; mean age 12) at a single CF Center. MRSA was present in 44% of subjects. Higher area-level deprivation was correlated with rural residence, lack of parental college education and lower household income (P < 0.001 for each). In a multiple regression model fully adjusted for patient-level sociodemographic covariates, clinical risk factors and clustering, neighborhood deprivation was associated with more than 2-fold increase in the odds of having MRSA [OR 2.26 (1.14-4.45), P < 0.05].

CONCLUSIONS

Neighborhood deprivation is a risk factor for MRSA in pediatric CF, doubling the odds of infection. Community-level socioeconomic risk factors should be considered when developing prevention strategies and treatment plans for MRSA infection in pediatric patients with CF.

Chronic Azithromycin Use in Cystic Fibrosis and Risk of Treatment-Emergent Respiratory Pathogens

RATIONALE

Azithromycin has been shown to improve lung function and reduce the number of pulmonary exacerbations in patients with cystic fibrosis. Concerns remain, however, regarding the potential emergence of treatment-related respiratory pathogens.

OBJECTIVES

To determine whether chronic azithromycin use (defined as three-times weekly administration) is associated with increased rates of detection of eight specific respiratory pathogens.

METHODS

We performed a new-user, propensity score-matched retrospective cohort study utilizing data from the Cystic Fibrosis Foundation Patient Registry. Incident azithromycin users were propensity score matched 1:1 with contemporaneous nonusers. Kaplan-Meier curves and Cox proportional hazards regression were used to evaluate the association between chronic azithromycin use and incident respiratory pathogen detection. Analyses were performed separately for each pathogen, limited to patients among whom that pathogen had not been isolated in the 2 years before cohort entry.

RESULTS

After propensity score matching, the mean age of the cohorts was approximately 12 years. Chronic azithromycin users had a significantly lower risk of detection of new methicillin-resistant Staphylococcus aureus, nontuberculous mycobacteria, and Burkholderia cepacia complex compared with nonusers. The risk of acquiring the remaining five pathogens was not significantly different between users and nonusers.

CONCLUSIONS

Using an innovative new-user, propensity score-matched study design to minimize indication and selection biases, we found in a predominantly pediatric cohort that chronic azithromycin users had a lower risk of acquiring several cystic fibrosis-related respiratory pathogens. These results may ease concerns that chronic azithromycin exposure increases the risk of acquiring new respiratory pathogens among pediatric patients with cystic fibrosis.

Antimicrobial susceptibility of microorganisms isolated from sputum culture of patients with cystic fibrosis: Methicillin-resistant Staphylococcus aureus as a serious concern

INTRODUCTION

Infection is a major cause of morbidity and mortality in patients with cystic fibrosis (CF). Antimicrobial resistance of the bacterial spp. particularly methicillin resistance in Staphylococcus aureus has caused a lot of attention. The aim of this study was to describe the prevalence of S. aureus, Pseudomonas aeruginosa and Burkholderia cepacia-complex as well as their antimicrobial susceptibility patterns in CF patients in an Iranian referral pediatrics Hospital.

MATERIAL AND METHODS

From March 2011 until February 2012, 172 samples were collected at the Children Medical Center (CMC), an Iranian referral hospital in Tehran, Iran. Sputum specimens were cultured for the following bacterial pathogens: P. aeruginosa, S. aureus, B. cepacia complex. Antimicrobial susceptibility was performed according to the Clinical Laboratory Standards Institute recommendations.

RESULTS

In our study, 54% of the patients (n = 93) harbored at least once S. aureus, 30% (n = 52) P. aeruginosa, and 2% (n = 3) Burkholderia cepacia. In 40 patients (23%), none of these organisms was grown. An increasing colonization rate of P. aeruginosa in the second decade of life was found. In contrast, the colonization rate of S. aureus was constant in both decades of life. Methicillin resistant S. aureus (MRSA) was detected in 40 isolates (43%). Among MRSA, no resistance against vancomycin, linezolid and quinupristin/dalfopristin occurred. The susceptibility of P. aeruginosa isolates to meropenem, imipenem, doripenem, levofloxacin and polymixin B were more than 90%.

CONCLUSION

The prevalence of MRSA has been rising. Since its impact on clinical outcomes, optimal prevention and treatment strategies are unclear, further studies to expand the knowledge about the infection control strategies and MRSA treatment are highly recommended.

Methicillin-resistant Staphylococcus aureus acquisition in healthcare workers with cystic fibrosis: a retrospective cross-sectional study

BACKGROUND

People with cystic fibrosis (CF) may work in healthcare settings risking nosocomial pathogen acquisition. The aim of this study was to determine the incidence of methicillin-resistant Staphylococcus aureus (MRSA) infection in adult healthcare workers with CF (HCWcf).

METHODS

Data was collected in this observational study on MRSA acquisition from 405 CF patients attending an adult CF centre in Australia between 2001-2012. Demographic and clinical characteristics were compared between HCWcf and non-HCWcf. A sub-analysis was subsequently performed to compare demographic and clinical characteristics between those patients (HCWcf versus non-HCWcf) that acquired MRSA. We also investigated rates of chronic MRSA infection and the outcome of eradication treatment in HCWcf.

RESULTS

A higher proportion of HCWcf acquired MRSA [n = 10/21] compared to non-HCWcf [n = 40/255] (P <0.001). The odds of MRSA acquisition were 8.4 (95 % CI, 3.0 - 23.4) times greater in HCWcf than non-HCWcf. HCWcf with MRSA were older (P = 0.02) and had better lung function (P = 0.009), yet hospitalisation rates were similar compared to non-HCWcf with MRSA. Chronic MRSA infection developed in 36/50 CF patients (HCWcf, n = 6; non-HCWcf, n = 30), with eradication therapy achieved in 5/6 (83 %) HCWcf.

CONCLUSIONS

The rate of MRSA incidence was highest in HCWcf and the workplace is a possible source of acquisition. Vocational guidance should include the potential for MRSA acquisition for CF patients considering healthcare professions.

Infection Prevention and Control Guideline for Cystic Fibrosis: 2013 Update

The 2013 Infection Prevention and Control (IP&C) Guideline for Cystic Fibrosis (CF) was commissioned by the CF Foundation as an update of the 2003 Infection Control Guideline for CF. During the past decade, new knowledge and new challenges provided the following rationale to develop updated IP&C strategies for this unique population:

1.The need to integrate relevant recommendations from evidence-based guidelines published since 2003 into IP&C practices for CF. These included guidelines from the Centers for Disease Control and Prevention (CDC)/Healthcare Infection Control Practices Advisory Committee (HICPAC), the World Health Organization (WHO), and key professional societies, including the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA). During the past decade, new evidence has led to a renewed emphasis on source containment of potential pathogens and the role played by the contaminated healthcare environment in the transmission of infectious agents. Furthermore, an increased understanding of the importance of the application of implementation science, monitoring adherence, and feedback principles has been shown to increase the effectiveness of IP&C guideline recommendations.

2.Experience with emerging pathogens in the non-CF population has expanded our understanding of droplet transmission of respiratory pathogens and can inform IP&C strategies for CF. These pathogens include severe acute respiratory syndrome coronavirus and the 2009 influenza A H1N1. Lessons learned about preventing transmission of methicillin-resistantStaphylococcus aureus(MRSA) and multidrug-resistant gram-negative pathogens in non-CF patient populations also can inform IP&C strategies for CF.

Clinical characteristics and epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in children with cystic fibrosis from a center with a high MRSA prevalence

BACKGROUND

We describe the clinical characteristics and epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in children with cystic fibrosis (CF) from the U.S. CF center with the highest MRSA prevalence.

METHODS

Medical records of children with CF were retrospectively reviewed from 1997-2009. MRSA clinical isolates from 2007-2009 were analyzed by polymerase chain reaction and pulsed field gel electrophoresis.

RESULTS

The prevalence of MRSA was 1% in 1997 and 49% in 2009. Fifty-five children (26%) had persistent MRSA infection. Sixty-eight percent of MRSA isolates were hospital-associated (HA) MRSA, of which 52% were pulsed-field type USA 100. Ninety-three percent of HA MRSA isolates were clindamycin resistant. Twelve children acquired MRSA before 1 year of age, 83% of whom were hospitalized prior to acquisition of MRSA. Ten of 11 sibling pairs carried indistinguishable MRSA strains. Children with persistent MRSA were hospitalized more often (P = .01), required inhaled medications more frequently (P = .01), and had higher rates of Pseudomonas aeruginosa coinfection (P < .001).

CONCLUSION

MRSA prevalence in children with CF is increasing, and most children are infected with HA MRSA. Exposure to health care facilities and gastrointestinal surgeries may facilitate early acquisition of MRSA. Siblings carry indistinguishable MRSA strains, indicating household transmission of MRSA. Children with persistent MRSA had worse pulmonary morbidity. Coinfection with MRSA and P aeruginosa is likely associated with further increased pulmonary morbidity.

Emerging bacterial pathogens and changing concepts of bacterial pathogenesis in cystic fibrosis

Chronic suppurative lower airway infection is a hallmark feature of cystic fibrosis (CF). Decades of experience in clinical microbiology have enabled the development of improved technologies and approaches for the cultivation and identification of microorganisms from sputum. It is increasingly apparent that the microbial constituents of the lower airways in CF exist in a dynamic state. Indeed, while changes in prevalence of various pathogens occur through ageing, differences exist in successive cohorts of patients and between clinics, regions and countries. Classical pathogens such as Pseudomonas aeruginosa, Burkholderia cepacia complex and Staphylococcus aureus are increasingly being supplemented with new and emerging organisms rarely observed in other areas of medicine. Moreover, it is now recognized that common oropharyngeal organisms, previously presumed to be benign colonizers may contribute to disease progression. As infection remains the leading cause of morbidity and mortality in CF, an understanding of the epidemiology, risk factors for acquisition and natural history of infection including interactions between colonizing bacteria is required. Unified approaches to the study and determination of pathogen status are similarly needed. Furthermore, experienced and evidence-based treatment data is necessary to optimize outcomes for individuals with CF.

Antibiotic Management of Methicillin-Resistant Staphylococcus aureus–Associated Acute Pulmonary Exacerbations in Cystic Fibrosis

Objective: To review the treatment of methicillin-resistant Staphylococcus aureus (MRSA)–associated acute pulmonary exacerbations (APEs) in cystic fibrosis (CF). Data Sources: A search of PubMed, MEDLINE, Cochrane Library and Clinicaltrials.gov databases through November 2014 was conducted using the search terms Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, pulmonary exacerbations, and cystic fibrosis. Study Selection and Data Extraction: All English-language research articles, case reports, and case series were evaluated. A total of 185 articles were identified related to MRSA and CF; 30 articles that studied treatments of MRSA APE in CF were included. Data Synthesis: The persistent presence of MRSA in the respiratory tract of patients with CF has been associated with higher morbidity and an increased risk of death. Limited clinical data exist supporting the efficacy of any specific antimicrobial currently available for the treatment of APE secondary to MRSA. Conclusions: Data extrapolated from other populations suggest that vancomycin and linezolid are appropriate first-line treatment options for the treatment of APE secondary to MRSA. Second-line options include doxycycline or minocycline and trimethoprim/sulfamethoxazole, each of which may be useful in patients coinfected with other respiratory pathogens, for which they may provide overlapping coverage. Ceftaroline and ceftobiprole are newer antibiotics that appear to have a potential role in the treatment of APE in CF, but the latter is not currently available to the US market. Although potentially useful, clindamycin is limited by high rates of resistance, telavancin is limited by its toxicity profile, and tigecycline is limited by a lack of demonstrated efficacy for infections that are similar to that seen in the CF population. Studies investigating the clinical utility of the above-cited antibiotics for APE in CF secondary to MRSA are desperately needed to broaden the treatment armamentarium for this medical condition.

What is the efficacy and safety of colistin for the treatment of ventilator-associated pneumonia? A systematic review and meta-regression

BACKGROUND

Experience with intravenous and aerosolized forms of colistin for the treatment of ventilator-associated pneumonia (VAP) in patients without cystic fibrosis is limited. We aimed to assess the safety and efficacy of colistin for the treatment of VAP.

METHODS

We searched MEDLINE and Cochrane Database of Systematic Reviews for studies comparing colistin vs other antibiotics for treatment of VAP in patients without cystic fibrosis. QUOROM guidelines were followed, the I(2) method was used for heterogeneity, and a random-effects model for odds ratio (OR) estimates.

RESULTS

Six controlled studies met the inclusion criteria. Clinical response did not differ significantly between colistin and control groups (OR, 1.14; 95% confidence interval [CI], .74-1.77; P = .56; I(2) = 0%). The efficacy of colistin was independent of study design (prospective OR, 0.89 [95% CI, .48-1.66; P = .71; I(2) = 0%]; retrospective OR, 1.45 [95% CI, .79-2.68; P = .23; I(2) = 0%]); randomized trials OR, 0.86 [95% CI, .43-1.74; P = .68; I(2) = 0%]). There was no indication of a significant change in clinical response after controlling for concomitant antibiotic treatment (intercept, 0.121; slope, 0.0315; P = .95). Treatment with colistin vs controls did not affect hospital mortality (OR, 0.92; 95% CI, .50-1.67; P = .78; I(2) = 34.59%) or nephrotoxicity (OR, 1.14; 95% CI, .59-2.20; P = .69; I(2) = 0%). Fourteen single-arm studies have been analyzed, and the results were in concordance with the findings of the controlled studies.

CONCLUSIONS

Our results suggest that colistin may be as safe and as efficacious as standard antibiotics for the treatment of VAP.

Multiple antibiotic-resistant Pseudomonas aeruginosa and lung function decline in patients with cystic fibrosis

BACKGROUND

The goal of this study was to determine the association of multiple antibiotic-resistant Pseudomonas aeruginosa (MARPA) acquisition with lung function decline in patients with cystic fibrosis (CF).

METHODS

Using data from Epidemiologic Study of Cystic Fibrosis (ESCF), we identified patients with spirometry data and MARPA, defined as PA (1) resistant to gentamicin and either tobramycin or amikacin, and (2) resistant to ≥1 antipseudomonal beta lactam. MARPA had to be detected in a respiratory culture after ≥2 years of PA-positive but MARPA-negative respiratory cultures. Multivariable piecewise linear regression was performed to model the annual rate of decline in forced expiratory volume in 1 second (FEV(1)) % predicted 2 calendar years before and after the index year of MARPA detection, adjusting for patient characteristics and CF therapies.

RESULTS

In total, 4349 patients with chronic PA and adequate PFT data were identified; 1111 subsequently developed MARPA, while 3238 patients were PA positive but MARPA negative. Compared with patients who did not acquire MARPA, MARPA-positive patients had lower FEV(1) and received more oral (p<0.013) and inhaled (p<0.001) antibiotic therapy. Mean FEV(1) decline did not change significantly after MARPA detection (-2.22% predicted/year before detection and -2.43 after, p=0.45). There was no relationship between persistent infection or FEV(1) quartile and FEV(1) decline.

CONCLUSIONS

Newly detected MARPA was not associated with a significant change in the rate of FEV(1) decline. These results suggest that MARPA is more likely to be a marker of more severe disease and more intensive therapy, and less likely to be contributing independently to more rapid lung function decline.

Epidemiology of borderline oxacillin-resistant Staphylococcus aureus in pediatric cystic fibrosis

A single-center retrospective study was undertaken in children with cystic fibrosis (CF) to evaluate (1) risk factors for acquisition; (2) molecular epidemiology; and (3) impact on disease progression of borderline oxacillin-resistant Staphylococcus aureus (BORSA) versus mecA-positive methicillin-resistant Staphylococcus aureus (MRSA). The study comprised of (1) identification of all children with at least one respiratory specimen positive for either BORSA or MRSA during the study period; (2) compilation of relevant clinical and epidemiological data from 12-month period leading up to first positive (index) culture; (3) microbiological and molecular characterization of index isolates and (4) measurement of subsequent clinical outcome. Thirty-eight children were identified with at least one positive isolate; 4 were excluded due to insufficient clinical or laboratory data. Eighteen children (53%) grew BORSA in their index culture. Children who acquired BORSA only (n = 16) were more likely to have had prior MSSA colonization (P < 0.0001). Usage of oral cephalexin (P < 0.01) and inhaled tobramycin (P < 0.03) prior to index culture was significantly and independently associated with acquisition of BORSA. The majority of BORSA isolates were hyper β-lactamase producers and susceptible to a greater range of antibiotics. Strain relatedness was not evident within the BORSA group. There was no difference in disease progression between the two groups. This is the first study to demonstrate that a significant proportion of S. aureus isolates with methicillin resistance in the CF population are BORSAs that lack mecA. Antibiotic pressure may lead to the development of BORSA in CF patients. Prospective studies are needed to assess its clinical impact.

Methicillin resistance and vancomycin heteroresistance in Staphylococcus aureus in cystic fibrosis patients

Methicillin-resistant Staphylococcus aureus (MRSA) infections are increasingly being reported among cystic fibrosis (CF) populations worldwide. In this paper, we sought to examine at the epidemiology, the molecular characterisation and the antibiotic resistance of MRSA isolates in our cohort of CF patients. All MRSA strains were collected prospectively at the University Hospital of Catania, Italy, during a two-year study between mid 2005 to mid 2007 and underwent molecular, pathotype and susceptibility characterisations. Our study demonstrates persisting infections with both hospital-associated (HA-) and community-associated (CA-)MRSA, including Panton-Valentine leukocidin (PVL)-positive strains, in our CF population with an overall prevalence of 7.8%. We demonstrated that, in these patients, persistence was sustained by either identical clones that underwent subtle changes in their toxin content or by different clones over time. The isolation of MRSA in our CF population aged 7-24 years was associated with an increased severity of the disease even if, due to the small sample of patients included and the paucity of data on the clinical outcome, these results cannot be conclusive. Furthermore, three strains were heteroresistant vancomycin-intermediate S. aureus (hVISA), questioning the use of glycopeptides in the treatment of MRSA infections in these patients.

The changing microbial epidemiology in cystic fibrosis

Infection of the airways remains the primary cause of morbidity and mortality in persons with cystic fibrosis (CF). This review describes salient features of the epidemiologies of microbial species that are involved in respiratory tract infection in CF. The apparently expanding spectrum of species causing infection in CF and recent changes in the incidences and prevalences of infection due to specific bacterial, fungal, and viral species are described. The challenges inherent in tracking and interpreting rates of infection in this patient population are discussed.

Staphylococcus aureus nasal colonization among pediatric cystic fibrosis patients and their household contacts

BACKGROUND

Little is known about the prevalence of Staphylococcus aureus nasal colonization and the epidemiology of methicillin-susceptible and methicillin-resistant S. aureus (MRSA) among cystic fibrosis (CF) patients and their household members.

OBJECTIVES

We sought to determine the epidemiology of S. aureus among children and adolescents with CF and their household members.

METHODS

Three CF centers enrolled case subjects with at least 1 MRSA-positive respiratory tract culture from 2001 to 2006 and control subjects with MRSA-negative cultures. S. aureus isolates from the anterior nares of CF subjects and their household members were assessed for staphylococcal chromosomal cassette (SCC) mec type. Strain similarity was determined by pulsed-field gel electrophoresis.

RESULTS

S. aureus nasal colonization occurred in 52.4% (22/42), 27.0% (17/63), and 25.0% (72/288) of case, control, and household participants, respectively. Case subjects and their contacts were more likely to harbor MRSA in their nares and be from a multipatient CF family. Of 31 MRSA strains, 10 (32.3%) were SCCmec type IVa, associated with community-acquisition. Overall, 27.6% of 98 households had > or =2 members colonized with closely related isolates. Household members were equally likely to be colonized with closely related strains of MRSA (20/31, 65%) versus MSSA (38/80, 48%).

CONCLUSIONS

This study demonstrated that household members of CF children harbor both MSSA and MRSA, including CA-MRSA, and that S. aureus is transmitted within CF households. Carriage of S. aureus by household members of CF children may have implications for infection control and treatment strategies. Future studies should monitor the distribution and virulence of SCCmecA types in patients with CF.

Genomic analysis of an emerging multiresistant Staphylococcus aureus strain rapidly spreading in cystic fibrosis patients revealed the presence of an antibiotic inducible bacteriophage

Background

Staphylococcus aureus is a major human pathogen responsible for a variety of nosocomial and community-acquired infections. Recent reports show that the prevalence of Methicillin-Resistant S. aureus (MRSA) infections in cystic fibrosis (CF) patients is increasing. In 2006 in Marseille, France, we have detected an atypical MRSA strain with a specific antibiotic susceptibility profile and a unique growth phenotype. Because of the clinical importance of the spread of such strain among CF patients we decided to sequence the genome of one representative isolate (strain CF-Marseille) to compare this to the published genome sequences. We also conducted a retrospective epidemiological analysis on all S. aureus isolated from 2002 to 2007 in CF patients from our institution.

Results

CF-Marseille is multidrug resistant, has a hetero-Glycopeptide-Intermediate resistance S. aureus phenotype, grows on Cepacia agar with intense orange pigmentation and has a thickened cell wall. Phylogenetic analyses using Complete Genome Hybridization and Multi Locus VNTR Assay showed that CF-Marseille was closely related to strain Mu50, representing vancomycin-resistant S. aureus. Analysis of CF-Marseille shows a similar core genome to that of previously sequenced MRSA strains but with a different genomic organization due to the presence of specific mobile genetic elements i.e. a new SCCmec type IV mosaic cassette that has integrated the pUB110 plasmid, and a new phage closely related to phiETA3. Moreover this phage could be seen by electron microscopy when mobilized with several antibiotics commonly used in CF patients including, tobramycin, ciprofloxacin, cotrimoxazole, or imipenem. Phylogenetic analysis of phenotypically similar h-GISA in our study also suggests that CF patients are colonized by polyclonal populations of MRSA that represents an incredible reservoir for lateral gene transfer.

Conclusion

In conclusion, we demonstrated the emergence and spreading of a new isolate of MRSA in CF patients in Marseille, France, that has probably been selected in the airways by antibiotic pressure. Antibiotic-mediated phage induction may result in high-frequency transfer and the unintended consequence of promoting the spread of virulence and/or antibiotic resistance determinants. The emergence of well-adapted MRSA is worrying in such population chronically colonized and receiving many antibiotics and represents a model for emergence of uncontrollable super bugs in a specific niche.

Reviewers

This article was reviewed by Eric Bapteste, Pierre Pontarotti, and Igor Zhulin. For the full reviews, please go to the Reviewers' comments section.

The impact of incident methicillin resistant Staphylococcus aureus detection on pulmonary function in cystic fibrosis

The incidence of methicillin resistant Staphylococcus aureus (MRSA) infection is increasing in cystic fibrosis (CF), but the impact of MRSA detection on clinical outcomes is unclear. Our objective was to determine whether incident detection of MRSA is associated with a change in pulmonary function over time in CF patients. We analyzed data from the Epidemiologic Study of Cystic Fibrosis (ESCF), a prospective observational study of CF patients in North America. Multivariable piecewise linear regression was used to model the impact of incident detection of MRSA on pulmonary function over time, measured by percent predicted forced expiratory volume in one second (FEV(1)% predicted), adjusting for potential confounders. There were 5,090 patients >or=6 years old who were MRSA negative for at least 2 calendar years. Five hundred ninety-three (12%) of these patients acquired MRSA during the years 2001-2003, with detection rates of MRSA during those years rising from 4.4% to 6.9%. MRSA positive patients had a lower FEV(1)% predicted and received more antibiotic and other therapies than patients who remained MRSA negative. After adjusting for antibiotic therapy and other potential confounders, MRSA positive patients also had a higher rate of decline in FEV(1)% predicted both before and after the incident culture, although the rate of FEV(1)% predicted decline did not change significantly after MRSA detection. In conclusion, although MRSA in CF was a marker for more aggressive therapy and may reflect increased disease severity, incident MRSA detection was not associated with a changing rate of FEV(1)% predicted decline.

Prevalence and antimicrobial susceptibility of microorganisms isolated from sputa of patients with cystic fibrosis

BACKGROUND

New emerging pathogens and associated antimicrobial resistance mechanisms have been observed in the respiratory tract of patients suffering from cystic fibrosis (CF) in the last years. Amongst others, the rate of metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa strains is growing. However, there are no published data on the prevalence of MBL-producing P. aeruginosa in CF patients to our knowledge.

METHODS

In this study, 271 sputum samples of 60 CF patients were collected during a 12-months period. Microbiological cultures and antimicrobial susceptibility tests of the most frequently isolated bacteria were performed.

RESULTS

464 bacterial and 414 fungal strains were isolated and characterized. 63.3% of the patients harbored Staphylococcus aureus, 50% P. aeruginosa, 16.6% Haemophilus influenzae, 15% Stenotrophomonas maltophilia and 13.3% non tuberculous Mycobacteria (NTM). Methicillin resistant S. aureus (MRSA) and MBL-producing P. aeruginosa were detected in 3 (5%) and 5 (8.3%) patients respectively. Among the fungi, Aspergillus fumigatus and Candida albicans showed the highest prevalence.

CONCLUSIONS

The detection of MBL-producing P. aeruginosa and MRSA in CF patients confirms that antimicrobial resistance patterns should be always kept under surveillance. Moreover hygiene regulations in CF clinics should prevent a further spread of resistant bacterial strains.

Infection Control Practice in Cystic Fibrosis Centers

In this article, the authors outline some of the major historical events that signaled the need to better understand mechanisms of infection in cystic fibrosis (CF). The authors discuss general principles of infection control, focusing on issues of particular importance to patients who have CF. The authors also describe the major pathogens associated with the CF airway, provide a review of findings from inpatient and outpatient studies of infection control, and provide an outline of future directions for investigation.

Presence of methicillin resistant Staphylococcus aureus in respiratory cultures from cystic fibrosis patients is associated with lower lung function

The prevalence of methicillin resistant Staphylococcus aureus (MRSA) infections is increasing in both the general population and cystic fibrosis (CF) patients. We hypothesized that MRSA infection of the conductive airways as seen in CF would be associated with more severe disease than that seen with methicillin sensitive S. aureus (MSSA). To test this hypothesis, we used data from the Epidemiologic Study of Cystic Fibrosis (ESCF), a large observational study of CF patients in North America, to compare CF patients with MRSA in their respiratory tract cultures to those with MSSA. During a 1-year time period from January 1, 2001 to December 31, 2001, data from 20,451 patients were collected by the ESCF, and 1,834 (7.5%) patients had respiratory tract cultures that were positive for S. aureus only. Compared to patients with MSSA only, patients with MRSA only had significantly more airflow obstruction, as measured by forced expiratory volume in 1 sec (FEV1). The mean FEV1 for patients 6-17 years old with MRSA was 80.7% predicted compared to 89.4% in the MSSA group (P<0.001). The likelihood of hospitalization and treatment with oral, inhaled, and intravenous antibiotics were all significantly increased in patients with MRSA compared to those with MSSA. Similar results were seen in patients >or=18 years old. The results of our study highlight the growing clinical impact of MRSA infections in CF patients.

Successful decolonization of meticillin-resistant Staphylococcus aureus in paediatric patients with cystic fibrosis (CF) using a three-step protocol

Methicillin-resistant Staphylococcus aureus (MRSA) is recognized as a bacterial pathogen in patients with cystic fibrosis (CF) although its clinical effects can be variable. The aim of this study was to evaluate the efficacy of a three-step decolonization protocol for MRSA (Belfast CF MRSA decolonization protocol). Of the 17 paediatric patients treated during the five years of the study, eight (47%) were successfully decolonized following one five-day course of oral rifampicin and fusidic acid. The success rate increased to 12 (71%) patients after a second five-day oral treatment course in the 11 patients who remained culture positive at the end of the first treatment cycle. In a further four patients, clearance was achieved with a course of intravenous teicoplanin, increasing the decolonization rate to 16 of 17 patients (94%). These results compare favourably with other published studies and show that MRSA decolonization can be successful in a high proportion of paediatric CF patients.

Emerging Options for Treatment of Invasive, Multidrug-ResistantStaphylococcus aureusInfections

Limited established treatment options exist for the treatment of serious, invasive infections caused by multidrug-resistant Staphylococcus aureus, most notably nosocomially acquired methicillin-resistant S. aureus (MRSA). Although vancomycin represents the gold standard for therapy of such invasive infections, reports of increasing in vitro resistance to vancomycin, combined with reports of clinical failures (with this and other antistaphylococcal agents), underscore the need for alternative therapies. Older agents with favorable in vitro activity available in both oral and intravenous dose forms include trimethoprim-sulfamethoxazole and clindamycin. Limited clinical data exist to support their routine use as initial therapy in the treatment of invasive disease. However, these and other options (e.g., tetracyclines) are being reexplored in the setting of increasing concern over MRSA acquired in the community setting. Newer treatment options for MRSA include linezolid, quinupristin-dalfopristin, daptomycin, and tigecycline. With the exception of linezolid, these newer agents require intravenous administration. Combination therapy may be considered in select invasive diseases refractory to standard monotherapies. These diseases include infections such as endocarditis, meningitis, and prosthetic device infections. Additional alternatives to vancomycin are under clinical investigation. Those in later stages of development include oritavancin, dalbavancin, telavancin, and ceftobiprole.

Multidrug-resistant organisms in cystic fibrosis: management and infection-control issues

Chronic infection and inflammation are the hallmarks of cystic fibrosis lung disease. As cystic fibrosis patients are living longer owing to more intense treatment, multidrug-resistant organisms are being isolated increasingly from patients' respiratory tracts. While the adverse effects of Pseudomonas aeruginosa and Burkholderia cepacia complex are well described, less is known about the clinical significance of other emerging multidrug-resistant organisms, such as methicillin-resistant Staphylococcus aureus and Stenotrophomonas maltophilia. Owing to multiple mechanisms of antimicrobial resistance, these organisms are difficult to treat and often require combination antibiotic therapy. Until more is known about their pathogenicity and effect on clinical outcomes, physicians should be aware of the potential transmissibility of these organisms and implement adequate infection control strategies.

Update on treatment of pulmonary exacerbations in cystic fibrosis

PURPOSE OF REVIEW

This review will define pulmonary exacerbations in cystic fibrosis and explain their importance in the pathophysiology and progression of this condition. I will stress the importance of prevention, where this is possible, and prompt treatment, where prevention has failed. The management of chronic pulmonary infection with Pseudomonas aeruginosa will be discussed, together with other, less tenacious organisms.

RECENT FINDINGS

Developments in the treatment of chronic pulmonary infection with P. aeruginosa include new data on antibiotic selection through sensitivity testing and alternative antibiotic dosing regimens. Therapies which target the P. aeruginosa biofilm will be discussed, including those which are currently in use (such as azithromycin) as well as those being evaluated in preclinical studies. Supportive care and the role of noninvasive ventilation are discussed.

SUMMARY

The prevention and prompt treatment of pulmonary exacerbations is a central component of cystic fibrosis care.

Fungal—bacterial interactions: a mixed bag of mingling microbes

Fungi and bacteria co-inhabit a wide variety of environments, from soils and food products to plants and mammals. Interactions between bacteria and fungi can have dramatic effects on the survival, colonization and pathogenesis of these organisms. There are instances where bacteria provide fungi with compounds that enhance the production of fungal virulence determinants. Other bacteria produce factors that are likely to inhibit pathogenesis by repressing fungal filamentation. Furthermore, mixed bacterial-fungal biofilms can have properties that are distinct from their single-species counterparts. Clinical studies, in combination with in vitro model systems, are necessary to understand how bacterial-fungal interactions impact human health.

Fatal pneumonia caused by Panton-Valentine Leucocidine-positive methicillin-resistant Staphylococcus aureus (PVL-MRSA) transmitted from a healthy donor in living-donor liver transplantation

Severe infections are the most dangerous complications in liver transplantation and their prevention is one of the major goals. A 60-year-old Saudi-Arabian female with decompensated hepatitis C liver cirrhosis received a right-lobe liver graft from her healthy daughter. After 9 days, the patient developed a rapidly progressive necrotizing pneumonia that was fatal in spite of extracorporal lung assist. The pneumonia was due to a Panton-Valentine Leucocidine-positive (PVL) methicillin-resistant Staphylococcus aureus (MRSA), or "community-acquired" MRSA, that had not been detectable in the patient preoperatively. The same strain of PVL-MRSA could be demonstrated in the nares of the asymptomatic donor, but not of other relatives, patients, or medical staff. These findings strongly suggest transmission of PVL-MRSA from the donor to the recipient. This case demonstrates a previously unknown, and potentially fatal, risk in living-donor liver transplantation: transmission of a severe infection from a healthy donor to the recipient.