Can throat swab after physiotherapy replace sputum for identification of microbial pathogens in children with cystic fibrosis?

Diagnosis and Management of Cystic Fibrosis Exacerbations

With the improving survival of cystic fibrosis (CF) patients and the advent of highly effective cystic fibrosis transmembrane conductance regulator (CFTR) therapy, the clinical spectrum of this complex multisystem disease continues to evolve. One of the most important clinical events for patients with CF in the course of this disease is acute pulmonary exacerbation (PEx). Clinical and microbial epidemiology studies of CF PEx continue to provide important insight into the disease course, prognosis, and complications. This work has now led to several large-scale clinical trials designed to clarify the treatment paradigm for CF PEx. The primary goal of this review is to provide a summary and update of the pathophysiology, clinical and microbial epidemiology, outcome and treatment of CF PEx, biomarkers for exacerbation, and the impact of highly effective modulator therapy on these events moving forward.

Airway Microbiology in Children with Cystic Fibrosis: A Prospective Cohort Study from Northern India

OBJECTIVE

The objective of this study is to find the organism profile and antimicrobial susceptibility patterns in children with cystic fibrosis (CF).

DESIGN

Prospective cohort study.

SETTING

Hospital-based study.

INTERVENTION

Sputum cultures/throat swabs were collected from the study population. Relevant details like anthropometry, systemic examination findings and investigations were entered in a pre-designed format. Sputum culture was subjected to microbiological analysis at the hospital microbiology laboratory.

MAIN OUTCOME MEASURE

Prevalence of positive sputum/cough swab culture in CF patients, their organism profile and antibiotic sensitivity.

RESULTS

A total of 63 patients were enrolled in the study. A total of 136 organisms were grown in our study population. Thirteen different organisms were isolated, which included five gram-positive bacteria, six gram-negative bacteria, eight Candida spp. and one filamentous. Antibiotic sensitivity profile of the Pseudomonas aeruginosa showed excellent sensitivity to all the aminoglycosides, piperacillin-tazobacteum and polymixin, similarly methicillin-sensitive Staphylococcus aureus, methicillin-resistant S. aureus and Enterococcus spp. were uniformly sensitive to vancomycin, linezolid and teicoplanin. Fungal isolates showed 100% sensitivity to all the antifungals tested including azoles and amphotericin B.

CONCLUSION

We observed 61% of culture positivity for different organisms in our study. Staphylococcus aureus and P. aeruginosa were the most frequently isolated organisms. Pseudomonas aeruginosa isolates were largely sensitive to aminoglycosides, carbapenems and polymixin. We found an unusually higher incidence of enterococcal infection in our study cohort with few vancomycin-resistant isolates.

Chest physiotherapy enhances detection of Pseudomonas aeruginosa in nonexpectorating children with cystic fibrosis

Lung damage in cystic fibrosis (CF) is strongly associated with lower airway infections. Early treatment of Pseudomonas aeruginosa is recommended. Pathogen detection requires sampling of lower airway secretions, which remains a challenge in nonexpectorating patients. Our hypothesis was that chest physiotherapy would improve the quality of airway secretion samples and increase the rates of pathogens detected in nonexpectorating patients.

This prospective multicentre study compared three successive methods for sampling airway secretions applied through the same session: 1) an oropharyngeal swab (OP), 2) a chest physiotherapy session followed by a provoked cough to obtain sputum (CP-SP) and 3) a second oropharyngeal swab collected after chest physiotherapy (CP-OP). Haemophilus influenzae, Staphylococcus aureus and P. aeruginosa growth cultures were assessed. Accuracy tests and an equivalence test were performed to compare the three successive methods of collection.

300 nonexpectorating children with CF were included. P. aeruginosa was detected cumulatively in 56 (18.9%) children, and according to the different collection methods in 28 (9.8%), 37 (12.4%) and 44 (14.7%) children by using OP, CP-OP and CP-SP, respectively. Compared with OP, the increased detection rate was +22% for CP-OP (p=0.029) and +57% for CP-SP (p=0.003). CP-SP had the best positive predictive value (86.3%) and negative predictive value (96.0%) for P. aeruginosa compared with the overall detection.

The results of this adequately powered study show differences in the rates of pathogens detected according to the sampling method used. Chest physiotherapy enhanced detection of P. aeruginosa in nonexpectorating children with CF.

Sputum collection after a chest physiotherapy session strongly enhances the detection of P. aeruginosa in nonexpectorating CF children compared with the commonly used oropharyngeal swab method. Oropharyngeal swab after physiotherapy may be an acceptable alternative.https://bit.ly/3757ewq

Acute Pulmonary Exacerbations in Cystic Fibrosis

With the improving survival of cystic fibrosis (CF) patients and the advent of highly effective cystic fibrosis transmembrane conductance regulator therapy, the clinical spectrum of this complex multisystem disease continues to evolve. One of the most important clinical events for patients with CF in the course of this disease is an acute pulmonary exacerbation. Clinical and microbial epidemiology studies of CF pulmonary exacerbations continue to provide important insight into the disease course, prognosis, and complications. This work has now led to a number of large scale clinical trials with the goal of improving the treatment paradigm for CF pulmonary exacerbation. The primary goal of this review is to provide a summary of the pathophysiology, the clinical epidemiology, microbial epidemiology, outcome and the treatment of CF pulmonary exacerbation.

Acute Pain Perception During Different Sampling Methods for Respiratory Culture in Cystic Fibrosis Patients

CONTEXT

Reliable identification of lower respiratory tract pathogens is crucial in the management of cystic fibrosis (CF). The multitude of treatments and clinical procedures are a considerable burden and are potentially provoking pain.

OBJECTIVES

As part of another study (NCT02363764), investigating the bacterial yield of three sampling methods, nasal swabs (NSs), cough swabs (CSs), and (induced) sputum samples ([I]SSs), in both expectorating patients (EPs) and non-expectorating patients (NEPs) with CF, the present study aimed to explore the prevalence of respiratory culture sampling-related pain as assessed by self-report within a cohort of children and adults.

METHODS

Literate patients with CF (aged six years or older) completed a questionnaire on pain perception related to the three aforementioned sampling methods (No/Yes; visual analogue scale for pain [VAS-Pain] [0-10 cm]). In addition, patients were asked to rank these methods by their own preference without taking into account the presumed bacterial yield.

RESULTS

In total, 119 questionnaires were returned. In the EPs-group, CS was most frequently (n%; mean VAS-Pain if pain [range]) reported as painful method: overall (n = 101; 12.9%; 1.8 [0.2-4.8]), children (n = 41; 22.0%; 1.4 [0.2-2.7]), and adults (n = 60; 6.7%; 2.5 [0.5-4.8]). Highest pain intensity scores were observed with NS overall (3.0%; 2.4 [0.3-6.2]) and in children (4.9%; 3.3 [0.3-6.2]), but not in adults (1.7%; 0.6 [-]).NEPs-children (n = 17) reported ISS most frequently and as most painful sampling method (17.6%; 2.0 [1.0-4.0]). The only NEP-adult did not perceive pain. NEPs preferred NS > CS > ISS (61.1%, 33.3%, 5.6%, respectively [P = 0.001]) as primary sampling method, whereas EPs preferred SS > NS > CS (65.7%, 26.3%, 8.1%, respectively [P < 0.0001]). Patients' preference for a specific method inversely correlated to pain perception and intensity in EPs (φ = -0.155 [P = 0.007] and ρ = -0.926 [P = 0.008], respectively), but not in NEPs (φ = -0.226 [P = 0.097] and ρ = -0.135 [P = 0.798], respectively).

CONCLUSION

A relatively large range of pain experiences was observed in patients with CF during respiratory culture sampling, which underlines the importance of individual pain assessment. Nevertheless, clinicians can confidently choose the sampling method based on validity over patients' preference.

Successful eradication of newly acquired MRSA in six of seven patients with cystic fibrosis applying a short-term local and systemic antibiotic scheme

Background

In individuals with cystic fibrosis (CF), colonization with methicillin-resistant Staphylococcus aureus (MRSA) was reported to be associated with a deterioration of pulmonary disease as reflected by an accelerated decline in lung function. Thus, an early eradication of MRSA could be beneficial in these patients. Here, we report on an intensified MRSA eradication protocol.

Methods

Since 2012 a protocol for the eradication of newly acquired MRSA has been used in our CF Clinic, combining oral rifampicin and fusidic acid, inhaled vancomycin, nasal mupirocin, local antiseptic treatment and hygienic directives all of which are applied for only 7 days during an inpatient hospital stay.

Results

Since 2012 seven patients (3 male, 4 female; age range 4 to 30 years) newly acquired MRSA. In 6 of the 7 patients (86%) successful eradication of MRSA was achieved upon first treatment using the protocol described above. In one patient a second course of treatment was performed which, however, also failed to eliminate the colonizing MRSA.

Conclusions

Our protocol led to an eradication rate of 86%. The impact of each individual component of the protocol remains to be determined.

Respiratory Bacterial Culture Sampling in Expectorating and Non-expectorating Patients With Cystic Fibrosis

Purpose: Different respiratory sampling methods exist to identify lower airway pathogens in patients with cystic fibrosis (CF), of which bronchoalveolar lavage (BAL), and expectorated sputum are considered the "gold standard." Because BAL cannot be repeated limitless, the diagnosis of lower respiratory tract infections in non-expectorating patients is challenging. Other sampling techniques are nasal swab, cough swab, and induced sputum. The purpose of this study (NCT02363764) was to compare concordance between the microbiological yield of nasal swab, cough swab, and expectorated sputum in expectorating patients; nasal swab, cough swab, and induced sputum in non-expectorating patients; nasal swab, cough swab, induced sputum, and BAL in patients requiring bronchoscopy ("BAL-group"); and to determine the clinical value of cough swab in non-expectorating patients with CF. Methods: Microbiological yield detected by these different sampling techniques was compared between and within 105 expectorating patients, 30 non-expectorating patients and BAL-group (n = 39) in a single CF clinic. Specificity, sensitivity, positive (PPV), and negative (NPV) predictive values were calculated. Results: Overall low sensitivity (6.3-58.0%) and wide-ranging predictive values (0.0-100.0%) indicated that nasal swab was not appropriate to detect lower airway pathogens [Pseudomonas aeruginosa (Pa), Staphylococcus aureus (Sa), and Haemophilus influenzae (Hi)] in all three patient groups. Microbiological yield, specificity, sensitivity, PPV, and NPV of cough swab and induced sputum were largely similar in non-expectorating patients and in BAL-group (except sensitivity (0.0%) of induced sputum for Hi in BAL-group). Calculations for Pa and Hi could not be performed for non-expectorating patients because of low prevalence (n = 2 and n = 3, respectively). In expectorating patients, concordance was found between cough swab and expectorated sputum, except for Hi (sensitivity of 40.0%). Conclusion: Our findings suggest that cough swab might be helpful in detecting the presence of some typical CF pathogens in the lower airways of clinically stable patients with CF. However, in symptomatic patients, who are unable to expectorate and who have a negative cough swab and induced sample, BAL should be performed as it currently remains the "gold standard."

Detection of Staphylococcus aureus in cystic fibrosis patients using breath VOC profiles

Staphylococcus aureus (S. aureus) is a common bacterium infecting children with cystic fibrosis (CF). Since current detection methods are difficult to perform in children, there is need for an alternative. This proof of concept study investigates whether breath profiles can discriminate between S. aureus infected and non-infected CF patients based on volatile organic compounds (VOCs). We collected exhaled breath of CF patients with and without S. aureus airways infections in which VOCs were identified using gas chromatography-mass spectrometry. We classified these VOC profiles with sparse partial least squares discriminant analysis. Multivariate breath VOC profiles discriminated infected from non-infected CF patients with high sensitivity (100%) and specificity (80%). We identified the nine compounds most important for this discrimination. We successfully detected S. aureus infection in CF patients, using breath VOC profiles. Nine highlighted compounds can be used as a focus point in further biomarker identification research. The results show considerable potential for non-invasive diagnosis of airway infections.

Infection and inflammation in induced sputum from preschool children with chronic airways diseases

BACKGROUND

We hypothesized airway inflammation can be detected non-invasively by induced sputum (IS) or peripheral blood eosinophilia, and IS can detect bacterial and viral infection in preschool children with airway disease, with results comparable to broncho-alveolar lavage (BAL).

METHODS

Preschool children with cystic fibrosis, recurrent wheeze, or wet cough underwent IS with nebulized hypertonic saline, chest physiotherapy, and oropharyngeal suction. Samples were analyzed for inflammation by cytology and bacterial culture, viral detection by PCR. Results were compared to BAL and blood in a sub-group undergoing clinically indicated bronchoscopy.

RESULTS

64 children (median age 33 [7-76] months) underwent IS without adverse events. IS was obtained from 61/64. Twenty out of sixty-four underwent BAL and IS, no IS was obtained in 2/23. Thirteen out of twenty-one (62%) had matching bacteria and viruses, 4/21 had positive BAL bacterial growth with negative IS, and 3/21 had negative BAL growth with positive IS. 67% of sputum samples were processed for cytology, 46% had <80% squamous cells; the proportion of squamous cells reduced with increasing age (r = -0.55, P < 0.01). IS was significantly more neutrophilic and less eosinophilic than BAL; 2/21 IS samples contained eosinophils compared to 17/23 BAL. There was a positive correlation between blood and BAL eosinophilia (r = 0.75, P < 0.01).

CONCLUSION

IS from preschool children can be used to assess infection. BAL and IS culture concurred in approximately two-thirds. However, inflammation was measureable in only one-third of IS samples and the cell differential was predominantly neutrophilic compared to BAL. Blood eosinophils may provide a better reflection of lower airway eosinophilia in this age group. Pediatr Pulmonol. 2016;51:778-786. © 2015 WileyPeriodicals, Inc.

Identification of new bacterial and fungal pathogens on surveillance bronchoscopy prior to sinus surgery in patients with cystic fibrosis

BACKGROUND

Flexible fiberoptic bronchoscopy was performed prior to functional endoscopic sinus surgery (FESS) while under general anesthesia to collect bronchoalveolar lavage fluid (BALF) for lower respiratory tract cultures in patients with cystic fibrosis (CF).

METHODS

A retrospective chart review was performed on all CF patients who underwent combined FESS and bronchoscopy between January 2009 and October 2010. Along with demographic data, bacterial, fungal, and acid fast bacillus culture data from BALF was collected and compared to oropharyngeal swab and sputum cultures obtained over the year prior to FESS and bronchoscopy.

RESULTS

A total of 77 patients were enrolled with mean age 12.5 ± SD 6.5 (range 2-29) years. Mean FEV1 was 86% ±18.4 (range 33-128) % of predicted. Patients averaged 6.5 (range 1-13) sputum or OP cultures in the year prior to FESS. BALF cultures identified a new bacterial pathogen in 19% (n=15) of patients, which altered antibiotic regimen immediately in two patients and sub-acutely in five patients. BALF cultures identified a new fungal pathogen in 42% (n=32) of patients, which resulted in the addition of antifungal therapy in eight patients. BALF cultures did not identify previously undetected AFB culture positive patients. No significant differences were found between patients with and without new discoveries of bacterial or fungal pathogens with regards to key clinical demographic data, lung function parameters, healthcare utilization, or need for antibiotics over the year prior to FESS. There was no relationship between the total number of respiratory cultures obtained in the year prior to bronchoscopy and the identification of new bacterial or fungal pathogens.

CONCLUSIONS

Surveillance BALF cultures obtained prior to FESS identified bacterial and fungal pathogens not previously detected by sputum or OP swab cultures in a cohort of CF patients with chronic sinus disease. Moreover, the identification of these new pathogens altered clinical management in a small number of patients.

How to use: bacterial cultures in diagnosing lower respiratory tract infections in cystic fibrosis

Respiratory infections are the leading cause of morbidity and mortality in cystic fibrosis. Certain bacteria, such as Pseudomonas aeruginosa, are associated with a worse clinical outcome than others, but can be completely eradicated if identified and treated early. The diagnosis of lower respiratory tract infections can be challenging in the non-expectorating patient, in whom upper airway samples, such as cough swabs, are a surrogate for lower airway sampling. However, the results of these often do not fit with the clinical picture, presenting a management dilemma. Frequently, clinicians are faced with a negative culture result in a progressively symptomatic patient and vice versa. When judging the clinical significance of a positive upper airway culture result in an asymptomatic patient, it is important to consider the prognostic significance of the organism cultured. Given that the reported sensitivity of upper airway swabs (which includes throat swabs) is variable, ranging from 35.7% to 71% for Pseudomonas aeruginosa, 50% to 86% for Staphylococcus aureus and 11% to 92% for Haemophilus influenza, upper airway samples may fail to identify lower airway infections. Therefore, in symptomatic children, a repeatedly negative upper airway swab should not be considered as reassuring, and alternative sampling methods, such as induced sputum or bronchoalveolar lavage, should be considered. Here we use some examples of common scenarios to illustrate how best to use bacterial cultures to aid management decisions in cystic fibrosis.

Exhaled breath condensate purines correlate with lung function in infants and preschoolers

RATIONALE

Although airway inflammation begins early in life in children with chronic respiratory diseases, current methods to assess this inflammation are invasive and entail significant risk. Measurement of exhaled breath condensate (EBC) purines and other biomarkers offers a less invasive method to assess airway inflammation; however, the feasibility and utility of EBC biomarkers in young children has not been established.

METHODS

EBC was collected from children <3 years old with cystic fibrosis or other lung diseases during clinically indicated infant pulmonary function tests (iPFTs). EBC concentrations of the purine biomarkers adenosine (Ado), adenosine monophosphate (AMP), and the dilution marker urea were measured using mass spectrometry.

RESULTS

EBC was successfully collected (average volume 330 ± 170 µl) from preschool children (age 2.3 ± 0.8 years) in 15 of 17 iPFTs. No significant changes in oxygen saturation (96.9 ± 1.6 start, 96.8 ± 1.7 end, P = 0.389) or respiratory rate (35.2 ± 7.5 start, 34.6 ± 7.9 end, P = 0.443) were observed during collection. Ado and AMP were successfully measured in 13/15 samples [8 cystic fibrosis (CF)]. EBC AMP to Ado ratio (AMP/Ado) negatively correlated with forced expiratory volume at 0.5 sec (FEV(0.5) , r = -0.71, P < 0.01) and positively with the ratio of residual volume to total lung capacity (RV/TLC, r = 0.66, P = 0.015). These correlations remained statistically significant in the subset with CF.

CONCLUSIONS

EBC can be safely collected and analyzed in preschool children using commercially available equipment. The EBC AMP/Ado ratio correlates with measures of infant lung function and may be a less invasive means of monitoring airway inflammation in this population.

The use of deep oral swabs as a surrogate for transoral tracheal wash to obtain bacterial cultures in dogs with pneumonia

OBJECTIVE

To determine agreement in bacterial culture and susceptibility (BC&S) between deep oral swab (DOS) and routine transoral tracheal wash (TOTW) in dogs with pneumonia.

DESIGN

Prospective study, performed between 2008 and 2010 with no follow-up period.

SETTING

University teaching hospital.

ANIMALS

Five puppies and 5 adult dogs with community or hospital-acquired pneumonia.

MEASUREMENTS AND MAIN RESULTS

A DOS was collected from each patient; dogs were then briefly anesthetized with propofol(a) for a routine TOTW. Routine microbiology techniques were used for culture. Positive culture results were obtained from all 20 swabs. Results of BC&S were compared between the 2 sites. In all puppies, there was no agreement between DOS and TOTW. In adult dogs, 2 patients with hospital-acquired infection (HAI) had complete agreement between the BC&S results from DOS and TOTW. Two adult dogs had some similarity in BC&S results, and the final dog had no relationship between cultures.

CONCLUSIONS

DOS is not an appropriate alternative to TOTW to obtain samples for BC&S in puppies with pneumonia. In adult dogs, traditional TOTW remains the gold standard, but DOS may be considered in dogs with suspected HAI. Further work is needed to confirm this preliminary finding.

Respiratory bacterial flora from healthy as well as respiratory symptoms' subjects

Respiratory system is the primary settlement place of opportunistic organisms and considered as chief carrier of common respiratory pathogens. The aim of the study was to know the opportunistic organisms present in the healthy subjects as well as subjects that were suffering from respiratory symptoms. The organisms were identified as per standard bacteriological protocol and pathogenicity tests of the identified organisms were performed in mouse model. Antibiotic sensitivity of the identified organisms was performed. The bacterial flora present in the throat swab of apparently healthy as well as subjects suffering from respiratory symptoms were: Staphylococcus spp. (39.44%) of which Coagulase positive Staphylococcus (21.13%) and Coagulase negative Staphylococcus (18.31%), Klebsiella spp. (19.72%), Pseudomonas spp. (15.49%), Proteus spp. (4.23%), E. coli (9.86%) and Bacillus spp. (11.27%). Among the isolates Staphylococcus, Klebsiella and Pseudomonas were the predominant species. Percentages of identified bacteria were higher in respiratory symptoms exhibiting individuals (53.52%) than apparently healthy individuals (46.48%). All coagulase positive Staphylococcus, Klebsiella spp. and Pseudomonas spp. isolated from respiratory symptoms' subjects were found to be pathogenic. The isolated bacteria were resistant to amoxicillin and ampicillin but sensitive to ciprofloxacin and norfloxacin. Isolated Pseudomonas spp. showed multidrugs resistant properties. The study provided information about the pathogenic organisms' present respiratory systems of apparently healthy as well as subjects suffering from respiratory symptoms. The pathogenic natures of the isolated organisms were determined to make aware of scientists as well as clinicians. Antibiotics sensitivity assays would provide information to the clinicians for the selection of appropriate antibiotics to treat their patients.

Pseudomonas aeruginosa serological analysis in young children with cystic fibrosis diagnosed through newborn screening

BACKGROUND

With newborn screening (NBS) for cystic fibrosis (CF), eradication of Pseudomonas aeruginosa (PA) is possible if PA detection occurs early. A serological response to infection likely precedes culture positivity in CF patients, so PA serological testing is very appealing in this population. However, controversies continue to exist about serology testing, titer cutoffs for enzyme-linked immunosorbent assay (ELISA) antibody tests, and their value in children with CF.

METHODS

This longitudinal, prospective study collected respiratory secretions as oropharyngeal swabs or expectorated sputum for culture and also sera over 6 years in 69 patients diagnosed by NBS. Serology assessed PA antibody titers against cell lysate, exotoxin A, and elastase. A novel statistical approach with weighted receiver operating characteristic (ROC) curves was used to determine best antibody titer cutoff values to predict subsequent PA positive cultures.

RESULTS

Using these weighted ROC curves, the order of sensitivity was found to be cell lysate, exotoxin A, and then elastase while age-specific cutoffs were better than fixed cutoffs previously used. Age-specific serological cutoffs both predict and detect PA respiratory infections with a higher sensitivity and specificity. Serological responses to the PA antigens determined that a response to cell lysate occurs significantly earlier than culture positivity.

CONCLUSIONS

Age-specific serological cutoffs rather than fixed values against common PA antigens improve early PA identification in infants and young children diagnosed with NBS. Regular serological assessment with age-specific cutoffs in these children appears to be a worthy diagnostic tool.

Exacerbations in cystic fibrosis. 1: Epidemiology and pathogenesis

With the improving survival of patients with cystic fibrosis (CF), the clinical spectrum of this complex multisystem disease continues to evolve. One of the most important clinical events for patients with CF in the course of this disease is an acute pulmonary exacerbation. Clinical and microbial epidemiology studies of CF pulmonary exacerbations continue to provide important insight into the course, prognosis and complications of the disease. This review provides a summary of the pathophysiology, clinical epidemiology and microbial epidemiology of a CF pulmonary exacerbation.

Investigation and management of suppurative cough in pre-school children

Suppurative cough can be defined as a cough where purulent sputum is produced. Chronic suppurative cough may be associated with the destruction of the bronchial wall (bronchiectasis). As mild forms of the disease are not associated with respiratory limitation or failure to thrive, such children may not present for investigation and therefore the true incidence of suppurative cough is difficult to gauge. Chronic suppurative cough remains an important health problem in developing countries and some indigenous populations of developed countries. The purpose of this review is to present the appropriate investigations and evaluate the evidence for current management strategies in children with suppurative cough. To accomplish this, a brief discussion on the aetiology of suppurative cough in childhood is presented. The most commonly identifiable cause of suppurative cough is cystic fibrosis. A detailed discussion on cystic fibrosis is beyond the scope of this review. Other causes of chronic suppurative cough in pre-school children may be classified according to congenital malformations of the airway, immunodeficiency, ciliary dysfunction and, unusually, acquired causes. Microbiology of sputum culture or bronchoalveolar lavage, assessment of immune function, the role of exhaled nitric oxide and ciliary studies, and medical imaging are discussed in detail. One can conclude that the evidence for management strategies for children with suppurative cough is, at best, level 3 evidence, i.e. non-randomised, controlled or cohort studies.

Diagnostic and prognostic value of serum antibodies against Pseudomonas aeruginosa in cystic fibrosis

BACKGROUND

Eradication of Pseudomonas aeruginosa in patients with cystic fibrosis (CF) is possible if initiated early in the course of colonisation. To detect P aeruginosa as early as possible is therefore a major goal. This study was undertaken to validate a commercialised test for the detection of serum Pseudomonas antibodies in patients with CF.

METHODS

A representative cross sectional analysis of serum antibodies against three Pseudomonas antigens (alkaline protease, elastase, and exotoxin A) was performed in 183 patients with CF of mean age 16.7 years and FEV1 85.9% predicted. The results were correlated with microbiological results from the previous 2 years to calculate sensitivity, specificity, positive and negative predictive values. The following 2 years were assessed to determine prognostic predictive values.

RESULTS

A combination of all three tested antibodies yielded the best results with a sensitivity of 86%, specificity of 96%, and a positive predictive value of 97%. These values were higher if only patients in whom sputum cultures were available were considered (n = 76, sensitivity 95%, specificity 100%, positive predictive value 100%). The prognostic positive predictive value was high in intermittently infected patients (83%) but low in patients free of infection (33%), whereas the prognostic negative predictive value was high in patients free of infection (78%) and low in intermittently infected patients (58%).

CONCLUSIONS

Regular determination of serum antibodies may be useful in CF patients with negative or intermittent but not with positive P aeruginosa status. A rise in antibody titres indicates probable infection and eradication treatment may be initiated even in the absence of microbiological detection of P aeruginosa.

Characterization of Pseudomonas aeruginosa isolated from chronically infected children with cystic fibrosis in India

BACKGROUND

Pseudomonas aeruginosa is the leading cause of morbidity and mortality in patients with cystic fibrosis (CF). With chronicity of infection, the organism resides as a biofilm, shows multi-drug resistance, diversifies its colony morphology and becomes auxotrophic. The patients have been found to be colonized with multiple genotypes. The present work was carried out to characterize P. aeruginosa isolated from children with cystic fibrosis using phenotypic and genotypic methods.

RESULTS

We studied 56 patients with CF attending the Pediatric Chest clinic at All India Institute of Medical Sciences, New Delhi, India during August 1998-August 2001. These patients were regularly followed up at the clinic. Out of 56 patients, 27 were culture positive for P. aeruginosa where 8 were chronically infected (Group1) and 19 were intermittently colonized with the organism (Group2). Patients under Group1 had significantly higher rates of hospitalization, death and colonization with different colony morphotypes (p < 0.05). The isolates from Group1 patients were the positive producers of extended spectrum beta lactamase. A total of 5 auxotrophs were recovered from 2 patients where one was chronically infected with P. aeruginosa and the other was a recently enrolled patient. The auxotrophs had the specific requirement for methionine and arginine. Molecular typing revealed 33 ERIC-PCR (E1-E33) and 5 PCR-ribotyping (P1-P5) patterns. By ERIC-PCR, 4 patients were colonized with 2-4 genotypes and the remaining 23 patients were colonized with the single genotype.

CONCLUSION

With chronicity of infection, P. aeruginosa becomes multidrug resistant, diversifies its colony morphology, acquires mucoidity and shows auxotrophy for amino acids. The chronically infected patients can be colonized with multiple genotypes. Thus in a particular clinical set up, high index of suspicion should be there for diagnosis of CF patients so as to prevent the delay in diagnosis and management of CF patients.