Airway Bacteria Research Articles

Diagnosing and preventing chronic suppurative lung disease (CSLD) and bronchiectasis

SummaryCurrent diagnostic labelling of childhood bronchiectasis by radiology has substantial limitations. These include the requirement for two high resolution computerised tomography [HRCT] scans (with associated adversity of radiation) if criteria is adhered to, adoption of radiological criteria for children from adult data, relatively high occurrence of false negative, and to a smaller extent false positive, in conventional HRCT scans when compared to multi-detector CT scans, determination of irreversible airway dilatation, and absence of normative data on broncho-arterial ratio in children.A paradigm presenting a spectrum related to airway bacteria, with associated degradation and inflammation products causing airway damage if untreated, entails protracted bacterial bronchitis (at the mild end) to irreversible airway dilatation with cystic formation as determined by HRCT (at the severe end of the spectrum). Increasing evidence suggests that progression of airway damage can be limited by intensive treatment, even in those predestined to have bronchiectasis (eg immune deficiency). Treatment is aimed at achieving a cure in those at the milder end of the spectrum to limiting further deterioration in those with severe ‘irreversible’ radiological bronchiectasis.

Reliability of Quantitative Real-Time PCR for Bacterial Detection in Cystic Fibrosis Airway Specimens

The cystic fibrosis (CF) airway microbiome is complex; polymicrobial infections are common, and the presence of fastidious bacteria including anaerobes make culture-based diagnosis challenging. Quantitative real-time PCR (qPCR) offers a culture-independent method for bacterial quantification that may improve diagnosis of CF airway infections; however, the reliability of qPCR applied to CF airway specimens is unknown. We sought to determine the reliability of nine specific bacterial qPCR assays (total bacteria, three typical CF pathogens, and five anaerobes) applied to CF airway specimens. Airway and salivary specimens from clinically stable pediatric CF subjects were collected. Quantitative PCR assay repeatability was determined using triplicate reactions. Split-sample measurements were performed to measure variability introduced by DNA extraction. Results from qPCR were compared to standard microbial culture for Pseudomonas aeruginosa, Staphylococcus aureus, and Haemophilus influenzae, common pathogens in CF. We obtained 84 sputa, 47 oropharyngeal and 27 salivary specimens from 16 pediatric subjects with CF. Quantitative PCR detected bacterial DNA in over 97% of specimens. All qPCR assays were highly reproducible at quantities ≥102 rRNA gene copies/reaction with coefficient of variation less than 20% for over 99% of samples. There was also excellent agreement between samples processed in duplicate. Anaerobic bacteria were highly prevalent and were detected in mean quantities similar to that of typical CF pathogens. Compared to a composite gold standard, qPCR and culture had variable sensitivities for detection of P. aeruginosa, S. aureus and H. influenzae from CF airway samples. By reliably quantifying fastidious airway bacteria, qPCR may improve our understanding of polymicrobial CF lung infections, progression of lung disease and ultimately improve antimicrobial treatments.

Real Time Lung Imaging for the Detection of Lung Injury and Alveolar Fluid Movement During Mechanical Ventilation

Experimental ventilator-induced lung injury (VILI) is characterized by alterations in alveolar epithelial and microvascular permeability that favors the systemic dissemination of lung borne cytokines or bacteria. Animal models of VILI have been shown relevant to patient care and outcome and help explaining why most patients with the acute respiratory distress syndrome do not die from respiratory failure but from multiple organ dysfunction. Recent experimental studies also showed that adverse ventilator patterns may propel airway secretions and bacteria to previously healthy lung regions. Noninvasive imaging techniques were used for years to study the net rate of protein flow across the pulmonary microvascular endothelium and the alveolar epithelium in vivo, during normal breathing and lung inflation. More recently, the two-way protein fluxes across the alveolo-capillary barrier and the intra-pulmonary dispersion of alveolar edema have been monitored during mechanical ventilation. These experiments have provided new insights on the mechanisms of experimental VILI that may be of clinical value. This review will describe the evolution of these techniques and their main physiological and pharmacological applications in the era of VILI.

Pulmonary exacerbations in cystic fibrosis with negative bacterial cultures

Pulmonary exacerbations are a major cause of morbidity in cystic fibrosis (CF) and likely contribute to lung function decline. Exacerbations are often associated with characteristic airway bacteria [CF related bacteria (CFRB)]. However, some patients do not have CFRB detected by culture during exacerbations. We sought to determine the proportion of airway cultures negative for CFRB during pulmonary exacerbations, and to characterize patients who were CFRB-negative versus CFRB-positive. We performed a retrospective study of patients with CF admitted for a pulmonary exacerbation. Patients were classified as CFRB-positive or CFRB-negative based on admission airway cultures. Demographics, clinical presentation, lung function, history of chronic Pseudomonas aeruginosa infection and improvement in lung function with treatment were compared between groups. There were 672 admissions for exacerbation involving 211 patients over 5 years. Seventeen percent were classified as CFRB-negative. Forty-one percent of bronchoalveolar lavage (BAL), 32% of throat and 10% of sputum samples were CFRB-negative. Among patients capable of expectorating sputum, the CFRB-negative group was younger, less likely to have chronic P. aeruginosa, had higher lung function and body mass index (BMI), and had a lower systemic inflammatory response on admission compared to those with CFRB-positive cultures. The two groups had similar numbers of patients with three or more signs and symptoms of a pulmonary exacerbation (88% vs. 92%). Both groups returned to baseline lung function following treatment. A significant number of patients with CF and pulmonary exacerbation did not have typical CFRB detected by culture. Patients without CFRB still had characteristic signs and symptoms of pulmonary exacerbation and responded to treatment. Understanding the causes of illness in these patients may improve the diagnosis and treatment of pulmonary exacerbations in CF.

Bacteria in the Lower Airways of Children with Asthma, Chronic Cough and Wheezing

Bacteria in the Lower Airways of Children with Asthma, Chronic Cough and Wheezing

Upper airway. 3: Sinonasal involvement in chronic obstructive pulmonary disease

This review presents the evidence that chronic obstructive pulmonary disease (COPD) is associated with significant sinonasal symptoms, inflammation and airway obstruction. Upper airway symptoms in COPD cause impairment to quality of life. The severity of upper airway involvement relates to that present in the lower airway, suggesting that the nose may be used to model the lung in COPD. More importantly, relationships between upper and lower airway bacteria and inflammation, and the association between sinusitis and treatment failure at exacerbation raise the possibility that nasal intervention in COPD may not only improve health status but may also affect important clinical outcomes such as exacerbation frequency.

Presence of Bacteria in the Lower Airways of Children with Chronic Cough and Wheezing

RATIONALE: To determine whether presence of bacteria in the lower airways plays a role in chronic cough and wheezing, we studied bronchoalveolar lavage (BAL) samples from children with cough and wheezing who underwent clinically indicated bronchoscopies.

Antibiotics at COPD exacerbations: the debate continues

The course of chronic obstructive pulmonary disease (COPD) is affected by the presence of exacerbations that are episodes of worsening of respiratory symptoms commonly triggered by airway infections, including respiratory...

Molecular identification of bacteria in bronchoalveolar lavage fluid from children with cystic fibrosis

Culture of bronchoalveolar lavage fluid (BALF) is the gold standard for detection of pathogens in the lower airways in cystic fibrosis (CF). However, current culture results do not explain all clinical observations in CF, including negative culture results during pulmonary exacerbation and inflammation in the absence of pathogens. We hypothesize that organisms not routinely identified by culture occur in the CF airway and may contribute to disease. To test this hypothesis we used a culture-independent molecular approach, based on use of rRNA sequence analysis, to assess the bacterial composition of BALF from children with CF and disease controls (DC). Specimens from 42 subjects (28 CF) were examined, and approximately 6,600 total clones were screened to identify 121 species of bacteria. In general, a single rRNA type dominated clone libraries from CF specimens, but not DC. Thirteen CF subjects contained bacteria that are not routinely assessed by culture. In four CF subjects, candidate pathogens were identified and include the anaerobe Prevotella denticola, a Lysobacter sp., and members of the Rickettsiales. The presumptive pathogens Tropheryma whipplei and Granulicatella elegans were identified in cases from the DC group. The presence of unexpected bacteria in CF may explain inflammation without documented pathogens and consequent failure to respond to standard treatment. These results show that molecular techniques provide a broader perspective on airway bacteria than do routine clinical cultures and thus can identify targets for further clinical evaluation.

RISK FACTORS ASSOCIATED WITH POSTCRANIOTOMY MENINGITIS

The authors conducted a retrospective cohort study to determine the incidence, bacteriological features, and risk factors for postcraniotomy meningitis. Patients older than 18 years who underwent nonstereotactic craniotomies between January 1996 and March 2000 and who survived for more than 7 days were included. Operations for placement of burr holes and shunts were excluded. Records of the first 30 postoperative days were abstracted. Host factors, types of craniotomy, and pre- and postoperative variables were evaluated as risk factors for meningitis Among 453 patients, there were 25 cases of meningitis. Eight out of 12 culture-positive cases were the result of gram-positive cocci. Four hundred twenty (92%) patients received antibiotic prophylaxis, most commonly a first-generation cephalosporin. In multivariate analysis, the risk of meningitis was increased by surgery that entered a sinus (odds ratio [OR], 4.49; P = 0.018), an increase in the American Society of Anesthesiologists score (OR, 1.72; P = 0.023), and increases in the number of days of external ventricular drainage (OR, 1.21; P = 0.049) and intracranial pressure monitoring (OR, 1.24; P = 0.002). Access of upper airway bacteria to the surgical wound, host factors as expressed by the American Society of Anesthesiologists score, and duration of device-related postoperative communication of the cerebrospinal fluid and the environment are major risk factors for postoperative meningitis after craniotomy.

Pulmonary bacterial co-infection in children ventilated for severe respiratory syncytial virus bronchiolitis is common

Sir, In a retrospective study on concurrent bacterial infection in infants ventilated for respiratory syncytial virus (RSV), bronchiolitis Kneyber et al. concluded that the “improvement in the diagnosis of a pulmonary concurrent bacterial infection is warranted to reduce the overuse of antimicrobial drugs” in this patient group [1]. This issue was highlighted by Andrews et al. in “Intensive Care Medicine’s Year in Review” 2005 article [2] as “Only a minority had evidence of bacterial infection”. Our view differs and we question this opinion/interpretation. A prospective study of 165 consecutive children in whom an admission broncho-alveolar lavage (BAL) sample was obtained found that up to 40% of patients admitted with severe RSV bronchiolitis were infected with bacteria in their lower airways [3]. This is in keeping with Kneyber et al. who found that 33% of children (9 of 24) in whom admission endotracheal aspirates were performed had a positive bacterial culture [1]. Duttweiler et al. retrospectively studied 127 infants admitted to intensive care for RSV bronchiolitis and found that 44% of those ventilated and endotracheally sampled had “concomitant bacteria pneumonia” [4]. Likewise, Randolph et al. retrospectively examined 165 previously healthy infants admitted to the intensive care unit with laboratoryconfirmed RSV infection and found that up to 38% of the intubated infants had “probable” or “possible” bacterial pneumonia [5]. Pulmonary bacterial co-infection is common in children ventilated for severe RSV bronchiolitis. The statement, “Only a minority had evidence of bacterial infection” [2] underscores the incidence in this patient group. Kneyber et al. [1] and Thorburn et al. [3] acknowledged that their studies may even have underestimated the actual number of concurrent bacterial infections. All the patients in both these studies [1, 3] received concomitant antibiotics, which limits any interpretation on the influence of antibiotics on outcome. This also limits comment on the “overuse of antimicrobials” [1, 2]. The only way to prove a definite impact of antimicrobials in this study population would be to carry out a randomized control trial. In the interim, one could argue that a bacterial co-infection rate of up to 40% in ventilated RSV patients is sufficient to warrant prophylactic/empirical antibiotics on admission to the paediatric intensive care unit (PICU). These critically ill children run a serious risk of developing bacterial pneumonia [6]. While awaiting further studies, we think that empirical antibiotic therapy appears to be justified in children with severe RSV bronchiolitis, pending the results of definitive cultures. “Improvement in the diagnosis of a pulmonary concurrent bacterial infection” can be achieved by obtaining lower airways secretions on admission to PICU in all patients. In the absence of finding bacteria in the lower airways, antibiotics can subsequently be stopped. References

Clinical and immunoregulatory effects of roxithromycin therapy for chronic respiratory tract infection.

The clinical and immunoregulatory effects of long-term macrolide antibiotic therapy for patients with chronic lower respiratory tract infections (CLRTI) were investigated. Clinical parameters and neutrophil chemotactic mediators in the epithelial lining fluid (ELF) of CLRTI patients (n = 10) were examined before and after 3 months oral administration of roxithromycin (RXM). The in vitro effects of RXM were also examined on the release of these mediators from alveolar macrophages (AM) and neutrophils. Arterial oxygen tension (p<0.05), vital capacity (VC) (p<0.001), %VC (p<0.05) and forced expiratory volume in one second (p<0.01) were improved after RXM treatment, but airway bacteria were not eradicated. Among the mediators, the levels of interleukin (IL)-8, neutrophil elastase (NE) and leukotriene B4 (LTB4) were higher in ELF than in plasma of CLRTI patients and they decreased after RXM treatment (n = 7, p<0.05 for each). RXM concentrations were significantly increased in the bronchoalveolar lavage cells of the treated patients. In in vitro experiments, RXM showed inhibitory effects on IL-8 release from AM and neutrophils. In conclusion, interleukin-8, neutrophil elastase and leukotriene B4 contribute to the neutrophilic inflammation in the airways of chronic lower respiratory tract infection patients and the clinical effects of roxithromycin may, in part, be attributable to the suppression of excess release of the chemotactic mediators from inflammatory cells.

Pseudomonas Aeruginosa in Hospitalized Patients with Infective Exacerbations of Bronchiectasis: Clinical and Research Implications

<i>Pseudomonas Aeruginosa</i> in Hospitalized Patients with Infective Exacerbations of Bronchiectasis: Clinical and Research Implications

Preoperative bacterial colonization of the upper airways does not predict postoperative airway infection in children.

The aim of this prospective non-interventional investigation was to study whether preoperative colonization of nasopharynx with potentially pathogenic airway bacteria carried an increased risk for the development of early postoperative bacterial airway infections after heart surgery in preschool children. Of the 91 patients studied, 62 (68%) were colonized preoperatively in the nasopharynx with Moraxella catarrhalis, Streptococcus pneumoniae, Haemophilus influenzae and/or Staphylococcus aureus. Nine children developed postoperative airway infections (four pneumonia, three bacterial bronchitis and two acute otitis media). Preoperative colonization was not significantly associated with increased risk for postoperative airway infection: 6/62 (10%) in colonized vs 3/29 (10%) in non-colonized children. Preoperative nasopharynx cultures in asymptomatic children should be avoided since it is unpleasant for the child, is not cost-effective, and may lead to unnecessary antibiotic treatment.

Preoperative bacterial colonization of the upper airways does not predict postoperative airway infection in children

The aim of this prospective non‐interventional investigation was to study whether preoperative colonization of nasopharynx with potentially pathogenic airway bacteria carried an increased risk for the development of early postoperative bacterial airway infections after heart surgery in preschool children. Of the 91 patients studied, 62 (68%) were colonized preoperatively in the nasopharynx with Moraxella catarrhalis, Streptococcus pneumoniae, Haemophilus influenzae and/or Staphylococcus aureus. Nine children developed postoperative airway infections (four pneumonia, three bacterial bronchitis and two acute otitis media). Preoperative colonization was not significantly associated with increased risk for postoperative airway infection: 6/62 (10%) in colonized vs 3/29 (10%) in non‐colonized children. Preoperative nasopharynx cultures in asymptomatic children should be avoided since it is unpleasant for the child, is not cost‐effective, and may lead to unnecessary antibiotic treatment.

High doses of aminoglycosides did not produce liver toxicity in patients with cystic fibrosis

Liver disease is common in patients with cystic fibrosis, but the pathogenesis is poorly understood. The chronic colonization of bacteria in the lower airways leads to repeated treatments with antibiotics, especially aminoglycosides in high dosages. To investigate the possible role of aminoglycoside treatment in the natural history of liver disease in cystic fibrosis, five patients were studied for 3 years. Four of the patients received repeated courses of antibiotics, in two of the patients at the time of the liver biopsies. One patient did not receive any aminoglycosides. Light and electron microscopical morphometry was done on liver biopsy specimens. The contents of fat and lysosomes were quantified and expressed as volume density of liver cell volume (%). The amount of fat calculated in this way (13-35%) was highest in one patient who had not received any aminoglycosides. The two patients being treated with aminoglycosides at the time of the biopsy showed small amounts of fat in their liver cells (0.2-1.5%); similar values were noted in some patients who had not been treated for years. The lysosomes did not show the specific changes previously reported to occur in the kidney, nor did the morphometrical quantitation reveal any abnormalities which could be related to the administration of aminoglycosides. The present study did not find liver toxicity related to aminoglycosides in repeated high therapeutic dosages given to patients with cystic fibrosis.

Predictive Value of Oropharyngeal Cultures for Identifying Lower Airway Bacteria in Cystic Fibrosis Patients

Identifying lower respiratory pathogens in young, non expectorating cystic fibrosis (CF) patients has been problematic. Bronchial secretions are difficult to obtain, and little is known about lower airway flora in these patients. We collected simultaneous bronchial and oropharyngeal specimens in 43 CF patients in optimal respiratory status, including both expectorating (17) and nonexpectorating (26) patients, to determine the predictive value of oropharyngeal cultures for identifying lower airway pathogens. An additional goal was to characterize the lower respiratory flora of these patients. Predictive values were defined as the proportion of oropharyngeal culture results that accurately reflected the results of bronchial cultures. Predictive values of positive oropharyngeal cultures in nonexpectorating patients were 83% (95% confidence interval 36 to 100%) for Pseudomonas aeruginosa and 91% (59 to 100%) for Staphylococcus aureus. Predictive values of negative oropharyngeal cultures were lower: 70% (48 to 86%) for R aeruginosa and 80% (52 to 96%) for S. aureus. A relatively high proportion of nonexpectorating CF patients less than 10 yr old had R aerusginosa (11 of 24, 46%) or Klebsiella species (5 of 24, 21%) in their lower airways. The isolation of Klebsiella was associated with younger age (p = 0.03) and recent administration of antistaphylococcal antibiotics (p = 0.05). Our results suggest that oropharyngeal cultures yielding R aeruginosa or S. aureus are highly predictive, but such cultures lacking these organisms do not rule out the presence of these pathogens in the lower airways of CF patients.

Establishing the Etiologic Diagnosis of Pneumonia

DOI: http://dx.doi.org/10.5915/23-1-14324 Pneumonia is a serious entity with a mortality in the U.S. of from 6-24%. Many invasive and non-invasive procedures are used to establish an etiologic diagnosis. An acceptable sputum smear is characterized by a low number of epithelial cells, higher number of leukocytes, and the presence of alveolar macrophages. A gram-stain provides good clues about pneumococcal, Klebsiella, and mixed anaerobic infections. Common problems include interpretation of streptococci as S. pneumoniae and missing H. influenzae. A culture of sputum is frequently unreliable because of contamination by the upper airway bacteria. Transtracheal aspiration can minimize the upper airway contamination. Broncho-alveolar lavage is helpful in diagnosing pneumocystis infections in AIDS patients. Double lumen catheter systems can obtain secretions from the site of pneumonia without contamination. Transbronchial biopsy provides tissue specimens for stains and cultures. Transthoracic needle aspiration provides diagnostic yield of 56 to 82% of cases with a false negative rate of 22%. Open lung biopsy is usually done in very sick, immunocompromised patients if other diagnostic procedures have been unsuccessful. Presented at the IMA 22nd Annual Convention Orlando, Florida, July 1989. Part of Symposium: Update on the Diagnosis and Treatment of Respiratory Tract Infection.

Proposal of an easy method to improve routine sputum bacteriology.

The study of bacterial flora of the lower respiratory tract is very important for the diagnosis of pulmonary infections and proper therapy but it has to face important methodologic problems. The main problem is contamination of the sputum during its passage through the upper airways. The present study suggests an improved procedure aiming first of all at reducing the specimen contamination by upper airway bacteria by means of a preliminary mouth wash, and secondly at comparing qualitative and quantitative cultures of spit with those of sputum. In our study bronchial lavage aspirate (BLA) cultures were used as a control. Both definite (80 patients) and random (20 patients) sequence sampling procedures were considered to show the importance of a correct sequential specimen collection. Bacteria isolated in the sputum and/or in BLA but absent in the spit were considered the most probable responsible for an eventual pulmonary infection. On the contrary a germ found in the spit and eventually in the sputum but not in BLA was considered responsible for only an eventual inflammation of the upper respiratory tract. Doubtful cases were solved by comparing the different bacterial concentrations in the various samples. A preliminary mouth washing procedure decreased the mean concentration of contaminants in the sputum: 3.6 +/- 7.5 x 10E8 (E = exponent) versus 3.7 +/- 7.2 x 10E7 CFU/ml spit versus sputum (80 patients) p less than 0.001. On the contrary if sputum preceded spit (12 out of the 20 randomly treated subjects), bacterial counts were not significantly different (2.1 +/- 5.7 x 10E8 vs. 1.3 +/- 2.9 x 10E8 CFU/ml, respectively, p = NS). In the group of correctly treated patients (80 subjects) only infrequently oral contaminants were found in BLA (12.5%). The finding of bacteria in BLA but absent in spit and/or sputum was rare (4.8%) suggesting that, at least in chronic obstructive lung disease (COLD) patients, spit and sputum quantitative and qualitative cultures may be sufficient for a good microbiologic examination in almost all the cases.

The significance of bacterial superinfection in influenza.

AbstractDuring an epidemic of influenza A2 var. Hongkong and a subsequent period of high incidence of influenza B in Stockholm from January through April 1969, 130 influenza cases were selected for a study on the effects of bacterial superinfection. Bacterial involvement was demonstrated through frequent cultures from nose, throat, nasopharynx and sputum samples, together with serologic reactions in acute phase and convalescence sera against potentially pathogenic airway bacteria. It was found that bacterial involvement could not be shown statistically to influence the maximum temperature recorded, but did increase the duration of fever, the incidence of pneumonia, leukocytosis, and erythrocyte sedimentation rates over 50 mm/l h. When indicated by both bacterial findings and significant antibody titer increase, it also resulted in a higher frequency of granulocytosis. The bacteria most often involved were pneumococci, dominating in acute respiratory illness also in influenza-free periods, but the severity...