Mycobacterial contamination of fibreoptic bronchoscopes

Resistance and cross-resistance to oxidising agents of bacterial isolates from endoscope washer disinfectors

Bacteria isolated from washer disinfectors using chlorine dioxide as a high-level disinfectant were exposed to peracetic acid, chlorine dioxide and hydrogen peroxide to investigate their susceptibility and possible bacterial cross-resistance to these highly reactive oxidising biocides. A standard suspension test was used to establish a rate of kill of these biocides against two stable isolates (Bacillus subtilis and Micrococcus luteus). Suspension tests demonstrated that 'in use' concentrations were not always effective to provide the required disinfection efficacy within recommended exposure times and in some instances a 60min exposure was necessary to achieve a reduction in number by a factor of 10(5). It appears that vegetative Gram-positive isolates can become resistant to oxidising agents in vitro, and that cross-resistance to related compounds can occur. Since these bacteria are deemed to be susceptible to highly reactive biocides, there should be further study of the resistance mechanisms in these isolates to explain their survival.

[Diagnostic flexible bronchoscopy. Recommendations of the Endoscopy Working Group of the French Society of Pulmonary Medicine]

These guidelines on flexible bronchoscopy depict important clues to be known and taken into account while practicing flexible bronchoscopy, in adult, except in emergency situations. This is a practical clarification. Safety conditions, complications, anesthesia, infectious risks, cleaning and disinfection are detailed from a review of the literature. Intensive care practice of bronchoscopy requires more attention due to higher risks patients and is discussed extensively. Standards and performances of the various sampling techniques complete this work. Indications for bronchoscopy, therapeutic and paediatric bronchoscopy are not covered in these guidelines.

Diagnóstico bacteriológico de la tuberculosis en Argentina: resultados de una encuesta nacional

Con el objetivo de evaluar recursos, prácticas y medidas de bioseguridad utilizados en el diagnóstico bacteriológico de tuberculosis y determinar la utilidad y alcance de las técnicas empleadas, se llevó adelante una encuesta transversal a laboratorios del sector público de Argentina utilizando un cuestionario estructurado. El análisis de los resultados mostró que la densidad de centros de microscopía y cultivo se encuentra al nivel o encima de lo recomendado por Organización Mundial de la Salud. El programa de control de calidad de microscopía cubre mayoritariamente los laboratorios con alta carga de trabajo. El promedio de baciloscopías/paciente fue bajo (1,6). El 25% de los laboratorios de cultivo empleaban protección respiratoria inadecuada. El aporte del cultivo a la confirmación de casos pulmonares en las jurisdicciones estuvo asociado a la proporción de muestras cultivadas. Globalmente, el porcentaje de pacientes pulmonares baciloscopía-negativa que fue confirmado bacteriológicamente fue de 18.9%; mientras que la may-oría de los casos extrapulmonares se confirmó sólo por cultivo (71,3%). Es prioritario aún el incremento del número de esputos estudiados por baciloscopía y cultivo, así como aumentar la cobertura de programa de control de calidad de microscopía; es fundamental proveer al personal de laboratorio de adecuada protección respiratoria y evaluación médica regular.

[Pathogenesis and environmental factors in ventilator-associated pneumonia]

Respiratory infections in intubated patients can derive from endogenous or exogenous sources. The major route for acquiring endemic ventilator-associated pneumonia (VAP) is oropharyngeal colonization by endogenous flora and leakage of contaminated secretions into the lower respiratory tract. However, a not inconsiderable percentage of VAP results from exogenous nosocomial colonization, especially pneumonias caused by resistant bacteria such as methicillin-resistant Staphylococcus aureus and multiresistant Acinetobacter baumannii or Pseudomonas aeruginosa, as well as by Legionella spp or filamentous fungi, such as Aspergillus. This article reviews the pathogenesis of VAP and the role of the intensive care environment as a source of pathogenic microorganisms.

Nosocomial transmission of imipenem-resistant Pseudomonas aeruginosa following bronchoscopy associated with improper connection to the Steris System 1 processor

OBJECTIVE

To assess nosocomial transmission of imipenem-resistant Pseudomonas aeruginosa (IRPA) following bronchoscopy during August through October 1998.

DESIGN

Traditional and molecular epidemiological investigation of a case series.

SETTING

University-affiliated community hospital.

PATIENTS

18 patients with IRPA bronchial-wash isolates.

INTERVENTIONS

We reviewed clinical data, performed environmental cultures and molecular analysis of all IRPA isolates, and observed disinfection of bronchoscopes.

RESULTS

Of 18 patients who had IRPA isolated from bronchoscopic or postbronchoscopic specimens, 13 underwent bronchoscopy for possible malignancy or undiagnosed pulmonary infiltrates. Following bronchoscopy, 3 patients continued to have IRPA isolated from sputum and demonstrated clinical evidence of infection requiring specific antimicrobial therapy. The remaining 15 patients had no further IRPA isolated and remained clinically well 3 months following bronchoscopy. Pulsed-field gel electrophoresis revealed that all strains except one were >95% related. STERIS SYSTEM 1 had been implemented in July 1998 as an automatic endoscope reprocessor (AER) for all endoscopes and bronchoscopes. Inspection of bronchoscope sterilization cycles revealed incorrect connectors joining the bronchoscope suction channel to the STERIS SYSTEM 1 processor, obstructing peracetic acid flow through the bronchoscope lumen. No malfunction warning was received, and spore strips remained negative.

CONCLUSIONS

The similarity of diverse connectors and limited training by the manufacturer regarding AER for bronchoscopes were the two factors responsible for the outbreak. Appropriate connections were implemented, and there was no further bronchoscope contamination. We suggest active surveillance of all bronchoscopy specimen cultures, standardization of connectors of various scopes and automated processors, and systematic education of staff by manufacturers with periodic on-site observation.

Identification of a contaminating Mycobacterium tuberculosis strain with a transposition of an IS6110 insertion element resulting in an altered spoligotype

Molecular fingerprinting with the IS6110 insertion sequence is useful for tracking transmission of Mycobacterium tuberculosis within a population or confirming specimen contamination in the laboratory or through instrumentation. Secondary typing with other molecular methods yields additional information as to the relatedness of strains with similar IS6110 fingerprints. Isolated, relatively rare, random events within the M. tuberculosis genome alter molecular fingerprinting patterns with any of the methods; therefore, strains which are different by two or more typing methods are usually not considered to be closely related. In this report, we describe two strains of M. tuberculosis, obtained from the same bronchoscope 2 days apart, that demonstrated unique molecular fingerprinting patterns by two different typing methods. They were closely linked through the bronchoscope by a traditional epidemiologic investigation. Genetic analysis of the two strains revealed that a single event, the transposition of an IS6110 insertion sequence in one of the strains, accounted for both the differences in the IS6110 pattern and the apparent deletion of a spacer in the spoligotype. This finding shows that a single event can change the molecular fingerprint of a strain in two different molecular typing systems, and thus, molecular typing cannot be the only means used to track transmission of this organism through a population. Traditional epidemiologic techniques are a necessary complement to molecular fingerprinting so that radical changes within the fingerprint pattern can be identified.

PCR based detection of mycobacteria in paraffin wax embedded material routinely processed for morphological examination

BACKGROUND

The incidence of mycobacterial infections has increased during the past five years. A prompt diagnosis is indispensable for initiating appropriate treatment. Because culturing of mycobacteria takes three to six weeks and sensitivity of microscopic detection of acid fast bacilli is low, amplification methods provide promising possibilities. Recently, the polymerase chain reaction (PCR) has been shown to be useful for confirming a mycobacterial infection, especially in cases with unexpected histological findings or lack of suitable material for culturing.

AIMS

To evaluate the impact of PCR based techniques in the detection of mycobacterial infections in uncultured routine histological specimens as an alternative to surgical pathology.

METHODS

Two hundred and twenty nine formalin fixed and paraffin wax embedded samples from 141 patients with clinical or histological suspicion of a mycobacterial infection were investigated using three different PCR assays and Southern blotting. PCR results were compared with histology and culture and the patients' clinical findings.

RESULTS

When using culture as the reference method, the sensitivity for the detection of mycobacteria of the tuberculosis complex was 90%, specificity was 92%, the positive predictive value was 81%, and the negative predictive value was 96%. The sensitivity for the detection of nontuberculous mycobacteria was 100% and specificity was 78%, the positive predictive value was 26%, and the negative predictive value was 100%. The patients' clinical findings supported the PCR positive results, indicating a mycobacterial infection in 11 of 18 initially culture negative cases and in 21 of 35 PCR positive cases without culture results.

CONCLUSIONS

These results indicate that PCR based techniques are sensitive, specific, and rapid methods for the detection of mycobacteria in routinely processed paraffin wax embedded and formalin fixed histological samples.

Future of flexible bronchoscopy

Despite some potential "threats" (Table 3), the future of bronchoscopy is likely full with ever expanding applications in clinical medicine and research (Tables 1 and 2). The role of bronchoscopy in lung cancer continues to expand and the usefulness of newer techniques needs to be established. The role of FB is also ever expanding in the immuno compromised host and critically ill patients. Future studies, however, should concentrate on patient outcome, especially survival and performance status. Therapeutic bronchoscopy has been extended to many areas and the emphasis of future research will likely continue to be at the molecular level rather than on studies of better instruments for retrieval purposes. The most exciting developments are likely to be in the field of gene therapy, which has made remarkable progress in the past decade. Gene therapy can be a powerful technology, but several hurdles must be overcome to make gene therapy a reality for treating human disease in the future. As the cost of technology continues to challenge health care delivery systems, a major challenge for the future of bronchoscopy is to evaluate new technologies and applications based on their impact on patient outcome, survival, and management of cost.