Nebulization equipment. A potential source of infection in gram-negative pneumonias

The microbial contamination of pressurised metered-dose inhalers anonymously sourced from the South-East Queensland Australia community population

OBJECTIVES

To provide preliminary evidence regarding the presence, identity and level of microbial contamination of metered-dose inhalers sourced from the community. To correlate the level of microbial colonisation to the visible presence of debris on the interior and exterior surface of the device mouthpiece.

METHODS

In this exploratory study, 45 post-use de-identified pressurised metered-dose inhalers were collected from the South-East Queensland Australian community. Prior to swabbing, the presence of visible debris on the internal and external surfaces of the mouthpiece was recorded for each device. Swabs taken from external and inner surfaces of the mouthpiece of each device were streaked onto standard growth media for colony counts. Individual colonies were selected and enriched then streaked onto a range of differential and chromogenic media for differential identification.

KEY FINDINGS

A total of 36 post-use pressurised metered dose inhalers (80%) were shown to be colonised by microbes relative to unused devices (P=0.01). Devices were primarily colonised by common respiratory flora, including Staphylococcus, Streptococcus and Haemophilus species. Of greatest concern was the positive identification of methicillin-resistant Staphylococcus aureus (18%) and extended-spectrum β-lactamase-producing Enterobacteriaceae (7%), Pseudomonas aerugonisa (2%) and Candida species (9%). The level of internal microbial contamination appeared to correlate to the presence of visible debris on the inside of the inhaler mouthpiece (P=0.06) but not external debris (P=0.59) while external contamination was not associated with internal (P=0.99) or external debris (P=0.63).

CONCLUSIONS

These preliminary data suggest that pressurised metered dose inhalers are potential reservoirs for bacteria. While this study was not aimed at determining the impact that contaminated pressurised metered-dose inhalers may have on the user, future research is being conducted to address the implications of these findings and the consequences they may have for the population of users.

Variability in incubator humidity practices in the management of preterm infants

AIM

To determine current practice and opinion in relation to incubator humidity use in the management of preterm infants in neonatal intensive care units (NICU's) within the Australian and New Zealand Neonatal Network (ANZNN).

METHODS

A survey was conducted in 26 NICU's in the ANZNN. A senior clinical nurse in each perinatal centre participated in a telephone survey that focused on local humidification practices and on the clinicians' views and experiences of humidity use.

RESULTS

All centres routinely used supplemental humidity in the management of preterm infants. The majority of centres (77%) had written protocols to guide practice. Eighty-eight per cent commenced humidity at a high level (relative humidity > or = 80%). There was wide practice variation in the gestational age parameters determining humidification use (all gestational ages up to 37 weeks), duration of use (3-77 days), timing of initiation (admission to 72 h after birth) and weaning practices. Perceived benefits of humidification included improved thermoregulation, skin integrity, and fluid and electrolyte balance and reduced transepidermal water loss. Perceived risks included sepsis and hyperthermia.

CONCLUSIONS

Our study confirmed that incubator humidity is used routinely in the management of preterm infants in the ANZNN. Wide variation in humidification practices across NICUs reflects the paucity of research evidence. Perceived benefits and risks of humidity use were consistent with available literature. To optimise the care environment and provide an evidence base for practice further research is warranted.

Mycobacterium gordonae pulmonary disease associated with a continuous positive airway pressure device

There are no formal recommendations on the proper handling and decontamination of respiratory devices for home use. We describe the case of a kidney transplant recipient who developed Mycobacterium gordonae pneumonia transmitted by his continuous positive airway pressure (CPAP) machine.

Evidence-based clinical practice

Healthcare professionals are trying to facilitate the use of evidence-based decision making for individual patients and patient populations they are privileged to serve. The authors describe an evidence-based multidisciplinary clinical practice model developed at the University of Colorado Hospital along with a clinical example of how the model was used to improve quality and decrease costs.

Ventilator-associated pneumonia

Mechanically ventilated patients are at a substantially higher risk for developing nosocomial pneumonia. Overall, there is a relatively constant 1&!TN!150;3% risk per day of developing pneumonia while receiving mechanical ventilation. The sensitivity and specificity of clinical criteria alone for diagnosis of ventilator-associated pneumonias (VAP) is low. Several techniques have been developed to sample and quantitate the lower respiratory tract to improve the diagnostic yield. Gram-negative bacillary pneumonias account for the majority of the VAP. Strategies for prevention of VAP such as use of sucralfate for stress ulcer prophylaxis and selective decontamination of the digestive tract have been the focus of many clinical studies. Cost-effective preventive measures are needed to combat the increasing antimicrobial resistance, growing population of immunocompromised patients and increasing number of mechanically ventilated patients.

Home nebulizer use among patients with cystic fibrosis

OBJECTIVE

To describe current patterns of home nebulizer use among patients with cystic fibrosis.

STUDY DESIGN

A population-based survey of home nebulizer practices among 227 patients with cystic fibrosis using nebulizers from 1993 to 1994 (Objective 1), and a prospective study of "typical" home use, including testing of performance and bacterial cultures in nebulizers after use, completed by 36 subjects (Objective 2).

RESULTS

Objective 1: 85% of subjects reported using jet and 8% ultrasonic nebulizers (categories not mutually exclusive); 15% used unknown brands. Most jet nebulizers were disposable models, which were used for > 14 days by more than half the subjects. Mixing of medications in a single treatment (other than cromolyn and a bronchodilator) was reported by 28% of patients. Objective 2: no apparent deterioration in aerosol particle size or output rate of returned nebulizers compared with new units was observed. Staphylococcus aureus was cultured from 55% and Pseudomonas aeruginosa from 35% of returned nebulizers. Concordance between nebulizer and sputum cultures was poor.

CONCLUSIONS

Although not generally tested for reusability, disposable nebulizers are generally used by patients for long periods. Medication mixing is common, although its effects on aerosol properties are unknown. Cystic fibrosis respiratory pathogens are frequently isolated from used nebulizers. Patient guidelines for home nebulizer use need to be established.

Outbreak of severe Pseudomonas aeruginosa respiratory infections due to contaminated nebulizers

During the six months from January-June 1994, 10 cases of severe and 11 of less severe pulmonary infection caused by Pseudomonas aeruginosa were diagnosed in patients with chronic obstructive airways disease. Possible sources were evaluated. P. aeruginosa was isolated from four of the 22 nebulizers tested. The relationship of isolates from the patients and nebulizers was confirmed by sero- and phage-typing, and by arbitrarily-primed polymerase chain reaction (AP-PCR). Three types were identified and the distribution of types in patients with severe infection was as follows (one patient had a multiple infection). Type I was isolated from two nebulizers and from sputa, and/or blood and/or bronchial protected specimen brush samples or bronchial lavage fluid from four patients. Type II came from the sputa of three patients and a third nebulizer; and type III from sputa and/or blood of four further patients and another nebulizer. The data provided evidence for the relation between P. aeruginosa as a cause of infection and the contamination of the nebulizers. When nebulizer mouthpieces were changed every 24 h and sterilized between patients, no more contamination occurred, and the outbreak ceased.

Treating childhood respiratory illness in developing countries: mist therapy without electricity

We have developed an effective and well-accepted method of providing mist for children with acute respiratory distress. This method can be especially useful in areas of the world where resources are limited.

Home nebulizers in childhood asthma. Parental perceptions and practices

Seventy five percent of 91 parents of asthmatic children (aged 6 months to 15.4 years) with home nebulizers, responded to a questionnaire that sought to document parental experience with this form of therapy. The most common indications for acquiring a nebulizer were inability to use metered dose inhalers and poor response or intolerance to oral medications. When the children were classified into those who used the nebulizer daily (27/69) and those who used it less than daily (42/69), we found that the daily users were more likely to be in the severest category of asthma, by parental assessment, prior to the home nebulization program (p = 0.0035). Retrospective, uncontrolled comparison before and after the acquisition of a home nebulizer showed significant decreases both in hospital admissions (1.7 vs 0.7; p less than 0.001) and total in-patient days (4.1 vs 1.7; p less than 0.0001). Home nebulizers are well tolerated by parents and children alike and may be associated with decreased morbidity.

Results of a survey of infection control practices for respiratory therapy equipment

The responses to a comprehensive survey of infection control practices for respiratory therapy equipment, previously published in the Readers' Forum section of Infection Control, are summarized in Tables 1 through 3. Responses were obtained from 205 United States hospitals; 65% were community hospitals and 38% had <500 ventilator days/year. In some cases, the total number of responses exceeded 100% because of practices that required multiple responses.

Contaminated medication nebulizers in mechanical ventilator circuits. Source of bacterial aerosols

The contamination rates of medication nebulizers inserted into mechanical ventilator circuits were studied. Semiquantitative techniques were used to sample the reservoir fluid from in-line nebulizers during the first 24 hours after a circuit change. In the initial survey, high levels of contamination (organism concentrations above 10(3)/ml) were present in 13 (68 percent) of the 19 nebulizer reservoirs, and bacterial aerosols were produced by 10 (71 percent) of 14 nebulizers. Gram-negative bacilli were the predominant organisms isolated. Nebulizer contamination originated primarily from reflux of contaminated condensate in the ventilator circuit. When nebulizers were cleaned after each treatment, a reduced rate of contamination was found. Small bacterial aerosols (less than 3 microns in size) were produced in vitro after inoculation of nebulizers with gram-negative bacilli in concentrations isolated from in-use nebulizers. Contaminated in-line medication nebulizers generate small-particle bacterial aerosols that may increase the risk of ventilator-associated pneumonia and therefore should be cleaned or disinfected after each treatment rather than every 24 hours.

Bacterial contamination of pressurized inhalers

The objective of this project was to determine the incidence, location, and potential transmission of bacteria from pressurized inhalers contaminated during normal use by pediatric patients. Patients' inhaler usage and cleaning patterns also were evaluated. Fifteen inhalers from 12 children were cultured at three separate sites: the mouthpiece, spray portal, and the spray itself. The patient and/or parent were interviewed to determine usage and cleaning patterns. No bacterial growth was found from any of the cultured sites or aerosol of the control inhalers. All of the mouthpieces and portals of the patient-used inhalers were positive for growth, which is significant (p less than 0.01). One patient-used inhaler was positive for bacterial growth from the aerosol, which is not significant (p greater than 0.05). These results demonstrate that despite inhaler contamination, bacteria are not significantly transmitted by the aerosol. Routine cleaning of inhalers to remove accumulated debris is recommended to prevent disruption of drug delivery.

Prevention of infection among patients with cancer

Recognition of the alterations of host defense allows a rational approach to preventing associated infections. One of the most effective strategies for preventing infection in the granulocytopenic patient is the combined use of oral non-absorbable antibiotics, laminar air-flow room reverse isolation with strict housekeeping techniques, low microbial diet, sterile water, and topical antiseptics and antibiotics. The prohibitive cost, however, warrants that this system be restricted to research settings. The suppression of aerobic Gram-negative bacilli and fungi and the preservation of colonization resistance with such combinations as trimethoprim-sulfamethoxazole and nystatin show promise in preventing infection in the granulocytopenic patient. Prevention of infection in neutropenic patients also requires attention to simpler but very effective measures such as immunizations, antimicrobial prophylaxis against intracellular and nonbacterial pathogens in high-risk patients, limiting invasive diagnostic and monitoring procedures, hand-washing by all personnel between visiting patients, oral hygiene, low microbial diets, axillary and perianal swabbing, and care with venipunctures and marrow aspirates. Finally, while the recommendations for prevention of infection are likely to continue to change with resulting improvement in patient care [92, 93], a tabulation summarizing current practices can be established based on our current knowledge (Table 1).

Direct dilution sampling, quantitation, and microbial assessment of open-system ventilation circuits in intensive care units

In a systematic approach, 37 duplicate samples of open system circuits (Bennett MA-1 ventilators) of patients in medical and surgical intensive care units were processed by direct and serial (APHA guidelines) dilutions. The paired difference test on 15 of the in-use circuitry solution samples indicated no difference between the direct and serial dilution methods (P less than 0.001). Seventy-seven additional respiratory therapy circuitry samples from similar intensive care patients were analyzed via a direct dilution method alone and processed microbiologically. The direct dilution procedure was a rapid and accurate means of evaluation of microbial contamination in the range of greater than or equal to 10 to less than or equal to 10(6) CFU/ml. High densities of organisms frequently were found. Sites of contamination included the proximal or patient end of the circuitry (heaviest), the nebulizer trap, and the distal or humidifier portions of the circuitry. The contaminants found were predominantly gram-negative nonfermenters: Acinetobacter calcoaceticus var. antitratus, Pseudomonas aeruginosa, Pseudomonas maltophilia, and Flavobacterium meningosepticum. Fermenters were Klebsiella pneumoniae, Proteus sp., Enterobacter cloacae, Citrobacter diversus, and Enterobacter agglomerans. Infrequently, gram-positive Streptococcus spp. and Staphylococcus spp. were noted.

Contamination of mechanical ventilators with tubing changes every 24 or 48 hours

We studied the contamination of ventilator circuits in order to assess the need for daily changes of tubing. Patients requiring continuous mechanical ventilation were randomly selected for tubing changes at 24 hours (Group 1) or at 48 hours (Group 2). Samples of inspiratory-phase gas from ventilators with standardized settings were cultured according to the tube-broth method of Edmondson and Sanford. The frequency of positive cultures from 128 ventilators in Group 1 (30 per cent) was not significantly different from that for 112 ventilators in Group 2 (32 per cent). Gram-negative bacteria were most frequently isolated from patient's sputum and ventilator inspiratory-phase gas, but no species predominated in either group of patients. Further studies performed with the Aerotest and Andersen air samplers confirmed that the levels of inspiratory-phase-gas contamination were low in both groups. In addition, quantitative analysis of colonization of the tubing demonstrated no significant increase in colonization between 24 and 48 hours. The absence of a significant difference in inspiratory-phase-gas contamination or tubing colonization suggests that ventilator tubing need be changed only every 48 hours.

Limulus amoebocyte lysate and direct sampling methods for surveillance of operating nebulizers

The Limulus amoebocyte lysate test for detection of endotoxin (Pyrogent; Mallinckrodt Chemical Co.) and the Easicult method (Orion Diagnostica) for detection of bacteria were compared with direct dilution sampling, a standardized technique for respiratory therapy surveillance previously developed in our laboratory. Tests of 206 reservoirs of nebulizers were done in three hospitals in Georgia. Forty-five percent of all reservoirs sampled were contaminated. Gram-negative, nonfermentative bacilli were the predominant contaminants. The results of the Limulus test and the Easicult system were in agreement with those of the direct dilution sampling tests approximately 84 and 90% of the time, respectively. Direct dilution of water samples onto blood agar plates was the most sensitive, reliable, and informative method for detecting viable bacteria. The Easicult and Limulus systems were sensitive enough to detect greater than or equal to 10(3) colony-forming units per ml. Positive Limulus tests and negative culture tests, reflecting detection of endotoxin but not of viable gram-negative bacteria, occurred in 20 of 206 (9.7%) instances. Positive cultures and negative Limulus tests were noted in 13 of 206 (6.8%) samplings. The Limulus test is a valuable procedure, for it can detect moderate-to-heavy microbial contamination within 1 h of testing and affords the opportunity to remove contaminated equipment from patients within minutes of a positive test result. These results demonstrate the potential value of the Easicult and Limulus tests for selective surveillance of operating nebulizers.

Selective nonroutine microbial surveillance of in-use hospital nebulizers by aerosol entrapment and direct sampling analyses of solutions in reservoirs

Effluent aerosols and liquid reservoir samples from 255 in-use hospital nebulization devices were analyzed by Aero-Test samplers (Olympic Corp.) and direct dilution procedures (0.1-, 0.01-, and 0.001-ml plated samples). Thirty-five percent (89 of 255) of the in-use hospital reservoir samples were positive by direct dilution, and 24% (61 of 255) were positive by Aero- Test samplers. Acinetobacter calcoaceticus var. anitratus was found either alone or in association with Pseudomonas spp. in 50% of all the contaminated in-use reservoirs. This indicates a high endemicity for Acinetobacter in the environment studied. Viable microbes in the reservoirs of contaminated nebulizers ranged from as few as 20 to >2 x 10(5) colony-forming units/ml. Microbial contamination at moderate to heavy levels (1 x 10(4) to >2 x 10(5)) was regularly detected by both procedures. Microbial densities of 10(3) colony-forming units/ml and less in contaminated reservoirs often were negative in the Aero- Test but positive by direct dilution techniques. These hospital-based results were similar to laboratory data obtained with sterile nebulizers intentionally contaminated in graduated densities with either Staphylococcus aureus or Pseudomonas aeruginosa. Sensitivity of the Aero- Test system was best when >/=10(4) colony-forming units/ml were present in the reservoirs of operating nebulizers. The manufacturer suggests that five or less colonies appearing after sampling on Aero- Test plates upon 48-h incubation does not indicate contamination of the reservoir. Our data show that even a single colony, particularly if it is typical, water-associated, gram-negative bacterial species, may well indicate low levels of reservoir contamination. Both the Aero- Test and direct dilution methods indicated the need for more rigorous management of the in-use respiratory therapy equipment in the hospital surveyed. These studies demonstrate the value of selective nonroutine surveillance for identifying potential or actual contamination problems of in-use nebulizing equipment, particularly when recommended care guidelines are not followed due to choice or unawareness. Ameliorative-corrective measures, which included routine 24-h substitution of old units with new sterile units, were initiated as a result of this surveillance program.

Reservoirs of pseudomonas in an intensive care unit for newborn infants: mechanisms of control

Potential reservoirs of pseudomonas within a neonatal ICU were evaluated. Colonization of infants by the same pseudomonas pyocin types could be classified as a cluster colonization (occurring over three to ten days), or serial colonization (occurring over longer times). Hands of personnel, sink surfaces, and solutions used to rinse nasopharyngeal catheters were identified as the principle reservoirs. Utilization of a liquid iodophor agent for hand washing and of acetic acid for rinsing suction catheters was associated with a significant reduction in the histologic evidence of sepsis and of pneumonia observed among autopsied infants.

Factors affecting comparative resistance of naturally occurring and subcultured Pseudomonas aeruginosa to disinfectants

A strain of Pseudomonas aeruginosa was isolated in pure culture from the reservoir of a hospital mist therapy unit by an extinction-dilution technique; its natural distilled water environment was used as a growth and maintenance medium. After a single subculture on Trypticase soy agar, the strain showed a marked decrease in resistance to inactivation by acetic acid, glutaraldehyde, chlorine dioxide, and a quaternary ammonium compound when compared with naturally occurring cells grown in mist therapy unit water. The following factors were observed to affect the relative resistances of naturally occurring and subcultured cells of the P. aeruginosa strain: (i) temperature at which the cultures were incubated prior to exposure to disinfectants, (ii) growth phase of the cultures at the time of exposure to disinfectants, (iii) nature of the suspending menstruum for disinfectants, and (iv) exposure to fluorescent light during incubation of inocula prior to testing. The applied significance of these findings may alter the present concepts of disinfectant testing as well as routine control procedures in the hospital environment.

Effectiveness of acetic acid, betadine, amphyll, polymyxin B, colistin, and gentamicin against Pseudomonas aeruginosa

The in vitro effectiveness of three germicides and three chemotherapeutic drugs against hospital-isolated strains of Pseudomonas aeruginosa was determined. Solutions of 1% acetic acid, 0.5% Amphyll, and 0.1% Betadine were bactericidal for six strains tested within 15 min at room temperature. Over a 3-year period at the Albany Medical Center Hospital, the percentages of strains of P. aeruginosa susceptible to polymyxin B, colistin, and gentamicin did not increase. During this 3-year period, polymyxin B and colistin were administered at the hospital but gentamicin was not.