Sometimes it’s what you can’t see that can hurt you. Improperly cleaned or sterilized reusable bronchoscopes, for example, can potentially transfer an infection from one patient to another—known officially as cross-contamination—and add more hospital-acquired infection cases to the books. 

In 2015, the FDA received a report from a manufacturer that one of its reusable bronchoscopes had potentially infected 14 patients. The bacteria involved were especially concerning due to high levels of resistance to most antibiotic treatments: carbapenem-resistant Enterobacteriaceae. 

The year before, the agency received 50 reports of infection or device contamination associated with bronchoscopes. The FDA launched on ongoing investigation as a result. Not following manufacturers’ cleaning and sterilization recommendations, and continuing to use the devices when they require maintenance or repair are leading risk factors, according to the September 2015 Safety Alert “Reprocessed Flexible Bronchoscopes: FDA Safety Communication – Risk of Infection.”

Illuminating Residual Contamination

Visual inspection alone is not always sufficient to detect all cellular and bacterial debris on reusable bronchoscopes. Swabbing surfaces and waiting for test results can take time. So what’s a potential solution?

Fortunately, adenosine triphosphate (ATP) testing can add an extra layer of protection, helping clinicians to determine if a reusable bronchoscope contains any residual micro-contamination between patients. 

Actively growing microorganisms generate ATP—a chemical involved in intracellular energy transfer—and will “light up” when clinicians inspect a surface with one of the commercially-available ATP bioluminometer. Because results expressed in relative light units are immediately available, the ATP bioluminescence is considered a rapid sterility test. 

ATP bioluminometers generally can detect a range of microbes that potential reside on improperly cleaned reusable bronchoscopes. These can include Staphyloccocus aureus, Escherichia coli, Pseudomonas aeruginosa, and others.1,2

Improving Test Reliability

No test is always perfect, including ATP bioluminescent meters, according to researchers. In one study, investigators compared four commercially-available devices to assess sensitivity, their correlation between readouts and actual microbial content of experimentally-contaminated surfaces, and to see if disinfectants alter the results.3 They found all four ATP meters provided consistent results over time, but different significantly in their microorganism detection sensitivity. In addition, disinfectants did in fact alter and cause variability in the ATP test results.

Another study of surface contamination in an ICU setting found varied cutoff ranges and no correlation between readings of two ATP testing devices used to detect multidrug-resistant organisms.4

A year later, the same lead author devised a solution—publishing a sampling algorithm that can correct for variations among ATP device measurements and analysis, regardless of device.5 The algorithm, the authors state, mitigates inherent variability in ATP testing and boosts the reliability of ATP testing for cleanliness monitoring in hospitals. 

Recommendations for Effective ATP Testing

“Because of its critical nature, cleaning should be regularly validated, verified and monitored. The role of cleaning in a healthcare setting has moved beyond simple aesthetics to being an integral part of a robust infection control program…Healthcare professionals should recognize the critical role that unerringly thorough cleaning has on the overall patient experience,” stated ATP hygiene-monitoring system manufacturer Neogen in a Q&A with five meter manufacturers.6

The same Q&A with various industry players also points out the importance of real-time sterilization results with rising concerns over healthcare-associated infections; the need for standardized and comprehensive programs for cleaning, often a combined effort between environmental services and infection control experts; and how ATP can be used to not only assess the cleanliness of bronchoscopes but also scope cabinets and carts in a hospital.

The Centers for Disease Control and Prevention recommends visual inspection and more in their guidance on flexible endoscopes.7 The CDC states:

“After manual cleaning, visually inspect the endoscope and its accessories. Visual inspection provides additional assurance that the endoscope and its accessories are clean and free of defects. Complex devices such as flexible endoscopes may require the use of lighted magnification or additional methods to assist with the inspection process.”

Beyond Bronchoscopes

Interestingly, researchers have also looked at ATP bioluminescence as a rapid way to detect a UTI in a urine sample; to monitor microbial safety “in a contemporary human cadaver laboratory,” and to study if clinician cell phones in an operating room increase the risk of bacterial contamination.  

1. Use of ATP Bioluminescence for Rapid Detection and Enumeration of Contaminants: The Milliflex Rapid Microbiology Detection and Enumeration System

2. The uses and abuses of rapid bioluminescence-based ATP assays.

3. How Reliable Are ATP Bioluminescence Meters in Assessing Decontamination of Environmental Surfaces in Healthcare Settings? PLoS One. 2014; 9(6): e99951.

4. A pilot study into locating the bad bugs in a busy intensive care unit (Am. J. Infect. Control. 2015;43:1270–5).

5. A suggested sampling algorithm for use with ATP testing in cleanliness measurement. 

6. Using ATP in Healthcare Settings. Infection Control Today. December 7, 2010.

7.  Essential Elements of a Reprocessing Program for Flexible Endoscopes—Recommendations of the Healthcare Infection Control Practices Advisory Committee.