Epidemiologists Trace Outbreak of Antimicrobial Resistant Organism

BALTIMORE, Md. -- Infection control experts at The Johns Hopkins Hospital say tighter rules governing use of a hand-held, high-pressure, water-pumping tool to wash and clean wounds should be adopted to improve the safety of wound care.

The Hopkins finding comes in response to the investigation of an outbreak of the antimicrobial resistant bacterium Acinetobacter baumannii at JHH during a two-month period in 2003. The organism infected 11 patients and was traced back to use of pulsatile lavage equipment for wound care. Three of these patients required admission to the intensive care unit for sepsis and respiratory distress.

In the future, staff using the water-gun like equipment will have to wear masks, gowns and gloves during procedures, which must also now be performed in private treatment rooms that are fully disinfected between patients to reduce the chances of cross contamination between patients and staff.

As an added response, the Food and Drug Administration (FDA), which supervises device safety, along with a leading manufacturer of the device have agreed to change the products labeling to include use of routine infection control procedures.

Hopkins already has instituted the new infection control procedures.

Changes at Hopkins and results of the study should change the way this common procedure is performed at other acute-care hospitals and long-term care facilities, said senior study investigator and hospital epidemiologist Trish Perl, MD, an associate professor of medicine and pathology at The Johns Hopkins University School of Medicine.

The Hopkins case study is believed to be the first investigation to relate an outbreak of this bacterium to the pulsatile lavage device, and its results were published in the latest edition of the Journal of the American Medical Association online Dec. 22, 2004.

The Hopkins investigative team traced the infection to the pulsatile lavage tool made by Bard-Davol Inc., and determined that the equipment sprayed the potentially dangerous bacteria into the air and onto surfaces in an open treatment room, with other patients nearby.

This was true even though staff correctly followed procedures for its use, added Perl. Germs were spread when patients and staff came in close contact with each other during procedures and possibly when fewer equipment parts were changed between patients. Guidelines for its use also applied only to healthcare workers, not to patients, prior to the outbreak.

Since finding the cause of the outbreak at Hopkins, the specific strain of the bacterium involved in the outbreak has not reappeared, even after 11 months of follow-up testing.

Antimicrobial resistance is a growing problem for patient safety in healthcare settings, such as hospitals and long-term care facilities, because traditional drugs are not effective for treating these infections, particularly among vulnerable groups of sick and elderly patients, Perl noted. To solve the problem, we are increasingly forced to rely on our basic tools of scientific investigation: finding the initial contact point, or source, of infection and putting in place the necessary steps to prevent an outbreak from happening in the first place.

The investigation began with an immediate review of medical records after an initial cluster of five patients became infected with the bacteria, a five-fold increase from previous months for rates of hospital-based infections. Culture results from patient samples of blood, sputum, urine and wounds also were reviewed. Specific samples, or isolates, of Acinetobacter were analyzed using pulsed-field gel electrophoresis, to determine and track the spread of the specific strain of the bacterium involved in the hospital outbreak.

The records helped the researchers to identify common treatments and other links between the infected patients. Of the five patients in the original cluster, one patient had a different strain of the bacterium, and had it upon admission, indicating that the infection was not picked up at the hospital, and removing it from the investigation of hospital-based cases. Of the remaining four patients, records showed that three had undergone pulsatile lavage treatment.

Subsequent culture testing of the open-space treatment room for performing the procedure showed widespread presence of A. baumannii -- on the disposable parts of the pulsatile lavage gun, including disposable tubing and suction canister, as well as on cleaned stretchers, the sink and nearby supply shelves.

Further surveillance and testing of 58 patients who had undergone wound therapy in the same procedure room as the initial patients showed that six more patients were infected, and five of these had received pulsatile lavage treatment.

By studying patients who had wounds but no infection with Acinetobacter as a control group, and comparing possible risk factors for developing infection, the researchers were able to confirm that pulsatile lavage treatment was a significant risk factor for the infection. Patients who had pulsatile lavage treatment were more than 30 times more likely to have infection than patients who were not treated with pulsatile lavage. Prior residence in a long-term care facility was also a significant risk factor, though no one facility was implicated, and it was unclear how this contributed to the outbreak. All other possible risk factors, including mechanical ventilation and administration of antimicrobial agents, were not found to be statistically significant.

Further investigation revealed that a change in the pulsatile lavage procedure had occurred two months prior to the outbreak. As a cost-saving measure, the disposable suction canisters for the guns were replaced daily or when full, rather than between each patient.

This case study shows the importance of infection control precautions when introducing a new technology or procedure for use in the health care setting, said the studys lead author, Lisa Maragakis, MD, a clinical fellow at Hopkins. Pulsatile lavage is used for wound care in a variety of settings. We want to make sure that those who perform the procedure know about the appropriate infection control precautions to prevent outbreaks of Acinetobacter or other antimicrobial resistant bacteria, such as Pseudomonas, which is also a growing problem.

Originally designed in the 1960s for use in the operating room, pulsatile lavage has been in wider use since the 1980s. Physical therapists and nurses most commonly perform the procedure, where sterile saline is flushed over a wound. A plastic shield prevents splashing, and another tube is used to suck water containing wound debris into a canister. The tubing and shield devices are disposable and not reused between patients. Approximately 3,000 pulsatile lavage procedures are performed annually at Hopkins.

The emergence of multidrug-resistant A. baumannii is a worldwide phenomenon, with numerous hospital outbreaks each year. It can lead to potentially fatal infections, such as ventilator-associated pneumonia, bloodstream infections and wound infections. The resilient organism can survive on environmental surfaces for months, making attempts to control and prevent it more difficult.

Funding for the study was provided by Hopkins and the Centers for Disease Control and Prevention (CDC). Other researchers involved in this study were Sara Cosgrove, MD; Xiaoyan Song, MD, MS; Denny Kim, MD, MPH; Patricia Rosenbaum, RN, CIC; Nancy Ciesla, PT, BS; Arjun Srinivasan, MD; Tracy Ross, BS; and Karen Carroll, MD.

Source: Johns Hopkins Medical Institutions