Contaminated Ultrasound Gel Source of Infection Outbreak

July 9, 2013

Pseudomonas aeruginosa bacteriaAccording to a press release issued by the Society for Healthcare Epidemiology of America (SHEA), a 2011 healthcare-associated outbreak of P. aerugenosa has been linked to contaminated ultrasound gel.

Investigators at Beaumont Health System near Detroit, Michigan determined the source of the bacteria causing the healthcare-associated infection was indeed contaminated ultrasound gel.  The findings were published in the August issue of SHEA’s journal Infection Control and Hospital Epidemiology (ICHE). The study underscores the need for increased scrutiny of contaminated medical products.

“Ultrasound is a critical healthcare tool used every day in both diagnostic and interventional procedures,” said Paul Chittick, MD, lead author of the study. “Although contaminated gel has been the cause of several documented outbreaks of infection, its potential role as a vehicle for spreading infections to patients is frequently overlooked.”

In December 2011, researchers uncovered an unusual cluster of P. aeruginosa in the cardiovascular surgery intensive care unit during routine infection control surveillance. The bug is known to increase the risk of bloodstream and respiratory infections in immune-compromised individuals. Sixteen patients became colonized or infected with the bacteria, with all cases occurring in the respiratory tract. The outbreak was found to have stemmed from bottles of ultrasound transmission gel used during cardiovascular surgery. Following replacement of this gel with a sterile product, no further cases occurred.

Cultures of gel from a bottle in use in the operating room grew P. aeruginosa that was identical to the outbreak strain. It was originally thought that the gel had likely become contaminated during use. However, sealed bottles of gel grew the same P. aeruginosa strain, proving that the product was contaminated during the manufacturing process at the plant of Pharmaceutical Innovations.

The FDA has subsequently issued a warning about the gel, alerting practitioners to the risk of infection.  The Beaumont Health System investigators have also recently published proposed guidelines in ICHE for the use of sterile versus non-sterile ultrasound gel.  The guidelines stress the importance of sterile, single-dose ultrasound gel to be used for all invasive procedures.  The guidelines also provide the appropriate storage and warning methods for the gel.

Photo: Centers for Disease Control and Prevention, Janice Haney Carr.

According to the CDC, Pseudomonas aeruginosa infection “is caused by strains of bacteria found widely in the environment; the most common type causing infections in humans is called Pseudomonas aeruginosa.” “Serious Pseudomonas infections usually occur in people in the hospital and/or with weakened immune systems. Infections of the blood, pneumonia, and infections following surgery can lead to severe illness and death in these people.”

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