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Pseudomonas aeruginosa Respiratory Tract Infections Associated with Contaminated Ultrasound Gel Used for Transesophageal Echocardiography — Michigan, December 2011–January 2012

In late December 2011, the Department of Epidemiology at Beaumont Health System (BHS) in Royal Oak, Michigan, noted an increase in the number of positive respiratory cultures in one surgical intensive-care unit (ICU), prompting further investigation. The increase in positive cultures was attributed entirely to Pseudomonas aeruginosa. Investigation by BHS staff members found that all of these positive cultures were related to use of ultrasound transmission gel from a single manufacturer during transesophageal echocardiography. Seven patients were infected with P. aeruginosa based on National Healthcare Safety Network (NHSN) criteria (1), and nine were colonized. Cultures from one open and one unopened bottle of the gel grew P. aeruginosa closely related to the outbreak strain based on molecular typing via repetitive extragenic palindromic polymerase chain reaction (rep-PCR). The Oakland County Health Department, the Michigan Department of Community Health, and the Food and Drug Administration (FDA) were notified of the findings. On January 23, all implicated ultrasound gel in multiuse bottles was removed from BHS facilities and replaced with a single-use, sterile ultrasound gel for all potentially invasive procedures. On April 18, FDA issued a Safety Communication* advising health-care professionals and facilities not to use certain lot numbers of the ultrasound transmission gel and further advising that the only ultrasound gel that is sterile is unopened gel in containers labeled as sterile. To date, no further respiratory cultures have been positive for P. aeruginosa.

Surveillance for nosocomial infection at BHS is driven by results of clinical microbiology cultures. Positive cultures are reviewed using a combination of microbiology reports and paper or electronic medical records to determine infections and colonizations. Initial review found P. aeruginosa in respiratory specimens taken from endotracheal tubes in 10 patients in a single surgical ICU in December. No cultures of these patients' surgical sites or blood grew P. aeruginosa. The same unit had averaged less than three respiratory tract cultures positive for P. aeruginosa monthly during the preceding 11 months and had only one infection by NHSN criteria during that period.

Review of the 10 P. aeruginosa cultures revealed that all patients had undergone cardiovascular surgery. No clustering by operating room, surgeon, operating room staff member, ICU room number, or nursing staff was observed. Because all isolates were from the respiratory tract, the initial focus included a review of postoperative nursing and respiratory-care practices, respiratory therapy equipment management, and anesthesia practice and equipment management. No clustering by respiratory medications administered was observed. Discussion with operating room staff members revealed that a unique aspect of these patients' surgeries included the use of an intraoperative transesophageal echocardiogram (TEE). TEEs involve the insertion of a probe with an ultrasound conducting tip into a patient's esophagus and are used during cardiovascular surgery to aid in visualization of the posterior of the heart. The TEE probe is coated with a coupling gel and then inserted by an anesthesiologist before surgical incision. Their duration of placement depends on the specific procedure being performed. Environmental cultures of TEE probes, storage tubes, and work surfaces were performed, and all TEE probes were inspected. All cultures were negative, and only one probe had a mechanical defect; this probe was removed from use.

Intensified surveillance (performing respiratory tract cultures on all mechanically ventilated patients in this surgical ICU) during January 6–20 identified six additional patients colonized with P. aeruginosa (of the 20 patients tested). All six of these patients also had undergone cardiovascular surgery. Surveillance respiratory cultures from another surgical ICU identified only one patient colonized (of the 11 patients tested) with P. aeruginosa; this isolate had a different antibiotic susceptibility pattern from those of the 16 isolates found earlier. Of the 16 patients identified during the outbreak, two had pneumonia, five had tracheobronchitis, and nine had respiratory tract colonization only. Time from surgery to identification of a positive culture from a respiratory tract specimen ranged from 2 to 14 days (median: 5 days). The patients had undergone various surgical procedures. Those who had undergone valvular surgery alone (n = 13) were at significantly higher risk (relative risk = 5.7, 95% confidence interval = 1.75–18.86) for Pseudomonas infection or colonization than those who had undergone coronary artery bypass grafting alone (n = 32) (Table). The investigation noted that patients undergoing valvular surgery have TEE probes in place during nearly the entire procedure, whereas those undergoing coronary artery bypass grafting had shorter durations of TEE use. A review of operative times found that procedures lasting ≥5 hours (n = 70) were more frequently associated with P. aeruginosa infection or colonization (relative risk = 6.4, 95% confidence interval = 0.89–46.45) than procedures lasting <5 hours (n = 30).

The investigation focused further on manipulations of the respiratory and gastrointestinal tract. An ultrasound transmission gel, Other-Sonic (Pharmaceutical Innovations, Inc., Newark, New Jersey), which was not labeled or sold as a sterile product, was used with TEE probes. The multidose containers of gel were collected and replaced with a single-use, sterile product on January 23. After this change, no additional respiratory cultures with P. aeruginosa were observed.

Molecular typing was performed on the 10 isolates on January 26, and all were determined to be >99% similar by rep-PCR. Cultures of the four previously opened Other-Sonic ultrasound transmission gel bottles removed from the operating room were performed; one of four samples grew P. aeruginosa, and molecular typing revealed it to be highly related (>99%) to the outbreak strain. Five other strains of P. aeruginosa isolated throughout the hospital during the outbreak period also were analyzed and determined to be unrelated to each other or the outbreak strain. Two bottles of sealed, unopened Other-Sonic ultrasound transmission gel subsequently were cultured, one of which grew P. aeruginosa. At this point a health-care system–wide recall of all bottles of Other-Sonic ultrasound transmission gel was initiated, local and state health departments were contacted, and FDA was notified. Additional molecular typing studies (using rep-PCR) showed that the Pseudomonas isolate from the sealed bottle also was >99% similar to the outbreak strain, strongly suggesting contamination of the product during manufacturing, packaging, storage, or shipping.

Reported by

Paul Chittick, MD, Victoria Russo, MPH, Matthew Sims, MD, Susan Oleszkowicz, MPH, Kara Sawarynski, PhD, Kimberly Powell, Jacob Makin, Elizabeth Darnell, Barbara Robinson-Dunn, PhD, Bobby L. Boyanton Jr, MD, Jeffrey Band, MD, Beaumont Health System, Royal Oak, Michigan. Corresponding contributor: Paul Chittick,, 248-551-0365.

Editorial note

This report describes an outbreak of Pseudomonas aeruginosa respiratory tract colonization and infection related to the use of contaminated ultrasound transmission gel. Sixteen cardiovascular surgery patients were affected during the outbreak, seven with infection per NHSN criteria, and nine with colonization. Initial investigation suggested the possibility that the TEE probes were the source of the outbreak, given that contaminated TEE probes have been linked to pulmonary infection outbreaks of Legionella previously (2). However, surveillance cultures of the probes were negative, and there was no evidence that all case patients were linked to the use of a particular probe. The ultrasound transmission gel, however, was contaminated with P. aeruginosa. Although contamination during use was initially suspected, the fact that one of two tested bottles of sealed, unopened product was contaminated with P. aeruginosa suggests that the contamination might have occurred before the product reached BHS.

Contaminated ultrasound gels have been associated with outbreaks of infection in various settings and with various organisms, including Klebsiella (3), Burkholderia (4,5), Achromobacter (6), and Staphylococcus aureus (7). Although most of these outbreaks were believed to have occurred from inappropriate use of products, in one circumstance it was determined that the gel had been contaminated at the site of production (4). Although these gels contain parabens or methyl benzoate, which are thought to render them bacteriostatic, some Gram-negative bacteria can degrade these components (4), and investigations of several reported outbreaks suggest extrinsic contamination of gels might easily occur (3,5–7). One study demonstrated that an ultrasound gel had no intrinsic antimicrobial properties (8), and interestingly, results of another in vitro study suggested Pseudomonas spp. might actually survive for shorter periods in ultrasound gel compared with S. aureus or Escherichia coli (9). No ingredient information is available publicly for Other-Sonic ultrasound gel.

Numerous products are available to be used as ultrasound transmission gels. No national guidelines exist in the United States recommending specific types of gel for specific procedures. However, in 2004, Health Canada issued recommendations for minimizing the health risks of using gels (10). These recommendations suggested use of single-use, sterile gels for invasive procedures that pass through a tissue, for all studies involving neonates, for all procedures involving sterile equipment or non-intact skin, and for procedures on intact mucous membranes. The results of this report further support a recommendation for the use of only sterile gels for invasive procedures and procedures involving contact with nonintact skin or mucous membranes. Moreover, because only unopened ultrasound gel containers labeled as sterile should be considered sterile and extrinsic contamination might easily occur, only single-use sterile products should be used for such purposes.


Pamela Bozigar, Mary Dietrich, Julie Jordan, MHSA, Paula Keller, MS, Rhea Sautter, MBA, Beaumont Health System, Royal Oak, Michigan.


  1. Horan TC, Andrus M, Dudeck MA. CDC/NHSN surveillance definition of health care-associated infection and criteria for specific types of infection in the acute care setting. Am J Infect Control 2008;
  2. Levy PY, Teysseire N, Etienne J, Raoult D. A nosocomial outbreak of Legionella pneumophila caused by contaminated transesophageal echocardiography probes. Infect Control Hosp Epidemiol 2003;
  3. Gaillot O, Maruejouls C, Abachin E, et al. Nosocomial outbreak of Klebsiella pneumonia producing SHV-5 extended-spectrum beta-lactamase, originating from contaminated ultrasonography coupling gel. J Clin Microbiol 1998;36:1357–60.
  4. Hutchinson J, Runge W, Mulvey M, Norris et al. Burkholderia cepacia infections associated with intrinsically contaminated ultrasound gel: the role of microbial degradation of parabens. Infect Control Hosp Epidemiol 2004;25:291–6.
  5. Jacobson M, Wray R, Kovach D, Henry D, Speert D, Matlow A. Sustained endemicity of Burkholderia cepacia complex in a pediatric institution, associated with contaminated ultrasound gel. Infect Control Hosp Epidemiol 2006;27:362–6.
  6. Olshtain-Pops K, Block C, Temper V, et al. An outbreak of Achromobacter xylosoxidans associated with ultrasound gel used during transrectal ultrasound guided prostate biopsy. J Urol 2011;185:144–7.
  7. Weist K, Wendt C, Petersen LR, Versmold H, Ruden H. An outbreak of pyodermas among neonates caused by ultrasound gel contaminated with methicillin-susceptible Staphylococcus aureus. Infect Control Hosp Epidemiol 2000;21:761–4.
  8. Muradali D, Gold WL, Phillips A, Wilson S. Can ultrasound probes and coupling gel be a source of nosocomial infection in patients undergoing sonography? An in vivo and in vitro study. Am J Roentgenol 1995;164:1521–4.
  9. Ohara T, Itoh Y, Itoh K. Ultrasound instruments as possible vectors of staphylococcal infection. J Hosp Infect 1998;40:73–7.
  10. Health Canada. Notice to hospitals: important safety information on ultrasound and medical gels. Ottawa, Canada: Health Canada; 2004. Available at Accessed April 11, 2012.

What is already known on this topic?

Medical gels have been linked to outbreaks of infection in several reports, including reports of gels contaminated at the site of packaging. As a result, Health Canada in 2004 issued recommendations for minimizing the risk for infection from medical gels. No such guidelines exist in the United States.

What is added by this report?

An outbreak of seven cases of Pseudomonas aeruginosa respiratory tract infection and nine instances of respiratory tract colonization was linked to contaminated ultrasound gel. P. aeruginosa isolates found in 10 patients, one of four opened gel bottles in use in the operating room, and one of two unopened, sealed gel bottles were found to be more than 99% similar by molecular typing.

What are the implications for public health practice?

Because of the risk that an ultrasound gel might be contaminated with P. aeruginosa or other bacteria, single-use, sterile products should be used for invasive procedures and procedures involving contact with nonintact skin or mucous membranes.

TABLE. Number of cultures positive and total number of surgical procedures among patients with respiratory tract cultures growing Pseudomonas aeruginosa, and patients with respiratory tract cultures growing P. aeruginosa per 100 surgical procedures performed, by type of surgical procedure — Beaumont Health System, Michigan, December 9, 2011–January 20, 2012

Type of surgical procedure

No. of cultures positive

Total no. of procedures


Coronary artery bypass (CABG)




Valvular surgery




CABG + valvular surgery




Minimally invasive valve repair








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