September 10, 2013 — An article entitled “Outbreak of Escherichia coli Infections Associated with a Contaminated Transesophageal Echocardiography (TEE) Probe” appears in next month’s (October, 2013) issue of the journal Infection Control and Hospital Epidemiology.

Written by Bancroft et al. (2013),* this article documents a community hospital’s cluster of patients whose blood or sputum samples tested “positive” for E. coli 1-4 days after cardiac surgery.

Another report of this outbreak by the Los Angeles County Department of Public Health can be read in its entirety by clicking here.

What is “TEE”? 

Transesophageal echocardiography — or, TEE — is a diagnostic procedure that uses a specialized device to display sonographic images of the heart, known as echocardiograms (which are distinguished from “ECGs,” or electrocardiograms).

This specialized device — known as a TEE probe — is inserted into the patient’s esophagus via the mouth. The distal tip of this probe features an ultrasound transducer that produces and detects inaudible ultrasonic sound waves.

During TEE, these waves are emitted towards and bounce off of the beating heart (which is near the probe’s placement in the esophagus). These reflected sound waves — or “echos” — are also captured by the TEE probe’s same transducer and enhanced by a computer to provide cardiologists with real-time images of the active heart.

(During transthoracic echocardiography, in contrast, the transducer yielding the images of the heart is instead placed non-invasively on the patient’s chest.)

Although without internal channels, the TEE probe is similar in certain aspects to some models of gastrointestinal (GI) endoscopes that are similarly equipped with an ultrasound transducer and used during “echo-endoscopy” to yield images of the GI tract (e.g., the esophagus, duodenum).

TEE is a risk factor for healthcare-associated infections of gram-negative bacteria including Legionella spp., Pseudomonas aeruginosa, and E. coli. Therefore, its proper reprocessing is required to prevent bacterial outbreaks. — Lawrence F Muscarella PhD


The likely cause of this outbreak of E. coli following TEE 

According to Bancroft et al. (2013), a contaminated TEE probe was implicated as the cause of this community hospital’s E. coli outbreak. Microbiological sampling of this TEE probe confirmed it to be contaminated (“positive”) with the outbreak’s strain of E. coli (as well as with Klebsiella pneumoniae).

Read Dr. Muscarella’s two related articles

Factors contributing to this TEE probe’s remaining contaminated after reprocessing and likely transmitting E. coli to the infected patients during TEE include a “physical defect” in the TEE probe, which may have protected the destruction of harboring E. coli during the probe’s cleaning and high-disinfection.

E. coli is a gram-negative bacillus commonly found in the lower GI tract as part of the intestine’s normal bacterial flora.

Readers may remember a published report by Tosh et al. (2011)** that documented a different, yet similar, outbreak of Pseudomonas aeruginosa at a hospital in Houston, Texas, in 2009 following arthroscopic procedures of the shoulder and knee.

Read Dr. Muscarella’s related article that discusses this outbreak in Texas following arthroscopy: “Study of a 2009 outbreak of Pseudomonas aeruginosa following arthroscopy in Texas.”

This outbreak was discussed on Fox News and NBC Nightly News, and its investigators, which included the renown physician Pritish Tosh, M.D., and other representatives of the Centers for Disease Control and Prevention (CDC), suggested that this outbreak was due to the complex physical designs of arthroscopic shaver hand-pieces and inflow/outflow cannulae, which retained infectious bioburden after cleaning.

According to Tosh et al. (2011), this retained bioburden presumably shielded and protected the outbreak’s strain of P. aeruginosa from contact with (and its destruction by) the pressurized steam that the hospital employed to “sterilize” these instruments after each of their clinical uses.

Read Dr. Muscarella’s peer-reviewed article, “Other possible causes of a well-publicized outbreak of Pseudomonas aeruginosa following arthroscopy in Texas,” which was published in Advances in Infectious Diseases.

Other reports of infections following TEE 

The reader may also find of interest the CDC’s report: “Pseudomonas aeruginosa Respiratory Tract Infections Associated with Contaminated Ultrasound Gel Used for Transesophageal Echocardiography — Michigan, December 2011–January 2012.”

These infections of P. aeruginosa, like those of E. coli reported by Bancroft et al. (2013), document respiratory infections arising from an instrument used in the GI tract, namely, the TEE probe.

In both cases, the infections may be due to the migration of bacteria from the oropharynx or GI tract, contaminated with P. aeruginosa or E. coli, respectively, during the insertion or placement of the TEE probe, into the respiratory tract.

Other reports of disease transmission due to a reusable device’s physical defect or its complex physical design include:

  1. Ramsey AH, et al. An outbreak of bronchoscopy-related mycobacterium tuberculosis infections due to a lack of bronchoscope leak testing. Chest 2002;121;976-981 – click here;
  2. Muscarella LF. Other possible causes of a well-publicized outbreak of Pseudomonas aeruginosa following arthroscopy in Texas. Advances in Infectious Diseases 2013 Jun;3(2):134-145 – click here; and
  3. Muscarella LF.  Early identification and control of carbapenemase-producing Klebsiella pneumoniae originating from a contaminated GI endoscope. Discussions in Infection Control (2013).

Bacterial transmission via a TEE probe or other, similar type of instrument may  indicate, among other deficiencies, inadequate storage or drying of the instrument. — Lawrence F Muscarella PhD


A quality system requires that one or more validated corrective and preventive actions (known as “CAPAs”), or recommendations, be developed and implemented for each deviation, error, or lapse identified during a bacterial outbreak’s investigation.

These recommendations, which are directed to the users of TEE probes and to the staff members responsible for reprocessing them, include the following:

1.  Whenever bacterial infections are associated with patients who recently underwent TEE (or GI endoscopy), consider reusable medical equipment, in general, and the TEE probe and its lubricant, or coupling, gel (or GI endoscope), in particular, as a potential source of the bacteria.

A.  During the investigation of a bacterial outbreak linked to TEE, microbiologically sample (as appropriate) the TEE probe (and/or coupling gel) using standardized and validated sampling/recovery methods, and after the reprocessing the probe having employed the medical facility’s routine cleaning and disinfection procedures.

2. Visually inspect the TEE probe — like a GI endoscope, bronchoscope or other type of flexible endoscope — for damage or a physical defect (e.g., a perforation or tear, a cracked surface, or fraying) before each use on a patient and before its reprocessing.

  • Also, visually inspect the TEE probe for contamination before its clinical use.
  • Do not use on patients a TEE probe that is damaged or contaminated.

3. Ensure proper cleaning, high-level disinfection and rinsing (e.g., using sterile or bacteria-free water), and drying of the TEE, as with most reusable medical equipment (classified as semi-critical).

  • In addition to E. coli and P. aeruginosa infections, instances of Legionella infections due to a contaminated TEE probe have been reported (see: Levy PY, et al. A nosocomial outbreak of Legionella pneumophila caused by contaminated transesophageal echocardiography probes. Infect Control Hosp Epidemiol 2003;24:619–22 – click here).

4. Properly store reprocessed, “patient-ready” TEE probes in accordance with their respective manufacturer’s instructions (e.g., in a dry, well-ventilated, dedicated storage area — not in an enclosed, moist environment where bacteria may proliferate).

  • Do not store TEE probes in a suitcase or other poorly ventilated setting. Improper storage of a TEE probe or other type of similar instrument can facilitate its re-contamination with, and the growth on its surfaces of, environmental bacteria. (If inadequately dried, multi-channeled instruments, such as GI endoscopes, are most susceptible to bacterial proliferation during storage.

5. Maintain surveillance of adequate resolution to detect gram-negative bacterial infections following TEE.

6. Review the medical facility’s policies, procedures, and practices to ensure that TEE probes and all other semi-critical instruments are being properly cleaned, high-level disinfected (or sterilized), dried and stored.

Click here to read Dr. Muscarella’s related blog “Disinfection or Sterilization of a Contaminated Reusable Instrument?”

Article by Lawrence F Muscarella PhD; posted 9/11/2013.


The supra-scripts “*” and “**” in the text, above, refer to the following two references, respectively:

* Bancroft EA, English LT, Terashita D, Yasuda L. Outbreak of Escherichia coli infections associated with a contaminated transesophageal echocardiography probe. Infect Control Hosp Epidemiol 2013 Oct;34(10):1121-1123.

** Tosh PK, Disbot M, Duffy JM, et al. Outbreak of Pseudomonas aeruginosa Surgical Site Infections after Arthroscopic Procedures: Texas, 2009. Infect Control Hosp Epidemiol 2011;32:12:1179-1186.

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