Patient Safety Forum |

Recognizing Laboratory Cross-ContaminationCross-Contamination in Culture-Positive TB Cases: Two False-Positive Cultures of Mycobacterium tuberculosis—Oklahoma, 2011

Matthew G. Johnson, MD; Phillip H. Lindsey, MD; Charles F. Harvey, DO; Kristy K. Bradley, DVM, MPH
Author and Funding Information

From the Acute Disease Service (Drs Johnson, Lindsey, and Harvey), Oklahoma State Department of Health, Oklahoma City, OK; Epidemic Intelligence Service (Dr Johnson), Centers for Disease Control and Prevention, Atlanta, GA; and Office of the State Epidemiologist (Dr Bradley), Oklahoma State Department of Health, Oklahoma City, OK.

Correspondence to: Matthew G. Johnson, MD, 1000 NE 10th St, Oklahoma City, OK 73117; e-mail: mgjohnson33@gmail.com

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.

Chest. 2013;144(1):319-322. doi:10.1378/chest.12-2294
Text Size: A A A
Published online

Mycobacterium tuberculosis (MTB) isolation from clinical specimens is the standard for TB diagnosis. Positive MTB cultures are rarely questioned, but false-positive culture rates range from 2% to 4%. In December 2011, two smear-negative, culture-positive TB cases were reported to the Oklahoma State Department of Health (OSDH) in people without TB signs or symptoms. OSDH TB control officers interviewed physicians and laboratory personnel, reviewed patient charts, traced epidemiologic links, and performed microbiologic studies to determine if these were true TB cases. Both specimens were found to have been processed on the same day, at the same laboratory, under the same hood, and by the same technician sequentially after a strongly smear-positive TB specimen. No epidemiologic links were identified among the three patients. Spoligotyping and 24-locus mycobacterial interspersed repetitive unit typing of the three specimens were identical. Only liquid media grew MTB in the two questionable specimens. A laboratory splash incident was suspected, whereby all three liquid media sample lids were open during inoculation rather than being opened one at a time, causing cross-contamination. Also, the two specimens were incubated for 2-3 weeks longer than standard protocol before MTB growth was observed. Patient 1 was not treated for TB because her physician doubted the culture result. Patient 2, an organ transplant recipient, began four-drug anti-TB therapy, and an investigation was initiated for transplant-associated TB. Adherence to strict laboratory techniques and recognizing the possibility of false-positive MTB cultures, especially when inconsistent with clinical data, are essential in preventing erroneous TB diagnoses.

Sign In to Access Full Content

Want to Purchase a Subscription?

New to CHEST? Become an ACCP member to receive a full subscription to both the print and online editions.
Want to access your Institution's subscription?
Sign in to your individual user account while you are actively authenticated on this website via your institution (Learn more about institutional authentication). We will then sustain your personal access to their content/subscription for 90 days, after which you can repeat this process.

Sign In to Access Full Content

Want to Purchase a Subscription?

New to CHEST? Become an ACCP member to receive a full subscription to both the print and online editions.




Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Sign In to Access Full Content

Related Content

Customize your page view by dragging & repositioning the boxes below.

CHEST Journal Articles
CHEST Collections
  • CHEST Journal
    Print ISSN: 0012-3692
    Online ISSN: 1931-3543