Nocardia Surveillance Under Way

Angie Cierzniewski
MPH Intern

The Indiana State Department of Health (ISDH), in partnership with the Centers for Disease Control and Prevention (CDC), is conducting surveillance of Nocardia infections. Nocardia bacteria are gram-positive, weakly acid-fast, gram-positive, and ubiquitous in the environment.  These bacteria cause opportunistic infections, including respiratory infections, abscesses, skin infections, and tumors. Risk factors for nocardiosis include being a transplant recipient, steroid use, advanced HIV disease, malignancy, chronic pulmonary disease, or intravenous drug abuse.

Historically, sulfonamides were the treatment of choice, but sulfonamide resistance has been reported in Europe, Japan, and the U.S.  Approximately 500-1,000 new cases of nocardiosis occur annually in the United States.  Overall, 80 percent of cases present as invasive pulmonary infection, disseminated disease, or brain abscess; 20 percent present as cellulitis.  Although incidence data are extremely limited,  the number of nocardiosis cases probably has increased recently due to the overall increased number of severely immunocompromised persons.  Currently, there is no national reportable surveillance system for nocardiosis.

From January 2000-December 2004, 72 Nocardia isolates obtained from Alabama residents with culture-confirmed nocardiosis were submitted to CDC for antimicrobial susceptibility testing at the request of the attending health care providers.  The CDC determined the species and evaluated the antimicrobial susceptibility patterns of all isolates.  The most common species identified (44%) was Nocardia nova.  Forty-nine (68%) of 72 isolates were resistant to sulfonamides, the highest resistance rate ever recorded in the U.S. These data demonstrate the importance of performing species identification and antimicrobial susceptibility testing for Nocardia and suggest that further monitoring is needed to determine the burden of nocardiosis caused by antimicrobial-resistant Nocardia and to determine the relationship between resistance, treatment, and patient outcome. 

To determine the true rate of antimicrobial resistance, the CDC is conducting short-term surveillance for resistance that would ideally capture all Nocardia isolates in a state and determine the timing of the course of disease and treatment, the species, and the resistance patterns.  Knowledge of the incidence of naturally occurring, initial resistance in Nocardia isolates will facilitate appropriate public health response, whether in the form of investigation, recommendation, or further evaluation.

For this three-year project, the CDC has implemented laboratory-based surveillance for nocardiosis by evaluating Nocardia isolates collected in various states, including Indiana. Nocardia isolates are submitted to CDC, consistent with ongoing practices for routine reference laboratory support. 

To support the appropriate interpretation of laboratory results, CDC requests information on recent use of antimicrobials and results of previous laboratory testing for each isolate.  Information is requested on the date of initial diagnosis, antimicrobial therapy, date of specimen collection, outcome of the infection, and previous laboratory results.  These data will allow the CDC to: 1) determine if the apparent increase in resistance represents a true increase in resistance or if it is an artifact;  2) describe the percent of newly diagnosed Nocardia infections that are antimicrobial resistant, 3) share data with local health care providers and public health entities for use in antimicrobial therapy planning, and 4) evaluate the usefulness and sustainability of the elements of the three years of Nocardia surveillance to determine viable ongoing surveillance efforts.  Subsequent years of this project will examine in-depth the laboratory and epidemiologic information associated with cases of nocardiosis.