A swab from a bartholin gland cyst was submitted to the microbiology lab with no other clinical history. Culture produced cream-colored, mucoid colonies on blood and chocolate agar after 48 hours of incubation at 35 C (image below). The culture grew a gram negative rod that did not grow on MacConkey agar, a distinguishing characteristic for Weeksella virosa. This ID was confirmed by MALDI-TOF.
Originally described in 1970 as a nonsaccharolytic flavobacterium, Weeksella virosa is an uncommon aerobic gram negative rod isolated most commonly from urine, cervix and vaginal specimens. There have been case reports, however, of isolation from blood and spinal fluid. In rare instances, the bacterium has been associated with pneumonia, bacteremia, peritonitis and UTIs, more often in patients with comorbidities including end stage renal disease, diabetes, and liver disease.
In one study of 100 patients, the organism was isolated in 2% of high vaginal swabs of the female genital tract from both symptomatic and asymptomatic females. In a separate study involving women with a high risk of STDs, the incidence climbed to 15%.
The characteristic yellow tinge of the colonies is secondary to a non-diffusable pigment. The organism is oxidase positive, indole positive and catalase positive.
There are no species-specific breakpoints. However, CLSI guidelines for other non-enterobacteriacea gram negative rods can be used. In vitro studies have found the organism to be resistant to aminoglycosides and nitrofurantoin.
Slenker, A et al. Fatal Case of Weeksella virosa Sepsis. Journal of Clinical Microbiology. P4166-4167. Dec. 2012.
-Agnes Balla, MD, is a 3rd year anatomic and clinical pathology resident at the University of Vermont Medical Center.
-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.