A 34 year old female presented to the emergency department with a chief complaint of nausea, vomiting and diarrhea as well as tenderness in her extremities. These symptoms had been present for the previous 4 days with multiple episodes of diarrhea, associated low grade fevers & chills and she had poor oral intake as a result. Her past medical history was significant for human immunodeficiency virus (HIV) and chronic kidney disease. She has not be compliant with her anti-retroviral therapy and infectious disease prophylactic medications. Her vitals were within normal range and her physical exam elicited tenderness to palpation of her extremities and torso. No rashes and no erythema are seen. Routine laboratory tests as well as infectious disease work up, which included blood, stool & urine cultures, C. difficile and ova & parasite exam, were ordered. Notable findings included a slightly elevated white blood count (11.3 TH/cm2), creatinine of 7.1 mg/dL, HIV RNA viral load of 671 VC/mL and an absolute CD4 count of 7 cells/cm2. Two days after collection, her blood cultures were signaled as positive by the automated instrument.
The pathogen of interest grew from two sets of blood cultures and the direct Gram stain showed Gram negative cocci arranged in pairs (Image 1). After 48 hours incubation, small, whitish colonies were observed on blood and chocolate agars. No growth was seen on the MacConkey plate (Image 2). The isolate was positive for both catalase and oxidase. It was identified as Neisseria gonorrhoeae by both MALDI-TOF MS and a Vitek NH card.
N. gonorrhoeae is the second most common sexually transmitted infection (STI) in the United States, only surpassed by Chlamydia trachomatis and they are often acquired together as a co-infection. Uncomplicated infections with N. gonorrhoeae typically present as acute urethritis with discharge. Asymptomatic infection occurs in 10% of males and upwards of 50% of females. As a result, females are at risk for the development of ascending infections and pelvic inflammatory disease leading to further reproductive issues. Disseminated gonococcal infection is uncommon (less than 1% of all gonococcal infections) but can occur and manifests as purulent arthritis with or without an accompanying dermatitis. In the case of our patient, her tenderness to palpation of the extremities could be a symptom of this disseminated septic arthritis.
In the laboratory, N. gonorrhoeae can be fastidious and requires special media such as chocolate, Martin-Lewis, modified Thayer-Martin or New York City agars as well as an enhanced CO2 environment in order to grow. The Gram stain of N. gonorrhoeae is described as Gram negative cocci with adjacent flattened sides and helpful biochemicals include catalase and oxidase (both positive). Traditionally, in order to further speciate members of the Neisseria genus, sugar fermentation was necessary. N. gonorrhoeae only ferments glucose, while another notable member, N. meningitides, ferments both glucose and maltose. Additionally, N. lactamica ferments glucose, maltose and lactose. Currently, commonly used methods of identification include API NH strips and automated instruments such as Vitek and MALDI-TOF MS.
Susceptibility testing for N. gonorrhoeae is usually limited to testing for beta-lactamase activity, although CLSI guidelines are available if deemed necessary. Current therapeutic guidelines recommend empiric treatment of uncomplicated infections with intramuscular ceftriaxone and oral azithromycin.
-Kristen Adams, MD, is a fourth year Anatomic and Clinical Pathology resident at the University of Mississippi Medical Center.
-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. She is the director of the Microbiology and Serology Laboratories. Her interests include infectious disease histology, process and quality improvement and resident education.
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How common it is to see GC growth on sheep blood agar?