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DISCUSSION
Francisella tularensis a bacterial zoonosis. The organism is a small gram-negative rod that is found predominately in the northern hemisphere (1). The organism is capable of survival in cold areas and moist environments such as water, soil, or decaying animal carcasses. Francisella tularensis infects rodents, rabbits, and ticks. It can be transmitted to humans via bites from infected arthropods, handling of infected animal tissue or fluids, ingestion or direct contact with water, food, or soil, and/or inhaling infectious aerosols. It is important to note that there is no documented human-to-human transmission (2).
The clinical presentation of Francisella tularensis varies and is dependent on how the organism is acquired. In general, there is an incubation period of about three to five days prior to symptom development. The initial symptoms are non-specific and include fever, chills, body aches, and fatigue. There are six major clinical presentation which include: ulceroglandular, glanduluar, oculoglandular, oropharyngeal, pneumonic, and typhoidal (2,3). This case discussion will be limited to oculoglandular and pneumonic disease. Oculoglandular disease represents a small percentage of tularemia cases and occurs when the organism acquires access to the conjunctiva. The symptoms are usually unilateral and include the following: pain, photophobia, increased tearing, conjunctival erythema, and tender regional adenopathy. This teenager had a form of oculoglandular tularemia know as Parinaud oculoglandular syndrome. Parinaud oculoglandular syndrome is characterized by conjunctivitis in one eye and a swollen lymph node in front of the ear on the same side (2). The clinical differential in this situation includes tularemia, Bartonella henselae, Sporothrix and herpes simplex infection. Pneumonic tularemia is what the laboratory workers were at risk of acquiring. The initial manifestations are non-specific and can progress to fever and a cough with little sputum production. The clinical differential with this presentation is broad and includes the following: Q fever, Psittacosis, Tuberculosis, pulmonary mycoses, pneumonic plaque and many community acquired pneumonias.
The diagnosis of Francisella tularemia is usually confirmed with serology in the presence of clinical suspicion. The organism rarely makes its way to the laboratory for identification. However, it is important to remember that Francisella tularensis is a tiny, poorly staining, gram-negative coccobacilli that requires cysteine for growth (1,2). Media that will support the growth of Francisella tularemia are chocolate agar, Thayer Martin agar, and buffered charcoal yeast extract agar (1,2). An example gram stain and agar plate growth patterns from the American Society of Microbiology can be seen in Figures 2 and 3, respectively (1)
A preliminary identification of Francisella tularemia as Haemophilus is a common laboratory error (4). Due to this there was potential aerosol production in the first laboratory because the culture and the Kirby Bauer susceptibility testing were handled outside of a biological safety cabinet. The laboratory personnel exposed during processing were required to get fever checks every morning for two weeks and had the option to receive prophylactic doxycycline. After this event a new protocol was put into place requiring that when small gram-negative rods are seen, all further work should be performed in a biological safety cabinet until Francisella tularensis and similar organisms are ruled out. The American Society of Microbiology has developed a protocol to rule out Francisella tularensis which can be found in Figure 4 (1). Fracisella tularensis grows better on chocolate then blood agar, does not require X and V factor, oxidase negative, catalase weak positive to negative, and is -lactamase positive (1). There should be no laboratory investigation that has the potential to produce aerosols such as Kirby-Bauer susceptibility and automated identification/sensitivity equipment. If an organism is received from an outside hospital, then the shipment is to be opened in a biological safety cabinet and begin with a gram stain or acid fast.
This case highlights the importance of communication between the clinical team and the laboratory when tularemia is in the differential and/or small gram-negative rods are seen on gram stain. Under these scenarios it is best to perform all following work in a biological safety cabinet until organisms such as Francisela tularemia or Brucella are ruled out.
REFERENCES
Contributed by Jacob A Smith, MD. William Pasculle, ScD.
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