Month: February 2017

Microbiology Case Study: 81 Year Old Man with Prior History of Bladder Cancer

Case history

An 81 year old man with prior history of bladder cancer treated with Bacillus Calmette–Guérin  (BCG) presented with dysuria. Three urine samples were sent for AFB culture.

Laboratory Workup

The urine samples were plated on 7H11 solid media and Middlebrook liquid media. Colonies grew in the liquid media in five days and the solid media in 6 days (Figure 1). The colonies were subcultured to 7H11 solid media and Lowenstein-Jensen (LJ) media.  At this time, the colonies were probed for Mycobacterium tuberculosis complex, M. avium complex and M. gordonae, all of which were negative.  The organism grew on all of the subcultured media within one day. This fulfilled the criteria for rapidly- growing Mycobacterium species given the organism had grown in less than 7 days on subculture from solid media to solid media.  The specimen was sent out to our reference laboratory for further speciation and was identified as Mycobacterium chelonae.

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Figure 1: 7H11 media with non-pigmented white colonies.

 

Discussion

Rapidly growing mycobacteria include many species, but the main clinically relevant species are M. fortuitum, M. chelonae, and M. abscessus. These organisms are widely distributed in nature and can survive nutritional deprivation and extreme temperatures. They have been isolated from soil, dust, natural surfaces, water, wild animals and domestic animals.  Risk factors for infection include patients with immunosuppression, organ transplant and autoimmune disorders. Immunocompetent patients are also at risk if they have had trauma or invasive medical procedures.  M. chelonae may cause a spectrum of human disease. The most common manifestations are cutaneous infection, osteomyelitis and catheter infections. Nosocomial outbreaks of M. chelonae have been reported and linked to various water sources, including water-based solutions, distilled water, tap water and ice.  Rapidly growing mycobacterium are generally resistant to the classic antituberculosis drugs (rifampin, ethambutol and isoniazid). M. chelonae is usually sensitive to aminoglycosides, however treatment should be determined by antibiotic susceptibility testing.  In our patient, we had expected the colonies to be M. bovis because of the patient’s history of BCG treatment which is a live attenuated strain of M. bovis. Cystitis induce by M. chelonae is a rare clinical manifestation. We believed this is a true infection, as opposed a contaminated patient sample, given the patient’s symptoms in conjunction with all three urine samples being positive for M. chelonae.

 

-Jill Miller, MD is a 4th year anatomic and clinical pathology resident at the University of Vermont Medical Center.

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-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.

Microbiology Case Study: A 22 Year Old Female with Recent Travel

Case History

A 22 year old female with recent travel to Nicaragua noted passage of a 10-12 cm long worm in her stool. She also noted some intermittent hematochezia over the past several days and had developed an itchy eczematous rash on her extremities.

Laboratory Diagnosis

Stool sample was submitted for ova and parasite exam. Stool sediment exam showed the presence of multiple fertilized eggs measuring 50 microns (Image 1). Based on the size of the egg, and the presence of the thick and yellow mammelated coat, she was diagnosed with an Ascaris lumbricoides infection.

 

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Image 1.

Discussion

Ascaris is the largest of the common nematode parasites of humans with females measuring 20-35 cm long and males measuring 15-31 cm. Notably, males have a curved posterior end. Infection is acquired through ingestion of the embryonated eggs from contaminated soil. In the larval migration phase of infection, diagnosis can be made by finding the larvae in sputum or in gastric washings. One female worm can lay up to 20,000 eggs, therefore enumeration of eggs does not correlate with worm burden. Both fertilized and unfertilized eggs can be easily be recovered using the sedimentation concentration from a fecal sample. It is estimated that 25% of the world population is infected with Ascaris and since transmission depends on fecal contamination of the soil, in areas where infection rates are high, mass population treatment plans with Abendazole have been successful.

 

-Agnes Balla, MD is a 3rd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

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–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.