Vol. 17, No. 34

Monday, September 14, 1998

1. Provided by David Protesi, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.

From August 28, 1998 to September 3, 1998 eight outbreaks were reported to the Maryland Department of Health and Mental Hygiene. From long term care facilities: one outbreak of acute febrile respiratory disease. Foodborne outbreaks: five outbreaks of food service facility-associated gastroenteritis of unknown etiology. One outbreak of scabies in an office setting and one cluster of probable pertussis in a family.

2. The Johns Hopkins Hospital. Information provided by Dr. Angelique Wolf, Department of Pathology.

Case report: A 48-year old female with a history of end stage renal disease secondary to focal sclerosing glomerulonephritis presented to clinic for follow-up two weeks after a living related kidney transplant. At that time it was noted that her creatinine had increased markedly to 5.1. A kidney biopsy revealed no evidence of acute rejection with only mild interstitial chronic inflammation. Over the next two days she developed nausea and increasing left lower abdominal pain over the site of the transplanted kidney. The following day she presented to an outside ED with similar but worsening symptoms and development of chills. Pertinent findings included: a temperature of 101.4ºF, left lower quadrant tenderness in the area of the transplanted kidney without rebound or guarding and a well healed abdominal incision without erythema, swelling or drainage. Relevant laboratory tests revealed a peripheral white count of 12,500, a creatinine of 5.3, and a urinalysis with 15-20 WBC's, 5-10 epithelial cells and moderate hemoglobin. The patient was transferred to The Johns Hopkins Hospital for further evaluation. An abdominal CT scan on admission revealed a 15x10 multiloculated fluid collection associated with the recently transplanted kidney in the lower left quadrant without evidence of hydronephrosis. Intraoperative findings revealed a urinoma adjacent to the site of ureteral anastomosis with no apparent leakage site identified. The urinoma was drained showing slightly opaque blood tinged yellow fluid. Initial evaluation of the fluid with gram stain showed numerous neutrophils but no identifiable organisms.

Organism: The organism was identified as Mycoplasma hominis using enriched media and broth specially formulated to support its growth and 16 S DNA sequencing technique provided contribution of culture results. Mycoplasmas are the smallest free-living microorganisms, (0.2-0.3mm in diameter). Their most striking feature is the absence of a cell wall: hence they do not take up Gram stain, and antibiotics that inhibit cell wall synthesis are ineffective. They are bound only by a flexible plasma membrane and therefore can assume a variety of shapes from round to filamentous. Mycoplasmas have a circular genome of double stranded DNA one-fifth to one-half as large as most bacteria (580 - 1,380 kilobase pairs). Because of their small genomes, mycoplasmas are fastidious and require complex enriched culture media for growth containing cholesterol, preformed nucleic acid precursors and a metabolites (i.e. arginine in the case of M. hominis). Most mycoplasmas are facultatively anaerobic, relatively slow growing and preferentially grow at 37ºC.

Mycoplasmas have been isolated from almost all mammalian and avian species and from a variety of plants and insects. They adhere to and colonize the mucous membranes of the host and are therefore found in the respiratory and genitourinary tracts. In humans who are immunocompetent, certain Mycoplasma species are frequently isolated from a particular site, for example, M. hominis from the genitourinary tract. They rarely invade tissue or the blood stream.

Clinical Manifestations: M. hominis is commonly isolated from women who have bacterial vaginosis and less often in patients with pelvic inflammatory disease. M. hominis has been shown to cause fever following abortion and postpartum endometritis, and wound infection following cesarean section. M. hominis from the maternal genitourinary tract colonizes neonates and has caused mycoplasmemia, meningitis, ventriculitis, brain abscess and pneumonia.

M. hominis also causes nongenitourinary infections in adults, particularly in immunocompromised hosts. In many cases, however, the source of infection is the genitourinary tract. Suspicion of mycoplasma infection must be heightened particularly in immunocompromised patients with lymphatic malignancies, massive trauma, sternal wounds, hypogammaglobulinemia, transplantation, or collagen vascular disease for whom there are findings of purulence in the face of negative cultures and smears.

There are nine reported cases of infection due to M. hominis in patients who have undergone renal transplantation with adequate data available in eight cases. All of the patients were febrile and five of eight were women with a mean age of 44 years. Predisposing factors were immunosuppressive treatment and urinary tract manipulation. Infection developed in most patients within six days after surgery and <3 weeks after kidney transplantation. M. hominis was the only pathogen isolated from the site of infection in five cases and was associated with a copathogen in three cases. One patient underwent nephrectomy without antibiotic therapy and the remaining seven patients received combined surgical and medical treatement. Of the eight patients, four lost allografts.

Laboratory diagnosis: M. hominis will produce nonhemolytic pinpoint colonies on blood agar, but the organisms cannot be visualized in Gram-stained smears of these colonies. The largest colonies of M. hominis usually have a classic "fried egg" appearance. Many isolations have been accomplished by transfer from anaerobic media often following blind subculture. M. hominis is best grown in mycoplasma broth or agar supplemented with 20% horse serum (for cholesterol), 10% fresh yeast extract (for preformed nucleic acid precursors), and arginine as a metabolite with a phenol red indicator. Specific antibiotics are added to inhibit ureaplasmas and other organisms. Differences in metabolic activity provide a useful means of identification of urogenital mycoplasmas. M. hominis organisms convert arginine to ornithine producing a rise in pH resulting in a color change to red. This color change occurs within a week of incubation and often within the first 48 hours. 16S DNA sequencing may be employed for confirmation after suspected identification of M. hominis.

Treatment: Tetracycline (i.e. doxycyline) is the antibiotic that is most frequently used to treat infections caused by M. hominis; however, with the emergence of tetracycline-resistant M. hominis strains, other agents, such as clindamycin or a fluoroquinolone (i.e. ofloxacin or ciprofloxacin), should be considered. In renal transplant patients, duration of treatment was noted to be >3 weeks.