By Carol A. Kemper, MD

E. gingivalis and Periodontal Disease in AIDS

Source: Lucht E, et al. Clin Infect Dis 1998;27:471-473.

Severe periodontal disease is a frequent occurrence in patients with HIV infection. While earlier studies suggest that many of these patients have significant alterations in their viral and fungal but not their bacterial oral microflora, the possible role of protozoal infection in gingival disease has not been previously explored. Lucht and associates examined the prevalence of various protozoa in salivary and dental plaque specimens in 45 patients with HIV and 15 HIV-negative controls. Peridontal disease was present in 13 of 45 (29%) HIV-positive patients compared with two of 15 (13%) HIV-negative controls.

Entamoeba gingivalis was the only protozoa found in the oral cavities of HIV-infected patients, where it was present in 10 (77%) of those with peridontal disease. Only one of the HIV-negative controls and none of the HIV-positive patients, without evidence of gingivitis, had E. gingivalis present in plaque specimens. No other protozoa were identified, including Cryptosporidium or Microsporidium species, or Pneumocystis carinii.

While good dental cleaning combined with topical solutions of 10% povidone-iodine solution and chlorhexidine mouth rinses are effective for many of these cases, oral metronidazole has been useful in cases of severe acute necrotic gingival disease—which may be, in part, explained by the known susceptibility of E. gingivalis to metronidazole. Metronidazole is a safe and effective therapy for HIV-infected patients with severe gingival disease.

An Odd Case of Cat Scratch Disease?

Source: Margileth AM, Baehren DF. Clin Infect Dis 1998;27:353-357.

This unusual case report describes a previously healthy 35-year-old male physician who presented with two months of fatigue and left shoulder pain. He was diagnosed with an inflammatory brachioplexy and treated with dexamethasone for one week. Two weeks later, he presented with a tender pectoral mass confirmed by MRI. He was diagnosed with myositis, and treated with prednisone for nearly three weeks during which time the mass continued to expand. Follow-up CT scanning confirmed the presence of a large abscess in the upper chest wall extending into the axilla, which spontaneously ruptured a few hours later before it could be surgically drained. A culture of the drainage yielded two colonies of Streptococcus pneumoniae. He rapidly improved with drainage and one week of cephalosporin therapy. Skin testing for cat scratch disease using a Bartonella henselae antigen was positive, but IFA and EIA serological studies for B. henselae and Bartonella quintana were negative.

More than two years after his initial presentation, the patient’s stored sera was retested using newer IFA tests to seven different Bartonella species. Only one titer was positive to B. clarridgeiae (Heller R, et al. J Clin Microbiol 1997; 35:1327-1331). Additional follow-up specimens from the patient confirmed the persistence of IgG antibody to B. clarridgeiae (titer, 1:256) On further questioning, the patient had three cats, originally stray, which had often scratched him. Blood samples from the cats were obtained, one of which was culture-positive for B. clarridgeiae.

Although the cat’s infection was identified more than two years after the patient’s initial presentation, Margileth and Baehren point out that infection can persist in cats for up to two years. Although the patient’s frequent exposure could have resulted in infection due to any number of Bartonella strains, the circumstances here suggest that the physician’s original infection, although highly unusual for cat scratch disease, may have been due to B. clarridgeiae—quite possibly the second documented human infection due to this organism.

I’ve Heard of Horse Pills!’

Source: Ringger NC, et al. Equine Vet J 1996;28:476-479.

Ringger and associates examined whether serum and CSF levels of ceftriaxone might be adequate for the treatment of bacterial meningitis in horses. Five healthy horses were administered a single IV bolus of ceftriaxone (50 mg/kg body weight). Peak serum levels of 145 microg/mL were achieved within 15 minutes, and a mean CSF concentration of 0.6 ± 0.14 microg/mL was obtained 3 hours later. The apparent volume of distribution was 331 mL/kg.

While this serum concentration compares favorably with those achieved in humans following a 2 g IV dose, the volume of distribution in horses is almost twice that of humans, and the CSF levels are lower. The other major difference being, of course, that most horses weigh about 400 kg. At this weight, a dose of 20 g. of ceftriaxone (about $600 worth) is necessary to achieve adequate equine CSF levels.