CASE REPORTS

Case 1. A 29-year-old woman was human immunodeficiency virus positive in stage B3 of AIDS. She was admitted to our hospital with left hemiparesia. A cerebral computer tomography scan showed a hypodense lesion in the left parietal lobe compatible with progressive multifocal leukoencephalopathy. A peripheral venous catheter was placed. While in the hospital the patient suffered a marked deterioration of her neurological situation, together with severe worsening of her general state, with alteration of pulmonary function, upper digestive tract hemorrhage, and fever peaks. Various antimicrobial therapies were administered, including clindamycin, ciprofloxacin, and the combination of fluconazole, meropenem, and sulfamethoxazole, in spite of the fact that no pathogenic microorganism was isolated in the various cultures requested, including the catheter culture. The patient's situation worsened and reached terminal stage, which led to the decision to suspend all medication and to maintain only sedation. Dermabacter hominis and Candida albicans were isolated from two blood cultures taken 48 h earlier. Treatment with fluconazole and vancomycin was initiated, but the patient died 24 h later.

Case 2. A 65-year-old male patient had a personal history of cardiopathy and broncho-obstructive pneumopathy. He was brought to our Emergency Service with thoracic pain, for which he was admitted to the Cardiology Department. While in the hospital he suffered a cardiorespiratory arrest, from which he recovered after cardiopulmonary reanimation although he was left with irreversible neurological sequelae. During the following days he suffered episodes of fever peaks for which antibiotic treatment with cloxacillin plus gentamicin was administered. After 4 days without fever and without antibiotic treatment he presented with a febrile peak of more than 38°C. At this point two blood cultures were taken and the catheter was removed for culture. The patient's condition deteriorated, and he died suddenly 48 h later. That same day D. hominis grew in the two blood cultures. The catheter culture was negative.

Microbiology. In both patients small gram-positive coccobacilli with a coryneform appearance were detected in two blood cultures per patient, processed with the VITAL system (bioMerieux, Marcy l'Etoile, France). These grew, after 24 h of incubation in an atmosphere enriched with 5% CO₂, in the subcultures performed on blood agar plates. The colonies were small and greyish-white with an intense and pungent odor. After 48 h the size of the colonies increased to 1 mm in diameter.

Discussion. Until recently the isolation of coryneform bacteria in clinical samples, especially in blood cultures, was usually considered synonymous with contamination. In recent years, there has been a progressive increase in the number of reports in the literature of clinical cases associated with the isolation of various coryneforms, and the number of convincingly documented descriptions of infections by this group of agents has enriched our knowledge of this subject, especially in terms of a more precise and reliable microbiological diagnosis of the genera and species involved. This diagnosis would include an initial screening based on the production or lack of production of catalase, motility, and the fermentation or oxidation capacity of the strain. With these basic data as a starting point, the use of commercial galleries (bioMerieux) provides a second stage, which in many cases is sufficient for the identification of the microorganism. Last, the quantitative and qualitative evaluations of the fatty acids of the bacterial wall, chromatographic analysis of mycolic acids, and, as a last resort, molecular-genetics techniques, in most cases, provide a precise identification, although the last techniques are only carried out in referral laboratories (3).