Candida albicans presents a well characterized EcoRI RFLP pattern of intensely staining bands. One of these bands, the dimorphic 3.7/4.2 kbp fragment shown to originate from the ribosomal RNA-encoding regions (rDNA), has been used by several investigators to subdivide C. albicans strains in two distinct subtypes. In the present manuscript, we report that an epidemiological study of 120 C.albicans strains revealed a significant correlation between these subtypes and susceptibility to 5-fluorocytosine, an antifungal agent extensively used for biotyping C.albicans. The 4.2 kbp strains being generally more susceptible than their counterparts to this agent and one of its metabolic by-product, 5-fluorouracil. A 379 nucleotides insertion in the 25S rRNA-encoding gene of 4.2 kbp type strains was shown to be responsible for the 3.7/4.2 size difference. This intervening sequence is typical of a group I intron by its site of insertion, its predicted secondary structure, and its self-splicing capability. Assuming there is a genuine causal relationship between presence of the intron and resistance to 5-fluorocytosine, one possible mechanism suggests that inhibition of self-splicing by the insertion of 5-fluorouracil residues in the 25S rRNA precursor might be responsible for the higher susceptibility of 4.2 kbp type strains.

One-hundred and five Candida albicans isolates from various anatomic sites of 28 patients, obtained at the onset of two consecutive episodes of well-documented recurrent vulvovaginitis, were typed by methods relying on physiologic or genomic markers. The isolates represented a wide variety of types, and neither a single biotype nor genotype was associated with recurrent vaginitis or a particular body site. Patients generally carried similar strains at various anatomic sites that persisted over time. Genomic methods indicated an 86% rate of relapse, which suggested that most recurrent vaginal infections are of endogenous origin. A similar evaluation with biotyping methods was inconclusive because of a lack of reproducibility, resulting from clonal variation or switching, and difficulties in establishing the number of phenotypic tests necessary to distinguish between identical and different strains. Therefore, Southern hybridization was considered the ideal reference method to study the epidemiology of C. albicans infections.

The pulmonary residence time of free and liposome-encapsulated tobramycin was studied with uninfected rats and rats infected with Pseudomonas aeruginosa. Chronic infection in lungs was established by intratracheal administration of 108 CFU of P. aeruginosa PA 508 prepared in agar beads. After 3 days, a single dose (300 ,ug) of free or liposome-encapsulated tobramycin was given intratracheally to both infected and uninfected rats. At various time intervals (0.25 to 16 h) after drug instillations, the remaining tobramycin was evaluated in blood, lungs, and kidneys by a microbiological assay. Intratracheal instillation of liposome-encapsulated tobramycin resulted in high and sustained levels of tobramycin in lungs of uninfected and infected rats over the 16-h period studied; however, the tobramycin levels were two times higher in uninfected rats. There was no tobramycin detected in the blood or kidneys from these animals. In contrast, the intratracheally instilled free tobramycin was cleared within 3 and 1 h from the lungs of uninfected and infected animals, respectively. These data suggest that the encapsulation of tobramycin in liposomes can result in a significant increase of its residence time within lungs. This study also shows that pulmonary infection was associated with a lowering of tobramycin levels in lungs.

Summary. Monoclonal antibodies (Mabs) were produced against outer-membrane proteins (OMPs) of Haemophilus infuenzae type b. The clones were screened by ELISA with outer-membrane preparations of H . inJuenzae type b and untypable strains as coating antigens. Antibodies directed against the proteins of mol. wt (lo3) 43, 37 and 13 were identified by immunoblotting of SDS-PAGE patterns of OMPs. Proteolytic enzyme treatments of the OMPs resulted in reduction of Mab reactivity as measured by ELISA. Furthermore, the absence of reactivity of Mab Hb-2 with a preparation of lipopolysaccharide confirmed the protein nature of its corresponding epitope. Binding assays with live bacteria showed that Hb-2 reacted with a cell surface-exposed antigenic determinant. Mab Hb-2 was bactericidal in vitro in the presence of complement. The characterisation of Hb-2 (IgG2,) by Western immunoblotting analysis revealed that it was directed against the 37 x 103-mol. wt OMP. In a dot-enzyme immunoassay, Hb-2 reacted specifically with 326 strains of H. inzuenzae type b. It did not cross-react with the other serotypes or untypable strains of H . infuenzae or with other bacterial species. This is the first report of a monoclonal antibody identifying a serotype-specific surface-exposed OMP of H . influenzae type b.

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