Inhibitory effects of different lactobacilli on Candida albicans hyphal formation and biofilm development.

The aim of this study was to investigate the effects of different species of Lactobacilli on hyphal formation and biofilm development by the opportunistic fungal pathogen Candida albicans. We employed 4 different Lactobacillus species, namely L. rhamnosus, L. acidophilus, L. plantarum and L. reuteri, and 2 C. albicans strains, the reference DAY286 and its isogenic hwp1/hwp1 mutant, the FJS24 strain. As assessed by morphological analysis and quantitative colorimetric assays, Lactobacillus crude filtrate supernatant fluids (CFSF) affected Candida, impairing both hyphal formation and biofilm production. The CFSF-mediated phenomenon occurred in a dilution- and time-dependent manner and was consistently observed, irrespective of the C. albicans HWP1 genotype.

Nramp1 gene affects selective early steps in macrophage-mediated anti-cryptococcal defense.

Cryptococcus neoformans is an opportunistic fungus responsible for severe and often recurrent meningoencephalitis in immunodepressed patients. Initial evidence suggests that C. neoformans is a facultative intracellular pathogen; however, the strategies by which C. neoformans undergoes survival and eventually proliferation have not been elucidated. We investigated the role of Nrampl gene in macrophage-mediated anti-cryptococcal defense. Using cell lines expressing the functional, mutated or knockout gene, it was established that Nramp1 (1) is not involved in the phagocytic event, (2) influences anti-cryptococcal activity in the early steps but not at later times, and (3) is unrelated to the biomolecular pathways through which C. neoformans impairs macrophage secretory response. Although the functional role of Nramp1 is still far from being elucidated, the present data add insight into its involvement in macrophage-mediated antimicrobial defense, particularly in the initial steps allowing C. neoformans growth inhibition.

Evidence of microevolution in a clinical case of recurrent Cryptococcus neoformans meningoencephalitis.

The aim of this study was to examine three serial isolates of Cryptococcus neoformans from a patient with AIDS for genotypical and phenotypical characteristics. The isolates were obtained during a first episode of cryptococcosis (simultaneous sampling of blood and cerebrospinal fluid) and after a relapse 3 years later (sampling of cerebrospinal fluid). Pulsed-field gel electrophoresis and random amplification of polymorphic DNA revealed that the blood isolate 1525 (first episode) was different from the two cerebrospinal fluid isolates (1526, first episode; 1782, relapse), yet the cerebrospinal fluid isolates were indistinguishable from each other regardless of the analysis performed. Phenotypical studies showed that isolate 1782 had significantly improved resistance to phagocytosis and killing by monocytes and polymorphonuclear cells and an altered efficacy in evoking cytokine response (augmentation of tumour necrosis factor-alpha, interleukin [IL]-1beta, IL-10, and interferon-gamma, decrease of IL-12). Interestingly, capsule size and antifungal drug resistance remained unchanged, while production of phospholipase and protease was consistently enhanced in the 1782 isolate with respect to the 1525 and 1526 isolates. In conclusion, in serial Cryptococcus neoformans isolates from a patient with AIDS, phenotypical changes but not molecular changes were documented, thus supporting the role of microevolution as a pathogenetic mechanism(s) for persistence/reactivation of fungal organisms.

Establishment of protective immunity against cerebral cryptococcosis by means of an avirulent, non melanogenic Cryptococcus neoformans strain.

The opportunistic fungal pathogen, Cryptococcus neoformans, shows a marked predilection for the central nervous system (CNS). This can be partially explained by its ability to synthesize melanin starting from the catecholamines, highly concentrated at the CNS level. Two cryptococcal strains, the avirulent non-melanogenic strain Sb26 and the virulent melanogenic revertant strain Sb26Rev, were used in a murine model of intracerebral (i.c.) infection, in order to evaluate their virulence and immunomodulating properties at the cerebral level. We found that, unlike Sb26Rev, Sb26 i.c. infection was never lethal regardless of the challenging dose. Sb26Rev infection resulted in massive CNS tissue damage, associated with little or no cytokine response, as established by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Differently, Sb26 infection failed to alter CNS structure, while inducing IL-12 p40, TNF-alpha, IL-1beta, IFN-gamma and iNOS specific-gene expression as well as IL-12, TNF-alpha and IL-1beta cytokine production. Interestingly, all Sb26 infected mice survived a subsequent lethal challenge with Sb26Rev. The phenomenon was associated with enhanced IL-12, TNF-alpha and IL-1beta production and was strictly specific, as shown by heterologous challenges and delayed type of hypersensitivity assay. Overall, we provide evidence that protective immunity against cerebral cryptococcosis is established by means of an avirulent strain of C. neoformans.

Differential effector and secretory functions of microglial cell lines derived from BCG-resistant and -susceptible congenic mouse strains.

Using congenic strains of mice susceptible (bcg(s)) or resistant (bcg(r)) to BCG, murine microglial cell lines, RR4.R (BCG-resistant) and RR8.S (BCG-susceptible), were established in vitro. Comparative studies revealed that, although phagocytic to a similar extent, RR4.R cells were more active than RR8.S cells in terms of antimycobacterial activity. Interestingly, cells of resistant genotype secreted more nitric oxide, TNF-alpha and IL-12, but less IL-6, than susceptible cells, when stimulated with IFN-gamma alone or in combination with lipopolysaccharide. Nevertheless, no significant differences were observed between the two cell lines in terms of IL-1 beta or IL-10 secretion, or on assessment of cytokine production following exposure to a massive dose of lipopolysaccharide. Overall, these data provide the first evidence that resistant/susceptible genotype influences antimycobacterial activity, NO and cytokine production in microglial cells, the prototype of cerebral macrophages.

Plasmid analysis in PPNG strains isolated in Italy.

Italian reports of PPNG strains are rare. In this paper we report the plasmidial characteristics of two strains: one harbouring 3.2 and 2.6 Mdal plasmids and the other 24.5, 4.5 and 2.6 Mdal plasmids. Restriction analysis was carried out on plasmids transferred to E. coli by transformation for "Africa" and conjugation for "Asia" plasmid.

Streptococcus mutans: classification in bacteriocin-types.

A sample of S. mutans bacteriocins was studied to obtain a useful outline of strain typing since their synthesis has proved stable and not under plasmidial control. The inhibiting effectiveness against 9 oral streptococci and the sensitivity of mutacins produced by 49 S. mutans strains to heat, chloroform and proteasic activity were evaluated. On the basis of our results the producing strains are classified into five different types. We examine the possibility of obtaining a useful typing with bacteriocins and we discuss the choice of the most suitable number of indicators to arrange the strains in a limited cluster number for epidemiological purpose, or to classify freshly isolated S. mutans strains into bacteriocin-types.

Production of bacteriocin-like substances by human oral streptococci.

A sample of human streptococci (mainly Streptococcus mutans species) from dental plaques was examined in order to evaluate the production frequency and activity spectrum of bacteriocin-like substances (mutacins). 89% of the 55 Streptococcus mutans strains produced substances with a wide spectrum of antibacterial activity. The bacteriocins produced showed a marked inhibitory activity against Gram-positive bacteria. Among the Gram-negative species tested, only Neisseria sicca was inhibited by 25% of Streptococcus mutans strains. Also, 16 strains belonging to oral streptococci other than Streptococcus mutans, were examined for their inhibitory capacity against the same indicator. The authors stress the importance of mutacins production in oral ecology and Streptococcus mutans pathogenicity.

In vitro antibacterial activity of enoxacin, a new pyridonecarboxylic acid.

The antibacterial activity of enoxacin was determined against 1015 strains of Gram-positive and Gram-negative bacteria, mainly freshly isolated from clinical specimens. The minimum inhibitory concentrations (MIC 50-75-90) were determined in comparison to three commonly used antibiotics: ampicillin, cefotaxime and gentamicin. Enoxacin has shown a broad spectrum of action and antibacterial activity in general higher that than of three currently available antibiotics. The antibacterial activity seems similar to that of other quinolones of second generation.

[The incidence and variation of transferable antibiotic-resistance in Salmonella strains isolated in Modena in the years 1975-1977 (author's transl)]. / Incidenza e comportamento della antibiotico-resistenza trasferibile in ceppi di Salmonella isolati a Modena nel triennio 1975-1977.

The antibiotic-resistance of 450 strains of Salmonella isolated by the Microbiology Unit of the hospital of Modena during the years 1975-1977 was examined. During the study, the following antibiotics were assayed: ampicillin, kanamycine, tetracycline, chloramphenicol, streptomycin, sulfonamides, trimethoprim, tobramycin, gentamicin and nalidixic acid. The transfer capacity of antibiotic-resistance was measured by the double conjugation of E. coli K-12. During the period studied, a remarkable reduction was noted in those strains with multiple resistance (3 or more elements) decreasing from 72.9% in 1975 to 23.5% in 1977. These phenomena are due to the decrease of the serum-type wien during the years under study. Antibiotic-resistance demonstrated itself most frequently to streptomycin and tetracycline; and chloramphenicol-resistance showed the highest transfer capacity (97.2%).