Microbios最新文献

The effect of suprainhibitory concentrations of quinolones (ciprofloxacin, enoxacin and norfloxacin) on the growth, hydrophobicity and motility of a nosocomial pathogen Serratia marcescens was studied. A postantibiotic effect (PAE) was induced by 2x of 4x MIC concentrations for 0.5 h. By using the 2x MIC concentrations all three quinolones induced equally long PAE approximately 1 h. The longest PAE of 5.4 h at 4x MIC concentration was induced by enoxacin. The results obtained showed that suprainhibitory concentrations of quinolones significantly stimulated the adhesion of S. marcescens to xylene, with the exception of enoxacin, which inhibited the adhesion to 61.2% at 4x MIC concentration. These results correlated with those in the salt aggregation test. The adhesion of strains to nitrocellulose filters did not influence the aftereffect of suprainhibitory concentrations of quinolones. Exposure of bacterial cells to suprainhibitory concentrations of ciprofloxacin and norfloxacin caused a reduction in motility, while this effect was more distinct at 4x MIC concentration. The results suggest that any consideration of postantibiotic effects should include the residual antibiotic effects on virulence factors, in addition to the defined suppression of bacterial regrowth.

Discrepancies among reports from different geographical regions worldwide on the association between the presence of cagA and peptic ulcer disease prompted this study on the predictive value of the cagA gene in Helicobacter pylori-associated gastroduodenal diseases in the Singapore population. H. pylori strains were obtained from 169 patients with a peptic ulcer, 83 with non-ulcer dyspepsia, and nine with gastric cancer. The presence of the cagA gene was evaluated by polymerase chain reaction (PCR). The expected 400 bp PCR product coding for the cagA gene was present in 232/261 (89%) H. pylori isolates. Of these, 151/169 (89%) strains from patients with peptic ulcer, 73/83 (88%) strains from patients with non-ulcer dyspepsia and 8/9 (89%) strains from cancer patients were positive for the cagA gene. There was no statistically significant difference between the prevalence of cagA-positive strains from patients with distinct clinical outcomes (p > 0.05). The prevalence of cagA-positive strains in the Singapore population is high regardless of clinical disease status. The results suggest that the cagA gene is not a universal virulence marker of H. pylori.

Candida albicans have a marked propensity to cause infections in AIDS patients. A virulent trait of C. albicans is the yeast-hypha transition (Y-->H) which is influenced, in vitro and in vivo, by several factors. Since azidothymidine (AZT) is used in HIV-positive patients, the effect, in vitro, of different concentrations of AZT on C. albicans Y-->H transition was evaluated. C. albicans isolated from HIV-negative and HIV-positive patients were used and strains of C. tropicalis isolated from HIV-positive patients were also tested. AZT concentrations from 0.01 microg/ml to 10 microg/ml did not have any influence on the Y-->H transition, whereas 100 microg/ml AZT significantly inhibited the germ tube formation. AZT did not influence the formation of pseudohyphae in C. tropicalis. It is suggested that C. albicans infection observed in HIV-positive patients was not influenced by AZT therapy, because at currently used dosages, the Y-->H transition was not expected to increase.

The haematological mechanisms in the course of liver abscess formation were evaluated. They were examined by employing viable cells of Fusobacterium necrophorum subsp. necrophorum and Fusobacterium necrophorum subsp. funduliforme in comparison with their endotoxins. Whole cell infection with F.n. necrophorum led to neutrophilia and to a concomitant monocytosis in parallel with those responses induced by the in vivo injection of its endotoxin. Viable infection with F.n. funduliforme was characterized by a sustained endotoxin-related monocytosis against neutropenia. The stimulatory impact of endotoxin on monocytes when released from a viable F.n. funduliforme infection suggested an inherently peculiar mechanism which differed from the induction of both neutrophilia and monocytosis when F.n. funduliforme endotoxin was administered alone. The neutrophilic inducing capacity of the F.n. necrophorum endotoxin was equally illustrated by its positive chemotactic effect on polymorphonuclear neutrophils in vitro. The data presented here emphasize the virulence of F.n. necrophorum viewed in reference to changes in leucocyte trafficking and as complemented by a relatively high endotoxin content.

The antibacterial pattern of tetracycline and bactrim was compared with that of the chloroform extract of two Pseudomonas strains using ten hospital strains each of Staphylococcus aureus and Escherichia coli. There was no perfect correlation between isolate source, antibiotic type and sensitivity. Both the synthetic and natural antibiotic agent exhibited antibacterial activities against resistant hospital isolates at high concentrations.

The behaviour of the p53 protein has been investigated in some human carcinomas associated with Epstein-Barr virus (EBV) but not in EBV-positive oral squamous cell carcinomas (OSCC). The present study aimed to compare the p53 protein expression in EBV-positive OSCC with that in EBV-negative OSCC. The cases had been gathered in a study previously published. An immunohistochemical technique with BP53-12 monoclonal antibody was applied on 74 of the 107 OSCC from the earlier work. The nuclear or cytoplasmic expression of the p53 protein was classified as, absent (0% of neoplastic cells positive), mild (<25% positive), moderate (25-30% positive), or extensive (>50% positive). The p53 protein was expressed by 60.8% of the OSCC. Out of the fourteen EBV-positive OSCC, 57.1% (8 cases) expressed p53, always in the nucleus and never in the cytoplasm. Of the 60 EBV-negative OSCC, 61.6% (37 cases) expressed the p53 protein. Of 37 cases 33 (89.1%) showed nuclear expression of p53 and nineteen cases (51.3%) revealed cytoplasmic expression. There was a statistically significant inverse correlation between cytoplasmic expression of the p53 protein and the presence of EBV DNA (p <0.01). Thus, the EBV-positive tumours less frequently expressed p53 in the cytoplasm. No evidence of an accumulation of the p53 protein in OSCC associated with EBV was recorded.

The specific nucleic acid fluorochrome SYTO-13 was used in flow cytometric analysis to assess changes in the density and heterogeneity of marine bacterial populations which biodegrade linear alkylbenzene sulphonate (LAS). Seawater samples with LAS and incubated in the laboratory (20 degrees C, 100 rpm, 30 days) were used to monitor LAS-degrading consortia. Flow cytometric studies and culture methods were used to characterize the LAS degrading bacterioplankton consortia. Fluorescence and scatter signals enabled us to define three regions (R1, R2 and R3) in the dual parameter cytograms. The distribution of the bacterial counts in these regions allowed us to monitor the formation and evolution of the consortia.

Pseudomonas species strain PXM, which is able to use dicamba (3,6-dichloro-2-methoxybenzoic acid; CAS 1918-00-9, Banvel) as its sole carbon source for growth, has been isolated. The catabolism of dicamba and some of its putative metabolic descendants correlates with the presence of a large and unstable plasmid.

Cellular levels of diaminopropane, putrescine and cadaverine, and decarboxylase activities to produce these diamines in six species (16 strains) of Haemophilus and four species (5 strains) of Actinobacillus belonging to the family Pasteurellaceae of the gamma subclass of the class Proteobacteria, were determined by high performance liquid chromatography (HPLC). Diaminopropane was ubiquitously distributed within all Haemophilus and Actinobacillus species, and L-2,4-diaminobutyric acid decarboxylase activity was detected in them. Putrescine and ornithine decarboxylase activity were found in H. aphrophilus, H. parainfluenzae and H. influenzae (type a, b, d, e and f except for type c) but not detected in H. aegyptius, H. parahaemolyticus, H. ducreyi and Actinobacillus species. Cadaverine occurred in H. aphrophilus, H. aegyptius, H. influenzae, H. parainfluenzae, A. actinomycetemcomitans, A. equuli and A. lignieresii, whereas their lysine decarboxylase activity was scarcely detected. Cadaverine was not found in H. parahaemolyticus, H. ducreyi and A. suis. The diamine profile serves as a phenotypic marker for the chemotaxonomic classification of the family Pasteurellaceae.

'Mal de Cadeiras' is a disease which causes great mortality in horses in the Pantanal Matogrossense region, Brazil. The agent of this disease is Trypanosoma evansi, a kinetoplastid flagellate which belongs to the Trypanosomatidae family, classified into the Salivarian section. Transmission occurs mechanically by haematophagous Diptera, mainly by Stomoxys sp. and Tabanus sp. and vampire bats. Outbreaks of Mal de Cadeiras in horses result in economic losses, thus limiting their use in cattle raising. Ten isolates of T. evansi recently derived from coati (Nasua nasua, Carnivora, Procyonidae), horses and dogs were compared, using schizodeme analyses from DNA digested by the restriction enzyme Hin fl. The results showed similar electrophoretic profiles for all isolates from wherever the host came. Homogeneity of isolates from domestic and sylvatic animals suggested two hypotheses: (1) the parasites circulated in only one transmission cycle;, and (2) independent cycles were not established in sufficient time to modify the molecular profiles of the isolates.