Microbios最新文献

The yeast microbiota present on the surface of grapes of two Vitis vinifera varieties, Pedro Ximénez and Tempranillo de Rioja, grown in the Montilla-Moriles region of southern Spain was identified. The changes between veraison and the physiological ripeness time during 3 years were monitored. Overall, the yeast microbiota isolated was of oxidative metabolism. Sporobolomyces roseus and Cryptococcus albidus species occurred at all physiological stages, in the two Vitis vinifera varieties, and the three seasons studied. On the other hand, Kloeckera apiculata was never detected and Saccharomyces cerevisiae was scarcely isolated, it was only present, testimonial, in Tempranillo de Rioja grapes during the 1992 vintage. The widest variety of yeast species was observed in the 1992 season, and in contrast, the lowest number of species in both varieties of Vitis was detected in the 1994 season.

The prevalence and persistence of amoxycillin-resistant organisms (ARO) in the dental plaque of adults was determined. Plaque samples from ten adults, who had not taken antibiotics during the previous 6 months, were screened for ARO on three occasions at intervals of 3 months. The ARO were tested for their susceptibility to amoxycillin and to amoxycillin plus clavulanic acid as well as their ability to produce beta-lactamases. The ARO were found in all subjects on at least one sampling occasion and in 87% of the 30 samples examined. Of the 36 ARO isolated, 33% were yeasts, 19% were staphylococci, 19% Actinomycetes spp. and 14% lactobacilli, whilst seventeen of the isolates produced a beta-lactamase and seven of these were sensitive to coamoxiclav. The proportion of ARO in an individual fluctuated widely over the study period. It is suggested that the ARO are frequently, though transiently, present in low numbers in the plaque of individuals who have not recently received antibiotics.

Staphylococcus aureus is a ubiquitous pathogen still implicated as a common cause of community- and hospital-acquired infections. This micro-organism has demonstrated an immense adapting capacity to rapid environmental changes. In recent years, multiresistant strains have caused increasing nosocomial infections in several parts of the world. In the period 1993-94, 455 clinical isolates were typed on the basis of traditional phage typing procedure and these data were compared with others from similar studies carried out at the Department of Microbiology, University of Concepción in 1960, 1972, and 1982. Throughout the years, phage groups have been shifting from group I to group III and examination of phage types show that types 80 and 80/81 which were the most virulent and resistant by the 1960s, had disappeared. Nowadays, types 75 and 54/75 are most frequently found, and these have been associated with methicillin-resistant S. aureus.

The occurrence of Vibrio vulnificus incoastal sea water and sand was investigated. Samples (286 in toto) were taken during the period between November 1993 and July 1994. Ten V. vulnificus isolates (6.9%) were recovered from sea water and two isolates were recovered from sand (1.4%). The total isolation rate for this period was 4.2%. In a longer period of investigation, from June 1996 until June 1998 (24 months), 1,248 samples were taken and 205 V. vulnificus isolates were recorded (32.8%) in sea water while only 18 isolates in sand (2.9%). The total isolation rate was 17.9%. The monthly occurrence of this bacterial species in the various beaches surveyed demonstrated that V. vulnificus is more frequent during the months of July, August and September. The increase in the number of isolates during the past 2 years started as early as March and finished as late as October. Antibiotic sensitivity testing revealed that this species is sensitive to most antibiotics, except polymyxin B and colistin. The relatively high isolation rate of this bacterium from sea water may be dangerous to bathers, fishermen and divers with predisposed wounds.

Enteroaggregative and other HEp-2 cell adherent Escherichia coli can produce acute and persistent diarrhoea in children and adults, but their prevalence in asymptomatic individuals in the community is not known. In this study, faecal specimens were obtained at 3-4 monthly intervals from 349 subjects constituting a 20% age-stratified sample of a rural community for a period of two years. HEp-2 cell adherent E. coli were found in 210 subjects, and repeat isolations of enteroaggregative E. coli belonging to the same serogroup were found in 12.6% of children less than 12 years of age, indicating that this organism can asymptomatically colonise the intestinal tract. These children may act as a reservoir of infection for the community.

The mycelial mat of Trichoderma reesei strain QM 6a was treated with 0.1% (w/v) colchicine solution for 14 days and designated M14. The cellulase productivity of strain M14 was not much higher than that of the original strain. When conidia of M14 were treated with ethylmethane sulphonate (EMS) solution, the cellulase hyperproducers, M14-1 and M14-2, were isolated using a selection medium containing Avicel. The DNA content of M14-1 and M14-2 was higher than that of the original strain. Cellulase productivity per mycelium of these strains increased and was higher than that of the original strain. The cellulase productivity did not change through ten generations when these strains were cultivated successively on a medium containing Avicel. It was concluded that cellulase hyperproducers, whose cellulase productivity per mycelium increased, could be obtained when the conidia of strain M14 were treated with EMS.

The suppression of bacterial growth of four Acinetobacter baumannii strains after 60 min exposure to meropenem at supra-inhibitory concentrations (postantibiotic effect; PAE) or at supra-subinhibitory concentrations (postantibiotic-sub-MIC effect; PA SME) was studied. The duration of the PAE was dependent on antibiotic concentration and on the strain. Meropenem at 2x or 4x the minimum inhibitory concentration (MIC), with the exception of one strain treated with 4x MIC, did not provoke suppression of bacterial growth compared with untreated controls. The highest concentration of meropenem (8x MIC) induced PAE for the strains tested in the range of 0.6-6.9 h. The effect of supra-subinhibitory concentrations of meropenem (2x, 4x or 8x MIC + 0.2x MIC) on bacterial growth was more efficient compared with supra-inhibitory concentrations alone. Two out of the four strains treated did not renew their growth. Bacterial suspensions exposed to meropenem showed reduced surface hydrophobicity. Decreases in hydrophobicity were associated with longer PAE and PA SME depending on the strain.

Controversy exists as to whether the coccoid form of Helicobacter pylori can exist in a viable form. Conversion of helical to coccoid morphology occurs in culture over several days. In this study, the morphology was correlated with parameters of genetic integrity in the reference NCTC 11637 strain over 21 days of culture. The capacity to regrow colonies of helical form was demonstrated from a culture where the coccoid form constituted up to 95% and negligible urease activity could be detected. Urease enzyme activity and its mRNA decreased between day 0 and 10 while 26 kD mRNA and 16S rRNA were expressed unchanged for up to 14 and 21 days of culture, respectively. Expression of mRNA for the Cag A gene behaved in a similar fashion to that of urease. No evidence of DNA fragmentation was detected. These data suggest that a viable form of non-urease producing H. pylori exists after short to intermediate culture and that some if not all of these viable bacteria have coccoid morphology.

Earlier work in vitro showed that oleanolic acid (OA) was a potential inhibitor of insoluble glucan (ISG) synthesis from mutans streptococci (MS). In this study, two oleanolic acid-cyclodextrin inclusion compounds (OA-CDs), oleanolic acid-G1-beta-cyclodextrin (OA-G1-beta CD) and oleanolic acid-beta-cyclodextrin (OA-beta CD), were assayed for their effects on ISG synthesis from Streptococcus mutans MT8148R, and on the growth of oral bacteria. OA-beta CD inhibited ISG synthesis by 55.3 and 37.4% at 62.5 and 15.6 micrograms/ml of OA, respectively. Both OA-CDs inhibited the growth of MS, S. sanguis, and S. salivarius at 4 to 8 micrograms/ml of OA. The anticariogenic effect of the OA-beta CD was examined in a rat-caries model. Rats in the infected control groups showed the highest caries score. The infected treatment group B (0.5% OA in diet) showed lower scores than the control group. These results suggest that OA-beta CD is a potential anti-caries agent.

The bactericidal activity of disinfectants and hot water against ten Escherichia coli O157:H7 strains, which were isolated from faeces of patients with enterohaemorrhagic E. coli infection, were evaluated and showed different DNA patterns. After exposure to 0.1% benzalkonium chloride, 0.1% chlorhexidine gluconate containing a nonionic surfactant, and 80% (v/v) ethanol, 99.99% of viable bacterial cells were killed at 20 degrees C within 15 s irrespective of the presence or absence of 0.1% albumin. On the other hand, after exposure to hot water, 99.99% of the bacterial cells were killed within 15 s at 70 degrees C. These results suggest that benzalkonium chloride, chlorhexidine gluconate containing a nonionic surfactant, ethanol, and hot water at 70 degrees C or more are effective for disinfection of E. coli O157:H7 in hospitals.