The Journal of applied bacteriology最新文献

Nine strains of Bacillus sphaericus toxic to mosquito larvae produced haloes of hydrolysis when cultured on casein-nutrient agar. In batch culture, protease synthesis by B. sphaericus BSE 18 occurred during exponential growth and was repressed by high concentrations of peptone. Extracellular protease from this bacterium showed optimal activity at about pH 10.2, was inhibited by phenylmethylsulphonyl chloride and chymostatin but not soybean trypsin inhibitor or EDTA. Hydrolysis of N-CBZ-glycine-nitrophenyl ester was consistent with the major enzyme being a serine protease.

Fifty-four of 310 (17%) samples of raw beef products contained Vero cytotoxin (VT)-producing Escherichia coli (VTEC) detected by DNA probes for the VT genes. VTEC strains examined in detail from a selection of the positive samples belonged to several O serogroups, some of which have been associated with human diarrhoea or haemolytic uraemic syndrome. Some of the strains possessed properties that may contribute to virulence in man. None of the food samples contained VT-producing E. coli O157 when tested by a combination of VT probe tests and colony immunoblotting with commercially available anti-O157 serum. Quantification of the immunoblotting technique indicated that O157 VTEC could be recovered from artificially-inoculated meat samples at a level of less than one organism per gram. Five of the food samples carried E. coli O157 strains that did not produce VT and differed in other properties from O157 VTEC.

The effects of suspension media and rate of freezing on the survival of Chlamydia trachomatis LGV2 and Chlamydia pneumoniae after lyophilization were assessed. The highest loss in infectious elementary bodies (EBs) occurred during lyophilization. The survival was higher after freezing at a rate of 1 degree C min-1 and lyophilization than that after rapid freezing at -70 degrees C or -196 degrees C. The recovery (+/- 5%) was higher when fetal calf serum (FCS) containing glucose, saccharose or lactose were used as lyophilization media than that (0.5-3%) when yolk-sac, skimmed milk or phosphate buffer containing sucrose, glutamine and 10% FCS (SPG) were used. After lyophilization, the survival was not affected in the tested range from 10(4) to 5 x 10(6) inclusion-forming units (ifu) ml-1 prior to freezing. After storage for 4 months at 4 degrees C, the numbers of ifu of both Chlamydia serovars that were recovered were identical to the numbers of ifu immediately after lyophilization. It was concluded that chlamydias can be stored and transported in lyophilized form. However, a loss of 95% in infectious EBs should be taken into account.

The susceptibility of chicks to colonization with Escherichia coli O157:H7 and other verotoxin-producing serotypes was studied. The E. coli colonized the caeca of both broilers and layers after oral administration of the challenge. The extent of colonization was dependent on challenge dose, age of chicks at the time of challenge, breed of chicks and length of time after exposure. A rapid increase in caecal colonization and a decrease in crop colonization was evident during the first few hours after challenge, with a maximum in the caeca at 6 h. Escherichia coli persisted in caecal contents as well as on caecal walls throughout the course of the experiments (14 d), but at much lower levels compared with the 6 h post-challenge.

The ecology of multiple antibiotic resistant (MAR) bacteria in the fresh-waters of the lower Niger Delta was studied in the Port Harcourt area, Rivers State. On the basis of decreasing pollution levels three zones, A, B, C, were recognized. Cell recovery by two viable count media, casein-peptone-starch (CPS) and plate count (PC) agar containing chloramphenicol, tetracycline, penicillin, streptomycin or ampicillin were compared in an initial study. Higher numbers of antibiotic resistant (AR) bacteria were recovered on CPS containing tetracycline, penicillin, streptomycin and ampicillin from the faecally-polluted New Calabar River (zone A) than on SPC agar containing similar antibiotics but the reverse was observed for forest stream (zone B) samples. Differences between the two media were also observed at individual sample sites. The proportions of strains of AR bacteria resistant to their primary isolation antibiotic varied from 55% (zone B) to 72% in the least polluted Isiokpo and Elele-Alimini streams (zone C), for ampicillin, and mostly < 50% for the other drugs in each zone. Thirty bacterial strains purified from the prevent colonial types on the count media without antibiotics included mainly species of Bacillus (12) and enterobacteria (18). Between five and 10 strains were resistant to > or = three antibiotics; seven were resistant to all five. The antibiograms of most strains were variable and depended on the method of drug application (discs or incorporation into agar), media and temperature of incubation (25 degrees, 37 degrees or 44.5 degrees C). Twenty-one strains were consistently resistant to ampicillin by the two methods; 10 to 19 were consistent for chloramphenicol, tetracycline and penicillin.(ABSTRACT TRUNCATED AT 250 WORDS)

New shuttle vectors based on a Prevotella ruminicola 9.5 kb cryptic plasmid (pRRI7) inserted within the Escherichia coli vector pKC71, carrying the Ccr/Emr Bacteroides marker, were constructed. These constructs (pKBR23-1 and pKBR23-2) were transferred into Bacteriodes distasonis, Bacteroides thetaiotaomicron, Bacteroides uniformis and into P. ruminicola NCFB 2202 either by conjugal mobilization or by electroporation. Another pRRI7 derivative based on pKC72, pKBR23-3, was smaller (13.1 kb) and non-mobilizable. By electroporation, it was transferred to Bact. distasonis and P. ruminicola. Being derived from pRRI7 which is compatible with the shuttle plasmid pRRI207, the host/vector combination involving P. ruminicola NCFB 2202 and pKBR23-3 offers new possibilities for genetic investigations in rumen anaerobic bacteria after further introduction of a second readily selectable marker within pRRI207 or pKBR23-3.

23S ribosomal RNa (rRNA) gene sequences of Streptococcus uberis and Strep. parauberis were determined by direct polymerase chain reaction (PCR) sequencing. Oligonucleotide probes specific for Strep. uberis and Strep. parauberis were designed from variable regions of the 23S rRNA gene sequence data. Molecular hybridizations with PCR-amplified rRNA gene targets provided a precise and reliable means of differentiating Strep. uberis and Strep. parauberis from each other and from other streptococcal species.

The large-subunit ribosomal RNA gene sequences of Leuconostoc carnosum, Leuc. mesenteroides, Leuc. oenos, Leuc. paramesenteroides and Lactobacillus confusus were determined by direct sequencing of enzymatically-amplified DNA. Comparative analysis of the large-subunit rDNA sequences revealed that the leuconostocs form three distinct lines of descent: Leuconostoc sensu stricto, Leuc. paramesenteroides group of organisms, and Leuc. oenos. The distance matrix tree constructed from the large-subunit sequence data was in excellent agreement with that derived from small-subunit sequences, and demonstrates the 'synchrony' of the two chronometers. The results of the present and earlier sequence analyses indicate the taxonomy of the genus Leuconostoc is in need of revision, and that the Leuc. paramesenteroides group of organisms and the species Leuc. oenos represent distinct phylogenetic units, separate from Leuconostoc sensu stricto.

Citrobacter freundii strain E69366 was detected in a colony immunoassay with a rabbit antiserum prepared to a strain of Escherichia coli belonging to serogroup O157. Lipopolysaccharide (LPS) was shown to contain the epitope(s) involved in antibody binding. LPS prepared from strain E69366, with hot phenol contained core-LPS that migrated to the water-phase and long-chain LPS that separated into the phenol-phase. A total of 36 strains of Cit. freundii were analysed for their LPS profiles by SDS-PAGE. Sixteen could be allocated into five groups (A(3), B(7), C(2), D(2) and E(2)) based on similarities in LPS profile. The remaining strains either expressed unique SDS-PAGE profiles (18) or did not express long-chain LPS (2). All strains with a profile 'A' reacted with the antiserum prepared to E. coli O157, whereas those with other profiles did not. The two strains of Cit. freundii expressing LPS profiles designated 'E' reacted with an antiserum prepared in rabbits to E. coli O45.

The distribution of water in the protoplast and integument of three populations of Bacillus sphaericus spores was determined by laser diffractometry together with the sizes of their integuments and protoplasts. The spores were produced at 15, 20 and 30 degrees C. Spores grown at 15 degrees C had protoplast and integument water contents similar to those produced at 20 degrees C, while those grown at 30 degrees C had significantly lower water contents than the other two populations. The inner (or protoplast) radii of the spores produced at 15, 20 and 30 degrees C were 0.41 +/- 0.02 microns, 0.42 +/- 0.01 microns and 0.38 +/- 0.02 microns whilst the outer (or whole spore) radii were 0.56 +/- 0.01 microns, 0.58 +/- 0.01 microns and 0.52 +/- 0.02 microns respectively. The ratios of integument to protoplast radius were 0.40 +/- 0.02, 0.43 +/- 0.07 and 0.41 +/- 0.03 respectively.