Acta pathologica, microbiologica, et immunologica Scandinavica. Section B, Microbiology最新文献

Thirty-six strains of yellow-pigmented Pseudomonas from clinical as well as non-clinical material and 11 reference strains of Pseudomonas were investigated by means of conventional bacteriological methods (a total of 53 different tests). Eighteen of the 36 yellow-pigmented strains could be classified as P. paucimobilis. Apart from the presence of lipid inclusions on beta-hydroxybutyrate, hydrolysis of DNA, and Tween 80 our results showed a high degree of accordance with other investigations. Eight strains showed characteristics compatible with inclusion in the CDC VE group; one orange-yellow strain showed the characteristics of P. vesicularis, and one was a pyoverdin negative, yellow P. putida. Eight strains remained unidentified. Strains of P. paucimobilis were most often resistant to antibiotics used for P. aeruginosa infections (viz. piperacillin, cefsulodin, ceftazidime) while the strains of the CDC VE group were often susceptible. Most strains were susceptible to the aminoglycosides. The difficulties in distinguishing yellow-pigmented strains of Pseudomonas from Flavobacterium spp. or Xanthomonas spp. are discussed.

The purpose of the present study was to investigate the effect of 20-hour pre-diffusion, i.e. placing the antibiotic-containing discs on the agar for 20 hours prior to inoculation, as compared to direct diffusion, i.e. placing the discs on the agar immediately after inoculation, for the newer 3. generation cephalosporins as represented by ceftazidime and ceftriaxone. Regression lines (zone sizes vs. inhibitory concentrations, as measured by plate-dilution) were constructed for three groups of bacteria chosen because of their differences in growth characteristics on agar: E. coli (n = 50), Enterobacter sp. (n = 35), and streptococci (n = 51). The results for both cephalosporins were: 20-hour pre-diffusion produced larger zones than direct diffusion, regression studies for 20-hour pre-diffusion as compared to direct diffusion resulted in greater variation in zone sizes, numerically lower slopes, lower residual variances and higher correlation coefficients, and regression lines were significantly different for the 3 groups of bacteria with direct diffusion but not so with 20-hour pre-diffusion. Considering the interpretation of zone sizes with disc diffusion for the cephalosporins tested, 20-hour pre-diffusion was superior to direct diffusion.

The in vitro activity of erythromycin against clinical isolates of Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae was examined by agar dilution and agar diffusion methods. The plates were incubated in air alone or in 8% CO2 and air. The minimal inhibitory concentrations (MICs) measured in air alone were lower for most of the isolates, compared to those found in 8% CO2. The greatest differences in MIC values were found for H. influenzae; the MIC 50% was 0.5 mg/l in air and 4 mg/l in 8% CO2. Sensitivity testing by the agar diffusion method (ICS) showed considerable differences between results obtained in air and in 8% CO2; the inhibition zones were generally smaller in CO2. The most marked reduction in zone sizes after incubation in 8% CO2 was seen with the H. influenzae isolates; 15 out of 43 isolates moved from the "sensitive" to "moderately sensitive" group. Sensitivity determination of aerobic bacteria for erythromycin should be performed in air alone in the routine laboratory.

The taxonomic relationship of 116 isolates of Pasteurella haemolytica was re-investigated by conventional phenotypic characterization. Seventy-nine characters were examined. Ninety strains were classified with previously described biovars of P. haemolytica. The remaining strains made up at least six new biogroups within the P. haemolytica-complex. "Key-characters" separating these groups included ornithine, L(+)arabinose, D(-)sorbitol, cellobiose, beta-glucosidase, glycosides and alpha-fucosidase. The taxonomic significance of these characters is uncertain. Determinations of genome size, mol% G + C in DNA and DNA:DNA hybridizations are in progress to obtain further information on the taxonomic significance of the present findings.

169 strains of P. multocida ssp. multocida, 24 strains of P. multocida ssp. septica, 22 strains of P. multocida ssp. gallicida, and 8 strains of P. avium and P. canis, respectively, were tested for toxin production in EBL-cell culture assay. Toxin production was only demonstrated in strains belonging to P. multocida ssp. multocida. Toxigenic strains were derived from pigs, calves, cats, dogs, rabbits and turkeys.

Density fluctuation during the cell cycle was investigated with group B streptococcus (GBS), type Ia, in isotonic medium. Maximum density occurred at late lag-phase, with a minimum at the middle of logarithmic growth. During the stationary phase the density remained stable. The buoyant density of serotypes Ia, Ib, II, III and a rough variant was determined by means of gradient centrifugation. In an isotonic milieu at the early stationary phase, the density of the strains varied in the range between 1.06 and 1.11 g/ml. Low ionic strength reduced the density of all strains. Neuraminidase-treatment increased the buoyant density of types Ia, Ib and III. The same pattern was seen in isotonic and hypotonic medium, although low ionic strength markedly augmented these differences. The influence of tonicity and neuraminidase-treatment was most prominent with types Ia and III, which may be due to relatively thicker polysaccaride capsules in these types.

The taxonomic relationship of 23 unclassified canine and feline strains of Pasteurellaceae and five strains received as Pasteurella spp. or Haemophilus influenzae-murium was investigated by phenotypic and genetic characterization. Eleven strains were classified with four recently described species of genus Pasteurella sensu stricto. Fourteen canine and feline strains formed a homogeneous group, tentatively designated taxon 16. Both phenotypic characters and mol% G + C in DNA and genome size indicate classification of taxon 16 with genus Pasteurella. DNA/DNA hybridizations, however, failed to locate taxon 16 on genus level with accepted or proposed species of the family Pasteurellaceae Pohl 1981. Two additional species obtained from rats and mice remained unclassified, in addition to a human isolate obtained from a dog-bite. The necessity of detailed phenotypic characterization within the family Pasteurellaceae Pohl 1981 needs to be stressed.

The present investigation was undertaken to determine whether the light or the heavy immunoglobulin chain is involved in the alternative, non-immune F(ab')2-mediated binding to staphylococcal protein A. Purified human polyclonal IgG was mildly reduced with dithiothreitol and alkylated with iodoacetamide. Intact IgG, purified light and heavy chains of polyclonal immunoglobulin G were tested in an inhibition assay for alternative non-immune F(ab')2-mediated binding to the protein A-carrying S. aureus, strain Cowan I. The IgG Fc-mediated binding to protein A was studied in parallel inhibition experiments. Heavy chains inhibited both the alternative F(ab')2- and the classical Fc-mediated binding to protein A. Isolated light chains were non-reactive. Intact IgG molecules were more potent inhibitors than isolated heavy chains tested in equimolar concentrations. Our results indicate that the alternative non-immune interaction between staphylococcal protein A and human immunoglobulins is mediated by structures expressed on the heavy immunoglobulin G chain. Thus, there are two separate protein A binding sites on gamma chains.

A three-month survey revealed 29 patients at our hospital with symptoms of acute pulmonary infection, from whom Branhamella catarrhalis was isolated from lower respiratory tract specimens, in 18 cases in pure culture. Approximately 2% of all respiratory tract specimens examined during the period yielded growth of B. catarrhalis. All except one patient suffered from chronic pulmonary disease, notably chronic bronchitis. A phenotypic comparison was made between 55 strains of B. catarrhalis, of which 50 were recent isolates from lower respiratory tract specimens, and 23 Neisseria strains representing Neisseria meningitidis, Neisseria gonorrhoeae, Neisseria cinerea, Neisseria flavescens, Neisseria mucosa, Neisseria pharyngis, and Neisseria lactamica. The morphology of B. catarrhalis colonies is very characteristic, and when the diagnosis is suspected, testing for the ability to hydrolyze tributyrin may confirm it within hours. Ability to produce deoxyribonuclease is another property which differentiates B. catarrhalis from the Neisseria species. Otherwise, the combination of nitrate reduction and failure to produce acid from glucose, maltose, and sucrose establishes the diagnosis.

According to Pharmacopoea Nordica, steam autoclaves should be regularly monitored by a specific Swedish preparation of Bacillus stearothermophilus spores. If another biological indicator (BI) is used for such a control, it should first be calibrated against the Swedish BI (SBI) and the two BIs should be equally thermoresistant. Attest No. 1262 BI (ABI) has previously been shown to be more thermoresistant than the SBI at 134 degrees C, saturated steam. The purpose of the present study was to compare the thermoresistance of the SBI and the ABI at 121 degrees C, saturated steam and prevacuum. Seven hundred and twenty units of each BI were heat-exposed in an Emmer 760 litre prevacuum, pressure-pulsing steam autoclave. After prevacuum with steam injection (manual or automatic preconditioning), the following incremental heat exposure times were used in triplicate (20 simultaneously tested units of each BI in each cycle) according to a randomized scheme: 5, 6 1/2, 8, 9 1/2, 11, 12 1/2, 14 and 15 min. The intra-chamber pressure and temperature were continuously monitored throughout the test and equilibration cycles. The heat-exposed BI units were cultivated and read as recommended by the manufacturers. SBI and ABI showed a survival-time of 8 min and 11 min respectively, and a kill-time between 14 min and 15 min for both BIs. Thus, the ABI had the narrower survival-kill window. Probit analysis testing of the results showed that the difference in thermoresistance, at 121 degrees C, saturated steam and prevacuum between Attest No. 1262 BI and the Swedish BI mentioned in Pharmacopea Nordica was not statistically significant.