- Volume 18, Issue 2, 1984

The induction of chemotactic activity of polymorphonuclear leukocytes (PMNL) by anaerobic and aerobic bacteria alone or in combination was evaluated. Washed cells as well as the supernate of Proteus mirabilis were chemotactic for leukocytes. The supernate of cultures of two strains of Bacteroides fragilis contained small amounts of chemotactic factors. No chemotactic factors were released from the non-fragilis Bacteroides strains. The supernates of cultures of anaerobic bacteria were capable of inhibiting chemotaxis of leukocytes to the chemotactic factors of P. mirabilis. P. mirabilis and two strains of B. fragilis generated chemotactic factors in serum but none of the other Bacteroides spp. tested were able to induce serum chemotactic factors.

The killing by human polymorphonuclear leukocytes of several species of bacteria, some of which were catalase positive, was examined in vitro in aerobic and anaerobic conditions. When all conditions other than the oxygen tension were identical, killing after 30 min was slightly greater in aerobic than in anaerobic conditions. However, after 60 and 120 min the difference between aerobic and anaerobic killing was smaller, and killing was nearly complete for all strains tested. These results conflict with the common opinion that oxygen is essential for efficient killing. Minor differences in experimental conditions can greatly influence results, and may be responsible for the discrepancy between this study and some previous studies on this subject.

The enzymic activity of 29 Haemophilus ducreyi strains on 28 substrates is described. The results are compared with those of seven other authors. There is agreement only about the presence of alkaline phosphatase and arginine aminopeptidase and the lack of glycosidases. Possible reasons for the contradictions in the eight reports are discussed.

Eighty-one bacterial strains representing 16 anaerobic species were tested in a sensitive binding assay for uptake of 125I-labelled human serum proteins. Fifteen of 36 Peptococcus magnus strains (42%) bound significant amounts of human serum albumin (HSA). None of the other bacterial species showed any affinity for HSA. All strains studied were incapable of uptake of human fibrinogen, fibronectin, haptoglobin or aggregated β 2-microglobulin. P. magnus strain Ra 4 was tested for binding of purified serum albumin from 11 animal species, and showed a binding profile similar to human group-C and -G streptococci, but different from Streptococcus pyogenes, Strep. zooepide-micus and Strep. dysgalactiae. Kinetic experiments showed that albumin binding was a rapid displaceable, time-dependent process, that could take place over a wide range of pH or salt concentrations. The albumin-binding component of P. magnus strain Ra 4 was resistant to heat and to periodate treatment, but sensitive to proteolytic enzymes.

Alpha toxin purified from Staphylococcus aureus strain Wood 46 and radioiodinated by the lactoperoxidase method retained full haemolytic activity and was used to study factors affecting binding to rabbit and horse erythrocytes. A relatively fixed percentage of added toxin bound to both cell types; the percentage bound was independent of temperature, pH, cell concentration and toxin concentration. Neither a 50-fold excess of native toxin nor Concanavalin A inhibited the binding of iodinated toxin to erythrocytes. The results suggest that differences in the sensitivity of erythrocytes to haemolysis do not reflect the abundance of high affinity toxin receptors on sensitive cells, but are more probably the result of differences in the intrinsic stability of the membrane and its sensitivity to perturbation by amphiphilic agents.

Secretion of α toxin by Staphylococcus aureus strain Wood 46 was preferentially inhibited by cerulenin, an antibiotic that stops fatty-acid synthesis by inhibiting β-keto acyl acyl carrier-protein synthetase. At the concentrations used, cerulenin had a negligible effect on cell growth and total protein synthesis, but reduced lipid synthesis by 50%. Extracellular and membrane-associated α toxin was absent in cultures treated with cerulenin, but toxin formation was resumed after either removal of the antibiotic or addition of exogenous fatty acids. The apparent absence of toxin precursor in membranes of inhibited cells favours inhibition at an earlier stage in toxin synthesis.

Samples from the posterior vaginal fornix of 102 women with various clinical conditions were analysed by a quantitative method. Aerobes were isolated from all but one of the specimens at a mean concentration of 7.2 log10 cfu/g and anaerobes from 92 specimens at a mean concentration of 8.1 log10 cfu/g. In most clinical conditions and in a control group of asymptomatic women, anaerobes outnumbered aerobes by about ten to one (one log10 unit). The most common organisms were aerobic and anaerobic lactobacilli, coryneforms, Staphylococcus epidermidis, Bacteroides spp. and anaerobic gram-positive cocci. Lactobacilli did not appear to confer any protective effect by excluding the presence of other organisms such as Gardnerella vaginalis or anaerobes. The isolation of anaerobic organisms from the vagina cannot be regarded as being of pathogenic significance without other supporting evidence.

The susceptibility of chicks to enteritis caused by Campylobacter jejuni was studied. Three-day-old chicks did not develop enteritis after oral infection but chicks infected within 12 h of hatching developed gastroenteritis. The incubation period correlated with the inoculum size. Initially, infected chicks developed blood- and mucus-containing stools, although watery diarrhoea often occurred late in the course of the disease. Recurrences of the enteric manifestations were common but only two out of 170 infected chicks died. C. jejuni was recovered from sites throughout the intestine; the highest concentrations were present in the caecum and large intestine. Both the upper and lower gastrointestinal tract were affected and cellular infiltration of the gastric mucosa and the intestinal lamina propria was observed. Organisms resembling C. jejuni were seen within the intestinal epithelium and lamina propria by electronmicroscopy. The newly hatched chick provides a reproducible and sensitive model of Campylobacter enteritis.

Fungi isolated from mouthrinse specimens during episodes of acute pseudomembranous fungal stomatitis and deep-seated mycoses in patients with haematological malignancies were tested for susceptibility to seven antifungal agents. Topical treatment of stomatitis with clotrimazole or chlorhexidine did not induce any change in the susceptibility of oral Candida albicans. Treatment of deeper mycoses with 5-fluorocytosine, however, resulted in a significant increase in oral strains resistant to this agent. Of C. albicans strains isolated, 7% were resistant to 5-fluorocytosine <32 μg/ml. One patient died of disseminated mycosis during treatment with this drug; the resistant C. albicans was isolated from the mouth, liver, spleen and kidneys. Strains of Torulopsis glabrata and C. krusei resistant to 5-fluorocytosine were also found in some patients. Organisms resistant to 5-fluorocytosine were generally sensitive to polyenes and imidazoles.

The role of temperate phage β in determining the serology and eltor-lytic phage sensitivity in Vibrio cholerae was investigated. The only serological change found in six host strains was a change to roughness. This was accompanied by failure to adsorb several of the lytic phages. Various phage-sensitivity changes were induced by phage β in two hosts at the post-adsorption level. In strain HP47, three types of progeny were obtained of which one was universally resistant to lytic phages. These untypable lysogens were culturally stable but gave rise to segregants of the rare phage-type 6 on single colony selection.

Reduced cell permeability and target penicillin-binding protein modification were investigated as mechanisms of intrinsic resistance in strains of Pseudomonas aeruginosa resistant to carbenicillin (MIC ≫ 128 mg/L) independently of β-lactamase production. The carbenicillin-resistant strains were also remarkably resistant to other β-lactams, quinolones, tetracyline and chloramphenicol, whereas carbenicillin-hypersusceptible strains (MIC ≪ 2 mg/L) were very sensitive to these antimicrobial compounds. These observations suggested a non-specific mechanism of resistance involving reduced permeability of the outer layers of the bacterial cell. However, carbenicillin-resistant and carbenicillin-sensitive strains had identical porin levels and the target penicillin-binding proteins of carbenicillin-resistant (MIC 256-2048 mg/L), carbenicillin-sensitive (MIC 64 mg/L) and carbenicillin-hypersusceptible (MIC 0.015 mg/L) strains were equally sensitive to β-lactams. Thus, subtle changes in porin function or additional outer-membrane barriers regulating permeability may be involved in intrinsic resistance.

Urogenital specimens of male patients and female prostitutes were examined for gonorrhoea in a gonococcal antigen enzyme immunoassay (Gonozyme®), by microscopic examination of stained smears and by bacterial culture. Out of 18 male patients, 14 showed positive reactions (all 14 by Gonozyme and by microscopy, but only eight by culture also). The sensitivity and specificity of Gonozyme was 100% in reference to microscopy. The predictive value for a positive test and for a negative test was 100%. The sensitivity of Gonozyme in reference to culture was also 100%, but the specificity was only 40%, because of the low yield of positive cultures. The predictive value for a positive test was 57% and for a negative test 100%. Out of 189 female prostitutes, 41 (22%) had a positive reaction in at least one test (Gonozyme, microscopy and culture were positive in 10; Gonozyme and culture in three; Gonozyme and microscopy in 14; Gonozyme alone in 11; culture alone in three). The sensitivity of Gonozyme was 100% and specificity 92% in reference to microscopy. The predictive value for a positive test was 63% and for a negative test 100%. In reference to culture, the sensitivity was 81% and specificity 86%. The predictive value for a positive test was 34% and for a negative test 98%. In prostitutes, the rate of asymptomatic infections was 14%, if one assumed that all Gonozyme-positive results were truly positive. Gonozyme proved to be the most sensitive method for screening female patients. To discriminate possibly false positive reactions, Gonozyme-positive specimens should be corroborated, preferably by bacterial cultivation.

The distribution of cryptic plasmids among 123 isolates of Providencia stuarti from a hospital ward during a prospective epidemiological study is reported. Two closely related stable plasmids (34 Kb and 36 Kb) were identified by restriction endonuclease digest analysis of plasmid DNA. One or other of these cryptic plasmids was carried by 40 isolates, the remainder were plasmid-free. A higher proportion of one cryptic plasmid (CPT-A) was found in environmental isolates than in isolates from patients. The serotype of all isolates of P. stuarti was 063 and they were epidemiologically related. Two of the eight patients colonised by P. stuarti carried all three possible variants: plasmid-free (PFI) strains or strains containing cryptic plasmid A (CPT-A) or cryptic plasmid B (CPT-B). The epidemiological significance of these results is discussed.