- Volume 42, Issue 6, 1995

Electronmicroscopy was used to observe morphological changes of the Pseudomonas aeruginosa PA0 bacteriophage F116 when treated with various biocides commonly used as antibacterial and antifungal agents. Because of its large size (145 nm) and its organised structure (an isometric head and a tail), it was possible to classify structural damage into eight categories. The morphological changes induced depended on the type of biocide used and its concentration. Glutaraldehyde increased the number of phages with empty heads. Peracetic acid and phenol altered the appearance of the viral genome packaged inside the head, produced fractured heads, and damaged the tail. Peracetic acid also induced folding of the phage heads. The alcohols tested also altered the head structure. Cetylpyridinium chloride induced mainly fractured head damage. Chlorhexidine had little effect on the structure of F116.

Polyacrylamide-agarose gel electrophoresis was used to study polymorphism of lactate dehydrogenase (LDH), nucleoside phosphorylase (NSP), phosphoglucose isomerase (PGI), hydroxybutyrate dehydrogenase (HBD), adenylate kinase (ADK) and esterases of 44 strains of Streptococcus pyogenes, 25 group G streptococcal strains, 11 “S. equisimilis” strains, seven S. dysgalactiae strains, four S. canis strains, three S. equi strains and seven S. zooepidemicus strains. Analysis of LDH, NSP, PGI, HBD and ADK provided valuable interspecies differentiation, by showing that four groups of strains corresponded to the four known DNA homology groups. Esterases showed greater intraspecies variation than the other enzymes. The combined analysis of the six enzymes indicated 31 zymotypes among S. pyogenes, 14 in group G streptococci and 11 in “S. equisimilis” strains. This was shown to be an effective technique for typing pyogenic streptococci.

A new small animal model of experimental Legionnaires′ disease is described in which the reconstitution of SCID-Beige mice with human peripheral blood leucocytes permits the in-vivo growth of Legionella pneumophila in the lungs of aerosol-challenged mice. Following infection, viable bacterial counts within the lungs of mice increased from 105 cfu/lung at the time of inoculation to a maximum of 1010 cfu/lung by 48 h post-inoculation. Two types of disease were detected in the lungs of infected SCID-Beige mice. An acute exudative bronchiolitis and bronchopneumonia were seen in the most severely affected mice and, in the less severely affected mice, lesions of subacute or chronic disease were seen with thickening of alveolar walls and consolidation of lung tissue. Human cells did not appear to be involved directly in the pathology but were required for the establishment of infection. Immunohistological staining of lung tissue revealed substantial amounts of bacterial antigen distributed in a pattern similar to that seen in human Legionnaires’ disease.

Four outbreak strains of Vibrio cholerae O139 from endemic areas of India and Bangladesh were found to carry lysogenic phage(s). All of these phage(s) produced turbid plaques characteristic of lysogeny on V. cholerae MAK 757 (El Tor, Ogawa) cells as well as on their VcA-1 lysogens but were unable to infect V. cholerae 154 (classical) cells, the universal host for all classical phages. Colonies in the turbid plaques were O139 lysogens and these developed an auxotrophic requirement, mainly for purines suggesting the integration of the prophage into the host chromosome. The immunity profile of the O139 phage(s) was similar to that of phage α but differed in the sensitivity of the phage lysogen of V. cholerae MAK 757 to subsequent infection by phage β.

The pheno- and genotypes of Shiga-like toxins (SLTs) in non-O157 Escherichia coli strains from patients with haemolytic uraemic syndrome were determined. The clinical isolates investigated were from Italy and Germany and belonged to serotypes O22:H8, O26:H−, O26:H11, O91:H−, O111:H− and O128:H−; one isolate was non-typable. SLT genotypes were analysed by complete nucleotide sequence analysis of the B-subunit genes. The results showed that 14 strains possessed slt-I alone, two contained slt-II alone and five isolates harboured both slt-I and slt-II genes. In only two strains were slt-II-related genes found, together with either slt-I or slt-II. These findings indicate that variants of SLT-II are rarely found in non-O157 E. coli isolates from patients with haemolytic uraemic syndrome. Polymerase chain reaction (PCR) with Taq cycle sequencing was found to be a suitable method for classification of slt genotypes.

Helicobacter pylori is important in the aetiology of peptic ulceration. Despite inducing an inflammatory response in the mucosa, the organism persists, suggesting that it has efficient protective mechanisms. Some bacterial and viral products modulate histamine secretion from inflammatory cells. Therefore, this study examined the modulatory effects of H. pylori preparations on histamine release from rat peritoneal mast cells and human basophils. Eleven clinical isolates of H. pylori were prepared in different ways: As whole washed bacteria, washed sonicated bacteria, and formalin-killed bacteria, and as outermembrane and lipopolysaccharide (LPS) extracts. Histamine release from mast cells or basophils was not elicited by any of these bacterial preparations alone. However, when mixed with various secretory stimulants, the bacterial preparations caused inhibition of histamine release from rat mast cells (calcium ionophore A23187, compound 48/80, concanavalin A, anti-rat IgE) and human basophils (A23187, N-formyl Met-Leu-Phe). The degree of inhibition ranged from 48% to 97%. These results indicate that H. pylori exerts an inhibitory effect on cells of the immune system that contributes to its persistence within the gastric mucosa.

Lymphocytes and monocytes from 25 patients infected with human immunodeficiency virus type-1 (HIV-1)—13 asymptomatic, seven with the AIDS-related complex (ARC) and five with the acquired immunodeficiency syndrome (AIDS)—were lysed and subjected to PCR with three primer pairs: SK38/SK39 (gag), SK68/SK69 (env) and SK29/SK30 (LTR). Amplified DNA was solution-hybridised with 32P-labelled probes (SK19, SK70 and SK31, respectively) and detected by PAGE-autoradiography. HIV-1 DNA was detected as follows. Asymptomatic patients: Monocytes—gag 61.5%, env 100%, LTR 0%; lymphocytes—gag 100%, env 92.3%, LTR 53.84%. ARC patients: Monocytes—gag 71.4%, env 57.1%, LTR 0%; lymphocytes—gag 100%, env 71.4%, LTR 71.4%. AIDS patients: Monocytes—gag 80.0%, env 100%, LTR0%; lymphocytes—gag 100%, env 60%, LTR 60%. The presence of HIV-1 DNA was confirmed in the monocyte fraction. In this cell subset, the env gene-directed primers were the most effective for amplification, whereas the LTR gene-directed primers failed to amplify HIV-1 DNA. The different pattern of amplification found in monocytes may suggest that these cells could be infected by a genetic variant of the virus.