- Volume 31, Issue 02, 1990

Murine monoclonal antibodies (MAbs) and immune rabbit serum were raised against the rough mutant of Salmonella minnesota strain R595. These antibodies were tested for their ability to inhibit LPS-induced B-cell mitogenicity and neutralise LPS toxicity in chick embryos. Immune rabbit serum inhibited both mitogenicity and LPS lethality. None of the MAbs or a cocktail of antibodies were able to neutralise LPS lethality in chick embryos. However, they were able to inhibit mitogenicity by varying degrees.

C3H/HeNMTV mice were immunised intraperitoneally (i.p.) with lipopolysaccharide (LPS) or detoxified LPS (D-LPS) derived from Salmonella typhimurium strain SR-11. In both cases, effective protection was achieved against a challenge dose of greater than 2x102 LD50 of the same organism given by i.p. injection. However, by comparison with LPS, approximately 6- to 10-fold more of D-LPS by weight was needed to protect mice to an equivalent degree. Histopathological studies showed that the initial lesions in infected mice protected with either LPS or D-LPS were composed of self-limiting abscesses which transformed into granulomas as the animals recovered. It is suggested that D-LPS may be modified to become a highly effective, non-toxic salmonella vaccine.

Several mechanisms that could contribute to the periodontopathogenic potential of Eubacterium yurii were investigated. All 18 strains examined produced RNAase and the metabolites H2S, indole and butyrate. Some strains produced phosphatase and DNAase. Methanol extracts of whole cells of E. yurii subspp. yurii and margaretiae stimulated bone resorption in vitro comparable to that produced by recognised periodontal pathogens. These results suggest that further studies should be performed to elucidate the role of E. yurii in periodontal disease.

Pseudomonas pseudomallei causes the disease melioidosis, with protean manifestations, protracted clinical course and unpredictable response to antimicrobial treatment. Intracellular location of the organism is suspected to be the cause of these properties. This study was undertaken to examine the intracellular growth of this bacterium. Intracellular growth and survival was assessed at different time intervals, by Gram´s stain and electronmicroscopic examination. During the first 5 h, the numbers of P. pseudomallei within phagocytes did not change significantly. By 18-21 h, gram-stained preparations revealed that P. pseudomallei cells completely filled the phagocytes and electronmicroscopy showed evidence of binary fission. During that time the number of cfu of P. pseudomallei growing simultaneously in vitro increased by log10 2-3. The phagocytes remained viable throughout the observation period and retained their capacity to produce an oxidative burst for the first hour of incubation. The ability of P. pseudomallei to survive and multiply in phagocytes shows that it is a facultative intracellular bacterium. This finding is relevant to the selection of antimicrobial regimens, and the management of the disease.

The cytogenetic effects of two attenuated viral vaccines (yellow fever vaccine and oral poliomyelitis vaccine) were assessed by means of the analysis of meiotic spermatocyte chromosomes in mice. In a dose of 0.5 ml, but not 0.1 ml, both vaccines induced a significant percentage of chromosomal aberrations after 7, 14 and 30 days. Euploidy was the major abnormality produced by yellow fever vaccine. The various abnormalities produced by oral polio vaccine were significant when pooled, but not when analysed individually. More abnormalities were produced by yellow fever vaccine than by oral polio vaccine.

The occurrence of various Pseudomonas aeruginosa strains in the sputum of 15 patients with cystic fibrosis (CF) was monitored over periods ranging from 2 to 60 months. Isolates of P. aeruginosa were typed by four different techniques, namely serotyping, active and passive pyocin typing, and phage typing. The maximum number of different serotypes found in the patients was three (one serotype in nine patients; two serotypes in five patients; three serotypes in one patient). Pyocin and phage typing showed no marked differences between strains of the same serotype in individual patients. Exacerbations of chronic respiratory infection were not associated with changes in the sputum flora, the composition of P. aeruginosa strains in which remains constant over long periods in patients with CF.

We have characterised 45 isolates of methicillin-resistant Staphylococcus aureus (MRSA) from Glasgow Royal Infirmary by means of simple biotyping, immunoblotting of exported proteins and restriction enzyme fragmentation patterns (REFP) of plasmid DNA. The strains were subdivided into four groups (A-D) on the basis of biotype. Immunoblotting and restriction enzyme fragmentation generated a number of unique patterns. Analysis of these patterns by means of Dice coefficients of similarity separated them into two major immunoblot groups (Blot1 and Blot2) and two major REFP groups (FP1 and FP2). There was strong positive correlation between Blot1 and FP1 groups and between Blot2 and FP2 groups. In addition, Blot1-FP1 isolates were almost exclusively of biotypes A or C, whereas Blot2-FP2 isolates were of biotypes B or D. The methods described here have provided comprehensive epidemiological information which has been valuable in studying the origin and spread of MRSA.