- Volume 34, Issue 3, 1991

During the period 1983–1988 the incidence of peritionitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) in Nottingham fell from 2.0 to 1.2 episodes/patient/year. Cefuroxime, given intraperitoneally for 10 days, as recommended in published guidelines, failed to cure 35% of episodes of peritonitis, although only 7% of the pathogens responsible for these episodes were resistant in vitro. Cefuroxime is probably no longer appropriate as first line treatment of CAPD peritonitis.

In a chemically defined medium in which the principal constituents were glucose, 18 amino acids, two purines and six vitamins, eight strains of coagulase-negative staphylococci grew as rapidly and heavily as in tryptic soy broth. Slime formation was slightly better in the defined medium than in tryptic soy broth.

Twenty isolates of Salmonella typhi from cases of typhoid during the 1989–1990 epidemic in Calcutta were examined. Most isolates (84% of all isolates in the epidemic) were resistant to chloramphenicol, ampicillin, tetracycline and streptomycin but were sensitive to nalidixic acid and ciprofloxacin. Plasmids of 120 kb and 14 kb were identified amongst the multi-drug resistant isolates of S. typhi. However, there was no plasmid in the antibiotic-sensitive isolates. The 120-kb plasmid was transferable and transconjugants were resistant to chloramphenicol, ampicillin, tetracycline and streptomycin. Restriction endonuclease analysis patterns after EcoRI digestion of the 120-kb antibiotic-resistance plasmids from the S. typhi isolates and transconjugants were similar.

Of 505 strains of Enterobacteriaceae responsible for significant bacteriuria and isolated from hospital patients in two Greek cities in 1989, 151 strains (30%) were resistant to trimethoprim (MIC 4 mg/L) and 220 (44%) were resistant to sulphamethoxazole (MIC 64 mg/L); 127 (84%) of the trimethoprim-resistant strains exhibited high-level resistance (MIC > 1024 mg/L) and 121 (80%) were additionally resistant to four or more other antibiotics. Plasmids were detected in 141 (93%) of the trimethoprim-resistant strains. Trimethoprim resistance was encoded on self-transmissible plasmids in 79 (52%) of the resistant strains, and in a further seven strains (5%), plasmids coding for trimethoprim resistance could be mobilised by X+ factor. Co-transfer of various other antimicrobial resistances with trimethoprim resistance was observed, tetracycline resistance being the most common. The low degree of linkage observed between trimethoprim resistance and resistance to streptomycin and spectinomycin suggests that Tn7 is relatively uncommon in Greece. Classification of trimethoprim-resistance plasmids on the basis of their antimicrobial-resistance patterns and molecular mass revealed 39 different profiles. Overall, these findings differ from those from other European countries where the prevalence of transferable high-level trimethoprim resistance is low and where chromosomal Tn7-encoded trimethoprim resistance is common.

The viability of four strains of Bordetella bronchiseptica, two strains of B. pertussis and one strain of B. parapertussis exposed to hyperimmune and pre-colostrum porcine serum was examined. Viable cell numbers (cfu/ml) of the B. pertussis strains and a rough strain of B. bronchiseptica (CSU-P-1) decreased by 99% and 99.99%, respectively, after exposure for 1 h to porcine hyperimmune serum. In contrast, smooth B. bronchiseptica strains and the B. parapertussis strain showed no significant decrease in viable cell numbers after the same treatment. B. bronchiseptica strain CSU-P-1 also showed a 99% decrease in viable cell numbers after exposure to pre-colostrum porcine serum for 1 h whereas the other strains tested showed no decrease in viable numbers under the same conditions. Heating the hyperimmune and pre-colostrum serum at 56° for 30 min resulted in the loss of bactericidal activity suggesting the involvement of complement in both systems. Analysis of silver-stained SDS-PAGE profiles of lipoplysaccharide (LPS) extracted from the bacterial cells indicated that the smooth strains of B. bronchiseptica and the B. parapertussis strain possessed high mol. wt O-side chain-like material, whereas the B. pertussis strains and B. bronchiseptica strain CSU-P-1 did not. Gel filtration of acid-hydrolysed LPS samples indicated two distinct carbohydrate peaks for the strains with high mol. wt O-side chain-like material, whereas the other strains each yielded one distinct peak. Western-blot analysis indicated a positive reaction for anti-B. bronchiseptica antibodies to the high mol. wt O-side chain-like material of all serum-resistant strains used in this study. The serum resistance of smooth B. bronchiseptica strains may be an important factor in their association with wound infections.

Monoclonal antibodies (MAbs) were raised against the major, 46–48-Kda outer-membrane proteins of Vibrio cholerae O1. The hybridoma clones were screened by enzyme-linked immunosorbent assay (ELISA) with cell-surface proteins of V. cholerae O1 as the coating antigen. Four hybridomas, which secreted anti-V. cholerae cell-surface-protein antibodies, were subcloned by limiting dilution and obtained as ascites in vivo. A MAb of the IgG1 subclass was isolated in good yield from the murine ascites by affinity chromatography with recombinant protein G-Sepharose 4B. It gave positive reactions, as determined by ELISA, against cell-surface proteins prepared from both biotypes (classical and E1 Tor) and both serotypes (Ogawa and Inaba) of V. cholerae O1. The MAb did not have any reactivity towards V. cholerae lipopolysaccharide preparations. Immunoblotting studies were performed on cell-surface proteins separated by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (1D SDS-PAGE) and also by two-dimensional (2D) electrophoresis with iso-electric focusing in the first dimension followed by SDS-PAGE in the second dimension. When proteins were separated by 1D SDS-PAGE, only one band at 46–48 Kda reacted with the MAb. This protein appeared to consist of two narrowly-spaced and cross-reactive bands when a nitrocellulose blot, obtained by 2D SDS-PAGE, was exposed to the MAb.

Twenty-six monoclonal antibodies (MAbs) directed against seven brucella outer-membrane proteins (OMPs) of 10, 16.5, 19, 25–27, 31–34, 36–38 and 89 Kda were screened for passive protection of mice; three MAbs (directed against 16.5, 25–27 and 36–38 Kda) reduced significantly the initial colonisation of the spleen measured 7 days after challenge. Although significant, the reduction in numbers of Brucella organisms in the spleen was low compared with that conferred by MAbs against lipopolysaccharide of smooth specificity (S-LPS). The three most protective MAbs belonged to two isotypes (IgG1 and IgG2a) and were specific for three different OMPs. No relationship between protection and binding of MAbs to the challenge S strain or its rough mutant was observed in the mouse model. The humoral protection depended mainly on antibodies directed against S-LPS, although some MAbs against OMPs had weak protective activity.

In a study of six laboratory strains of Helicobacter pylori, two different modes of bacterial adherence to HEp-2 cells were found. Electronmicroscopy revealed that strains known to possess soluble haemagglutinin adhered intimately to the cell surfaces, with cupping of the plasma membrane and coalescence of glycocalyces at sites of attachment. Strains of H. pylori without soluble haemagglutinin also attached, but did not induce membrane cupping or show glycocalyx fusion. Light microscopy did not distinguish between these patterns of adherence. Bacterial attachment was unaffected by pre-treatment of HEp-2 cells with neuraminidase. Exposure of the bacteria to trypsin or to colloidal bismuth subcitrate (CBS) before being added to HEp-2 cells markedly impaired bacterial adherence. This effect of CBS may contribute to the known efficacy of bismuth therapy in patients with H. pylori-related gastritis.