- Volume 47, Issue 11, 1998

Twenty-four gentamicin-resistant isolates of Enterobacteriaceae, obtained from the clinical laboratories of three health centres in Nablus, Palestine, were tested for susceptibility to neomycin, kanamycin, tobramycin and amikacin. Resistance rates were 29.2% for neomycin, 58.3% for kanamycin, 45.8% for tobramycin and 8.3% for amikacin. Fourteen (58.3%) isolates were noted to be multiresistant, i.e., resistant to gentamicin and two or more other aminoglycosides; resistance to gentamicin, kanamycin and tobramycin was the most common pattern of multiple resistance. This pattern implies the involvement of adenyltransferase ANT(2")-I activity. Plasmid profiles and curing experiments suggested a plasmid localisation of gentamicin, neomycin, kanamycin and tobramycin resistance genes. However, a chromosomal location is proposed for plasmid-deficient strains. Cross-resistance in two isolates to all aminoglycosides tested suggested membrane impermeability to aminoglycosides as the mechanism of resistance.

Seven different agar-based media were compared to determine the optimal set of culture media for primary isolation of Haemophilus ducreyi. Also, a new method for sampling genital ulcers – with a disposable sterile plastic loop – and processing specimens that provides a standardised inoculum for culture of H. ducreyi on various media is described. A total of 202 patients with genital ulcer disease was enrolled in this study. A sterile swab or plastic loop was used to sample the base of the ulcers and ulcer material was suspended in sterile phosphate-buffered saline. A 100-μl sample of this suspension was mixed with an equal volume of tryptic soy broth containing IsoVitaleX and centrifuged for 1 min. This suspension was used to inoculate the different media. Plates were incubated at 33°C in micro-aerophilic conditions and examined for growth of H. ducreyi after 48 h. Of the 202 specimens, 77 (38.1%) were culture positive for H. ducreyi. None of the agar bases supported the growth of all H. ducreyi strains. Based on this observation, we recommend the universal use of Mueller-Hinton agar base supplemented with chocolate horse blood and IsovitaleX (MH-HBC) and Columbia agar base supplemented with bovine haemoglobin, activated charcoal, fetal calf serum and IsovitaleX (C-HgCh) to enable comparison of prevalence figures for chancroid. In addition, the novel sampling technique described in this study eliminates sampling bias normally associated with genital ulcer specimens.

Thirty clinical isolates of Burkholderia cepacia from cystic fibrosis (CF) patients in the UK and Denmark were characterised, together with other clinical isolates and laboratory strains of B. cepacia, B. gladioli and B. vietnamiensis. Outer-membrane protein (OMP) profiles were determined, and the organisms were typed genotypically by pulsed-field gel electrophoresis after DNA restriction analyses with XbaI and DraI. This latter method revealed four clusters among the clinical isolates studied; one of these contained isolates of the UK and intercontinental CF epidemic lineage ET12, a cluster which appeared to contain three subtypes. Each of the four clusters appeared less closely related to laboratory strains of B. cepacia than were laboratory strains of B. vietnamiensis, but more closely related to both these species than to B. gladioli. Two types of OMP profile were distinguished among the clinical isolates and strains, and were designated A and B. In type A isolates the major proteins had mol. wts of 39, 27 and 18 kDa. Type B strains additionally contained a group of proteins in the size range 80–90 kDa, although detection of these depended upon the conditions for sample denaturation. In most cases, the OMP type correlated with the genotype, suggesting that examination of OMPs might be of value in the initial characterisation of isolates.

The polymerase chain reaction (PCR) was evaluated retrospectively for its ability to detect Ureaplasma urealyticum and Mycoplasma spp. in respiratory tract specimens obtained from adult patients with AIDS. Mycoplasma DNA was detected in specimens from 12 of 84 patients. Of the 107 specimens tested, 13 and seven positive PCR results were obtained with the genus- and species-specific oligonucleotide primers used, respectively, in two different steps. With the latter, one sample was positive for U. urealyticum plus M. hominis, another for M. fermentans plus M. salivarium, and five others were positive for M. salivarium. The unexpected detection of U. urealyticum DNA in respiratory secretions from an adult AIDS patient suggested that this urogenital mycoplasma could have a role in determining or exacerbating respiratory tract infections in the HIV-positive population, but that its low rate of isolation could be related to the frequent failure of methods used currently to detect mycoplasmas.

Interleukin-2 (IL-2)-activated lymphocytes interact directly with, and inhibit, the growth of Candida albicans hyphae. C. albicans-stimulated natural killer (NK1.1+) lymphocytes were demonstrated to secrete a soluble product capable of directly affecting C. albicans yeast forms. Antibodies specific for interferon-γ completely eliminated the antifungal activity of the NK1.1+ lymphocyte product and diminished the antifungal activity of NK1.1+ lymphocytes against C. albicans. Antibodies specific for other cytokines had no such effect. These data demonstrate that C. albicans-stimulated NK1.1+ lymphocytes have antifungal activity against C. albicans yeast cells via the release of interferon-γ. This antifungal activity was demonstrable only against the yeast form of the fungus, with no effect on C. albicans hyphae.

The effect of some antibacterial compounds present in human milk were tested for antiviral activity against respiratory syncytial virus, Semliki Forest virus and cytomegalovirus. These included the gangliosides GM1, GM2 and GM3, sialyl-lactose, lactoferrin and chondroitin sulphate A, B and C, which were all tested for their ability to inhibit the viruses in cell culture. Of the compounds tested, only the ganglioside GM2, chondroitin sulphate B and lactoferrin inhibited the absorption and growth of respiratory syncytial virus in cell culture, and none inhibited the growth of Semliki Forest virus, indicating that lipid antiviral activity was not associated with any of the gangliosides. While the concentrations of these two compounds required to inhibit respiratory syncytial virus were in excess of those present in human milk, sialyl-lactose concentrations similar to those present in human milk increased the growth of cytomegalovirus. Lactoferrin was confirmed as inhibiting both respiratory syncytial virus and cytomegalovirus growth in culture even when used at lower concentrations than those present in human milk. The antiviral activities of GM2, chondroitin sulphate B and lactoferrin were tested when added to an infant formula. Lactoferrin continued to have antiviral activity against cytomegalovirus, but a lower activity against respiratory syncytial virus; ganglioside GM2 and chondroitin sulphate B still maintained antiviral activity against respiratory syncytial virus.