- Volume 43, Issue 1, 1995

The bactericidal activity of two new 4-quinolones, DU-6859a and DV-7751a, was investigated against strains of Escherichia coli, Staphylococcus aureus, S. epidermidis, Streptococcus pneumoniae and Enterococcus faecalis. DU-6859a and DV-7751a were more bactericidal than any 4-quinolone tested previously. Furthermore, DU-6859a was unique among 4-quinolones in being able to kill Ent. faecalis after incubation for only 3 h in nutrient broth. The bactericidal mechanisms of DV-7551a were similar to those of other 4-quinolones, but, uniquely, DU-6859a possessed additional bactericidal mechanisms against both Str. pneumoniae and Ent. faecalis. This may explain the unusually potent bactericidal activity of this agent against these species. These results show that DU-6859a is a unique extended-spectrum 4-quinolone, which should prove to be superior to established 4-quinolones.

Strains of Haemophilus influenzae type b were collected as part of an epidemiological study of bacterial meningitis in the North East Thames Region (NETR) of England. Subclones of H. influenzae were identified by outer-membrane protein typing and multilocus enzyme electrophoresis. These were compared with subclones of H. influenzae type b isolated from elsewhere in the UK. The subclone ET 12.5/OMP 3L was identified in 68% of isolates from cases of meningitis from the NETR. In the isolates from elsewhere in the UK, this subclone was identified in 79% of sterile-site isolates and 91 % of isolates from non-sterile sites. This subclone predominated in patients of different ages and from different ethnic groups, which suggests that non-Caucasians are infected with the subclone predominating locally. Since ET 12.5/OMP 3L subclone is the most abundant strain isolated in virtually all other Western European countries, these results provide additional evidence that the genetic diversity in the H. influenzae type b population in Europe is relatively restricted.

Sporadic examples of infection with multi-resistant Acinetobacter spp. have occurred in Nottingham hospitals since at least 1977, punctuated by more prolonged outbreaks involving larger numbers of patients, particularly those confined to the intensive therapy unit (ITU) with severe underlying disease. In the most recent outbreak, 11 patients were infected with multi-resistant Acinetobacter strains and 26 patients were colonised. Four of the infected patients died directly or indirectly from infection with multi-resistant Acinetobacter spp., either while in the ITU or after discharge to a general ward. The mean interval from admission to the first isolation of a multi-resistant Acinetobacter strain was 6.7 and 12.1 days in the infected and colonised groups, respectively. Multi-resistant Acinetobacter strains were isolated most frequently from the respiratory tract, and eight patients had probable or suspected pneumonia caused by a multi-resistant Acinetobacter sp. All infected patients were treated with imipenem, with or without an aminoglycoside, except one patient who died before a diagnosis of acinetobacter infection was confirmed. Multi-resistant Acinetobacter spp. were isolated from various environmental sites in the ITU, and patient and environmental isolates were found to be related closely by biotyping, antibiograms, pulsed-field gel electrophoresis of chromosomal fingerprints and ribotyping. The outbreak was controlled ultimately by transfer of infected or colonised patients to an isolation cubicle, cohort nursing, emphasis on the importance of hand washing before and after patient contact and when handling case notes, and the use of disposable aprons and gowns during patient contact. These measures were combined with closure of the ITU for decontamination purposes on two separate occasions. Continued surveillance of ITU patients and occasional environmental sampling has proved to be important in preventing and controlling subsequent outbreaks of infection by this increasingly important nosocomial pathogen.

Chronic pyelonephritis was successfully produced in female BALB/c mice with Escherichia coli after introduction of the bacterial inoculum by the ascending route. E. coli strain 31-B, a nalidixic acid-resistant derivative of strain TN675 expressing type-1 pili, and E. coli strain BH-5, a mutant of 31-B, not expressing type-1 pili, were used in the model. Both the strains were able to induce chronic renal inflammation in the experimental animals. Whereas the initial colonisation was greater with strain 31-B, its non-pilate mutant BH-5 caused a significantly greater inflammatory response and also caused renal scarring observable 5 months after the infection.

A commercial method (RAPIDEC™ur; bio Mérieux UK Ltd, Basingstoke) and an in-house scheme based on conventional tests were compared for the identification of 179 commonly encountered gram-negative urinary pathogens. The methods identified correctly to genus level 97% and 84% of organisms, respectively. RAPIDEC ur was superior at identifying Escherichia coli, due to the detection of β-glucuronidase activity, but less cost-effective than the in-house scheme.

Campylobacter jejuni is the commonest cause of acute bacterial enteritis in the UK. However, in this case a 74-year-old lady underwent gastroscopy for an upper gastrointestinal haemorrhage and was noted to have a gastric ulcer. Gastric biopsy revealed spiral gram-negative bacteria and culture yielded a moderate growth of C. jejuni. Identification was confirmed by growth characteristics, biochemical tests and PCR amplification of the species-specific flagellin gene—fla A. To prevent misidentification, it is important that laboratories routinely culturing gastric biopsies for Helicobacter pylori should perform a rapid urease test and not rely solely on microscopic morphology.

Fifty clinical strains of Chlamydia trachomatis were studied by denaturing gradient gel electrophoresis (DGGE) of bacterial DNA amplified by the polymerase chain reaction (PCR). The strains belonged to the three most commonly encountered serovars in developed countries—D, E and F. Six reference strains, including the serovar Da strain, were also studied. The DNA sequences explored encompassed the four variable domains (VDs) of ompl, the gene encoding the major outer-membrane protein (MOMP). The corresponding regions in the MOMP contain the species-, subspecies- and serovar-specific epitopes. The four distinct serovars were clearly differentiated by specific migration pattern. No sequence variations were observed among strains of serovar F. However, variant strains within serovars D and E were found, which exhibited migration patterns different from those of the reference strains and these were sequenced directly. According to the observed sequence variations, serovar D strains could be divided into three stable representative groups (D, D1 and D2). Two variants were identified among serovar E strains. No biological differences were observed for the variant strains in terms of growth properties, ecology or pathogenicity. All the nucleotide substitutions detected in the VDs were non-synonymous at the protein level and, for the serovar D strains, could account for differences identified by specific monoclonal antibodies. These substitutions could be involved in antigenic drift, driven by the immune pressure of the host, leading to the emergence of serovariants. The data may explain, in part, chlamydial infection recurrences and could have critical implications for developing rational vaccine strategies.