P. M. Hawkey

Non-pathogenic Escherichia coli versus mesalazine for the treatment of ulcerative colitis: a randomised trial.

BACKGROUND Ulcerative colitis has been suggested to be caused by infection and there is circumstantial evidence linking Escherichia coli with the condition. Our aim was to find out whether the administration of a non-pathogenic strain of E. coli (Nissle 1917) was as effective as mesalazine in preventing relapse of ulcerative colitis. We also examined whether the addition of E. coli to standard medical therapy increased the chance of remission of active ulcerative colitis. METHODS This was a single-centre, randomised, double-dummy study in which 120 patients with active ulcerative colitis were invited to take part. 116 patients accepted; 59 were randomised to mesalazine and 57 to E. coli. All patients also received standard medical therapy together with a 1-week course of oral gentamicin. After remission, patients were maintained on either mesalazine or E. coli and followed up for a maximum of 12 months. A two-stage, conditional, intention-to-treat analysis was done. FINDINGS 44 (75%) patients in the mesalazine group attained remission compared with 39 (68%) in the E. coli group. Mean time to remission was 44 days (median 42) in the mesalazine group and 42 days (median 37) for those treated with E. coli. In the mesalazine group, 32 (73%) patients relapsed compared with 26 (67%) in the E. coli group. Mean duration of remission was 206 days in the mesalazine group (median 175) and 221 days (median 185) in the E. coli group. INTERPRETATION Our results suggest that treatment with a non-pathogenic E. coli has an equivalent effect to mesalazine in maintaining remission of ulcerative colitis. The beneficial effect of live E. coli may provide clues to the cause of ulcerative colitis.

Gastroduodenal dysfunction and bacterial colonisation of the ventilated lung

The source of ventilator-associated pneumonia (gastric or oropharyngeal flora) remains controversial. We investigated the source of bacterial colonisation of the ventilated lung in 100 consecutive intensive-care patients. Gram-negative bacilli were isolated from the lower respiratory tract in 19 patients. Bacteria isolated from the stomach contents either previously or at the same time were identical to lower respiratory isolates in 11 patients. No gram-negative oropharyngeal isolate was identical to a lower respiratory tract isolate. Gastric bacterial overgrowth with gram-negative bacilli was associated with the presence of bilirubin in the stomach contents. Detectable bilirubin was also associated with subsequent acquisition of gram-negative bacilli in the lower respiratory tract. Only 5 gastric aspirate specimens with pH < 3.5 contained gram-negative bacilli. These results establish a relation between duodenal reflux and subsequent bacterial colonisation of the lower respiratory tract. Restoration of normal gastroduodenal motility might help prevent pneumonia in intensive-care patients.

Exceptional desiccation tolerance of Acinetobacter radioresistens

The taxonomy of the genus Acinetobacter, which includes several important nosocomial pathogens, has been confused due to a lack of discriminatory phenotypic characteristics for identification. Molecular methods such as amplified ribosomal DNA restriction analysis (ARDRA) now enable the accurate identification of species. Ten clinical isolates of Acinetobacter radioresistens had genospecies confirmed by ARDRA but the APJ 20NE system, commonly used in clinical microbiology laboratories, mis-identified them as Acinetobacter lwoffii. Desiccation resistance of Acinetobacter spp. is an important attribute for their survival in the clinical environment. We investigated the ability of A. radioresistens to survive desiccation using an established glass surface model and compared the results to A. lwoffii and Acinetobacter baumannii. The 10 strains of A. radioresistens were extremely resistant to desiccation and survived for an average of 157 days at 31% relative humidity (RH). In contrast, two strains of A. lwoffii and three strains of A. baumannii survived for an average of three and 20 days respectively, at 31% RH, which was used as an approximation to climatic conditions in UK hospitals. A. radioresistens is thus well adapted for survival in the hospital environment and carriage on human skin and yet it is reported less frequently than A. lwoffii amongst clinical isolates. Cases of A. radioresistens infection may be under-reported due to mis-identification as A. lwoffii and further studies that use molecular identification methods are required to elucidate the role of A. radioresistens in human disease.

A new selective differential medium for isolation ofStenotrophomonas maltophilia

A new selective differential medium for the isolation ofStenotrophomonas (formerlyXanthomonas) maltophilia was developed. The medium, VIA agar, contained vancomycin, imipenem, and amphotericin B as selective agents and incorporated a mannitol/bromothymol blue indicator system. Compared withXanthomonas maltophilia Selective Medium (XMSM), VIA agar was less inhibitory toStenotrophomonas maltophilia and was more selective than XMSM in preventing the growth of unwanted bacteria from contaminated specimens. Although vancomycin-resistant strains ofEnterococcus faecium may grow on VIA agar, these can be easily distinguished fromStenotrophomonas maltophilia because of mannitol fermentation.

PCR for the detection and typing of campylobacters

The flaA gene of Campylobacter sp. was amplified using PCR. Primers were chosen which amplified 1.3 kb of the flaA gene in Camp. jejuni and Camp. coli. ‘Campylobacter upsaliensis’ amplimer was approximately 1.7 kb in size and was easily distinguishable. Other species of campylobacter failed to yield amplimer. The amplimer was digested with Alu 1 which demonstrated considerable restriction fragment length polymorphism and should allow the development of a rapid novel typing scheme which does not rely on previous culture of campylobacter strains.

Incidence of Listeria spp. in Pre-cooked, Chilled Chicken Products as Determined by Culture and Enzyme-linked Immunoassay (ELISA)

One hundred and two samples of ready-to-eat, pre-cooked, chilled chicken were examined for Listeria spp. using culture and a commercially available enzyme linked immunoassay (ELISA). Overall, 29 (28%) samples contained Listeria spp. as determined by culture, Listeria monocytogenes being present in 27 (26.5%) samples. In comparison with culture, the ELISA yielded no false positives. However, the technique detected Listeria spp. in only 24 of 29 culture-positive samples.

Staphylococcal pneumonia in ventilated patients: a twelve-month review of cases in an intensive care unit

We reviewed staphylococcal lower respiratory tract infections in our intensive care unit over a 12-month period. Staphylococcus aureus was isolated from tracheal aspirates more commonly in patients with intracranial trauma (P < 0.001), between one and six days (mean = 3) after admission to the intensive care unit. Bacteriophage typing of all S. aureus lower respiratory tract isolates from the 17 patients with head injury did not provide evidence for a common external source of infection or patient-to-patient transmission.

Co-existent cross-infection with Streptococcus pneumoniae and group B streptococci on an adult oncology unit

An outbreak of respiratory infection in an adult oncology unit is described where there was evidence of co-existent cross-infection with Streptococcus pneumoniae serotype 14 and Lancefield group B streptococcus type Ia. The presumed route of transmission was droplet spread from patient to patient. No further cases arose after the ward had been closed to new admissions and all symptomatic patients were treated with erythromycin. We suggest that patients with pneumococcal pneumonia on units housing elderly debilitated patients should be isolated. Infection control teams should be aware of the ability of Lancefield group B streptococci to spread by cross-infection among adult patients.

Listeria in Yoghurt

Part of this work was presented at the 160th meeting of the Pathological Society of Great Britain and Ireland, Royal Postgraduate Medical School. Hammersmith Hospital, London, January 1990.Cultured dairy products are increasingly used in a number of disorders. Dairy products are often implicated in sporadic and epidemic cases of listeriosis. One hundred samples of yoghurt were examined for the presence of Listeria spp. Listeria spp. were not detected in any sample. Reasons for this are dismsed. It is concluded that the risk of acquisition of listeriosis fiom the medical use of yoghurt is low.

Principles of molecular typing: a guide to the letters

The investigation of infection clusters in hospitals caused by the same bacterial species requires the differentiation of strains using some form of typing. Traditionally, methods have relied upon the characterization of phenotypic properties such as biotype, serotype, bacteriophage type and antibiotic susceptibility profile. Although many of these methods are cheap and technically simple to perform, they lack discrimination. Some systems were developed for specific species or genera with the result that the reagents are specially adapted for those species and are not generally applicable. Variation in the expression of phenotypic characteristics can lead to poor reproducibility for some methods. To circumvent many of these problems, a major research effort has been directed to developing genotyping methods which rely on a range of techniques developed for molecular biology. These techniques have revolutionized the investigation of cross-infection in hospitals and community. Some methods, such as plasmid fingerprinting, require minimal equipment and are cheap, whereas genomic DNA extraction, digestion and hybridization methods are both expensive and technically demanding. Methods can be broadly classified into three groups: i) plasmid analysis, ii) total genomic DNA digestion and display, and iii) PCR based methods. This paper will review the most frequently used methods and explain the processes involved