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Comparisons were made between the O-serotype, API 20E profile, site of isolation and antimicrobial resistance of clinical isolates of Enterobacter cloacae. Correlations were found between autoagglutinable strains and urinary-tract infection, and API 20E profile 3305573 and strains isolated from blood. The proportion of strains sensitive to amikacin, gentamicin, cefotaxime, cefuroxime and trimethoprim were 100%, 93%, 91%, 83% and 89%, respectively. No individual resistances or patterns of resistance were associated with O-serotype or biochemical profile. Strains isolated from urinary-tract infections were the most resistant, 40% being resistant to five or more antimicrobials compared to 18%, 12% and 4% for strains from blood, wounds and sputum, respectively. There were no readily identifiable phenotypes within E. cloacae that possessed unique characteristics that could contribute to infections in hospitals.

An outbreak of colonisation and infection with a netilmicin resistant strain of Serratia marcescens occurred in a special care baby unit. S marcescens was isolated from a total of 13 babies; significant infection occurred in five, of whom two died. Epidemiological investigation failed to detect a common source but gastrointestinal colonisation of babies formed a prolonged and possibly important reservoir for infection. Containment proved difficult until the unit was closed to new admissions, and even then spread to a temporary unit ensued. O Serotyping and bacteriophage typing disclosed a single epidemic strain. This produced an aminoglycoside acetylating enzyme (AAC(6')) conferring resistance to netilmicin and tobramycin and moderate resistance to amikacin. Use of gentamicin resulted in the isolation of serratia with increased resistance to all aminoglycosides, and, similarly, increased resistance to third generation cephalosporins emerged with their use.

Despite the sparsity of Pseudomonas aeruginosa in the environment colonisation and infection with this organism was found at several sites by selective culture in 20 out of 46 patients in an intensive therapy unit. Three patients developed Ps aeruginosa pneumonia. Serial serogrouping and phage typing identified multiple strains in the unit and in the same patient. Rectal carriage occurred in 16 patients but rectal strains did not subsequently appear in tracheal aspirates; strains varied in their affinity for the upper respiratory tract. Colonisation was not directly related to length of stay and was detected in 16 of those colonised within 24 hours of admission. In intubated patients, who were colonised more frequently than those not intubated, upper respiratory tract colonisation correlated strongly with low initial arterial pH values. Personnel were probably responsible for cross infection among patients when the unit was busy. Strain differences and the susceptibility of patients also influenced colonisation and infection. Elimination of major reservoirs of Ps aeruginosa and compliance with procedures to control cross infection remain essential if patients in hospital are to escape colonisation by the organism.

Carbenicillin resistance in strains of Pseudomonas aeruginosa isolated in Britain is mediated more frequently by "intrinsic factors" than by beta-lactamase production. Intrinsically carbenicillin-resistant isolates almost invariably were more resistant to azlocillin, cefoperazone, cefotaxime, ceftazidime, chloramphenicol, tetracycline and nalidixic acid than were carbenicillin-susceptible strains. This cross-resistance to different classes of antimicrobials suggested an impermeability-based mechanism of resistance, perhaps involving the outer membrane. The structure and composition of the outer membrane of the pseudomonas cell also influences the O-serotype specificity and the susceptibility to many bacteriophages. We therefore examined these properties for possible relationships to antibiotic resistance. Carbenicillin-resistant (122) and -sensitive (127) P. aeruginosa strains from 24 hospitals were compared. Serotype O:1, O:3, O:6, O:10 and O:11 strains predominated in both groups. Non-typable and polyagglutinating strains were infrequent in both groups. With one possible exception, none of 18 bacteriophages showed a significant preference for carbenicillin-resistant or -sensitive strains. Variation between strains was observed in the electrophoretic profile of LPS and this could be related in part to serotype, but not to antibiotic resistance. Our results contrast with those of earlier small-scale studies which have claimed relationships between surface properties and antibiogram in P. aeruginosa, and suggest that interpretation of the minor changes in LPS sometimes observed in association with the development of antibiotic resistance in vitro requires caution.

A study of serological, bacteriocine and phage typing of Serratia marcescens was made. Specific O-antisera of adequate titre were relatively simple to prepare but H-antisera exhibited many heterologous agglutination reactions amongst the type strains. Most of these cross-reactions were not reproduced when immobilization tests with H-sera were performed. Direct haemagglutination tests were used to establish the presence of fimbriae amongst the H-type strains and the results of agglutination tests with non-fimbriate variants of strains indicated that fimbrial antibody in high titre was present in some sera. Replicate typing of 100 pairs of cultures by the phage-typing method indicated that small variations in pattern were common and that larger variations occurred occasionally. Therefore differences in pattern of less than two strong reactions should not be taken as evidence that strains can be distinguished. Cultures of S. marcescens, 273 in total, from six outbreaks of infection in British and European hospitals were typed by O-serology, H agglutination and immobilization tests, phage typing and bacteriocine susceptibility by a cross-streaking method. The typability of strains by each method was high but the results suggested that no single method was sufficiently discriminating to be used alone for typing. Comparison of the H-type and typing patterns of members of the same O serogroup from incidents of infection showed that reliable results were obtained by H-typing or by phage and bacteriocine typing after the application of the appropriate 'difference' rule. The greatest discrimination between strains of the same O-group was obtained by the use of H-typing or phage typing.

Aspects of intracranial aerocele are described and exemplified by two cases which presented to the Plastic Surgery Unit. Austin Hospital, Melbourne, as radiological findings incidental to facial injury. The first case illustrated the occasional problem of identifying the site of dural tear; a fracture could not be identified on X-ray film or at operation, and this can make subsequent dural repair more difficult. The second case was associated with florid clinical signs of facial fractures which were supported by X-ray findings. Both patients underwent surgery for the primary injury, and received prophylactic therapy with antibiotic agents because of the risk of meningitis associated with dural tears. In neither case did intracranial air persist beyond 14 days; therefore, dural repair was not performed. It is important to look for evidence of dural damage when dealing with facial injury either in the casualty or in the subsequent management of the patient.

Two hundred and twenty-five reversed saphenous vein femoropopliteal bypass graft procedures were performed on 186 patients with occlusive vascular disease. These grafts were followed for a mean of 19 months, with the longest period being 64 months. Numerous factors ascertained before, during, and after operation were analyzed using a life-table technique to see how these factors correlated with graft patency. The internal diameter and wall thickness of the vein grafts appeared to significantly influence graft patency. The best results were obtained using veins with a large internal diameter and a thin wall. In contrast, none of the other factors studied (which included age, sex, blood pressure, height, weight, indication for surgery, diabetic state, serum lipids, angiographic data, the site of the upper and lower anastomoses, the use of spliced vein segments, the type of vein preparation and the consumption of cigarettes before operation) were useful predictors of graft patency. It is suggested that vein diameter and vein wall thickness should be taken into consideration when analyzing the results of saphenous vein femoropopliteal bypass graft procedures, and also that the assessment of these factors may influence the choice of graft material for a femoropopliteal bypass graft.