In an effort to provide guidelines for standardizing aeration times for plastics sterilized with ethylene oxide, an Aeration Index has been developed. Based on the rate of diffusion of ethylene oxide in selected polymers, the Index provides an indication of the aeration time at ambient temperature (23°C) for the ethylene oxide concentration in freshly sterilized plastics to drop to 50 parts/106.

Using direct agglutination methods, a simple serological scheme for the classification of Bacteroides fragilis is described. Twenty strains of B. fragilis were selected by a process of successive screening from 151 strains obtained from various sources. O-antigens were prepared from the 20 strains, and used to raise antisera in rabbits.

Each of the 20 antisera reacted with its homologous antigen and eight antisera cross-reacted with other subspecies. These cross-reactions were successfully removed after absorption of the antisera with the cross-reacting antigens, resulting in 19 type-specific antisera, titres ranging from 40 to 320, and 19 distinct serotypes of B. fragilis. There was no correlation between the antigenic and the biochemical characteristics of these strains and no cross-reactions occurred with other gram-negative anaerobes, B. melaninogenicus, Sphaerophorus necrophorus and Fuso-bacterium necrogenes.

Strains of California encephalitis virus (snowshoe hare subtype) were isolated from 8 of 475 pools comprising 23747 unengorged female mosquitoes of five species collected at three of six locations throughout the Mackenzie Valley of the Northwest Territories, Canada, from latitudes 60 to 69° N between 10 and 24 July 1976. Minimum field infection rates included 1:2734 for Aedes communis, 1:256 to 1:3662 for A. hexodontus and 1:911 to 1:1611 for A. punctor. Northway virus was also isolated from 1 of 3662 A. hexodontus mosquitoes collected at Inuvik (69° N, 135° W). Transmission of CE virus by A. communis infected by feeding on virus in defibrinated blood and incubation at 0, 13 and 23 °C for 13–20 days clearly demonstrates the importance of this species as a natural vector, and transmission of CE virus by Culiseta inornata after incubation at 0 and 13 °C following intrathoracic injection strengthens evidence of its role as a natural vector. Immunofiuorescence was less reliable than imunoperoxidase for detection of CE viral antigen in mosquito salivary glands.

Samples of frozen precooked rock lobster meat from five South Australian fish-processing plants situated in the West Coast and south-east regions were tested over a period of six months during the 1974/5 lobster fishing season. The most probable number (MPN) of E. coli and coliforms, Staphylococcus aureus and Salmonella, as well as total plate count (TPC) were determined in 480 samples. Monthly geometric mean TPC ranged from 1600/g to 25,000/g. The highest geometric mean of the MPN of coliforms and E. coli were 4·9/g and 1·8/g respectively. The highest geometric mean number of staphylococci was 18·6/g. Salmonella was not detected in the 480 units tested. Only 0·4% of the samples had TPC exceeding 100,000/g. Coliforms and E. coli were not present in 76·1% and 92·7% respectively of the samples tested. Staphylococcus aureus was not detected in 67·7% of the samples. The numbers of organisms in 82% of the samples fall within the microbiological standards proposed by the National Health and Medical Research Council of Australia for frozen precooked foods. The results of this study demonstrate the microbial quality of precooked lobster meat attainable when good manufacturing practices are used.

Of 485 persons who replied to a questionnaire after attending a European Congress in September 1974, diarrhoea was experienced by 4 of 143 British residents and 2 of 342 visitors to the United Kingdom. This extremely low incidence of travellers' diarrhoea contrasts with the high incidence reported in travellers from countries with cool climates and north European standards of hygiene to countries where these conditions do not hold.

Forty-four haemagglutinating viruses were isolated from the pooled tracheal/cloacal swabs of the dead birds from 170 consignments of caged birds arriving at Heathrow Airport over a period of 6 months. Two isolates were identified as Newcastle disease virus but the remaining 42 were all identified as influenza viruses with Hav 7 Neq 2 antigens. All the consignments from which influenza viruses were isolated originated in India but had widespread destinations. The NDV isolates were from birds originating in central America and destined for Japan.

Campylobacter fetus was isolated from five recent cases of human vibriosis, of which two were adults and three were children. One adult presented with pericarditis and the other with recurrent pyrexia. Campylobacter fetus subsp. intestinalis which resembled cattle strains serologically, was isolated under CO2 or anaerobic conditions from blood cultures of these patients. Two of the three children had kwashiorkor and the third was only 8 days old. Isolates identified as Campylobacter fetus subsp. jejuni were cultured from blood of these patients, two of whom had diarrhoea. Three patients succumbed, despite adequate antibiotic therapy. The epidemiology of the disease is discussed and it is suggested that infection may have been from the patients' own flora.

A metabolic inhibition test based upon phosphatase production is described. This is of value for those Mycoplasma species which produce phosphatase but which cannot be examined by the previously published metabolic inhibition techniques.

The extensive laboratory investigations of respiratory disease in the U.K. over many years have demonstrated the frequency with which influenza viruses, both A and B, are found each winter. Only rarely are none isolated.

These findings correlate well with other indicators of influenza such as increases in sickness benefit claims and in deaths attributed to influenza and pneumonia.

However, outside these demonstrable peaks of incidence influenza viruses have been found to circulate over considerably longer periods often first appearing as early as November and continuing through to April or even May. But there has been no regular or predictablepattern determined.

The period of 1968–76 has seen a series of differently developing influenza winter epidemics caused by a series of the H3N2 virus. The contributions of virus isolation and serology to influenza surveillance is discussed.

The effect of a sublethal dose (0·5 LD 50) of influenza A/WSN (H0N1) administered intranasally in the 1st and 3rd weeks of pregnancy was studied in C3H inbred mice. Maternal and neonatal mortality rates were significantly increased by infections in the 3rd week of pregnancy, but not in the 1st week. Infections during the last part of the 1st week significantly depressed the growth rate of neonates. No evidence of viraemia, transplacental transmission or congenital malformations were observed from infections during either week. The results are discussed in terms of a possible model for human influenza infections during pregnancy to determine the potential risks to the mother, fetus and neonate.

The ability of certain Escherichia coli strains to produce enterotoxin is determined by transmissible plasmids. It is therefore possible that any E. coli strain might be able to acquire such a plasmid and that the correlation between enterotoxigenicity and serotype might be random. However, recent studies show that the enterotoxigenic strains so far described belong to a restricted range of serotypes. Enterotoxigenic strains of E. coli O6.H16 and E. coli O148.H28 have been associated with outbreaks of diarrhoea in several countries, therefore strains of E. coli belonging to these serotypes were selected for further study.

Twenty-three strains of E. coli O6.H16 and 14 strains of E. coli O148.H28 were examined; 20 strains of E. coli O6.H16 and all 14 strains of E. coli 0148.H28 were enterotoxigenic but strains of E. coli O6 with flagellar antigens other than H16 and strains of E. coli O148 with flagellar antigens other than H28 were not enterotoxigenic. The examination of single colony subcultures derived from the E. coli O6.H16 strains showed that in some strains loss of enterotoxigenicity had occurred in a proportion of colonies.

The transfer of an R factor from donor E. coli introduced into the rumen of adult sheep to strains of the coliform microflora resident post rumen in the lower gastro-intestinal tract was found to be greatly increased when the animals were subjected to a short period of starvation (ca. 24–48 h). This also resulted in coliform organisms containing the resistance determinants of the R factor being excreted for much longer periods, sometimes for months afterwards. As no antibiotic treatment was given to the animals during these experiments, possession of the R factor should have conferred no selective advantages on the host cells and other plasmids could possibly be transferred similarly in vivo in sheep or other ruminants and perhaps also within the gut of monogastric animals.

A simple method for the bacteriocine typing of Serratia marcescens without the use of induction was sought. The results of a mutual inhibition experiment with 89 unrelated cultures indicated that a bacteriocine-susceptibility method would give more discrimination between strains than would a bacteriocine-production method. A cross-streaking technique for bacteriocine-susceptibility typing without previous induction was developed, and its performance was compared with that of another susceptibility-typing method in which cell-free lysates of the producer strains were obtained by induction with mitomycin C.

Replicate typing of the same collection of cultures by both methods indicated that small variations in pattern were common and that larger variations occurred occasionally. Differences in pattern of less than two strong reactions in the mito-mycin-C induction method, and of less than three strong reactions in the cross-streaking method, should therefore not be taken as evidence that strains can be distinguished.

Sets of cultures of Ser. marcescens, 178 in total, from a number of supposed incidents of infection in hospitals, were used to evaluate the two bacteriocine-typing methods; all of the cultures were also O serogrouped. Comparison of the typing patterns of members of the same O serogroup from clear-cut incidents of infection confirmed that results of acceptable reliability could be obtained by either bacteriocine-typing method by the application of the appropriate 'difference' rule. When so interpreted, the cross-streaking method appeared to be slightly the more discriminatory.

The greatest discrimination between strains was obtained by the use of a 'hierarchical' typing system in which the strains were first O serogrouped, and the cross-streaking method of bacteriocine typing was then used to make subdivisions within O serogroups.

The European rabbit flea Spilopsyllus cuniculi (Dale) was introduced into Australia to act as a vector of myxoma virus. It was first released in the semi-arid Mallee region of Victoria in 1970 where epizootics caused by field strains of myxoma virus occur each summer. Introductions of the readily identified Lausanne strain were made annually following the release of the flea. The introductions were successful and the strain persisted for up to 16 weeks despite competition from field strains.

The Lausanne strain is more readily spread by fleas than the Glenfield strain which has been widely used in rabbit control. The ability of the Lausanne strain to persist and its effective transmission compared with the Glenfield strain may be due in part to the more florid symptoms of the disease.

In the Cambridge area, 143 patients infected with Corynebacterium haemolyticum were found during the period May 1967 to December 1974. The pharynx was the commonest site of infection and 100 of the 137 pharyngeal infections were in patients aged between 15 and 25 years. Such patients usually had a sore throat; about half of them also had a maculopapular rash. The organism and the clinical features which we have come to regard as typical of this infection are briefly described.

Water beds in use in this hospital were found to be contaminated with Pseudomonas aeruginosa. The addition of sodium hypochlorite, giving a final concentration of 200 parts/106 available chlorine, was found to be effective in preventing microbial contamination over a 6-month study period.

In a prolonged field trial a 4% chlorhexidine digluconate detergent scrub (HibiscrubR), that had earlier proved to be an effective hand disinfectant, was studied in hospital wards. Finger tips were found to harbour more bacteria than the hand dorsum and the samples collected from them yielded more information on the bacteriological and dermatological effects of hand disinfectants in practice.

In wards with a relatively low hand-washing frequency (less than 20 times in 8 hours) the bacteriological results resembled those obtained by in-use tests with volunteers. In the neonatal unit where the hand washing frequency was remarkably high, even occasionally over 100 times/8 h shift, an increase in the bacterial colony counts of the majority of the staff was recorded both before and after hand washing already after using the preparation for 1 week. Age, occupation and hand-washing frequency all correlated with the bacteriological results. Twenty-seven out of 37 persons complained of side effects such as wounds of finger tips and redness or heavy drying of the skin. Wounds, particularly on finger tips, resulted in the failure of disinfection. An increase in bacterial counts was sometimes noted without any dermatological or subjective changes. Drying of the skin was complained of less often when no increase in skin bacteria occurred.

After the changeover of washing practice to a detergent followed by a rinse with spirit solution containing chlorhexidine and glycerol a decrease was recorded in the bacterial counts. It is concluded that more attention should be paid to long-term testing of hand washing and disinfection methods to ensure optimum final results in practice. It is obvious that the knowledge obtained from short time in-use testing cannot be applied to all conditions of use.

Wild rabbits (Oryctolagus cuniculus) from one study area in England have been used over a period of 11 years to investigate the possible appearance of innate resistance to myxomatosis. Rabbits of 4–6 weeks old were captured alive, retained in the laboratory until at least 4 months old, and then infected with a type of myxoma virus which kills 90–95% of laboratory rabbits. Observations were made of symptoms, mortality rate and survival times.

In the first 4 years of the study (1966–9), mortality rates were not significantly different from those of laboratory rabbits, although survival times of wild rabbits were appreciably longer. In 1970, the mortality rate amongst wild rabbits was 59%, in 1974 it was 17%, and in 1976 it was 20%, thus showing that a considerable degree of inherited resistance to myxomatosis has developed.

The types of myxoma virus most commonly isolated from wild rabbits in Great Britain in recent years have been those which cause 70–95% mortality in laboratory rabbits. Therefore, if the degree of innate resistance demonstrated is widespread in Great Britain, there are serious implications regarding the size of the rabbit population, because myxomatosis has been an important factor in holding rabbit numbers at a relatively low level.

The resistance of Salmonella dublin to eight antibacterial drugs was assessed wider diagnostic laboratory conditions. Two techniques were used consecutively and the differences in the results are described. Strains of S. dublin isolated from either calves, adult cattle or abortion material showed no differences in resistance for either of the techniques, though differences between the two techniques were found.

The effect of ventilation on airborne contamination was studied in a new operating suite containing operating rooms with conventional ventilation (17−20 turnovers/h) and operating rooms with zonal ventilation, where the turnover in the central part of the room was˜80/h. The efficacy of the ventilation was first examined with gas tracer experiments and found satisfactory. Experiments using potassium iodide particles showed the transfer between adjacent rooms in the suite to be less than 10−3% with closed doors and from 1% to 2·5 × 10−2% when the doors were opened once a minute. The transfer between two adjacent operating rooms was calculated to be˜10−4%. There is thus little risk of spread of airborne infection between operating rooms.

Experiments with potassium iodide particles showed that in operating rooms with zonal ventilation the particle concentration in the centre of the room was about one-tenth that in the periphery; in conventionally ventilated operating rooms the concentration was about one-half. With bacteria-carrying particles generated by human activity the concentration in the centre of operating rooms with zonal ventilation was about half that in the periphery both during experimental activity and operations; in conventionally ventilated operating rooms it was about equal in both cases. Bacterial counts at the periphery were found to be lower in rooms with zonal ventilation (˜ 50 c.f.u./m3) than in conventionally ventilated (˜ 70 c.f.u./m3).