Milk from 150 local mothers has been assayed for bacteriostatic activity for milk-sensitive and milk-resistant indicator strains of Escherichia coli. Activity is greatest in colostrum which is active directly against all strains of E. coli. One week after delivery of the baby, milk is active against the milk-sensitive strain and becomes active against the milk-resistant strain in the presence of physiological amounts of bicarbonate and iron-binding protein. This activity decreases within 2–4 days on keeping milk unheated at 4 °C but is preserved for at least 4 months and often up to 2 years in milk heated to 56 °C then stored at 4 °C or in milk frozen, unheated, at −28 °C provided it is not repeatedly thawed and frozen. Later lactation milks are usually indistinguishable in activity from 1-week post-partum milk but may be less stable on storage particularly if frozen. Lyophilization in vacuo preserves activity of early-lactation milk for at least 6 months.

Heating milk to above 65 °C causes a progressive loss of activity which can be partially restored by adding bicarbonate and iron-binding protein. Iron abolishes the activity of milk and reduces that of colostrum.

By means of techniques of analyses of survival data developed for cancer trials it is possible to study aspects of the natural history of the infection of schistosomiasis on the intermediate host of transmission, the snail.

The simultaneous study of three response variables is largely based on a model of Lagakos (1976). When using this approach in the schistosomiasis setting it seems inappropriate to assume that one process, the duration of latency, follows an exponential distribution. Thus this stage is modified to follow a normal distribution and the derivatives required to obtain maximum-likelihood estimates and approximate variances of all parameters are provided.

Simple graphical tools for assessing the validity of distributional assumptions in survival data are available from industrial research. The reader's attention is drawn to a paper by Nelson (1972). The relevance and application of these methods to the current problem are described in Section 4.

In the event that the times to death of prepatent and patent snails do not follow exponential distributions as assumed in the primary model, a further modification is introduced to enable either or both to follow Weibull densities.

Lastly it is possible to adapt both the primary model of Section Three and the modified model of Section Five to allow for the inclusion of auxiliary variables or covariates. Again the required derivatives to obtain maximum likelihood estimates and approximate variances are provided.

I wish to thank Sheila Gore, Stuart Pocock and Professor Michael Healy for many useful discussions. Sheila Gore and Professor Peter Armitage provided many recommendations for the improvement of the manuscript for which I am most grateful.

Bacteriostatic activity for milk-sensitive and milk-resistant strains of Escherichia coli is reduced when IgA is removed from milk by precipitation. Lysozyme is not involved in bacteriostasis and can be removed without loss of activity; heavy bentonite absorption however removes some lactoferrin causing partial loss of activity.

The heat-labile antigen eliciting bacteriostatic antibody for E. coli is present in milk-sensitive and milk-resistant strains and in some other Enterobacteriaceae, e.g. salmonella; it cross reacts with the antigen in others, e.g. proteus and enterobacter. The antibody is therefore likely to be present in all human milk as a result of the normal commensal gut flora and with widespread activity.

The incidence of Staphylococcus aureus in the nose, throat and superficial wound infections of 99 office staff, 129 psychiatry staff and 115 surgical staff was studied over a 4-week period with the purpose of assessing the potential risk to hospital personnel of staphylococcal infection. Incidence rates, both average and cumulative, were essentially similar in the three groups but certain differences in the ecology of the staphylococcal phage groups were observed. Surgical staff appeared to have a more labile pattern of carriage. As in other Scandinavian studies throat carriage rates were high. Staphylococcal carriage seems largely to depend on individual characteristics rather than environmental factors.

Topical medicaments used in the treatment and prevention of pressure sores in patients in three hospitals were examined for Pseudomonas aeruginosa and Staphylococcus aureus contamination. Contamination rates were found to vary between hospitals and were affected by differences in the packaging of the product and in the method of application used by the nursing staff.

Indirect haemagglutination (IHA), agglutination and complement fixation tests (CFT) for Bordetella pertussis antibodies were compared on paired sera from 52 suspected cases of whooping cough and single sera from 83 children with no recent history of whooping cough. All three tests detected serotype antibodies 1, 2 and 3, but the IHA test was the most sensitive; in seven cases it was the only test to show a rise in titre. It is recommended, particularly with vaccinated children, that the serological diagnosis of whooping cough should be based upon a rise in titre. There should be a gap of at least 2–4 weeks between serum samples, depending on the age and vaccination state of the child. The CFT appears to detect a different antibody from that detected by the other two tests, and in three cases it was the only test to show a rise in titre.

A virus was isolated from pox-like lesions in camels during an outbreak of camelpox disease which occurred in December 1977 in an area near the Iraqi–Iranian border. It was identified serologically as a virus of the Orthopoxvirus group. The biological properties of the isolate indicated that it was probably identical with strains of camelpox virus isolated from Iran, Egypt, Kenya and the U.S.S.R.

An infusion of E. coli endotoxin (10 μg) into the mammary gland of the cow 16 h before experimental infection with St. agalactiae prevented the establishment of mastitis. A clinical examination of the affected gland did not reveal signs of inflammation, all organisms were eliminated from the milk by 36 h after infection. Mammary glands not pretreated with endotoxin, and injected with the same number of viable streptococci, showed signs of severe inflammation, the milk yield was reduced and the injected pathogen could be isolated from the gland for up to 14 days when sampling was discontinued. The injection of endotoxin alone produced a rapid increase in the cell count of the milk, there were some signs of inflammation and 80% of the cells in the milk were neutrophils. The cell counts in the milk remained above normal for 7–10 days. Untreated control quarters appeared to be unaffected by the injection of E. coli endotoxin into an adjacent quarter, on the other hand the injection of St. agalactiae into the adjacent quarter on the same side of the udder produced a cell response which reached a peak after 2 days and returned to preinoculation levels by the fourth day. No inflammation was observed in these control quarters and no streptococci were isolated from the milk.

Three enrichment broths, selenite F, Muller-Kauffmann tetrathionate and Rappaport, were examined for their efficiency in salmonella isolation. The three media, prepared from single ingredients in the laboratory, were compared with their commercial equivalents. Laboratory-prepared media were more efficient for isolating salmonellas from sewage-polluted natural water samples. A pre-enrichment stage using buffered peptone water was employed throughout the investigation. The size of inoculum from the pre-enrichment medium was relevant to successful salmonella isolation. Inocula studied were 1 ml and one loopful (3 mm diameter loop). The smaller inoculum gave better results with Rappaport, the larger with selenite and tetrathionate. Using the optimal inocula, Rappaport was the most efficient enrichment broth of the three fluid media in this study.

Sera collected from the indigenous population of the Tana River valley during the Tana River Expedition in 1976 were examined for neutralizing antibody to Tanapox virus. Antibody was found in 9·2% of the population in infected areas. This result and the presence of antibody in four children indicated that infection had continued to occur in the area since the 1962 outbreak.

Evidence of the presence of salmonellas in a paediatric ward, a special care baby unit, a maternity unit and a hospital kitchen was obtained by culture of sewer swabs, faeces and food samples. The survey was designed to cause as little administrative interference as possible. The technical aspects of the survey did not strain laboratory facilities. Minimal secondary spread of salmonella infection was experienced.

One thousand, nine hundred and seventy-seven pharmaceutical products used in the home were examined for microbial contamination. Viable micro-organisms were recovered from 14.0% of samples. Medicines used in the home are apparently not exposed to the same opportunities for contamination as those used in hospital.

f2 bacteriophage in the presence of fetal calf serum (at a final concentration of 10%) was exposed to six commonly used disinfectants for times of 10, 20 and 30 sec. At the end of exposure times skim milk neutralized the disinfectant activity and residual virus was assayed using the plaque technique. The 6 disinfectants considered were Javex, sodium hydroxide, ethanol, Wescodyne, One Stroke Ves-Phene and Sonacide. A 0.25% (w/v) solution of sodium hydroxide and 1/50 Javex (1200 parts/106 chlorine) were the most effective of the six disinfectants considered since 105 f2 bacteriophage were inactivated in 30 seconds in each instance. Since a 0.25% (w/v) solution of sodium hydroxide had a pH of 12.5 this made it too caustic to use as a disinfectant in many practical situations. It was concluded therefore that Javex at some dilution less than 1/50 (greater than 1200 parts/106 chlorine) was the most practical of the six disinfectants to use. Ethanol (95%, v/v) inactivated 103 f2 bacteriophage in 30 seconds while 1/20 Wescodyne and undiluted Sonacide inactivated 101 virus particles. Ves-Phene at a dilution of 1/50 was a completely ineffective virucide during the 30 sec exposure. The resistance of f2 bacteriophage to inactivation by these six disinfectants was compared with that of echovirus 11 and coxsackievirus B5. In all instances except exposure to undiluted Sonacide, f2 was comparable in resistance to inactivation and in many cases had greater resistance.

The European rabbit flea was first released in Victoria in August 1969 at Werribee. Releases were made on five different land forms. At one site the first flea was recovered 2 weeks after release. Fleas were recovered between 4 and 6 weeks after release at the other sites. Differences in establishment and spread on the different land forms were due to physically restricted movement of some rabbit populations. By June 1971 80% of rabbits were infested but an occasional young uninfested rabbit was still found in August 1978. Infestation numbers were higher than in the Mallee region especially on pregnant does.

Twenty-seven babies from one deprived housing area in Glasgow were followed-up regularly, for periods varying between 2 months and 11 months (mean 7 months), in a prospective study of the viruses to be found in their stools by electron microscopy. Weekly stool specimens were collected in the home together with a history of the baby's health. Additional stool specimens were obtained, up to a maximum of one per day, during admissions to hospital. Over 500 specimens were obtained at home and another 320 in hospital. A wide variety of viruses (over 200 recognizates) were detected and it has been possible to plot their temporal relation to disease episodes. It became apparent that virus excretion was frequently unaccompanied by evidence of illness and it has not been possible to describe a typical illness syndrome associated with any of the morphological types of virus observed.

The results suggest that, in one area of Glasgow at least, patterns of virus excretion in young babies are complex and will need further elucidation before the need for a vaccine to prevent infantile diarrhoea could be defined.

A bacterial spore test has been developed which enables the efficacy of the sterilizing cycle recommended by the British Pharmaceutical Codex (1973) for bottled fluids to be accurately monitored. During a 14-month period this test detected faults in 3.3% of the sterilizing cycles, representing five distinct episodes of sterilization failure that passed unnoticed by the conventional controls of physical measurements and sterility testing. There were no failures of sterilization as detected by conventional techniques which were not indicated by the spore test.

Twelve grade school and junior high school students had oral exposures to hepatitis B surface antigen (HBsAg) positive saliva via contact with contaminated musical instruments. The 12 exposed students and 18 students who served as age and sex matched controls were tested for the presence of HBsAg and antibody to the hepatitis surface antigen (anti-HBs) at 2 weeks, 8 weeks and 6 months after exposure. All students were negative for HBsAg and anti-HBs on all dates tested and reported no illness during that time suggestive of viral hepatitis. There was no evidence of viral hepatitis, type B transmission from the exposure. The students probably experienced the maximum possible oral exposure from direct or fomites contact, since there was no cleaning of the musical instruments between use by the students and teacher. Based on these results, the risk of transmission of viral hepatitis, type B from oral contact with fomites is unlikely.

A solid-phase micro-enzyme-labelled immunosorbent assay (ELISA) using guinea pig antiserum against purified (140S) inactivated foot-and-mouth disease (FMD) virus has been usedin a sandwich technique to specifically measure 140S virus in the presence of 12S material.

Growth agglutination and growth inhibition tests were established for the diagnosis of Brucella abortus infection. The former involves the agglutination of living organisms while the latter is a bactericidal test. Using mouse, guinea-pig, rabbit and bovine serum it was shown that the growth agglutination test is approximately ten times, and the growth inhibition test one hundred times, more sensitive than the conventional tube agglutination test. It is suggested that these techniques may be of assistance in diagnosing bovine brucellosis in situations in which the tube agglutination test results are suspected of being falsely negative.

The effect of long-term exposure to cigarette smoke on the height and specificity of the secondary humoral immune response to influenza was investigated in a murine model system. It was shown that if mice were pre-immunized with a sub-lethal infection of influenza virus and then exposed to cigarette smoke daily for 36 weeks, they were able to mount a secondary immune response of normal height on subsequent challenge with the homologous virus strain. The response, however, was less specific than that elicited in control mice, with high titres of cross-reacting antibody by haemagglutination-inhibition to the following strain in the same antigenic series. Recall of antibody to the previous strain in the antigenic series was not observed in either control or smoke-exposed animals. These results serve to correct an earlier discrepancy between the murine system and human studies in which the response to influenza infection in mice was depressed by prolonged exposure to cigarette smoke, whereas in man the response of smokers did not differ significantly from that of non-smokers. This apparent discrepancy had been caused by a lack of previous experience of influenza in the mice, which had therefore mounted a primary response, compared with the secondary response observed in the human studies.