A method is presented with which the mechanical cleaning effect of flushing disinfectors can be estimated independently of the thermal disinfecting effect of the hot flushing water. This makes it possible to specify the demands to be placed on the disinfecting effect of flushing with water of 85°C or more.

Bacillus stearothermophilus spores suspended in faeces were used as indicators because of their non-sensitivity to the hot-water temperature. Their elimination by flushing could thus be attributed to the mechanical effect of the water and not to the disinfecting effect of the temperature. A simple bacteriological technique was used, and the elimination factor (EF) was calculated as the ratio of the number of micro-organisms in the contamination before and after flushing. By using flushing water below 50°C for 130 s the EF on a bedpan was about 104–106. The effect of flushing with water of the same temperature for only half that time was somewhat weaker and when the temperature was raised to 85 °C after half the flushing time the effect was somewhat stronger.

It can be presumed that the conventional disinfecting phase with hot (85 °C) water for about 45 s in the commonly used flushing units could be substantially shortened and the costs of their use thereby reduced.

Oral treatment of mice with various doses of neomycin or polymyxin B was performed in order to determine which dose caused substantial suppression of aerobic gram-negative rods. In addition the effect of the various doses on Streptococcus faecalis and on other factors of the colonization resistance (CR) of the digestive tract were studied. It was found that polymyxin B was effective in suppressing sensitive gram-negative bacteria following daily doses of 3·2 mg/ mouse, and that even extremely high daily doses of 9·7 mg/mouse did not affect the CR. Neomycin was effective in suppressing Enterobacteriaceae species following oral daily doses of 5·4 mg/mouse. With this dose, however, the CR was somewhat decreased which was also evidenced by the increased concentration of beta-aspartyiglycine in the faeces and the increased size (weight) of the caecum in these animals. Suppression of Sir. faecalis was seen from doses of 24 mg/mouse on.

The present method of analysis of data from comparative field trials of acuterodenticides was compared with two alternative methods of analysis, using computer simulation techniques. One of the proposed alternative analyses, the use of post-treatment census takes as a percentage of pre-treatment census takes in an analysis of variance, was found to be more accurate, to avoid a theoretical difficulty associated with the present method, and is computationally much simpler.

Laboratory tests indicated that the optimum concentration for pyriminyl in rat baits was between 1% and 3%. In field trials in which 0·5% pyriminyl (the concentration in commercial use) was compared with 2·5% zinc phosphide for the control of rats on farms, the pyriminyl treatments were significantly less effective than the zinc phosphide even when the poisoned baits were left down for 7 days instead of 1 day after prebaiting. Both poisons were as effective in medium oatmeal bait as they were in medium oatmeal containing 5% corn oil and 5% sugar.

The pathways of infection in swine vesicular disease have been studied by (i) an estimation of the amounts of virus required to produce infection by different artificial inoculation procedures; (ii) the distribution and amounts of virus in various tissues of pigs killed at intervals after contact infection; (iii) an investigation of the susceptibility to virus infection of pig tissue explants.

The results show that pigs can be infected by a number of pathways and that the skin, as the most susceptible tissue, is probably the most frequent route of infection.

A total of 475 Salmonella strains belonging to 5 serovars, isolated from a pig farm which had been heavily contaminated with Salmonella for the past 2 years were tested for antibiotic susceptibility and detection of R plasmids. Thirty-three Escherichia coli isolates from the same farm were also examined in a similar way.

Out of 475 strains 348 (73·2%) were resistant to one or more antibiotics such as tetracycline (Tc), streptomycin (Sm), sulfadimethoxine (Su), chloramphenicol (Cm) and kanamycin (Km), and 247 (85·2%) out of 290 strains belonging to 3 serovars examined harboured conjugative R plasmids. There was no change in the pattern of drug resistance during this survey nor any variation in the pattern of resistance of R plasmids, whatever the serovar. The antibiogram pattern Tc Sm Su, mainly S. typhimurium, was common among Salmonella strains. Among the transferred resistance patterns, the thermosensitive R plasmids conferring the Te marker detected in this study were Fi-, and belonged to incompatibility group H1, whereas the R plasmids conferring Sm Su resistances which coexisted in the same host were Fi+, and compatible with the reference R plasmids tested. The la plasmid conferring Cm resistance alone was isolated from S. anatum and the FII plasmid conferring Sm Km resistances was also isolated from S. typhimurium. In contrast, the 33 E. coli strains examined were resistant to three or five antibiotics and most of the resistance markers were located on conjugative R plasmids. la plasmids conferring Cm resistance alone or FIT plasmids conferring Cm or Km markers were common in the E. coli strains. H1 and H2 plasmids conferring multiple resistance markers were also found in them. The genetic properties of R plasmids derived from Salmonella or E. coil strains are compared, and the potential spread of R plasmids between strains of Salmonella andE. coli is discussed.

Lugol's solution destroys the biological activities of Newcastle disease virus (NDV) after 15 s incubation at 37 °C. The rates of inactivation are slower at lower temperatures and at acid pH. At 4 °C and pH 5·8, the functions associated with the virus membrane, (haemolysis (HL), cell fusion and infectivity) are inactivated within 32 min, while haemagglutination (HA) and neuraminidase (N) are resistant to inactivation for serval hours. Adjustment of NDV, Sendai and influenza A virus allantoic harvests to pH 5·8 and subsequent treatment with undiluted Lugol's solution (pH 5·8) for 15 min has a minimal effect on HA but results in complete loss of infectivity. It is suggested that iodination could be a useful method for vaccine production with membrane-bound viruses. It is postulated that the separation and dissociation of the membrane-associated properties of paramyxoviruses from the glycoprotein functions is due to the higher affinity of iodine for the lipids. Iodine could react with the carbon–carbon double bond (C=C) of the unsaturated fatty acids. This could lead to a change in the physical properties of the lipids and membrane immobilization.

A deterministic model to compare various control strategies for parasites having two hosts is presented. When applied to Echinococcus granulosus, Taenia hydatigena and T. ovis, the model shows that maximum progress would be achieved when both the difinitive and the intermediate host are treated simultaneously. This type of model may prove of value in studies on the control of other towhost parasites.

The changes in the titres of immunoconglutinin (IK), conglutinin and heterophile antibodies were measured in calves vaccinated with Br. abortus Strain 19. The IK titres rose rapidly following vaccination but returned to normal within ten weeks.

A survey of the sera of over 300 cattle showed no significant correlation between the Brucella STA titre and of these ‘non-specific’ indicators. It is concluded that they are of little assistance in the serodiagnosis of brucellosis.

Fifteen strains of Escherichia coli which had been collected in previous studies from animals and meat were studied.

They belonged to serotypes considered enterotoxigenic and were examined for the production of the heat-labile and heat-stable enterotoxins. Only one of these strains (O8. Hnt) isolated from a Cheshire produced heat-labile enterotoxin. Another strain (O8.H9) isolated from a cowpat in another part of Cheshire gave results suggesting production of small amounts of the heat-stable enterotoxin. The ecological aspects of these results are discussed.

Campylobacter jejuni was isolated from the stools of 148 patients with symptoms and 57 symptomless subjects, and from a milk sock filter, following an outbreak of enteritis associated with consumption of unpasteurized milk. The incubation period rantged from 2–11 days with a peak at 5 days. There were no secondary cases. The attack rate was around 50% Cases occured in all age groups but were maximal in the 1–10 age group. Recovery from symptoms was complete in the majority in less than 1 week. No long term excretors were indentified. There were no differences between culture positive individuals, with or without symptoms, in age or sex distribution or duration of excretion.

Five quarters of the udders of two lactating cows were infected by intramammary inoculation with Campylabacter coli/jejuni in doses ranging from 2·6 colony-forming units (c.f.u.) to 3·8 × 109 c.f.u. The infected quarters developed clinical mastitis and the campylobacters were reisolated in large numbers from the milk. The milk from the uninfected quarters, and blood and faeces remained free of the organisms. The campylobacters could only be isolated by incubation of culture plates in a microaerobic atmosphere. The results showed that C. coli/jejuni can cause mastitis in the cow and that the bovine udder is a potential source of C. coli/jejuni in raw milk.

This technique for the cultural examination of urine provides, within 24 hours, using a single Petri dish, the colonial appearance of any bacteria present on MacConkey agar and on blood agar, a rough colony count of the bacteria present, their sensitivity to four chemotherapeutic agents, isolated colonies from which further sensitivity tests can be done if necessary and the opportunity to scrutinize contaminating organisms that, even thought present in only small numbers, may be of help in diagnostic problems.

In a study comparing the responses of institutionnalized Down's syndrome (DS) and non-Down's (ND) inmates to enterovirus infections, the frequency of wild enteric viruses and the excreation patterns of oral polio vaccine (OPV) viruses were similar in both groups. Antibody titres developed to poliovirus types 2 nad 3 following vaccination were similar in DS and ND and ND vaccinees, but the responses to type I virus was signifcantly less in DS vaccinees. As judged by the development of poliovirus antibody in non-vaccinees, the spread of virus from OPV-immunized to unimmunized subjects in the institution was not noticeably different in DS and ND subjects.

An unexpected finding was that the excretion patterns of all three serotypes of poliovirus were strikingly similar for each individual to individual. The similarity of excreation occurred despite wide differences within an individual in the titres of neutralizing serum antibodies to the three serotypes. It is suggested that the rate at which a given individual eliminates enteroviruses may be largely determined by factors, the activities of which atre not reflected in serum antibody titres.

Serological typing was used as an epidemiological tool in the investigation of 524 outbreakes of Clostridium perfringens food poisoning in the United Kingdom and 37 outbreaks in other countries.

Five thousand five hundred and fifty-four (77%) of 7245 strains of C. perfringens association 561 outbreaks were typable with the 75 Food Hygiene Laboratory antisera; in 354 (63%) of these outbreaks were typable with the 75 Food Hygiene Laboratory antisera; in 354 (63%) of these outbreaks a specific serotype was established as being responsible for the outbreak.

An assessment is made of the ability of two additional sets of antisera, prepared against 34 American and 34 Japanese strains of C. perfringens, to increase the number of strains which can be typed. The extent of cross-reaction between the three sets of antisera was determined and the results are discussed in relation to the source and history of the type strains.

The increasing use of intensive cytotoxic chemotherapy for patients with solid tumors enhances the risk of opportunistic infection to levels formerly seen only in patients with acute leukaemia, and prevention of infection is a major concern. A relatively simple regimen of isolation, topical antisepsis, and orally administered non-absorbable antibiltics was stuidied in 18 patients. Sixteen of 21 studies were performed using portable laminar ait flow apparatus and five with isolation only. All patients became severly neutropenic but there were no major infections. Microbiological results showed effective decontamination of the skin, which was maintained without recolonization or acquisition of new organisms. The ears, nose and throat were effectively decontaminated only when the regimen was intensified. Colonization with Pseudomonas aeruginosa, a major pathogen in compromised hosts, did not occur. The propective regimen is less expensive than regimens previously desribed, is acceptable to patients, and requires no modification of existing hospital rooms. It merits further evaluation in patients with common cancers who receive intensive cytotoxic drug therapy.

Surveys conducted since 1956 on the antibiotic resistance of the Escherichia coli in faecal specimens from pigs entering Chelmsford Market have revealed that despite the implementation of the Swann Report in 1971 pigs are still an enormous reservior of tetracycline-resistant E. coli with conjugative ability.

Increasingly large amounts of E. coli resistant to streptomycin and sulphonamides were found in specimens examined in recent years unitl in 1979 the amounts present approached those of tetracycline-resistant organisms.

E. coli resistant to chloramphenicol, ampicillin, neomycin, furazolidone or spectinomycin were present, usually in low concentration, in a considerable proportion of the specimens at each yearly examination but the concentration and incidence of these organisms showed no obvious sign of increasing with time. Much of this resistance, except to furazolidone, was of the transferable type.

Until 1979 the incidence of faecal specimens containing trimethoprim-resistant E. coli was very low. It increased significantly in that year, most of the resistance being plasmid-, or possibly transposon-determined.

The result of surveys performed in a Cambridgeshire market in 1978 and 1979, which showed that a high proportion of faecal specimens contained low concentrations of trimethoprim-resistant E. coli, in general resembled those of the corresponding Chelmsford surveys, suggesting that all the Chelmsford surveys may have accurately reflected the position in the national pig herd.

Inoculated orally, 16 Salmonella typhimurium strains belonging to 12 phage types varied greatly in their abilityto kill 1-day-old chickens; variation was noted even between strains of the same phage type. Fourteen strains belonging to 11 food poisoning serotypes other than S. typhimurium were practically non-lethal whenexamined in this manner. All of them were lethal by the intramuscular route but some were more so than others. Twowere more lethal by this route than one of the S. typhimurium strains that was highly lethal when given orally.With age, chickens rapidly became resistant to fatal infection with the food poisoning strains; given orally, a S.typhimurium strain killed 79 % of 1-day-old chickens but only 3 % of 2-day-old chickens. Of 2 specific poultrypathogenic strains, one, of S. gallinarum, was lethal by oral inoculation to chickens of all ages but the other, of S. pullorum, was only lethal to very young ones.

Some salmonella strains, such as those of S. infantis and S. menston, were more efficient at infecting and colonizing the alimentary tract of chickens than were the more virulent S. typhimurium strains, the S. gallinarum and S. pullorum strains and a S. cholerae-suis strain.