Considerable errors arose when the plate count method was used to determine the number of bacteria on dehydrated vegetables. Bacteria probably occurred on the surface of the vegetables only.

Plate counts tended to be greater when suspensions were prepared at higher temperatures over the range 10–40° C. Counts often increased by 20% and sometimes by 50% in the short period allowed in the standard procedure (25 min.), probably owing to multiplication of bacteria. Changes in the volume of suspensions, caused by rehydration of vegetables, led to small errors for which allowance could be made. Larger variations in count arose from sampling errors through differences in the number of bacteria on individual strips and, to a lesser extent, through imperfect distribution of bacteria in suspensions. The relation of plate counts to the actual number of bacteria on the vegetables was uncertain.

However, the error in counting a single sample (— 65% to + 150%) was appreciably smaller than that in counting successive samples from the same factory (about fivefold) and this in turn was less than the variation between different factories (up to a thousandfold). The plate count could therefore be used with some confidence as a general guide to the state of factory hygiene.

The author is grateful for assistance given by Dr M. Stephenson, F.R.S., of the Biochemical Laboratory, Cambridge, and by Dr M. Ingram, Dr H. G. Wager and others of the Low Temperature Research Station, Cambridge.

1. An epidemic of a dysenteroid nature, largely ambulatory, due to B. dysenteriae (Sonne), affecting some 100 nurses without transference to any hospital case in the wards served by this section of the nursing staff, is described.

2. Sonne's bacillus was isolated from sixteen out of forty-two cases examined.

3. The probable cause was infection of food during preparation in the kitchens by a carrier.

4. A case of infection from laboratory cultures is described.

5. Notes are given of investigations upon the colonial appearance, biochemical and agglutinogenic reactions and pathogenicity to rabbits of the organism isolated, and also upon the presence of agglutinins in the blood of infected cases.

6. One case of infection in a rabbit by feeding experiments is described.

When mussels are allowed to function in sea water the main changes occurring in the water are depletion of dissolved oxygen and lowering of pH value. Provided the faeces and pseudo-faeces are not disturbed the increase in the content of organic matter is not appreciable. If the supernatant water is removed and aerated with diffused air the water is re-oxygenated, the pH value is restored to its original level, and the water so treated may be re-used for immersing a fresh batch of mussels. The process of re-use may apparently be continued indefinitely.

Under these conditions a high degree of cleansing is achieved by the mussels, the count of coli-aerogenes bacteria being reduced to a small fraction of the original; counts of bacteria in the water, on the other hand, are subject to large fluctuations. It was considered advisable for this reason to chlorinate the water between each cycle of cleansing in order to immerse the mussels on each occasion in water which itself was reasonably certain to be free from coliform bacteria, potentially including pathogens.

Experience showed that the greatest difficulty involved in the use of chlorine was in removing residual chlorine so that it would not inhibit functioning of the mussels when the water was re-used. After trials of various alternatives it was concluded that the most satisfactory method was to determine by means of small-scale tests the smallest quantity of chlorine (below the break-point) required to give a residual concentration of 0·05–0·10 p.p.m. in the re-used water and then to add the corresponding quantity with precision to the bulk of water by means of a dosing apparatus while the water was being pumped from the mussel tank to the aeration tank. After a period of contact of 1 hr. the water was aerated for a further hour. A series of trials in a semll-scale plant showed that this treatment ensured that residual chlorine in the water being added to the mussels did not exceed 0·05 p.p.m.; as a result the mussels functioned satisfactorily and the degree of cleansing attained was comparable with that attained in the existing mussel-cleansing tanks in which sterilized fresh sea water is used for each cycle of cleansing. Although the concentration of residual chlorine was small the mussels kept the water so clear that this concentration was effectively bactericidal and the bacterial quality of the water was usually comparable with that of good drinking water. Low temperatures retard the metabolic activity of mussels and below 4° C. this is so marked that the degree of cleansing achieved is unsatisfactory. For this reason it is recommended that the temperature of the re-used water should be maintained at 6° C. (43° F.) or above.

Oysters were found to be satisfactorily cleansed by a process of re-use similar to that adopted for mussels, provided the temperature of the water was maintained at 54° F. (12·2° C.) or rather higher.

Small-scale trials showed that artificial sea water, prepared by dissolving in fresh water suitable quantities of the major constituents of natural sea water, could be successfully re-used for cleansing mussels.

Phthisis (pulmonary tuberculosis) is distinguished from nearly all other infectious diseases by its protracted duration and by the prolonged disability which it imposes upon enormous numbers of the total working population. It is further distinguished by the complexity of the influences which are regarded as affecting its spread or capable of controlling its prevalence. It is therefore of the first importance that the relative values of measures for controlling phthisis should be closely studied, and that special attention should be given to those which promise the greatest yield for a given expenditure. In particular it is important to be aware of any which can be set to work without the delay and expense involved in creating a new service. The present paper is intended as a contribution to this study. The facts collected in it and others of a similar kind deserve more extended investigation than it has been possible for me to give them in the intervals of official work. They are put forward here without any illusions as to the inevitable shortcomings of their presentation but with a conviction that from the economic standpoint they are of fundamental importance in the prevention of phthisis.

We studied, for two years, the prevalence of indigenous human enteric viruses in wild oysters gathered each month from the bottom of Mikawa Bay, Aichi Prefecture, Japan. Viruses were detected periodically in 9 out of 54 oyster pools prepared by the acid or polyethylene glycol precipitation method although all these 9 pools met current national bacteriological safety standards. Since most of the serotypes of the enteric viruses detected in the oysters were identical with those of viruses isolated from sick children living in the area, it is suggested that contamination of enteric viruses in the oysters would depend on the prevalence of enteric viral infections in the local inhabitants.

Early detection of highly pathogenic avian influenza (HPAI) in its natural reservoirs is a prerequisite for preventing disease spread to humans. The risk of introduction of H5N1 HPAI was assessed in order to design a risk-based surveillance system in Spain. Areas at highest risk for H5N1 HPAI followed a northeast–southwest direction, with two significant clusters located in the north and the southwest of the country. Most (83%) of the veterinary units (VUs) obtained fewer samples than would have been expected if samples had been collected using a risk-based design. In October 2009, a HPAI outbreak was reported for the first time in a Spanish layer farm located in a VU at high risk for HPAI, but no samples were collected. This risk-based surveillance approach will increase the cost-effectiveness of HPAI surveillance in Spain and can be easily extended to and adopted by other countries and regions throughout the world.

This study was carried out to investigate the effect of desert conditions on the pattern of delayed hypersensitivity to mycobacteria in school children aged 6–10 and 11–18 years. A new range of tuberculins prepared from ultrasonic lysates of living mycobacteria belonging to 12 different species was employed. Three centres were chosen for study, a sea port and two desert towns differing greatly from each other. The results obtained were compared with those of a previous study using the same reagents in Kenya.

As expected both the range of mycobacterial species to which the children reacted, the rate of acquisition of specific hypersensitivity with age and the total percentage of children reacting to individual reagents differed from centre to centre. The harsh desert conditions of Ajdabia produced the least, and the proximity of the people's dwellings to those of their farm animals in Kufra produced the most positive reactors to essentially environmental species. The greatest number of reactors to our Tuberculin were found in Benghazi where the cosmopolitan urban conditions probably lead to a high contact with open cases of tuberculosis. As assessed by skin test reactivity, immunization with BCG in Libya was much less effective than in Kenya. The interpretation of the differences between the results from the different test centres and between those for Libya and Kenya are discussed.

We present two complementary model-based methods for calculating the risk of international spread of the novel coronavirus SARS-CoV-2 from the outbreak epicentre. One model aims to calculate the number of cases that would be exported from an endemic country to disease-free regions by travellers. The second model calculates the probability that an infected traveller will generate at least one secondary autochthonous case in the visited country. Although this paper focuses on the data from China, our methods can be adapted to calculate the risk of importation and subsequent outbreaks. We found an average R0 = 5.31 (ranging from 4.08 to 7.91) and a risk of spreading of 0.75 latent individuals per 1000 travellers. In addition, one infective traveller would be able to generate at least one secondary autochthonous case in the visited country with a probability of 23%.

Past studies exploring risk factors for fluoroquinolone (FQ) resistance in urinary tract infections (UTIs) focused only on UTIs caused by Gram-negative pathogens. The epidemiology of FQ resistance in enterococcal UTIs has not been studied. We conducted a case-control study at two medical centres within the University of Pennsylvania Health System in order to identify risk factors for FQ resistance in enterococcal UTIs. Subjects with positive urine cultures for enterococci and meeting CDC criteria for healthcare-acquired UTI were eligible. Cases were subjects with FQ-resistant enterococcal UTI. Controls were subjects with FQ-susceptible enterococcal UTI and were frequency matched to cases by month of isolation. A total of 136 cases and 139 controls were included from 1 January 2003 to 31 March 2005. Independent risk factors [adjusted OR (95% CI)] for FQ resistance included cardiovascular diseases [2·24 (1·05–4·79), P=0·037], hospitalization within the past 2 weeks [2·08 (1·05–4·11), P=0·035], hospitalization on a medicine service [2·15 (1·08–4·30), P<0·030], recent exposure to β-lactamase inhibitors (BLIs) [14·98 (2·92–76·99), P<0·001], extended spectrum cephalosporins [9·82 (3·37–28·60), P<0·001], FQs [5·36 (2·20–13·05), P<0·001] and clindamycin [13·90 (1·21–10·49), P=0·035]. Use of BLIs, extended spectrum cephalosporins, FQs and clindamycin was associated with FQ resistance in enterococcal uropathogens. Efforts to curb FQ resistance should focus on optimizing use of these agents.

Estimating the lengths-of-stay (LoS) of hospitalised COVID-19 patients is key for predicting the hospital beds’ demand and planning mitigation strategies, as overwhelming the healthcare systems has critical consequences for disease mortality. However, accurately mapping the time-to-event of hospital outcomes, such as the LoS in the intensive care unit (ICU), requires understanding patient trajectories while adjusting for covariates and observation bias, such as incomplete data. Standard methods, such as the Kaplan-Meier estimator, require prior assumptions that are untenable given current knowledge. Using real-time surveillance data from the first weeks of the COVID-19 epidemic in Galicia (Spain), we aimed to model the time-to-event and event probabilities of patients’ hospitalised, without parametric priors and adjusting for individual covariates. We applied a non-parametric mixture cure model and compared its performance in estimating hospital ward (HW)/ICU LoS to the performances of commonly used methods to estimate survival. We showed that the proposed model outperformed standard approaches, providing more accurate ICU and HW LoS estimates. Finally, we applied our model estimates to simulate COVID-19 hospital demand using a Monte Carlo algorithm. We provided evidence that adjusting for sex, generally overlooked in prediction models, together with age is key for accurately forecasting HW and ICU occupancy, as well as discharge or death outcomes.

Six of 12 men wintering at an isolated Antarctic base sequentially developed symptoms and signs of a common cold after 17 weeks of complete isolation. Examination of specimens taken from the men in relation to the outbreak has not revealed a causative agent.

The importance of carrier animals (those in whom virus persists after recovery from disease or acute infection) and their potential role in the spread of disease remain open questions within foot-and-mouth disease epidemiology. Using simple probabilistic models we attempt to quantify the effect of emergency vaccination – and especially the time of application – on the likely number of such animals, using data from challenge experiments on both cattle and sheep to determine the probability of persistence in diseased and subclinically infected animals. We show that the number of persistently infected animals in a group is predominantly determined by the number of animals initially infected on premises – the high variability of which ultimately limits the accuracy of any predictions of carrier numbers based upon transmission models. Furthermore, results suggest that, within a cattle herd, carrier numbers may be increased if challenge occurs shortly after vaccination. We show that the quality of inspection is the principal factor influencing whether or not carrier herds occur and that, by reducing clinical signs, the application of vaccination in regularly checked stock also results in an increase in undetected persistently infected animals. Where clinical detection would be poor regardless of the use of vaccination (i.e. particularly in sheep), vaccination will result in a reduction in the probability of a group containing undetected carriers: otherwise there is a benefit only if vaccination is applied sufficiently far in advance of any challenge. The implications of the results for serosurveillance are discussed, including the requisite test sensitivity and practices for successful implementation.

Clinical manifestations of acute bronchiolitis (AB) vary from minimal disease to severe respiratory failure. The response to respiratory viral infections is possibly influenced by genetic polymorphisms linked to the regulation of the inflammatory response. In the present study, we investigated whether interleukin-8 (IL-8) and interleukin-17 (IL-17) genetic variants are associated with the severity of AB. A group of Brazilian infants hospitalized with AB and a control group (infants with no or mild AB, without hospitalization) were genotyped for four IL-8/IL-17 variations. For replication, we studied an Argentinean population sample of infants with mild and severe AB. IL-8 polymorphism (rs 2227543) and IL-17 (rs2275913) variants showed significant associations with the severity of AB. The effect of the IL-8 variation could be replicated in the Argentinean sample. This finding suggests that IL-8 variations may influence the severity of AB in young infants. Further genetic association studies in low- or middle-income populations are necessary with the aim of expanding knowledge in this area.

The question of non-specific formation of antibodies is of considerable theoretical and practical importance, and is closely related to the problem of “non-specific immunisation” which has attracted attention in therapeutics during recent years.

The Rideal-Walker and Chick-Martin tests depend on end-point methods for comparing bactericides. End-point methods have a number of disadvantages: (1) It is difficult, if not impossible, to estimate end-points accurately. (2) The nature of the test demands a standard time. The results at any standard time will be arbitrary. If the sensitivity of the organisms varies in the two solutions tested, the coefficients obtained will vary with the time chosen as standard. It is impossible to estimate the manner in which the survivor times of the organism are distributed, by end-point methods, and therefore the standard tests in current use do not ascertain whether the result is arbitrary or not. This can only be appreciated if the tests are repeated using different times.

Apart from the difficulties associated with end-points, the coefficients obtained in the present tests are calculated from one concentration of phenol and one concentration of test bactericide. This is also an arbitrary value, for the relative activity of two bactericides will depend on relative values of the concentration exponent, n, for each bactericide; if both phenol and the test bactericide have identical values of n the coefficients will be the same at all concentrations which are compared, but if values of n are different then different coefficients will be obtained for every different concentration compared. As a corollary, unless the value of n for the test bactericide is the same as that of phenol, it is illogical to transfer the phenol coefficient obtained at one concentration to the pure substance, for this procedure implies that the phenol coefficient applies to any concentration of the test bactericide. This is only true when the concentration coefficients of phenol and test bactericide are the same. The standard methods offer no value for n.

All these difficulties can be avoided if the rate of death is followed in both phenol and test bactericide, by viable counts. Two methods of interpreting the results are discussed:

(1) The comparison of reaction rates, calculated by the formula This method is complicated by the occurrence of lag period at the start of the reaction between organism and bactericide. This lag period varies in extent in different experiments (often extending up to 50% of the deaths) and makes the interpretation of the results difficult. The lag period has been shown to be a manifestation of, the distribution of logarithmic survival times (Withell, 1942), and is a function of the standard deviation of the logarithmic survivor times (λ). This fact is taken into account in method (2).

(2) The use of the time required for 50% response as a method of comparing bactericides. This time has been symbolized L.t. 50 and is analogous to the lethal dose for the 50% response (l.d. 50) widely used in biological assay. If a logarithmic time scale is used, the logarithmic survival times are found to be approximately normally distributed and consequently probit-logarithm of time lines are straight and in the case of phenol 0·5 % and para-chlor-meta-cresol 0·05% these lines are parallel. In this case a logarithmic time scale means that the comparative times for all percentage responses are equal. In cases where the probit-logarithm-of-time lines are not parallel this would indicate that the standard is unsuitable for the test, for any methods of assay based on a use of a standard to which the organism gives a different response-time relation from that which they give to the test substance or bactericide, are likely to give arbitrary results.

L.T. 50 has been chosen because of the simplicity of the idea underlying it, and because a similar function, L.D. 50, has been used with success in biological assay work. There is also a solid mathematical backing for the use of L.D. 50 in assays involving biological response.

It is suggested that by means of l.t. 50, phenol and the test bactericide can be compared in the following way:

(a) determine the relative speeds of action of the two solutions at any convenient concentrations;

(b) determine the concentration coefficient (ή) of both phenol and test bactericide by means of comparative l.t. 50 values;

(c) determine the temperature coefficient for each substance by similar methods.

From these observations the relative efficiency of the two bactericides can be calculated at any temperature and concentration. If two sets of figures are obtained, one with a vegetative organism, and the other with a sporing organism, a great deal of information can be summarized. It has been shown that an 0·05% solution of parachlor-meta-cresol is approximately one and a half times as efficient as an 0·5% phenol solution (against a Micrococcus). The comparative figure is about 1·0 when Bact. coli is used.

FROM time to time certain organisms, all closely similar, have been encountered in this laboratory which from their unusual occurrence and unfamiliar behaviour presented some difficulty in their identification. An account of some of them and of the cases from which they were derived is here given, and an attempt is made to correlate the organisms. If the result of the investigation shows that they belong to a single group of pathogenic bacilli, the important fact will be illustrated from the short accounts of the cases that a wide range of clinical manifestations may be met with in association with this group of bacteria.

Serological surveys among representative population samples have proved rare given their reliance on invasive sample collection. We therefore completed the first population-based postal survey of immunity in England and Wales using new oral fluid technology. This paper examines the feasibility of this new methodological approach. Nearly 5500 oral fluid samples were collected, with individual demographic and social data via a questionnaire, from persons under 45 years of age recruited through general practices. Instructions were accurately followed with only 1% of samples returned without risk-factor data. The overall response rate was 40%. Response was independently associated with age, sex and location. Response was highest in children aged 5–14 years, adult females and in rural locations. This approach allowed the successful collection of comprehensive individual risk data, but response rates in adults must be improved if oral fluid surveys are to routinely complement serological surveillance.

In Australia, hepatitis B (HBV) vaccination is recommended for injecting drug users (IDUs), Indigenous adults and prisoners. We compared immunity to HBV in prisoners and the general population obtained from national serosurveys in 2007. Individuals with HBV surface antibody (HBsAb) positive sera were considered immune from past infection [HBV core antibody (HBcAb) positive] or from vaccination (HBcAb negative). Male prisoners aged 18–58 years had a higher HBsAb seroprevalence than the general population (46·4% vs. 39·4%, P = 0·061). Comparison of HBcAb results was possible for males aged 18–29 years. In this group, higher HBsAb seroprevalence was due to past infection (12·9% vs. 3·0%, P < 0·001), rather than vaccine-conferred immunity (35·3% vs. 43·4%, P = 0·097). All prisoner groups, but especially IDUs, those of Indigenous heritage or those with a previous episode of imprisonment had higher levels of immunity from past infection than the general population (19·3%, 33·0%, 17·1%, respectively, vs. 3·0%, P < 0·05). Indigenous prisoners, non-IDUs and first-time entrants had significantly lower levels of vaccine-conferred immunity than the general population (26·4%, 26·2% and 20·7% respectively vs. 43·4%, P < 0·05). Improving prison-based HBV vaccination would prevent transmission in the prison setting and protect vulnerable members of the community who are at high risk of both infection and entering the prison system.

The Antarctic provides unusually simplified conditions for the study of the persistence and exchange of micro-organisms of the upper respiratory tract. The work reported here was done while the author was in the Falkland Islands Dependencies Survey and the United States Antarctic Research Program.

Staph, aureus and Staph, albus persisted in the noses, and a-haemolytic streptococci in the throats of men throughout long periods of isolation and semi-isolation in Antarctica.

On the whole, men kept their own strains (phage types) of Staph, aureus despite living in very close contact with each other.

Persistent carriers of Staph, aureus (90% or more positive swabs per individual) continued to carry this organism for as long as 2 years in Antarctica. Data from men at Wilkes and Hallett IGY Stations indicated that there was a decrease in the intermittent and occasional carrier rates, resulting in a much lower total carrier rate after 12 months Antarctic isolation.

Evidence is presented to suggest that β-haemolytic streptococci had disappeared from throats after 12 months of isolation. It is thought that the absence of upper respiratory infections in these communities is due to absence of the bacterial or viral agents.

There is an urgent need for further work on the carriage of micro-organisms in the present unique epidemiological conditions of the Antarctic, and for better laboratory facilities there.