The occurrence of resistance to gentamicin in strains of Staphylococcus aureus with different phage patterns in two hospitals is described. The data suggest transfer of gentamicin resistance between different strains. In the strains investigated the determinant for resistance to gentamicin (parallel resistance to kanamycin and tobramycin) is located on the chromosome. The transfer of this resistance determinant in a mixed culture of donor and recipient cells in vitro is mediated by transduction because it is dependent upon lysogenicity of the donor for a serogroup-B phage and because it can be inhibited by γ-globulin. The transfer is always associated with lysogenization of the recipient cells by this phage.

A search for nasopharyngeal carriers of Streptococcus pneumoniae was conducted in 573 children hospitalized in Durban, South Africa. Study subjects were divided into two groups, comprising 305 new admissions and 268 patients who had been hospitalized for more than 24 h. Of the 573 children 178(31%) yielded pneumococci on nasopharyngeal culture; 99 (32%) and 79 (29%) children in the new admission and in-patient categories respectively. Twenty-one (12%) pneumococci were resistant to penicillin, including 11 strains that were resistant to more than one antibiotic. Resistant pneumoeoeei belonged exclusively to serotypes 6 and 19 (Danish nomenclature), which were also the commonest serotypes among penicillin-sensitive strains. Factors that correlated with carriage of penicillin-resistant Pneumococci were hospitalization for more than 24 h, young age and recent exposure to beta-lactam antibiotics.

Infants' stools were examined for the presence of Clostridium difficile and its cytotoxin in a study performed over a one-year period on a special care baby unit. Overall, 21% of infants were colonized, but the organism was only recovered in a seven-month period during which its weekly prevalence in the group varied from zero to 44%, with a distinct clustering of colonized infants being observed. Tests for the presence of cytotoxin in the stools and in supernatants of broth that had been inoculated with each isolate were negative. The factors predisposing to colonization were a prolonged stay in the unit, low birth weight, younger gestational age and being nursed in an incubator. The organism was recovered only once from an environmental screen.

An antibiogram, used in conjunction with toxin production, was helpful in distinguishing these isolates from a collection obtained from other units in the hospital. We conclude that Cl. difficile was acquired by nosocomial spread although we did not establish the precise mechanism involved.

The detection of para-cresol by gas–liquid chromatography was found to be specific but insufficiently sensitive as a screening test for the organism's presence in the stools. It could only be demonstrated in infants whose birth-weights were less than 2500 g, and no association was observed between the type of feed and para-cresol presence in stools.

Neomycin and polymyxin B, used during selective decontamination of the gastrointestinal tract, were studied for their effect on the human faecal flora in vitro. The selective effect was found to be associated with a relative insusceptibility of the obligate anaerobic flora as compared with the facultatively anaerobic Gram-negative rods (Escherichia coli). Both neomycin and polymyxin B were bound by human faeces, in contrast to ampicillin. The results may explain the selective effect of neomycin and polymyxin B on the human flora in vivo.

Solid media were compared for their ability to recover salmonellae from seagull faecal material after pro-enrichment in buffered peptone water and enrichment in Rappaport's broth. Of the 847 specimens examined 96 were found to be positive for salmonellae. Use of Brilliant Green agar containing sulphamandelate supplement resulted in the detection of salmonellae from each of the 96 samples found to be positive and was the most efficient medium tested. Brilliant Green agar lacking the supplement was the least effective medium, salmonellae being isolated from only 80 samples using this medium.

All of the media tested were shown to support the growth of a wide range of salmonella serotypes, although Salmonella typhi and S. dublin did not form colonies on those media which contained Brilliant Green. Hynes' modification of deoxycholate citrate agar was shown to be considerably less inhibitory to salmonellae after ageing for four days. Ageing of other media had no significant affect on their ability to support the growth of salmonellae.

Stability of aminoglycoside resistance has been investigated in 20 strains of Staphylococcus aureus resistant to gentamicin (16 strains were also resistant to methicillin). In view of previous reports that incubation at elevated temperatures can hasten the loss of unstable antibiotic resistance, we passaged strains daily in a liquid medium for 24 days at 43 °C. The nine strains which were resistant to neomycin kept their aminoglycoside resistance virtually intact, whereas most of the other 11 strains (sensitive to neomycin) lost almost all their resistance to gentamicin and kanamycin after 5 days. It thus appears that the stability of aminoglycoside resistances in Staph. aureus is closely linked to the resistance of the strains to neomycin. This finding has important possible consequences in terms of the advisability of the clinical usage of preparations containing neomycin or framycetin for topical application and bowel sterilization.

The Rappaport–Vassiliadis enrichment medium (RV medium)in 10 ml quantities (RV/43 °C, 10 ml) inoculated with 0·1 ml of pre-enrichment medium (P medium) was found more efficient in the isolation of salmonellae from 409 pre-enriched samples (mainly meat products), than the original Rappaport medium incubated at 43 °C (R/43 °C) and the RV medium in 5 ml quantities (RV/43 °C, 5 ml) inoculated with 0·01 ml of P medium (P < 0·001, in both instances). Therefore, the inoculum from pre-enriched foods should not be less than 0·l ml in 10 ml of RV medium.

The RV/43°, 10 ml was also better (P < 0·01) in detecting samples containing salmonellas than the original Rappaport medium incubated at 37 °C (R/37 °C, 10 ml) and the modification R25 of R medium incubated at 37 °C. The R25 modification was used in 10 ml quantities (R25/37 °C, 10 ml) inoculated with 0·1 ml of P medium and in 5 ml quantities (R25/37°, 5 ml) inoculated with 0·01 ml of P medium. The last two R25 procedures were of the same efficiency in isolating salmonellas from meat products.

The co-transfer of plasmid-borne genes governing resistance to gentamicin, tetracycline, erythromycin and chloramphenicol has been demonstrated on human and mouse skin. Two different gentamicin resistance plasmids have been studied in detail; both appear to have the ability to mobilize in vivo otherwise non-transferable resistance plasmids from coagulase-negative to coagulase-positive staphylococci. This emphasises the role of the skin in maintaining a pool of resistance genes available to pathogenic staphylococci.

An epidemic caused by Serratia marcescens that involved 26 infants admitted to the Neonatal Intensive Care Unit (NICU) and 82 infants admitted to the Nursery of the 2nd Medical School of Naples is reported. Two different biotypes of S. marcescens with two completely different epidemiological patterns were identified. The prevalent biotype (A8b trigonelline –) was isolated in the delivery room, in the operating room, in the Nursery and in the NICU from items, healthy infant excreters and affected infants; the second biotype (A3a) was isolated only in the NICU from staff, two healthy infant excreters and two affected infants. Colonization of the throat and the gastrointestinal tract was frequent. Infected and colonized infants were the most important reservoir for serratia in the Nursery and in the NICU particularly for the type strain A3a. A mucus aspiration apparatus contaminated in the delivery room and the contamination of several instruments and items probably had a major role in the initiation and maintenance of the spread of the A8b strain. Mass contamination of the nursery has been related to overcrowding and a lack of the control measures; the transfer of high-risk colonized infants caused spread in the NICU.

In the NICU the attack rate was 26%; 69% of infants became ill; the case fatality ratio was 19%. Epidemiological investigation of the infants at risk showed some factors predisposing to infection with serratia. The hygienic measures failed to control the spread of serratia and it was necessary to refuse new admissions to pregnant women in order to decontaminate and re-organize the wards.

A Salmonella agona strain has caused a hospital outbreak of gastroenteritis in a pediatric unit in Rio de Janeiro. It bears two plasmids, a small (6·5 MDa molecular weight) plasmid coding for type B colicin production and a larger one (36 MDa molecular weight) determining resistance to ampicillin, gentamicin, kanamycin and trimethoprim-sulphamethoxazole. The R-plasmid, but not the Col-plasmid, is self-transferable to a Escherichia coli recipient strain. Curing for the R-plasmid was achieved by treatment with 0·05 % SDS followed by incubation at 44°C. It has not been possible to cure the S. agona strain for its Col-plasmid.

Erythema infectiosum (EI) or fifth disease is a mild, acute exanthematous disease, occurring mainly among children, for which a causative virus has long been sought. In May 1983 an outbreak of exanthematous illness was reported in a primary school in North London. Children attending the school were investigated by questionnaire and 162 (43·9%) reported an illness with the features of EI. In each of 36 cases investigated virologically the illness was associated with parvovirus infection. Moreoever, pre-existing antibody to parvovirus was correlated with protection from EI in 16 of 17 close family contacts of cases. We propose therefore that EI is the common manifestation of infection with the human parvovirus.

One hundred and eighteen herpes simplex virus isolates were typed in a diagnostic virology laboratory using their standard procedure by pock size on the chorioallantoic membranes (CAMs) of fertile hen's eggs. Forty-three were typed as type 1 and 75 as type 2. The isolates were then sent to a research laboratory in which they were typed blind, with or without subsequent passage in tissue culture, by neutralization with type-specific antisera. Discrepant results were found with only two isolates. The isolates were then typed by the more time-consuming but unambiguous method of restriction endonuclease analysis of their DNAs. Typing by this method confirmed the typing by neutralization and established that typing by pock size on CAMs was correct in about 98% of cases.

The Kermack & McKendrick theory of epidemics has been applied to data on deaths from influenza and influenzal pneumonia in Greater London in the years 1950–78. As a whole the theory gives a good description of the data, and the estimated values of the parameters can be plausibly related to the natural history of the disease. However, the possibility exists that the agreement is merely empirical, and field studies would be required to confirm its validity.

Between February and March 1981 an epidemic of hepatitis occurred in Kolhapur City, Maharashtra State, India. Approximately 1200 cases of jaundice were reported; more than 300 patients were hospitalized and three died. The epidemiological investigations showed a distinct concentration of cases in municipal ward E of the city. Investigations of the ward E water supply system disclosed gross contamination of raw water with sewage at source. The serological studies revealed that the aetiological agent responsible for this epidemic was neither hepatitis A virus nor hepatitis B virus but was likely to have been due to a non-A, non-B hepatitis virus.

Four groups of pregnant sows were inoculated with type O1 foot and mouth disease (FMD) oil emulsion vaccine at various times before farrowing and samples of the sow's serum, colostrum and milk, and piglet's serum, collected during the first week after farrowing, were analysed for FMD virus neutralizing activity.

No FMD neutralizing antibodies were detectable in the piglets serum at birth but they were present 1·5 h after suckling and peak titres were reached 1–3 days later. There was no significant difference between the antibody titres of colostrum samples collected from different teats at farrowing. However, similar samples collected 3 days later showed significant (P < 0·005) fore to hind variation. The principal FMD virus neutralizing antibody class present in the sow's serum at farrowing and in their 3-day-old piglets was governed by the inoculation schedule employed. When the last vaccinations were given ≃ 30 days before farrowing (dbf) the predominant FMD virus neutralizing class was IgG. However, when the sows were vaccinated only ≃ 12 dbf the predominant class was IgM. A significant correlation was observed between the sow's serum titres and colostrum titres at farrowing (r = 0·90), and also between sows colostrum titres at farrowing and their 3-day-old piglets serum titres (r = 0·99).

Small rodent (vole) sera were collected from three different locations in Norway. One of these was within the distribution area for Ixodes ricinus, and a tick-borne encephalitis (TBE) virus strain had been isolated from ticks collected there (Traavik & Mehl, 1977). The two other locations were outside the I. ricinus area, one in southern Norway, the other at nearly 70° N. The sera were tested for TBE antibodies by hemagglutination inhibition (HI), hemolysis-in-gel (HIG) and complement fixation (CFT). All sera were also tested for HI antibodies to Uukuniemi (UUK) virus, and some positive TBE HI reactions were verified by separation of immunoglobulins and serum lipoproteins in NaBr gradients.

Animals containing TBE virus antibodies reacting in all three serological tests and animals with UUK HI antibodies were detected only from the location within the I. ricinus area. From the two locations outside the I. ricinus area we found animals which had antibodies reacting with TBE virus in HI and HIG, but not in CFT. Antibodies to UUK were not detected. The results indicate that flavivirus(es) related to, but not identical with TBE viruses are transmitted by other vectors than I. ricinus in parts of Norway.

Nephropathia epidemica (NE) antigen was detected by IFAT (indirect fluorescent antibody technique) in the lungs of 14 of 97 bank voles (Clethrionomys glareolus) collected in three endemic areas. The distribution of antigen positive voles within an endemic location was scattered. Antibodies to Korean hemorrhagic fever (KHF) virus antigens were detected by IFAT in 12 of 14 NE antigen positive bank voles and in 15 of 83 that were antigen negative. NE antigen positive voles exhibited higher antibody titres. Antibodies to KHF were demonstrated in sera from C. rutilus and C. rufocanus collected more than 200 km north of the distribution area for C. glareolus. It appears likely that these vole species can serve as virus vectors for NE cases occurring north of the bank vole area. NE antibodies cross-reacting with KHF virus seem to diminish with time after infection in some NE patients, while for others such cross-reacting antibodies were detected up to 12 years after the disease. Antibodies to KHF were detected in eight of 106 healthy forestry workers with no clinical history of NE. No serological cross-reactions were detected between NE/KHF antigens and representative Bunyaviridae present in Norway. NE/KHF-like viruses appear widespread in Norway, both within and outside of the distribution area of the bank vole.

To determine the pathogenic potential of the vesiculovirus Piry for domestic animals, two ponies, two steers, three sheep, three goats and three pigs were inoculated intradermally in the tongue or, in the case of the pigs, in the snout, heel and coronary band. Inoculated animals were housed in one room and allowed to mingle freely with an equal number of uninoculated contact animals of each species. Clinical signs of infection, consisting of elevated temperature and ulcers at the inoculation sites, were only observed in the ponies, but all inoculated animals developed specific antibody following inoculation. In addition, one of the contact sheep had neutralizing antibody to Piry at 7 and 29 days post inoculation suggesting a contact infection. Virus was not demonstrated in tissues, other than tongue, of any animal.

The failure of Piry virus to produce lesions in steers, sheep, goats and pigs and only limited ulcerations in ponies suggests that this virus is not similar pathogenically to New Jersey and Indiana strains of vesiculoviruses which produce classical vesicular stomatitis.

Lethal infections were produced by inoculation into suckling mice and hamsters, adult hamsters and embryonating chicken eggs. Further, lethal infections followed contact of adult female hamsters with their inoculated litters.

A preparation of infectious human rotavirus, isolated from faeces and resuspended in wastewater effluent, was shown to be inactivated by chlorine, chlorine dioxide, ozone and peracetic acid. Infectivity was assayed in MA 104 cells by the detection of cell-associated viral antigen by immunofluorescence. The inactivation curves were similar to those reported for other enteric viruses. Human rotavirus was at least as resistant as poliovirus, coxsackievirus, echovirus and f2 coliphage and was strikingly less sensitive to inactivation than the simian rotavirus, SA11. The latter was generally the most sensitive of the six tested viruses yet is often taken as being representative of the human rotaviruses.