Spreading of Salmonellas during Cattle Slaughtering

The spread of salmonellas during the slaughtering of cattle in the Berlin (West) slaughterhouse was investigated. The slaughterline was divided into 12 areas. During the first examination, which lasted eight months, the equipment and implements at each stage of slaughter, and faeces of cattle were tested. Salmonellas were not isolated from any of the 226 samples of faeces whereas 14 isolations (1.8%) were made from the 768 swabs taken from equipment. Most isolates were obtained within the step of opening the abdominal cavity.
In a second survey 61 (4.3%) of 1392 swab samples and 2 (0.75%) of 267 faeces samples were positive. Of the different processing steps, cutting off the hooves and loosening the skin of legs gave the highest recovery of salmonellas. Moderate recoveries were obtained after opening the abdominal cavity. Removal of head, loosening the skin of head, removing the hide and splitting the breastbone and the carcass did not result in the isolation of the organism. Salmonella anatum was the most common isolate. The same serotypes were isolated from both carcasses and equipment.     

The Removal of Salmonellas in Conventional Sewage Treatment Processes

The numbers of salmonellas in raw sewage entering a treatment plant varied hourly and diurnally; their peak concentration preceded the peak influent waste water flow into the plant by about 2 hours. Salmonellas were detected in all raw influent samples collected from 2 sewage works and the mean population level at the daily peak period was 3000 organisms/1. On average. 70–80% of the salmonellas were removed during primary sedimentation when upwards of 74–84% of solids were removed. Biological treatment and secondary sedimentation removed a further 70–100% of the pathogen. Compared with the activated sludge process the trickling filters were less efficient in removing salmonellas and they were adversely affected by increased loading following rainfall. Considering the whole treatment process, the Guildford works with its activated sludge treatment removed an average of 99–83% salmonellas while the Woking works with its trickling filter plant removed an average of 93–04% of the organisms. The large variance in the numbers of salmonellas in the final effluent from the trickling filters suggest that greater emphasis should be placed on the actual quality of the effluent rather than on percentage removal efficiencies.     

Assembly of bacteriophage T7. Dimensions of the bacteriophage and its capsids.

The dimensions of bacteriophage T7 and T7 capsids have been investigated by small-angle x-ray scattering. Phage T7 behaves like a sphere of uniform density with an outer radius of 301 +/- 2 A (excluding the phage tail) and a calculated volume for protein plus nucleic acid of 1.14 +/- 0.05 x 10(-16) ml. The outer radius determined for T7 phage in solution is approximately 30% greater than the radius measured from electron micrographs, which indicates that considerable shrinkage occurs during preparation for electron microscopy. Capsids that have a phagelike envelope and do not contain DNA were obtained from lysates of T7-infected Escherichia coli (capsid II) and by separating the capsid component of T7 phage from the phage DNA by means of temperature shock (capsid IV). In both cases the peak protein density is at a radius of 275 A; the outer radius is 286 +/- 4 A, approximately 5% smaller than the envelope of T7 phage. The thickness of the envelope of capsid II is 22 +/- 4 A, consistent with the thickness of protein estimated to be 23 +/- 5 A in whole T7 phage, as seen on electron micrographs in which the internal DNA is positively stained. The volume in T7 phage available to package DNA is estimated to be 9.2 +/- 0.4 x 10(-17) ml. The packaged DNA adopts a regular packing with 23.6 A interplanar spacing between, DNA strands. The angular width of the 23.6 A reflection shows that the mean DNA-DNA spacing throughout the phage head is 27.5 +/- less than 2.2 A. A T7 precursor capsid (capsid I) expands when pelleted for x-ray scattering in the ultracentrifuge to essentially the same outer dimensions as for capsids II and IV. This expansion of capsid I can be prevented by fixing with glutaraldehyde; fixed capsid I has peak density at a radius of 247 A, 10% less than capsid II or IV.     

Structural aberrations in T-even bacteriophage. IX. Effect of mixed infection on the production of giant bacteriophage.

To date, the production of T-even bacteriophage with giant heads has been achieved in two ways: (i) by use of canavanine-arginine treatment of Escherichia coli B cultures infected by wild-type bacteriophage (Cummings and Bolin, Bacteriol. Rev. 40:314-359, 1976; Cummings et al., Virology 54:245-261, 1973), which give a size distribution of giants that is phage specific (Cummings et al., Virology 54:245-261, 1973); and (ii) by infection with certain missense mutants of T4D gene 23 (Doermann et al., J. Virol. 12:374-385, 1973; ICN-UCLA Symposium on Molecular Biology, p. 243-285, 1973) or temperature-sensitive mutants of gene 24 (Aebi et al., J. Supramol. Struct. 2:253-275, 1974; Biljenga et al., J. Mol. Biol. 103:469-498, 1976). We now report the effect of mixed infection with several mutants of T4D on both the production and the size of giant bacteriophage. We found that gene 24 mutant is a critical partner for the production of giants. Infection using T4.24 mutants together with either T4.23 mutants, T4B+ or T6+ led to the formation of giants with heads 10- to 14-fold longer than normal-length heads. Infection with amber 24-bypass 24 double mutants of T4D led to the production of giants when gene 23 mutant was used to co-infect. Addition of canavanine to the co-infected cultures could alter the size distribution of giants, depending on which phage were used to coinfect. Gene 22 mutants had a modifying effect on these results. In the absence of canavanine co-infection with gene 22 mutants prevented the production of giants, and in the presence of canavanine giants of 1.5 to 5 head lengths were found. We have interpreted these results to mean that critical concentrations of gene products 22, 23, and 24 interact to control head length in T-even bacteriophage.     

Survival of Salmonellas and Ascaris Suum Eggs in a Thermophilic Biogas Plant

In a continuous biogas plant, receiving manure from 200 dairy cows and 400 calves and young stock, survival of salmonellas and Ascaris suum eggs was studied. The bacteria and parasite eggs were kept in filter sacs in the manure that had a temperature of 55°C. No viable salmonellas or Ascaris suum eggs could be found after 24h in the digester. Survival of salmonellas and Ascaris suum eggs was also studied in the manure pit where the manure was stored after digestion. The temperature in the manure pit varied between 22–27°C. Salmonellas survived 35 but not 42 days. On day 56, when the experiments had to be stopped, 60% of the Ascaris eggs were viable.     

Thymineless bacteriophage induction in Staphylococcus aureus. I. High-frequency transduction with lysates containing a bacteriophage related to bacteriophage phi 11.

A thymine-requiring mutant of Staphylococcus aureus, strain 8325 (PI258)thy, undergoes prophage induction and lysis after thymine starvation. Four different phages were isolated from the lysate in low titers, among which was a phage designated phi 14, which differs from phage phi 11 in its immunity locus. The thymineless induced lysates of strain 8325(PI258)thy transduce the penicillinase plasmid at high frequency (10(-1), whereas transduction of chromosomal markers is inefficient. A plasmic-cured derivative of strain 8325(PI258)thy is also lysed by thymine starvation and be used for high-frequency transduction of other plasmids. Reconstitution of a strain of S. aureus that responds to thymine starvation was only partially successful, but this system can effectively be used to transduce plasmids or plasmid derivatives.     

Transduction of bacteriophage lambda by bacteriophage T1.

When bacteriophage T1 was grown on bacteriophage lambda-lysogenic cells, phenotypically mixed particles were formed which had the serum sensitivity, host range, and density of T1 but which gave rise to lambda phage. T1 packaged lambda genomes more efficiently both when the length of the prophage was less than that of wild-type lambda and when the host cell was polylysogenic. Expression of the red genes of lambda or the recE system of Escherichia coli during T1 growth enhanced pickup of lambda by T1, whereas packaging was reduced in recB cells. If donors were singly lysogenic, the expression of transduced lambda genomes as a PFU required lambda-specified excisive recombination, whereas lambda genomes transduced from polylysogens required only lambda- or E. coli-specified general recombination to give a productive infection.