- Volume 7, Issue 3, 1974

Four unsaturated fatty acids were allowed to undergo varying degrees of autoxidation before being tested for antibacterial activity against Staphylococcus aureus, Escherichiu coli, Clostridium welchii, and Bacteroides sp. The degree of inhibition was proportional to the degree of unsaturation of the fatty acid and to the duration of its autoxidation. Some of the antibacterial activity of fatty acids described in the past could be accounted for by autoxidation products.

Growth limitation was shown to affect the toxicity of whole organisms of Escherichia coli (strain MRE160) as determined by an LD50 method with the Porton strain of mouse. Glycerol limitation produced the most toxic organisms and limitation of sulphur the least toxic. The findings are discussed as a possible approach to the preparation of less toxic bacterial vaccines.

A defined medium containing mineral salts, glucose and vitamins was developed in which large amounts of enterotoxin were produced by Escherichia coli strain P16 (serotype 09; K9) if the culture was well aerated during incubation for at least 48 hours and the pH was controlled to between 7.4 and 8.1.

After gel filtration of the supernates, the fractions with enterotoxic activity obtained from cultures in the defined medium contained considerably less ultra-violet-light absorbent material than did the corresponding fractions from cultures in “syncase” medium.

Complement-fixing and neutralising antibodies to herpes-simplex virus usually appear in the CSF of patients with herpetic encephalitis during the second third week of illness and may be of diagnostic value. The ratio of serum to CSF antibody titres is, as a rule, in the range of 1:1 to 16:1. The antibodies may persist in the CSF for 6 to 18 months after recovery from the acute stage of the disease; their detection, even in the absence of an obvious history of acute encephalitis, probably implies infection of the central nervous system within the past 18 months. However, we cannot yet be certain that absence of these antibodies from the CSF excludes the diagnosis in patients with the clinical picture of herpes-simplex-virus encephalitis and a rising titre of specific anti-bodies in the serum. The titres are probably not affected by the systemic use of specific anti-herpetic drugs.

In nine patients with oral or genital primary herpes-simplex-virus infection, examined by the indirect immunofluorescence technique, IgG and IgM anti-bodies were both present by the sixth day. Significant titres of IgM persisted for 8 weeks or more. No changes in antibody titre were observed in three patients with clinical recurrences; in only two of five patients with a history of recurrences was IgM detectable, and at low levels. Eight adult patients with herpes-simplex encephalitis (HSE) showed serum IgG and IgM antibody responses similar to those seen in the non-encephalitic primary infections, although in one of the cases the IgM antibody was detected only after sucrose density-gradient fractionation of the serum. Another patient with HSE and a past history of cold sores had a low, unchanging level of IgM antibody in the serum that persisted for about 10 weeks. IgG antibody, but no IgM antibody, was found in the CSF of the patients with HSE.

Intranasal inoculation of Mycoplasma pneumoniae into hamsters caused pneumonia characterised by peribronchial and perivascular cuffing by lymphocytes. Hamsters immunosuppressed by treatment with anti-thymocyte serum developed a much less severe pneumonia. The numbers of organisms isolated from the lungs of immunosuppressed animals were greater than those obtained from the lungs of immunologically normal animals but there was no evidence that extrapulmonary spread occurred. These results indicate the importance of cell-mediated mechanisms in the pathogenesis of this mycoplasma-induced pneumonia. The hamster model may help to establish the role of cell-mediated immunity in resistance to this type of infection.

Eleven hundred and twenty-eight strains of anaerobic diphtheroids from human skin could be divided into two groups according to their colonial morphology on casein-yeast-lactate-glucose agar and their susceptibility to lysis by bacteriophages. Members of group I were sensitive and those of group I1 resistant to the action of phage. Biochemical tests confirmed this division among 200 strains, and permitted a subdivision of group I1 into a proteolytic and a non-proteolytic subgroup-IIA and IIB respectively. A simple scheme, based on colonial morphology, phage susceptibility, the production of indole, nitrate reduction, DNAase, gelatinase and caseinase formation, haemolysis, and the acidification of sucrose, sorbitol, and trehalose, could be used for the classification of these organisms.

Members of group I were most numerous on the skin of the scalp, forehead, and back, and in follicular material from the alae nasi. Group-IIA strains were found most often in the axilla, and group-IIB strains were occasionally present in small numbers at all sites.

Fifty strains of Haemophilus influenzae and 30 strains of H. parainfluenzae were clearly differentiated by the requirement of H. influenzae strains for haemin on a proteose-peptone basal medium and with an inoculum of 1-20 cells. No evidence was obtained for a wide range in haemin requirements; 10 strains of H. influenzae examined in detail required 2-10 pg haemin per ml. The two species were dissimilar also in the amount of NAD required; the strains of H. influenzae grew well in the presence of NAD 0.2-1.0pg per ml, whereas most strains of H.parainfluenzae required 1.0-5.0pg per ml and three strains required NAD 25 pg per ml for optimal colony size. Nitrate was essential for the anaerobic growth of H. parainfluenzae but not of H. influenzae.

The drop-plate method of “simultaneous antagonism” used by others for the detection of bacteriocinogeny in group-A streptococci is unsuitable to differentiate the inhibitory action of true bacteriocines from that of peroxide produced by the test strains. Among 36 group-A streptococcal strains examined, 78 % displayed inhibitory activity on appropriate indicator strains but failed to do so when tested under anaerobic conditions or in the presence of catalase. Most of these strains were shown to give a positive peroxide test on heated blood agar, all of them released hydrogen peroxide during growth in aerated liquid cultures as measured quantitatively by polarography, and none of them lost its inhibitory effect in the presence of trypsin. No strains were encountered that, apart from bacteriophages, produced any catalase-stable, trypsin-sensitive inhibitory substances. For inhibitory effects to be considered to reflect the action of bacteriocines, it is therefore necessary to show that inhibition cannot be ascribed to the toxic effect of liberated peroxide.

Extracellular products of 13 selected strains of staphylococci were separated and detected by the electrophoretic localisation technique. Seven haemolysins were recognised, and were designated α, αl, cationic β, anionic β, δ, δ1 and ∊. These migrated respectively c. 18, 18, 36 and 30 mm towards the cathode and 0, 10, and 14 mm towards the anode. Two lipases migrating 3 and 18 mm towards the anode, one gelatinase migrating 36 mm towards the anode, two nucleases migrating 20 and 32 mm towards the anode and one phosphatase remaining at the origin were also recognised.