- Volume 14, Issue 3, 1981

An unusual intracellular circular or oval structure was discovered during a morphological study of Bacteroides fragilis by electronmicroscopy. The structure is complex, composed of multiple concentric layers surrounding a central region. The dimensions and profile are consistent in all the sections observed. The sections illustrated may represent various stages in the morphogenesis of the complete structure.

The physicochemical properties, stability and localisation of lipase from the anthropophilic dermatophyte Epidermophyton floccosum have been investigated. The lipase was best secreted by older cultures at an optimum pH of 6·5–7 in the temperature range 40–45°C. Neither the skin-surface lipids nor the body temperature of man significantly affected the activity of the lipase.

Trace element and phosphate requirements for the synthesis of vascular-permeability factor (PF) by Vibrio cholerae strains B1307 and VC12 were investigated. While magnesium appeared to be indispensable for strain VC12, small amounts of PF were synthesised by strain B1307 in the presence of iron, zinc and manganese. However, even in the latter strain, maximum synthesis was recorded only in magnesium-containing media. Phosphates in the range 0·75–6·00mm controlled the synthesis of PF by both strains.

H-specific agglutinating sera to Pseudomonas aeruginosa were prepared by immunisation with partially purified flagella. The results of agglutination and immobilisation tests with rabbit sera prepared against the flagella of six H-type strains showed that the sera had high titres and were H specific.

Cross-absorption tests revealed that one strain (H-3) possessed a distinct antigen not present in any of the others. Two groups of strains (H-1, H-2 and H-5; H-4 and H-6) each possessed a distinct major antigen. Members of these two groups could be distinguished by their minor antigens.

Strains of Pseudomonas aeruginosa from hospitals were typed by O and H serology and bacteriophage typing. The H sera were prepared against purified flagella of six type strains.

The most common O serogroups were O6, Ol1, O16 and O10, and together these groups represented more than half of the total number of strains. O subgrouping proved useful for the further division of groups 02 and 06.

Percentage H typability was high, and many H patterns were found. Comparison of H typing and phage typing as a means of making subdivisions within O groups showed that, although the general discriminatory power of the two methods was similar, H typing performed better than phage-typing in the more common O serogroups.

The skin flora of 20 normal subjects was sampled from 7-cm2 sites on the volar forearm, forehead and ball of the foot. Interactions between all aerobic and anaerobic strains isolated from the same site were examined by a deferred-antagonism technique. Seventeen subjects possessed inhibitory strains on at least one skin site. Of the Micrococcaceae tested, 20·6% were inhibitory. Of the aerobic diphtheroids, more strains were sensitive (19·2%) than inhibitory (5·1%). Inhibitory Micrococcaceae and aerobic diphtheroids revealed intergeneric and intrageneric inhibition. Antagonistic propionibacteria were found (7·4%) but no sensitive strains. Several Micrococcaceae were specifically antagonistic towards only one strain isolated from the same skin site; no sensitive strains from other skin sites or other subjects were found. Quantitative sampling showed that only 17·5% of the inhibitory strains clearly dominated their skin sites numerically.

The factors influencing the incorporation of 3H-thymidine (3H-Tdr) in the DNA of Mycobacterium leprae within macrophages derived from human blood have been evaluated. Fifty strains of M. leprae derived from skin nodules of patients with lepromatous leprosy were studied for their ability to incorporate 3H-Tdr. Control macrophages of the same donor maintained alone, or with autoclaved M. leprae, showed low levels of baseline 3H-Tdr incorporation. During a 15-day period of pulsing, 27 of the M. leprae strains incorporated 3H-Tdr at levels of 216–2834% of the incorporation by control cultures. Significant incorporation was observable by the second week of culture and cumulative increases occurred by the third week. A 24-h pulse with 3H-Tdr was inadequate for a detectable increase. A minimal duration of 4–5 days of continuous pulsing was required to obtain a significant increase in the incorporation of 3H-Tdr. Of the 50 M. leprae strains, 23 (46%) failed to incorporate the radiolabel. This failure was apparently not related to differences in the disease status of patients, to the transport conditions for the biopsies, to morphological indices of the extracted M. leprae or to the origin of the host macrophages.

An outbreak of hospital-acquired klebsiella infection was investigated by means of six different typing schemes. Interpretation of the information generated by these schemes proved difficult and allowed only tentative conclusions to be reached concerning the origin of some strains. Consequently, the results were subjected to computer analysis by means of a numerical taxonomic programme adapted for the purpose. A dendrogram was constructed giving the percentage similarity between strains. It established the source of four atypical strains and showed that three of them were derived from the original clone. This form of numerical epidemiological analysis could have useful applications in the investigation of hospital-acquired infection.

Separate groups of mice challenged intravenously with either the blastospore or hyphal forms of the same strain of Candida albicans were examined for comparative mortality rates, organ localisation, and tissue and cellular response to the organisms. Blastospores were more rapidly and consistently fatal to mice than the hyphae. Relatively more hyphal elements than blastospores were initially localised in the lungs but more blastospores than hyphal elements were trapped in the liver. The cells of both forms were more effectively killed in the lungs than in other organs. Blastospores initially found in the kidneys increased rapidly in numbers, but hyphal inocula either grew slowly in the kidneys or were eliminated. After mice were challenged with either hyphae or blastospores the initial inflammatory response in the lungs and liver was predominantly of polymorphonuclear leukocytes, but macrophages were the first inflammatory cells to be seen in kidney sections. Peripheral blood counts showed a leukocytosis in mice of both groups although only blastospores resulted in increased numbers of circulating atypical lymphocytes. The results indicated that lungs may play a more important role than ether reticuloendothelial organs in innate resistance to vascular invasion by either of the morphological forms of C. albicans, and macrophages may be crucial to host resistance to renal invasion by this fungus.

The influence of haemolysin production on virulence was studied in an experimental mouse model. Urinary strains of Escherichia coli can be divided into three virulence groups by determining their kinetics in the mouse kidney after intravenous injection. Virulent strains of groups II and III were more often haemolytic than avirulent group-I strains. Haemolytic virulent strains often caused haemo-globinuria in the mice, and killed the mice more rapidly than did non-haemolytic virulent strains. No relationship was found between α-haemolytic activity and virulence in wild-type haemolytic strains. When haemolysin production was reduced or eliminated by treatment with actinomycin-D or rifampicin, six out of seven group-II strains tested gave the same results as avirulent group-I strains. However, the kinetics in the mouse kidney of four haemolytic group-III strains tested was not changed after reduction or elimination of haemolysin production; only a small decrease in toxicity was observed. It is concluded that haemolysin production by E. coli is a decisive virulence factor in most of the mouse-nephropathogenic group-II strains, but not in the virulent group-III strains.

Responses of peripheral lymphocytes from the blood of 20 healthy volunteers were determined in vitro by measurement of tritiated thymidine uptake in the presence of six different antigens prepared from Candida albicans. Crude antigens (disintegrated cells, culture filtrate) produced greater lymphoblast reactivity than purified preparations (cytoplasmic proteins, cell-wall mannan).

Reactions to soluble mannan were uncommon but the number of subjects who responded to them increased from one to 14 when the material was rendered particulate by adsorption on to latex particles. Lymphocyte responses were also elicited by intact, heat-killed yeast cells.