Pseudomonas aeruginosa extracellular toxicity in infant mice and the protective effect of antitoxin A.

The toxin A-content of crude extracellular preparations from Pseudomonas aeruginosa has been measured by ELISA. Using infant mice as test animal, the toxicity of these preparations was evaluated. The LD 50 in infant mice was determined at 80 ng of purified toxin A in saline. With ten microliters of rabbit antitoxin A serum given together with purified toxin, the LD 50 increased to 2,500 ng. Generally there was no correlation between the LD 50 of the extracellular preparations, their quantity of toxin A as measured by ELISA, and the protective effect of antitoxin A.

Treatment of large congenital naevi. A review and report of six cases.

To minimize the significant risk of early malignancy, and to obtain acceptable cosmetic results we have treated five infants with large congenital naevi by full-thickness resection of the thickest part and superficial excision of the remaining parts of the naevus. The treatment was followed by rapid healing with little pigmented skin and minimal scarring. One patient treated at the age of six years showed a less favourable cosmetic result. Our experience confirms that the major part of the potentially malignant tissue can be removed and a greatly improved appearance achieved by early surgery. Additional surgery is usually necessary and should be completed before school age to prevent permanent psychological and social effects. Large congenital naevi are rare and difficult to treat. Their treatment should be centralised to regional hospitals that serve large populations.

Exotoxin A from various Pseudomonas aeruginosa cultures: in vitro activity measured by enzyme-linked immunosorbent assay (ELISA).

An enzyme-linked immunosorbent assay (ELISA) for the detection of Pseudomonas aeruginosa exotoxin A (toxin A) was developed. The level of toxin A produced by fresh P. aeruginosa isolates was compared to the level of toxin A produced by twelve-months-old subcultures derived from the same strains. Results obtained with the ELISA showed that toxin A was produced in similar amounts both by the fresh isolates and the subcultures. The production of toxin A seems to represent a stable property of the assayed P. aeruginosa strains. This is in contrast to other exoproducts from the same strains, such as extracellular proteinases. Some proteinases were produced at very different levels when freshly isolated P. aeruginosa cultures were compared with their twelve-months-old counterparts, confirming earlier reports in this respect.

[Treatment of large congenital pigmented nevi]. / Behandling av store medfødte pigmentnaevi.

Large congenital nevi present a difficult therapeutic problem, since the surgeon must seek to achieve two objectives: To minimize the risk of malignancy; To obtain an acceptable cosmetic result. The first objective calls for early and radical excision of all pigmented areas; this may be impossible because of the operative risk, and the risk of leaving the patient with a deformity or disfiguring scars. The cosmetic indication may justify less aggressive surgery. Relatively new experience indicates that removal of the superficial layers of the nevus shortly after birth is followed by healing with non-pigmented or much less pigmented skin. By combining the removal of the superficial layers of skin with full-thickness resections and reconstructive plastic surgery, it is possible in most cases to achieve a favourable cosmetic result and, at the same time, reduce risk of early malignancy. Wherever possible, the surgical treatment should be completed before the age of five or six years in order to prevent long-lasting psychologic and social effects of the nevus deformity.

Observations on Pseudomonas aeruginosa proteolytic and toxic activity in experimentally infected rats.

To bypass natural resistance against Pseudomonas aeruginosa infection, a granuloma pouch model to be experimentally infected was established in rats. This experimental model also permitted easy collection of wound exudate. In general, the animals either died or became very ill and were consequently sacrificed within the first 12 days, or they (6 of 16) survived in good condition after 20 days. The virulence of recently isolated strains compared to twelve-months old subcultures of the same strains showed no major differences in clinical pattern. In the first seven days following the start of the infection, all animals presented a fall of elastase activity in the wound exudate. Toxin A was present in the exudate, sometimes in relatively high levels, but there was no correlation between toxin level and the clinical development. As a rule, spontaneous rupture of the granuloma pouch, apparently unrelated to the concentrations of either elastase or toxin A in the exudate, was beneficial to survival. In the present experimental infectious context, neither P. aeruginosa elastase nor toxin A seemed to play any isolated lethal nor pathogenetic role.

Variation of endopeptidase activities in cultures of Pseudomonas aeruginosa strains.

Pseudomonas aeruginosa strains have been assayed for endopeptidase activities in cultures of recently isolated variants, as well as in cultures from two-months-old variants derived from the same strains. Using chromogenic peptides, information was gained on both extracellular and cell-bound endopeptidases. Production of extracellular endopeptidases detected in the recent isolates tended to decrease or was abolished in the two-months-old sub-cultures. Their pattern of activities also showed some distinct differences between the strains. By means of caseinate precipitation, the production of extracellular endopeptidases was found to present important variations, both according to the strain, and according to the duration of the incubation time. The cell-bound endopeptidases were found to be relatively stable features, independent of the time passed since isolation. Their pattern of activities was also rather similar among the strains.

Pseudomonas aeruginosa virulence factors: modifications by sub-inhibitory concentrations of carbenicillin or gentamicin.

A virulent strain of Pseudomonas aeruginosa was assayed for adhesion to HEp-2 cells, production of toxin A, and production of elastase, in the presence of sub-inhibitory concentrations of carbenicillin and gentamicin. Both antibiotics, assayed in a concentration of 1:12 of their minimum bactericidal concentration (MBC), inhibited the production of toxin A. Gentamicin at this concentration totally abolished the production of elastase, whereas carbenicillin had little or no effect on this factor. Both antibiotics inhibited the bacterial adhesion, but in different ways. While gentamicin had a strong activity of slow onset, carbenicillin had a transitory activity of rapid onset, with return towards normal values after 90 min incubation.

Correlation between adhesion of Pseudomonas aeruginosa bacteria to cell surfaces and the presence of some factors related to virulence.

Recent isolates of Pseudomonas aeruginosa strains and 12-month-old subcultivated variants of the same strains have been assayed for adhesiveness to HEp-2 cells. P. aeruginosa adhesion factors were located both to the bacterial surface and extracellularly. Generally, loss of adhesiveness upon subcultivation could be restituted by adding extracellular factor from the recent isolate. While the extracellular adhesins were neutralized by non-specific serum factors, the surface-bound adhesins of a recent isolate were blocked by antibodies only.

Pressure- and temperature-dependent adhesion of Pseudomonas aeruginosa to HEp-2 cells.

Pseudomonas aeruginosa bacteria adhere to human epitheloid (HEp-2) cells in culture. Under normal atmospheric conditions (1 ATA), this adhesion increased significantly when the temperature rose from 22 to 37 degrees C. Under hyperbaric atmosphere (= air, 7 ATA) conditions, a similar, significant enhancement of bacterial adhesion to the cells was noted when the temperature rose. If the temperature was kept stable at 22 or 37 degrees C and the pressure was increased from 1 to 7 ATA, a pressure-induced enhancement was observed. This was statistically significant, at both temperature levels. Temperature-induced or -stimulated adhesion may help to explain some outbreaks of P. aeruginosa infections, for instance in whirlpools. The enhancement of this phenomenon under hyperbaric atmosphere conditions could have some relevance to recurrent P. aeruginosa otitis externa, a most common nuisance among professional divers.

Spread of subclinical Chlamydia pneumoniae infection in a closed community.

Chlamydia pneumoniae infections may spread subclinically. The present investigation took place in a military setting. Sera drawn when the conscripts had entered their military service 2 months previously had been kept frozen and were available. In a camp with 500 people, 35 (7%) developed clinical symptoms of pneumonia. The infection was serologically verified with C. pneumoniae-specific micro-immunofluorescence technique. Of 40 healthy controls, 21 turned out to fulfil the serological criteria of infection, thus, representing subclinical cases. These 21 cases, when extrapolated to the whole camp, equalled a rate of 49% which, added to the 7% of pneumonic cases, gave a total infection rate of 56%. Pre-existing IgG antibodies were demonstrated in 10% of the pneumonic cases, 48% of the subclinical cases, and 89% of the non-infected, healthy controls. Without the access to pre-epidemic sera permitting us to establish 4-fold titre rises, the spread of subclinical C. pneumoniae infection would have been noted at 5%, and not 49% as here demonstrated.