Search

An L-form of Serratia marcescens has previously been shown incapable of producing the red pigment, prodigiosin, characteristic of the parent bacteria. Mutants of S. marcesens, unable to form one or the other of the two prodigiosin precursors, 4-methoxy-2,2'-bipyrrole-5-carboxaldehyde or 2-methyl-3-n-amylpyrrole, were used to test the nature of the L-form defect. The L-forms failed to form sufficient amounts of either precursor to be detected by the appropriate mutant, and, when furnished the precursors, failed to couple them to form prodigiosin.

A stable L-form of Streptococcus faecalis (T(53)) was transferred in media containing decreasing concentrations of sucrose until it grew in medium without added osmotic stabilizer. This L-form (designated T(53I)) was compared with T(53) from which it was derived. The survival of these two L-forms suspended at different osmolalities showed that maximal survival for T(53I) was 350 to 400 milliosmolal and for T(53) was 900 to 1,000 milliosmolal. Both peaks were at the osmolality of their growth media. Measurement of intracellular potassium and sodium showed that the concentration of these ions was reduced in T(53I).

The activity of methacycline against microbial L-forms and their parent bacteria was compared with that of oxytetracycline, chlortetracycline, tetracycline, and demethylchlortetracycline, as well as with that of 22 other antibiotics which included examples of major groups of antibiotics. The L-forms and bacteria used were Streptococcus faecalis, S. faecium, S. faecalis var. zymogenes, Staphylococcus aureus (three strains), Proteus mirabilis (two strains), Pseudomonas aeruginosa, Escherichia coli (two strains), Sarcina flava, Serratia marcescens, and Klebsiella pneumoniae. The five tetracyclines had similar activities and were more active against L-forms than bacterial forms, except that the bacterial form of S. flava was more susceptible than the L-form. In general, other antibiotics (except the penicillins) were more active against L-forms than bacterial forms. There were certain exceptions where the bacterial form was more susceptible than the L-form. These included the effect of polymyxin B and colistin on P. aeruginosa, E. coli, and P. mirabilis, and the effect of gentamicin on P. aeruginosa, E. coli, S. flava, and S. marcescens.

Mice immunized subcutaneously with heat-killed Escherichia coli were protected from pyelonephritis produced by the intravenous route, but there was little or no protection from ascending infection. No significant protection from ascending or hematogenous pyelonephritis was demonstrated when immunization was accomplished by injecting heat-killed E. coli into the bladder. Heat-killed E. coli injected either subcutaneously or into the bladder protected mice from early endotoxic death after intravenous or bladder challenge.

Bacteriocin activity of Streptococcus faecalis var. zymogenes was tested against a variety of bacteria, L-forms, and mycoplasmas. Both a partially purified liquid preparation and a colony overlay technique were used. Other S. faecalis strains were the only bacteria whose growth was inhibited. The liquid preparation inhibited growth of all but three of the tested L-forms (whether derived from gram-positive or gram-negative bacteria), and two of these exceptional organisms were inhibited when the colony overlay technique was employed. On the other hand, the L-form of Streptobacillus moniliformis and all 33 tested mycoplasmas grew readily in the presence of the bacteriocin when either method was employed. It is suggested that the presence of cholesterol in the Streptobacillus and mycoplasmal membranes, unique in this regard among procaryotic cells, may be responsible for the differential pattern of growth inhibition.

Little data are available regarding L-form phagocyte interactions. Due to difficulty with more conventional methods, a serum-free technique of surface phagocytosis employing cellulose ester micropore filters, fluorochrome staining, and reflecting fluorescence microscopy was developed. Intracellular localization of L-frms was confirmed by electron microscopy. In timed experiments, phagocytosis of a group D Streptococcus (ATCC 23241) and its L-form (T53I) were maximal at 30 min, although the bacteria were consistently better phagocyted. Phagocytosis of an Escherichia coli (strain Yale) and its L-form was also demonstrated with the same technique. The lesser phagocytosis of L-forms may be related to their lower chemotactic activity.

Streptococcus faecalis, incubated in osmotically stabiliz medium in the presence of 1000 units of penicillin per milliliter, accumulated rather than extruded sodium; they accumulated much less potassium than control cells did. These changes were not due to binding of sodium by cell-wall fragments of cells treated with penicillin. Because penicillin had no effect on cation concentrations in stable protoplasts and nongrowing bacterial cells, this effect appeared to be related to the production of the penicillin-induced lesions of the cell wall.

Earlier workers suggested that synergism of polymyxin and sulfonamides occurred because sulfonamides produced changes in the cell wall which permitted the more ready access of polymyxin. We tested this hypothesis by using L-forms, which lack cell wall. The demonstration that synergism of polymyxin and sulfonamides occurs in L-forms of Proteus mirabilis and Staphylococcus aureus suggested that the synergism is a result of some mechanism other than alterations of the cell wall.

Two patients developed reticulum cell sarcomata after they had been treated with azathioprine and prednisone in the course of cadaveric renal transplantation. Both had terminal widespread herpes simplex virus infection.Immunosuppressive therapy could be responsible for an increased risk of malignant lymphomata either directly or by facilitating infection with oncogenic viruses.