Experimental pulmonary candidiasis in modified rabbits

Pulmonary lesions induced by an intratracheal inoculation of Candida albicans into rabbits in untreated control, bovine serum albumin (BSA)-sensitized and C. albicans-sensitized groups were examined immunohistochemically to clarify the localization of IgG, IgM and C3. In the control group no inflammatory cells were immunoreactive for IgG and only a few macrophages for IgM and C3, whereas in the BSA- and C. albicans-sensitized groups there were a small number of IgG-positive polymorphonuclear leukocytes and IgM- and C3-positive macrophages in the lesions, the latter group being more prominent. Furthermore, epithelioid granulomatous lesions at the late stage in the C. albicans-sensitized animals showed scattered epithelioid cells containing IgG as well as abundant IgG- and IgM-positive plasma cells. These immunohistochemical results were considered to support the estimation that immune complexes contributed to the modification of fungal lesions in the C. albicans-sensitized hosts, although non-immunological defense mechanisms seemed to be more important in the elimination of the fungus.     

Experimental pulmonary candidiasis in modified rabbits

The present experiment was performed in order to analyze and compare the histopathological features of Candida infection in various states of host defense capacity. The pulmonary lesions were induced by an intratracheal inoculation of 10⁸ live cells of Candida albicans into each of the rabbits in the following 4 groups: 1) untreated controls, 2) animals sensitized non-specifically to bovine serum albumin (BSA), 3) those sensitized specifically to formalin-killed C. albicans cells, and 4) those treated with cyclophosphamide and mitomycin C. The animals were sacrificed at appropriate intervals up to 16 days after inoculation. At autopsy, the lungs were cultured and then subjected to histopathological, electron microscopic and enzyme cytochemical examinations.In the healthy control animals, the fungal lesions consisted of polymorphonuclear leukocytes (PMN) at the initial stage, gradually changing to granulomatous inflammation, which contained no peroxidase-positive macrophages. In the animals sensitized non-specifically to BS A exudative macrophages appeared in the lesions, the nature of which did not differ from that of the control animals. In the animals sensitized specifically to Candida cells, more extensive infiltration of PMN was observed at the initial stage, a fact which may suggest the participation of the Arthus phenomenon in the development of the lesions. Furthermore, an epithelioid cell transformation of the macrophages in the granulomatous lesions may also suggest that immune complexes contributed to their formation. In the drug-treated animals, the lesions consisted of necrotic or less prominent cellular foci which correspond to the features of human candidiasis in debilitated states, and the inoculated fungi grew progressively to form pseudohyphae. An asteroid structure protruding radially from the surface of the fungal cells and attaching to primary lysosomes in the phagocytes was observed occasionally. This structure seems to be formed when the function of the phagocytes in the defense mechanisms against the fungi is suppressed to some extent.From the results of the present experiment, we would emphasize that PMN play an initial role in the elimination of C. albicans cells in the lung, and that macrophages then contribute to the formation of the lesions immunologically or non-immunologically.     

Stimulus-permeability coupling in rat pulmonary macrophages challenged by Pseudomonas aeruginosa

Summary Electron probe X-ray microanalysis (XRMA) of freeze-dried ultrathin sections provides the capability of measuring intracellular elemental content. This methodology was used to investigate the stimulus-permeability coupling responses associated with phagocytosis of Pseudomonas aeruginosa by cultured pulmonary alveolar macrophages (PAMs) of rats. PAMs were challenged with P. aeruginosa suspended in Gey's buffer at a bacteria to PAM ratio of 501 for 1 h at 37° C. A 1-mm³ pellet of the unchallenged control PAMs, challenged PAMs and P. aeruginosa alone was quench-frozen in nitrogen-cooled, liquid propane, and 0.1-m cryosections were cut at -100° C. X-ray spectra were collected for nucleus and cytoplasm of 39 control PAMs, 36 challenged PAMs and 40 P. aeruginosa. Concentrations (mmole/kg dry weight) were obtained for Na, Cl, K, Ca, Mg, P, S for each cell. In the control PAMs, the content was similar to other mammalian cells. Moreover, there were no differences in elemental content between nucleus and cytoplasm. In the challenged PAMs, Na concentration was 4 times that of control PAMs (p<0.001) whereas Cl was double (p<0.001), K was 29% lower (p<0.001), and Ca was 4 times higher (p<0.05). The elemental concentration profile in the P. aeruginosa was distinctly different from that of the PAMs: higher Na, Ca, Mg, but lower Cl and K values. These results demonstrate elemental content changes in cultured PAMs challenged with P. aeruginosa that indicate a stimulus-permeability response by membranes associated with the phagocytic process.     

Dynamics of growth of atypical mycobacteria in different liquid cultivation media

The dynamics of growth ofMycobacterium smegmatis, M. fortuitum andM. phlei in liquid media used also for cultivation of typical mycobacteria (Sauton, Youmans, Kirchner, Šula) was compared with that in Davis and Merrill media. In the Merrill medium glucose (as the only organic component) was replaced with another carbon source and the effect of this modification was investigated. The results obtained show that the Merrill medium, its modification in particular, is suitable for cultivation ofM. smegmatis andM. fortuitum. 2-Oxoglutarate and succinate are important as the sole carbon sources in the case ofM. fortuitum andM. phlei respectively.     

Qualitative and quantitative changes of bone marrow cells in sensitized rabbits

Bone marrow of adult rabbits was dynamically investigated during the sensitization of animals with the complete Freund's adjuvant containing 10 per cent human gammaglobulins (five intramuscular injections of 1 ml adjuvant, one per week). Smears, imprints and paraffin sections from tibial and femoral bone marrow were examined in normal, unsensitized animals, and a week after the third, the fourth and the fifth antigenic stimulations. The differential count of about 10,000 elements of 20-25 smears and imprints allowed the establishment of normal and modified myelograms at each sacrificing term. A high increase in the number of monocytes, small lymphocytes and plasma cells was noticed after the third antigenic stimulation, with statistically significant values as compared to controls. The increase in the number of lymphocytes--including both T and B cells--was more marked after the 3rd antigenic stimulation, later on the proportional increase diminished, the proliferation maintaining itself "en plateau". The ratio between myeloblastic-myelocytic and erythroblastic-erythrocytic elements doubled after the third antigenic stimulation and increased up to six times after the fifth one, due to an absolute decrease of the erythroblastic-erythrocytic line.     

Contact sensitivity in rabbits sensitized with dinitrophenylated Mycobacterium tuberculosis

The conjugation of Mycobacterium tuberculosis with DNFB results in the formation of a haptenated preparation that induces the formation of contact sensitivity when administered subcutaneously. This contact sensitivity can be measured in vivo by topical application of the free chemical and in vitro by lymphocyte transformation. The antigens suitable for the in vitro detection are those preparations obtained by the haptenation of cell membranes. Haptenation of serum proteins, of homologous and heterologous origin, does not produce antigens suitable for in vitro assay. The antigen requirements for the in vitro transformation assay of contact sensitivity are similar for adjuvant induced sensitivity as well as for free chemical induced sensitivity.     

Growth characteristics of atypical mycobacteria in water and their comparative resistance to disinfectants.

With the increasing significance of group IV atypical mycobacteria as etiological agents in a variety of infections, studies were conducted to determine their growth capabilities in water and their comparative resistance to disinfectants used to decontaminate hospital equipment. Isolates of Mycobaterium chelonei (TM strains) from peritoneal fluids of patients and peritoneal dialysis machines were able to multiply in commercial distilled water, with generation times at 25 degrees C ranging from 8 to 15 h. Levels of 10(5) to 10(6) cells per ml were attained, and these stationary-phase populations declined only slightly over a 1-year period. Results of studies to determine resistance to disinfectants showed the following. (i) TM strains of M. chelonei cultured in commercial distilled water showed survivors in 2% aqueous formaldehyde (HCHO) solutions up to 24 h; in 8% HCHO, only a 2-log reduction in viable counts was observed over a 2-h sampling period. Reference ATCC strains of M. chelonei and M. fortuitum were rapidly inactivated, with no survivors after 2 h of exposure to 2% HCHO or 15 min of exposure to 8% HCHO. (ii) In 2% alkaline glutaraldehyde, TM strains survived 60 min. whereas ATCC strains showed no survivors after 2 min of contact time. (iii) All M. chelonei and M. fortuitum strains survived 60 min of exposure to concentrations of 0.3 and 0.7 microgram of free chlorine per ml at pH 7.     

Surrounded by mycobacteria: nontuberculous mycobacteria in the human environment

A majority of the Mycobacterium species, called the nontuberculous mycobacteria (NTM), are natural inhabitants of natural waters, engineered water systems, and soils. As a consequence of their ubiquitous distribution, humans are surrounded by these opportunistic pathogens. A cardinal feature of mycobacterial cells is the presence of a hydrophobic, lipid-rich outer membrane. The hydrophobicity of NTM is a major determinant of aerosolization, surface adherence, biofilm-formation, and disinfectant- and antibiotic resistance. The NTM are oligotrophs, able to grow at low carbon levels [>50 μg assimilable organic carbon (AOC) l⁻¹], making them effective competitors in low nutrient, and disinfected environments (drinking water). Biofilm formation and oligotrophy lead to survival, persistence, and growth in drinking water distribution systems. In addition to their role as human and animal pathogens, the widespread distribution of NTM in the environment, coupled with their ability to degrade and metabolize a variety of complex hydrocarbons including pollutants, suggests that NTM may be agents of nutrient cycling.