Enhanced in vitro engulfment of Listeria monocytogenes by rabbit polymorphonuclear leukocytes in the presence of sera from immune rabbits.

The role of immune serum in the engulfment of Listeria monocytogenes by polymorphonuclear leukocytes (PMNLs) of rabbits was documented employing an in vitro assay. Three serovarieties of L. monocytogenes, viz. serovars 1/2a, 4a and 4b, were separately incubated with PMNLs of nonimmune rabbit and high titre homologous or heterologous antisera. Normal rabbit serum was used as control. The number of L. monocytogenes per neutrophil was counted in stained smears in each assay and opsonic indices were calculated. Higher opsonic indices, i.e. 2.50, 2.09 and 2.56 for the three strains respectively, were obtained when bacteria were engulfed in the presence of homologous antisera as compared to when the bacterial cells were incubated with heterologous antisera, opsonic indices being in the range of 0.87 to 1.63. These results are indicative of a possible role of specific serum factors in at least the internalization of L. monocytogenes by PMNls of rabbits and therefore in the host defenses against Listerial infections.

A comparative study of unpassaged and animal passaged cultures of Listeria monocytogenes in rabbits.

Variants of a parent culture of Listeria monocytogenes were prepared by passaging it several times through rabbits. The resulting isolates (V1 to V6) were investigated and compared with the parent culture with particular emphasis on their phenotypic characters and their pathogenicity for rabbits. The variants maintained the morphological, cultural, biochemical and serological features of the parent strain. Although no significant decrease was noted in the total extracellular protein produced, 10 mg/ml of a 6-day culture broth grown at 34 degrees C for V6 as compared to 12.3 mg/ml for the parent culture, the phosphocholine-specific phospholipase C (PC-PLC) activity diminished with passaging. Pathogenicity for rabbits, as determined by viable count of the organism per gram of the infected organ, increased at each passage. Animals infected with V6 revealed a mean of 2.2 x 10(9) CFU/g of spleen as compared to the parent culture which had a count of 5.0 x 10(6) CFU/g. These observations indicate a lack of direct correlation between in vitro production of PC-PLC and virulence of L. monocytogenes for rabbits.

Correlation between production of listeriolysin O by variants of Listeria monocytogenes and their virulence for rabbits.

L. monocytogenes serovar 1/2a NCTC 7973 was passaged through rabbits and the severity of infection at each passage was determined by counting viable bacteria from infested organs and recording the time of death. A comparative evaluation of the levels of hemolysin produced in vitro by the original and six variant cultures (V1-V6) was done by determination of hemolytic units (CHU). While virulence of the cultures enhanced at each passage (2.2 x 10(9) CFU/g of the spleen for V6 as compared to 5.0 x 10(6) CFU/g spleen for the parent culture), the CHU decreased considerably, 3 CHU for the V6 as compared to 40 CHU for the parent strain. The results suggest that the level of in vitro production of listeriolysin may not parallel the pathogenicity of L. monocytogenes for rabbits.

Evaluation of serum peptide banding patterns of patients on hemodialysis therapy by discriminant analysis.

The present study was directed towards determining serum protein abnormalities, with emphasis on protein deficits in patients on short- and long-term hemodialysis. Serum protein profiles of healthy controls and chronic and end-stage renal failure patients on hemodialysis were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. A total of 104 distinct peptide bands in the molecular weight range of 23 kDa to 300 kDa were encountered for both healthy and patient populations. The SPSS/PC+ discriminant analysis employing group mean statistics revealed significant protein deficits in the patient population. As many as 72 (69.23%) of the 104 individual peptide bands had lower mean scores for the patients as compared to the healthy subjects. In all, 21 (29.2%) of these peptide bands belonged to the high molecular weight range of 185 kDa to 300 kDa while 13 (18.1%) were located in the low molecular weight range of 23 kDa to 36 kDa. To show that patients and healthy controls can be categorized into their respective groups on the basis of their serum protein profiles, a 100% correct classification was established by group membership prediction analysis. Furthermore, using minimization of Wilk's lambda as the criterion for variable selection, it was found that the 285 kDa, 265 kDa, 250 kDa, 155 kDa, 125 kDa, 110 kDa, 32 kDa, 27.5 kDa, 26 kDa and 23.5 kDa serum peptide bands were the most important in classifying an individual as healthy or diseased.

Lymphocyte sub-populations in a group of heroin addicts in Pakistan.

A study on a group of fifty heroin abusers was conducted to analyse their immunocompetence. Absolute numbers of lymphocytes and their sub-populations in the peripheral blood were used as the parameter. Sub-populations of lymphocytes were distinguished on the basis of their ability to form rosettes with sheep's erythrocytes. Another group of fifty individuals comprising non-abusers was studied as control. The mean values for total lymphocytes and the T-cells in non-abusers were within the expected normal range, while those obtained for the heroin abusers were below normal value. Difference between the cell counts of the two groups was statistically significant. The mean of non-rosetting cells of the two groups of population studied did not differ significantly. Results indicate a marked deficiency in the cellular immune compartment of the subjects with not much impairment of the humoral immune system. The chi-square test for independence between lymphocyte counts and drug abuse revealed a degree of association with 88% confidence.