Evaluation of conventional & serological methods for rapid diagnosis of cryptococcosis.

BACKGROUND & OBJECTIVE: Cryptococcosis is a chronic infective condition affecting the central nervous system. Unless diagnosed early and specific treatment instituted it can be fatal. There is an urgent need for a rapid and specific diagnostic tool for better management of the patients. Conventional methods such as culture and India ink are specific but cumbersome and time consuming. Serological methods of detection are rapid but have problems of false positivity and cross-reactivity with other micro-organisms. We carried out this study to compare and evaluate the conventional methods with serological methods of detection of cryptococcal meningitis. METHODS: A comparative evaluation of conventional methods (India ink and culture) with LAT (latex agglutination test) and EIA (enzyme immunoassay) was done in 127 CSF samples using culture and EIA as reference separately. RESULTS: India ink was positive for Cryptococcus in 72.4 per cent of the samples; 56 per cent were culture positive; LAT positive were 85 per cent and 79.5 per cent were positive by EIA. When culture was positive, all other tests were in agreement to it. However, when culture was negative there was significant difference between the pair of discordance of various diagnostic tests. Culture was 83.46 per cent in agreement to India ink, 76.3 per cent to EIA and 70.8 per cent to LAT. EIA was 92.9 per cent in agreement to India ink and LAT; 6.3 per cent showed false positive by LAT. INTERPRETATION & CONCLUSION: EIA is valuable in establishing diagnosis when culture is negative for cryptococcosis. EIA is more specific and has potential advantages over LAT as it gives clear discrimination of positive from negative results. Thus, EIA may be used as a simple, rapid, and reliable serological test for early detection of cryptococcal antigen in clinical samples like CSF in routine laboratories.

Prevalence of Aspergillus species in clinical samples isolated in an Indian tertiary care hospital.

CONTEXT (BACKGROUND): In recent times, it has become important to determine the prevalence of different Aspergillus species in clinical samples in view of difference in antifungal susceptibility noted in some species. AIMS: To determine the species prevalence of Aspergillus isolates in various clinical samples received in the Mycology Laboratory at our institute. METHOD: Over a period of 4-years, a total of 18,731 samples were processed, and species identification carried out by standard microbiological methods. RESULTS: Four hundred and fifty six samples (2.43%) were culture positive for Aspergillus species. A.flavus (46.93%) was the most common isolate, followed by A.fumigatus (37.72%) and A.niger (15.35%). It was observed that A.fumigatus was the predominant species isolated from blood and respiratory specimens, A.flavus was predominantly isolated from nasal polyps whereas A.niger predominated in nail specimens. Culture positivity was highest in the age group 12-65 years and in males. Sixty-nine patients (15.13%) were admitted to the intensive care unit. CONCLUSIONS: The study highlights the diverse manifestations caused by Aspergillus species in human beings and also throws light on the different species prevalent locally. The knowledge would prove useful in selecting empirical antifungal therapy and formulating prophylactic and pre-emptive strategies.

Diketopinic acid-a novel reagent for the modification of arginine§.

Diketopinic acid has been synthesized and shown to be a reagent of choice for specific, reversible modification of the guanidine groups of arginine residues. Diketopinic acid is a yellow crystalline substance and the carboxyl group of the reagent is a convenient handle for attachment to other molecules. The adducts of diketopinoyl derivatives with the guanidine group are cleaved by 0·2 M o-phenylenediamine at pH 8–9. The modification and regeneration of arginine and of arginyl residues in soyabean trypsin inhibitor and insulin are presented as demonstrations of the use of the reagent. The use of diketopinoyl resin in the separation of oxidized A and B chains of insulin has been discussed.