Evaluation of a polymerase chain reaction for the diagnosis of tuberculosis

A polymerase chain reaction for the specific detection of Mycobacterium tuberculosis has been developed and evaluated for clinical applicability. Primers were designed to amplify a 240 base pair region in the MPB 64 protein coding gene (nts 460-700). From among 15 different DNA templates tested (including 10 species of mycobacteria) PCR amplified the DNA from M. tuberculosis complex only, demonstrating its exquisite specificity. Sensitivity studies using serial ten-fold dilutions of M. tuberculosis bacilli determined the limit of detectability to be 10 organisms. A total of 143 clinical specimens were analysed. This consisted of 26 known non-tuberculous specimens (control group) and 117 specimens received at the Tuberculosis Diagnostic Service of AIIMS (test group). None of the specimens in the control group was positive by PCR. Out of 117 specimens in the test group, 19 were culture positive for mycobacteria and 17 of these isolates were identified as M. tuberculosis. All the specimens from which M. tuberculosis was grown were also PCR positive. The remaining two isolates were identified as mycobacteria other than M. tuberculosis and these two specimens were PCR negative. An additional 14 culture negative specimens were PCR positive yielding an overall M. tuberculosis positivity rate of 26.5% (31/117) compared to 14.5% (17/117) by culture. The superior sensitivity of PCR over culture was more evident in non-pulmonary cases where PCR picked up 10 cases in addition to three culture positives out of 69 specimens. On the other hand, out of 48 pulmonary specimens only four cases in addition to 14 culture positives were picked up by PCR.

Rapid diagnosis of tuberculous meningitis by polymerase chain reaction

The polymerase chain reaction (PCR) in cerebrospinal fluid was compared with conventional bacteriology and an enzyme-linked immunosorbent assay (ELISA) for cerebrospinal fluid antibodies in the diagnosis of tuberculous meningitis (TBM). PCR was the most sensitive technique; it detected 15 (75%) of 20 cases of highly probable TBM (based on clinical features), 4 (57%) of 7 probable cases, and 3 (43%) of 7 possible cases. ELISA detected 11 (55%) of the highly probable cases and 2 each of the probable and possible cases. Culture was positive in only 4 of the highly probable cases. Among the controls (14 pyogenic meningitis, 3 aseptic meningitis, 34 other neurological disorders), 6 subjects tested early in the study (2 pyogenic meningitis, 4 other disorders) were PCR positive. Second DNA preparations from their stored cerebrospinal fluid samples were all PCR negative, suggesting that the false-positive results were due to cross-contamination. 18 PCR-positive TBM samples retested were all still PCR positive. The antibody ELISA was positive in 3 controls despite the use of a high cutoff value.

Study of an outbreak of epidemic conjunctivitis in Delhi in 1986

An epidemic of acute conjunctivitis occurred in Delhi during July-September 1986. The clinical presentation in total of 350 patients were characteristic of acute haemorrhagic conjunctivitis (AHC). Bacterial cultures from conjunctival swabs were sterile in 85 out of 105 (80%) patients, virus cultures in Vero and HeLa cells were negative in 30 patients. However, conjunctival scrapes from 20/30 (66.7%) patients showed specific cytoplasmic fluorescence with enterovirus 70 (EV 70) antiserum, suggesting EV 70 to be the etiologic agent of the epidemic.

A cytotoxic substance produced by a wild culture of Lactobacillus casei D-34 against tumour cells

A wild lactic culture isolated from dahi (fermented milk) sample and characterised as L. casei D-34 was found to be significantly cytotoxic (34-36%) against three tumour cell lines, HeLa, HEp-2 and HFS-9. The cytotoxic substance (CS) was found to be in the culture supernatants, protein in nature, with a molecular weight ranging from 17,000-20,000. The crude culture supernatant was partially purified by dialysis and ion exchange chromatography as anionic, cationic and neutral fractions. Among the fractions, except for the anionic fraction, others were found to be highly cytotoxic against all three tumour cell lines. The cationic, neutral and pooled (anionic:cationic:neutral in 1:1:1 ratio) fractions showed 50, 70, 70% cytotoxicity against Hep-2 cells, 70, 88, 94% against HFS-9 cells and 50, 89, 90% against HeLa cells respectively. Pooled fraction was found to exhibit higher percent of cytotoxicity compared to individual fractions indicating a synergistic effect. (3H)-thymidine incorporation studies revealed that CS and its fractions inhibited DNA synthesis in tumour cells. The CS was stable towards heat and pH changes.

Cytotoxic activity of lactobacilli isolated from plant and dairy sources

Forty four cultures of Lactobacilli isolated from their natural sources such as dahi, raw milk and fermenting rice-pulse doughs etc. along with four standard strains of Lactobacilli were assayed for their cytotoxic activity against three secondary tumour cell lines. Three cultures isolated from dahi samples and identified as Lactobacillus casei D-34, L. casei D-48a, L. plantarum D-70a along with one standard strain L. casei B 1922 exhibited significant cytotoxic activity in the range of 30 to 36%.

Correlation of histologic types of carcinoma of the uterine cervix and human papillomavirus and herpes simplex virus type 2 DNA sequences in the uterine cervical biopsies

Forty patients with invasive cancer of cervix from New Delhi were examined for the presence of human papillomavirus (HPV) and herpes simplex virus (HSV) type 2 DNA sequences in a Southern hybridization assay. Data were analysed according to the histologic type of cancer. HPV DNA sequences were detected in 82.5% biopsies and HSV-2 DNA sequences were found in 10% biopsies. HPV-16 DNA sequences were found either alone or together with HPV-18 and/or HSV-2 Bgl II N fragment in 55% biopsies from keratinizing squamous cell carcinoma, whereas HPV-18 sequences were found in 35% biopsies. Similarly, 50% biopsies from patients with non keratinizing squamous cell carcinoma contained HPV-16 DNA and 38.9% biopsies had HPV-18 DNA. HSV-2 Bgl II N DNA sequences were present in 10% biopsies which were also positive for HPV-16 and/or HPV-18 DNA sequences. Two biopsies from adenocarcinoma of uterine cervix contained HPV-18 and HPV-16 DNA sequences. Therefore, no significant correlation seems to exist between HPV-types and histologic types or grades of differentiation of tumor.

Rubella infection: the Indian scene

Few studies have probed the problem of rubella in India. These few investigated seroepidemiology in female populations, carried out serosurveillance of pregnant women, and assessed the role of prenatal rubella in the causation of congenital malformations. Seroepidemiologic surveys showed that greater than 80% of women of childbearing age (15-34 years) in three cities of northern India had rubella antibodies, as detected by the hemagglutination-inhibition (HAI) test, whereas only 56.8% of such women in Calcutta in eastern India had rubella antibodies. No studies have been done in other areas of India. Serosurveillance of pregnant women in Delhi showed that none of the 47 pregnant women lacking rubella HAI antibodies delivered congenitally malformed babies, although six women seroconverted during pregnancy. However, in Lucknow one of the 62 pregnant seronegative women delivered a baby with expanded congenital rubella syndrome after having had a clinically inapparent infection at 16-18 weeks of gestation. In addition, retrospective studies of infants with congenital malformations do suggest that prenatal rubella often was responsible for their condition.