Virulence potential of Group A streptococci isolated from throat cultures of children from north India.

Background & objectives: Rheumatic fever (RF)/rheumatic heart disease (RHD) caused by Group A streptococcus (GAS) are more prevalent in north India as compared to the western world, where invasive diseases are common. This could be due to variation in the virulence of GAS in different geographic locations. Hence, we studied the virulence potential of GAS isolated from the throat of children from north India. Methods: Fifty GAS isolated consecutively, from children with mild pharyngitis (20), severe pharyngitis (24) and asymptomatic pharyngeal carriers (6), were characterized by emm typing and opacity factor (OF). Adherence and internalization of GAS in HEp-2 cells and opsonophagocytosis in convalescent serum samples were studied. Results: Twenty emm types, six sequence types, and one non-typeable GAS were circulating in the community. emm type 74, 11, 68, StI129 and NS292 were most prevalent. Twenty seven (54%) GAS isolates were OF negative. Sixty five per cent of the most prevalent emm types were OF negative indicating their rheumatogenic potential. Adhesion of GAS ranged from 0.1 to 100 per cent. Forty eight per cent of GAS were highly adherent. Invasion of GAS in HEp-2 cells ranged between 0 to 30 per cent. Only 20 per cent isolates exhibited highest invasion. GAS were opsonophagocytosed with highly divergent efficiency ranging from 0 to 91.7 per cent. Nineteen GAS were not opsonophagocytosed and 15 multiplied during the assay. Isolates of the same emm type also varied in their virulence potential. Interpretation & conclusions: GAS isolates from the throat of children from north India belonged to several emm types, majority were OF negative, excellent adherents but poor invaders. This explains why throat infections in these children tend to lead to ARF/RHD rather than invasive diseases. A few isolates exhibiting high invasion efficiency indicate that GAS throat cultures can also lead to invasive diseases.

Group A Sstreptococcus virulence factors genes in north India & their association with emm type in pharyngitis.

Background & objectives: Group A streptococcal (GAS) pharyngitis, especially among children, leads to high prevalence of rheumatic fever (RF)/rheumatic heart disease (RHD) in India, as compared to the western world where invasive diseases are common. GAS encodes numerous virulence factors that cause diseases by exhibiting extraordinary biological diversity. Hence, we studied the virulence factors genes of GAS isolated from the throat of children with pharyngitis and also asymptomatic carriers. Methods: Fifty GAS isolates cultured from throats of north Indian children aged 5-15 yr with mild pharyngitis (20), severe pharyngitis (24) and asymptomatic pharyngeal carriers (6), during 2000-2003 along with reference M1 strain were emm typed and characterized for virulence factors genes by PCR. The presence of virulence factors was also checked for their association with emm type in pharyngitis. Results: Twenty emm types, six sequence types, and one non-typeable strain were found circulating in north India. The five most prevalent types were emm 74 (12%), 11 & StI129 (8% each) and emm 68 and NS292 (6% each). The spe B gene was found to be significantly higher (P=0.0007) in opacity factor (OF) negative isolates. emm 3, 11, 77, 86, 87, 109 and StI129 showed maximum virulence factors genes. Interpretation & conclusions: GAS isolates collected from throats of children from north India possess highly virulent antigens. This study also supports concept of isolate-associated virulence rather than type relatedness.

Epidemiology of group a streptococcal pharyngitis & impetigo: A cross-sectional & follow up study in a rural community of northern India.

Background & objectives: Group A streptococcus (GAS) causes a wide array of human diseases. Epidemiological picture of streptococcal infection in India is not complete. Hence, disease burden due to GAS in 5-15 yr old school children in northern India was studied and emm typing of GAS isolates was carried out to help in designing prevention strategies. Methods: A cross-sectional survey was carried out among 4249 school children (5-15 yr) from Raipur Rani Block of Panchkula district in Haryana during 2000-2002; 334 children were followed up fortnightly for one year. Standard clinical and microbiological procedures were used for collection of swabs from throat and skin and confirmation of GAS and its emm types. Results: Of the 4249 children studied, 658 (15.5%) had pharyngitis; 579 of them could be swabbed, of which 2.8 per cent had GAS. From 3591 children without pharyngitis, 3385 who could be swabbed, GAS was found in 1.3 per cent of them. Impetigo was rare (0.7%), but 7.1 per cent (2/28) children had GAS. In the followup study, 17.4 per cent (776/4447 child-contacts) had pharyngitis, 761 could be swabbed and 2.4 per cent had GAS; among those without pharyngitis, 2016 swabs could be taken and GAS was found in 1.3 per cent; whereas only 2.6 per cent (2/75) of skin sores had GAS. Three children had GAS pharyngitis twice during follow up. Fourteen different GAS emm types were found. emm 71, 77 and 81 constituted 69 per cent of the pharyngeal isolates. GAS pharyngitis and impetigo were more common in winters and summers respectively. Interpretation & conclusions: In north India, pharyngitis was more common than impetigo. Most prevalent emm types of GAS in this region differ from those included in M protein-based vaccines.

DNA flow-cytometry on fine needle aspiration cytology of lymph node: how helpful is it?

The diagnostic value of DNA content analysis by flow cytometry (FCM) has rarely been evaluated in combination with fine needle aspiration cytology (FNAC). In this present study, the value of DNA FCM in distinguishing malignant lesions from benign enlarged lymph nodes on FNAC material has been investigated. DNA FCM was done from FNAC materials of 58 cases of lymph node swellings Becton Dickinson's flow cytometer (USA) along with 'Cell Quest' program was used for the analysis of DNA ploidy and S & G2-M phase cells. There were 16 cases of reactive lymphoid hyperplasia, 8 cases of metastatic carcinoma and 34 cases of non Hodgkins lymphoma (NHL). DNA FCM showed 12 aneuploid case and 46 diploid case. All the cases with DNA aneuploidy were malignant. None of the benign cases showed aneuploidy on DNA aneuploidy were malignant. None of the benign cases showed aneuploidy on DNA histogram. Out of the 46 diploid cases, 11 cases showed high S & G2-M Phase cells (> 10%). Nine out of these 11 cases were malignant on FNAC. The sensitivity and specificity of DNA FCM were 50% and 87.5% respectively. None of the low grade NHL was detected by DNA FCM. In conclusion, DNA aneuploidy and high G2-M phase cells (> 10%) are good indicators of malignancy in lymph node aspirate. However DNA FCM is relatively costly and thereby its role as an adjunctive technique needs careful re-evaluation.

A flowcytometric study of CD4+ & CD19+ cell lymphopenia in patients with alopecia areata.

Twenty five patients with alopecia areata and 20 healthy controls were studied by flowcytometry employing direct two colour immunofluorescence in erythrocyte lysed whole blood. A significant reduction was observed in helper/inducer (CD4+) lymphocytes (29.4 +/- 7.4 vs 39.45 +/- 8.0, P < 0.01) and B (CD 19+) lymphocytes (11.04 +/- 6.57 vs 15.0 +/- 5.05, P < 0.01) in comparison with healthy controls. Decrease in T-lymphocytes (CD3+) and suppressor/cytotoxic (CD8+) was not significant and activated (HLADR+) lymphocytes and natural killer cells (CD16+ and CD56+) were within normal limits. Our findings suggest a significant T helper (CD4+) and B (CD19+) cell lymphopenia in alopecia areata.

Evaluation of RNA rich fraction of Litmosoides carinii in induction of protection in infected rats.

The RNA rich fraction of adult L. carinii worms was evaluated in evoking a protective response in infected rats. The RNA immunization was seen to be effective in limiting the microfilaraemia in peripheral blood as well as the adult worm burden. The antibodies to both RNA antigen and adult worm antigen were high in this group of animals at the peak of infection. The RNA immunization was seen to evoke hyperresponsiveness in lymphocytes to mitogens like adult worm antigen, PHA and Con A.

Correlation of zymodeme patterns, virulence & drug sensitivity of Trichomonas vaginalis isolates from women.

Characterization of T. vaginalis strains isolated from symptomatic and asymptomatic subjects was done by isoenzyme analysis. The pathogenicity of these isolates was checked in mouse model and in vivo drug susceptibility was determined. The isolates from symptomatic and asymptomatic individuals could not be grouped on the basis of isoenzyme analysis alone. All the strains except one, were pathogenic for mice, and metronidazole (50 mg/kg body weight) was effective in protecting the mice from T. vaginalis infection.