The reliability and rapidity of the coagglutination technic and its comparison with precipitin technic in the grouping of streptococci.

Three methods of the grouping of 170 strains of beta-hemolytic streptococci belonging to Groups A, B, C, F, and G by capillary and agar-gel precipitation using Lancefield extract and by coagglutination of antibody-coated protein A-containing staphylococci were compared. Capillary and agar-gel precipitin technics correctly grouped all 170 strains, with no cross-reaction. One hundred sixty-nine out of the 170 strains were also correctly grouped by the coagglutination technic, and the one strain with a cross-reaction was correctly grouped after blood--agar subculture. Although 20 of the 170 strains showed minor cross-reactions by the coagglutination technic, the specific groups were easily and unquestionably detected, and the minor cross-reactions were easily overcome. A rapid method of grouping by coagglutination technic using 4--6-hour broth culture, done on 75 strains, showed that 73 strains could be correctly grouped by the rapid method and two after overnight incubation. Thus, the coagglutination technic of grouping was found to be easy, reliable, and economical, and could be adopted in any routine diagnostic laboratory as a rapid grouping procedure.

Streptococcal antibodies and complement components in tropical post-streptococcal glomerulonephritis.

Anti-deoxyribonuclease "B' was elevated in 94.9% of 59 cases of post-streptococcal glomerulonephritis studied, whereas ASO was elevated only in 54.4% of cases showing that the ADNB titre is a more sensitive indicator of antecedent streptococcal infection than ASO, in tropical countries with a high prevalence of pyoderma. Serum C3c (beta 1A) levels were significantly decreased, especially in the early phase of the illness and returned to normal with remission. C4 levels were decreased only in the early phase of the illness, suggesting involvement of the alternate pathway subsequent to classical pathway activation.

Bacterial identification in the diagnostic laboratory: how much is enough?

The major impetus for bacterial identification came after the advent of solid culture media. Morphological appearance of bacterial colonies was often sufficient for their identification in the laboratory. Even in modern times, preliminary identification of most cultivable bacteria is based on such morphological characters. Advances have been made media for the presumptive identification of common organisms encountered in clinical samples. Phenotypic characterisation of bacteria with, physiological tests with a battery of biochemical tests differentiate related bacterial genera as well as confirm their identity. . Each laboratory can select its own method(s) of identification, provided they are based on scientific / epidemiological evidence; clinical laboratory and standards institute (CLSI) is a widely accepted organization and laboratories in many parts of the world follow its recommendations for bacterial identification. Some of the latest advances in identification include Matrix Assisted Laser Desorption Ionization - Time of Flight Mass Spectroscopy (MALDI-TOF) is a state of art facility used for fast and reliable species-specific identification of bacteria including Mycobacteria and fungi including yeasts. However the single most important factor that decides the method of bacterial identification in any laboratory is the cost involved. In the final analysis, selection of tests for bacterial identification should be based on their standardization with proper scientific basis. Considering the cost and lack of easy availability of commercial kits, we have put forward a simplified and rapid method of identification for most commonly encountered bacterial pathogens causing human infection in India.

Micro-indirect hemagglutination test for detection of antibodies to the Ibc protein of group B Streptococcus.

A micro-indirect hemagglutination test was developed for detecting antibody against the Ibc protein of group B Streptococcus. Formalin-preserved, tanned sheep erythrocytes were sensitized with a partially purified preparation of Ibc protein from a type Ic strain of group B streptococci. A total of 76% of 103 sera from pregnant and nonpregnant women had demonstrable antibody against this protein, with titers ranging from 10 to 320. Examination of five pairs of mother and cord sera revealed passive transfer of these antibiodies from mother to infant. This testing on a limited number of sera also revealed that elevated antibody titers against Ibc protein were more common among carriers of group B streptococci, especially those harboring strains with Ibc protein antigen, than among noncarriers. The technique described was found to be simple, specific, sensitive, and reproducible and may be of value in assessing the immune status of pregnant women as well as for epidemiological purposes.

Rapid screening of fecal samples for Vibrio cholerae by a coagglutination technique.

A coagglutination procedure for detecting Vibrio cholerae was applied directly to 125 watery fecal samples received in the laboratory for bacteriological culture: many of these were from suspected cases of cholera. Of 47 bacteriologically proved cases of cholera, 44 (93.6%) gave positive results by the coagglutination method. There was a good correlation between the coagglutination method, dark-field microscopy, and culture.

Antimicrobial activity of amniotic fluid in South Indian women.

Samples of amniotic fluid obtained from 48 South Indian women in the third trimester of pregnancy were studied for antimicrobial activity. The growth of Staphylococcus albus, Candida albicans and Clostridium perfringens was inhibited by nearly all samples studied while the growth of Staphylococcus aureus, Escherichia coli and Bacteroides fragilis was inhibited by 50%, 42% and 18% of samples respectively. The growth of Streptococcus faecalis was not inhibited. Using radial immunodiffusion, IgG was measurable in all 10 samples studied (mean 23 mg/dl), whereas IgA was measurable in only three of these samples (mean 1.32 mg/dl). However, while specific IgA against C. albicans was detected by indirect immunofluorescence in 93% of samples, specific IgG against C. albicans was detected in only 26% of samples (P less than 0.001). Amniotic fluid obtained from parous women had greater inhibitory activity against E. coli (P less than 0.05) than did the amniotic fluid obtained from nulliparae.