Biomedical subjects

S D Pillai

Publications and source records attributed to S D Pillai.

24 records · Page 2Linked to original sources

PubMed1994

Bacterial populations in the groundwater on the US-Mexico border in El Paso County, Texas.

In El Paso County, Texas, 73 domestic wells were sampled using a variety of selective media to determine the extent of bacterial contamination of the groundwater on the US side of the United States-Mexico border. Thirteen wells were contaminated by fecal coliforms, whereas other wells contained a variety of bacterial genera including some potential pathogens that normally would not be detected by standard methods of water testing.

Acinetobacter↗

PubMed1994

Identification of capsule-forming Bacillus anthracis spores with the PCR and a novel dual-probe hybridization format.

Anthrax is a fatal infection of humans and livestock that is caused by the gram-positive bacterium Bacillus anthracis. The virulent strains of B. anthracis are encapsulated and toxigenic. In this paper we describe the development of a PCR technique for identifying spores of B. anthracis. Two 20-mer oligonucleotide primers specific for the capB region of 60-MDa plasmid pXO2 were used for amplification. The amplification products were detected by using biotin- and fluorescein-labeled probes in a novel dual-probe hybridization format. Using the combination of PCR amplification and dual-probe hybridization, we detected two copies of the bacterial genome. Because the PCR assay could detect a minimum of 100 unprocessed spores per PCR mixture, we attempted to facilitate the release of DNA by comparing the effect of limited spore germination with the effect of mechanical spore disruption prior to PCR amplification. The two methods were equally effective and allowed us to identify single spores of B. anthracis in PCR mixtures.

Animals↗

PubMed1993

Specific detection of Salmonella spp. by multiplex polymerase chain reaction.

Three sets of oligonucleotide primers were used in the polymerase chain reaction (PCR) assay to detect Salmonella species. phoP primers specific to the phoP/phoQ loci of coliform pathogenic bacteria such as Salmonella, Shigella, Escherichia coli, and Citrobacter species served as presumptive indicators of enteric bacteria. In addition to the phoP primers, the Hin and the H-1i primers, which targeted a 236-bp region of hin/H2 and a 173-bp region of the H-1i flagellin gene, respectively, were used. Both Hin and H-1i primers are specific to motile Salmonella species and are not present in Shigella, E. coli, or Citrobacter species. Thus, by multiplex PCR amplification, Salmonella species including Salmonella typhi, Salmonella typhimurium, Salmonella paratyphi A, and Salmonella enteritidis can be specifically detected. Optimal reaction conditions have been described to demonstrate this specific, sensitive detection of Salmonella species. By using agarose gel electrophoresis for detection of the PCR-amplified products, the sensitivity of detection was 10(2) CFU after 25 cycles of PCR and 1 (10(0)) CFU after a 50-cycle double PCR. The efficacy of these primers was demonstrated on environmental isolates which had previously been confirmed as Salmonella species by the use of conventional cultural techniques. In addition, positive amplifications resulted from Salmonella species in environmental samples including soil and water.

Animals↗

PubMed1992

Polymerase chain reaction and gene probe detection of the 2,4-dichlorophenoxyacetic acid degradation plasmid, pJP4.

Specific and sensitive detection of indigenous and introduced degradative organisms is an essential prerequisite to their use in remediation of toxic waste and soil systems. Procedures were employed for the use of polymerase chain reaction and gene probes for sensitive detection of the 2,4-dichlorophenoxyacetic-acid-degrading bacterium, Alcaligenes eutrophus JMP134(pJP4). Two 20-mer oligonucleotide primers were identified for amplification of a 205-bp region of the tfdB gene of pJP4, and optimum conditions for amplification were determined. Both the polymerase chain reaction amplification process and hybridization with the 5'-end-labelled probe were found to be specific to organisms containing plasmid pJP4 or its derivative pRO103. Detection limits were determined for the template supplied either as bacterial cells or purified plasmid DNA. The detection was sensitive up to an initial inoculum of 3,000 CFU or 156 pg of total plasmid DNA. However, when the amplified product was transferred to a nylon membrane and hybridized with the 5'-end-labelled probe, the detection sensitivity increased to 300 CFU or 15.6 pg of plasmid DNA. This sensitive detection method is more specific than use of traditional indicator media (M. A. Loos, Can. J. Microbiol. 21:104-107, 1975). An oligonucleotide (20 bases) complementary to a sequence internal to the 205-bp region was synthesized and utilized as a probe to confirm the specificity of the detection.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1991

Rapid method for processing soil samples for polymerase chain reaction amplification of specific gene sequences.

Bacterial cells can be differentially separated from soil colloids on the basis of their buoyant densities. By using this principle, a modified sucrose gradient centrifugation protocol has been developed for separating bacterial cells from most of the soil colloids. Since the bacterial cell suspension still contained some colloidal soil particles, which inhibited polymerase chain reaction amplification, a new "double" polymerase chain reaction method of analysis was adopted for amplification of Tn5-specific gene sequences. This new protocol allowed rapid detection of small numbers (1 to 10 CFU/g) of bacterial cells present in soil samples.

Base Sequence↗

PubMedDate not supplied

A rapid method for screening for Salmonella typhimurium in a chicken cecal microbial consortium using gene amplification.

A rapid sample processing method has been developed to detect low numbers of Salmonella typhimurium in a chicken cecal microbial consortium. Using phoP-specific primers under stringent amplification conditions and gene probe analysis, fewer than 100 colony-forming units (CFUs) were detectable when pure cultures were employed. When the polymerase chain reaction assay was run on cecal contents from birds infected with S. typhimurium, only positive cecal samples containing as few as 700 CFUs reacted to the assay, and the negative bird samples reacted only when the samples were spiked with S. typhimurium cells. The method employed for sample processing is simple and provides a sensitive means of detecting S. typhimurium-specific sequences in trace amounts in the presence of mixed chicken cecal microbial populations.

Animals↗