Use of an alkaline phosphatase-labeled synthetic oligonucleotide probe for detection of Campylobacter jejuni and Campylobacter coli

Development and evaluation of immunochromatographic assay for simple and rapid detection of Campylobacter jejuni and Campylobacter coli in human stool specimens

An immunochromatographic assay (Campy-ICA) using a newly generated single monoclonal antibody against a 15-kDa cell surface protein of Campylobacter jejuni was developed. When cell suspensions of 86 C. jejuni strains and 27 Campylobacter coli strains were treated with a commercially available bacterial protein extraction reagent and the resulting extracts were tested with the Campy-ICA, they all yielded positive results. The minimum detectable limits for the C. jejuni strains ranged from 1.8 x 10(4) to 8.2 x 10(5) CFU/ml of cell suspension, and those for the C. coli strains ranged from 1.4 x 10(5) to 4.6 x 10(6) CFU/ml of cell suspension. All 26 non-Campylobacter species tested yielded negative results with the Campy-ICA. To evaluate the ability of the Campy-ICA to detect C. jejuni and C. coli in human stool specimens, suspensions of 222 stool specimens from patients with acute gastroenteritis were treated with the bacterial protein extraction reagent, and the resulting extracts were tested with the Campy-ICA. The Campy-ICA results showed a sensitivity of 84.8% (28 of 33 specimens) and a specificity of 100% (189 of 189 specimens) compared to the results of isolation of C. jejuni and C. coli from the stool specimens by a bacterial culture test. The Campy-ICA was simple to perform and was able to detect Campylobacter antigen in a fecal extract within 15 min. These results suggest that Campy-ICA testing of fecal extracts may be useful as a simple and rapid adjunct to stool culture for detecting C. jejuni and C. coli in human stool specimens.

Laboratory approaches to infectious diarrhea

Future applications of advanced molecular diagnostics in clinical laboratories will enhance significantly capabilities to diagnose bacterial, parasitic, and viral agents in the early course of disease through enhanced assay sensitivities and specificities and improved turnaround times, theoretically leading to more timely and directed therapeutic intervention. Until such time, clinicians must continue to rely on clinical judgment and the diverse battery of traditional culture techniques, direct examination (including light microscopy and electron microscopy), and immunoassays that are available. Cost considerations and the ever-increasing array of infectious agents responsible for infectious gastroenteritis will continue to drive the development of practice guidelines to assist practitioners with reasoned and reasonable approaches to management of diarrheal illnesses.

Microtitre plate hybridization system for detection of thermophilic Campylobacter rRNA

A microtitre plate nucleic acid probe hybridization system was developed for the detection of ribosomal RNA from thermophilic Campylobacter (Camp. jejuni, Camp. coli, Camp. lari and Camp. upsaliensis). A specific DNA probe obtained by amplification of 23S rRNA sequences using the polymerase chain reaction technique was immobilized on a microtitre plate, and used for hybridization with target 23S rRNA from cell lysates. The RNA-DNA hybrids thus formed in the wells were detected by an immunoenzymatic assay using a monoclonal antiRNA-DNA hybrid antibody. The sensitivity of this system was 2.7 x 10(4) cells ml(-1). This simple, sensitive and inexpensive hybridization and immunoenzymatic assay system should facilitate the detection of Campylobacter in food and clinical samples.

Microtitre plate riboprobe system for detection of ultrasonicated Campylobacter jejuni genomic DNA

Microtitre plate nucleic acid probe hybridization systems were developed for the detection of thermophilic Campylobacter and Campylobacter jejuni. Specific RNA probes obtained by in vitro transcription of DNA templates synthesized by polymerase chain reaction using two sets of specific primers incorporating bacteriophage T7 promoter sequences were immobilized on a microtitre plate. The hybridizations were carried out on samples of genomic DNA sheared by ultrasonication. Optimum conditions for the ultrasonic treatment were determined in order to obtain the highest degree of hybridization with immobilized RNA probe. Finally, detection of RNA-DNA hybrids in the wells was accomplished by an immunoenzymatic assay using a monoclonal anti-RNA-DNA hybrid antibody. This rapid, simple hybridization and immunoenzymatic assay system will facilitate the detection of Campylobacter in foods and clinical samples.

Allele-specific hybridization of lipoprotein lipase and factor-V Leiden missense mutations with direct label alkaline phosphatase-conjugated oligonucleotide probes

Direct label alkaline phosphatase (AP) conjugated oligonucleotide probes (AP-DNA) were prepared to assess their utility for allele-specific detection of single base substitutions. Oligonucleotide conjugates were designed to detect point mutations in the genes for lipoprotein lipase (LPL) and coagulation factor-V (FV). Genomic DNA samples, including ones known to harbor point mutations in the genes for LPL and FV, were prepared from whole blood and subjected to polymerase chain reaction (PCR). PCR products were analyzed by Southern hybridization with the allele-specific AP-DNA probes and restriction endonuclease analysis. Thermal profiles for hybridization indicate optimal allele-specific selectivity was achieved with temperatures ranging from 45 degrees C to 55 degrees C at a total Na divided by concentration of 150 mM. Under these conditions the base changes studied were easily discriminated with allele specific hybridization signals in excess of 200:1 as estimated by scanning densitometry. Complete concordance was observed between hybridization and restriction analyses for 175 LPL and 201 FV clinical and reference samples. The total time for analysis of the PCR products was less than 2 h with a dot blot hybridization protocol.

Probes and polymerase chain reaction for detection of food-borne bacterial pathogens

DNA-hybridization and the polymerase chain reaction (PCR) are techniques commonly used to detect pathogenic bacteria. In this paper, the use of these techniques for detection of Salmonella, E. coli, V. cholerae, non-O1 Vibrio, Yersinia enterocolitica, Campylobacter, Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, and C. botulinum is reviewed with emphasis on application in food microbiology. In food control, DNA-techniques have most often been used in a 'culture confirmation' fashion, i.e. bacteria are enriched and sometimes even purified by traditional culture procedures and thereafter identified by the use of DNA-based methods. The most desirable approach is, however, to detect organisms directly in the food, but major problems remain to be solved before this can be routinely performed.

Evaluation of a PCR based assay for specific detection of Campylobacter jejuni in chicken washes

An assay for Campylobacter jejuni based on the polymerase chain reaction was developed in our laboratory and shown to be a sensitive and specific method to identify this bacterium in pure culture. This assay was evaluated as a method to rapidly detect C. jejuni attached to chicken carcasses. Chicken carcasses were sampled for PCR using three methods including pre-enrichment of the washes, direct plating of the washes and differential centrifugation of the washes prior to testing. It was found that plating the wash solutions on Campy Cefex plates prior to performing PCR was the most specific and reliable of the three treatment methods evaluated.

Rapid and sensitive detection of Campylobacter spp. in chicken products by using the polymerase chain reaction

The polymerase chain reaction (PCR) after a short enrichment culture was used to detect Campylobacter spp. in chicken products. After the 16S rRNA gene sequence of Campylobacter jejuni was determined and compared with known sequences from other enterobacteria, a primer and probe combination was selected from the region before V3 and the variable regions V3 and V5. With this primer set and probe, 426-bp fragments from C. jejuni, Campylobacter coli, and Campylobacter lari could be amplified. The detection limit of the PCR was 12.5 CFU. Chicken samples inoculated with 25 CFU of Campylobacter spp. per g were PCR positive after an 18-h enrichment, which resulted in 500 CFU/ml of culture broth. This PCR-culture assay was compared with the conventional method on naturally infected chicken products. Both methods detected the same number of positive and negative samples; however, the results of the PCR-culture assay were available within 48 h.

Oligodeoxynucleotide probes for Campylobacter fetus and Campylobacter hyointestinalis based on 16S rRNA sequences

Deoxyoligonucleotide probes were constructed for the identification of Campylobacter fetus and Campylobacter hyointestinalis based on 16S rRNA sequence data. Probes were targeted to hypervariable regions of 16S rRNA. Specificity of oligonucleotide probes was tested in a colony blot assay with type strains of 15 Campylobacter and Arcobacter species as well as in a slot blot format using genomic DNA extracted from field strains of C. fetus and C. hyointestinalis. Two oligonucleotides were constructed for C. fetus that hybridized with equal specificity with each of 57 biochemically confirmed isolates of C. fetus but not with any other Campylobacter species. The C. hyointestinalis probe reacted with 47 of 48 biochemically confirmed field isolates of C. hyointestinalis. In Southern blot hybridization of BglII digests of genomic DNA, the respective probes reacted within three restriction fragments of either C. hyointestinalis (7.2, 8.2, and 10.1 kb) or C. fetus (7.0, 7.7, and 9.0 kb). This suggests multiple copies of genes encoding 16S rRNA.