PCR-ELISA I: Application to simultaneous analysis of mixed bacterial samples composed of intestinal species

Sixteen oligonucleotide identification probes, designed in this study or adapted from literature, were tested for a PCR-ELISA application to simultaneously detect under standardised conditions selected intestinal bacteria, lactobacilli and bifidobacteria. The level of specificity obtained with most of the probes fulfilled the set criteria. The lack of efficiency of PCR performed with the primers, proposed to be specific for the entire eubacteria domain, and compromises made in hybridisation conditions due to simultaneous usage of multiple probes reduced the sensitivity of the PCR-ELISA test. The method was, however, found to be suitable for detecting predominant members of the intestinal flora. Applicability of the PCR-ELISA test could be further widened using primers with a more restricted specificity in the PCR step, as was demonstrated for the detection of Bifidobacterium with genus-specific primers. Advantages of the PCR-ELISA method include convenient performance and the possibility to test rapidly large amounts of samples with a multitude of probes.

Continuous cultivation of Penicillium chrysogenum. Growth on glucose and penicillin production

A series of constant-mass, continuous cultivations of the penicillin producing mold Penicillium chrysogenum was carried out using a chemically defined medium with glucose as the growth-limiting component. The stoichiometry for growth of P. chrysogenum on glucose was characterized in terms of mass-yield and maintenance coefficients. Saturation kinetics with respect to glucose was used to describe the glucose consumption rate at steady-state conditions. Transient data indicate that the maximum rate of glucose consumption at a particular set of operating conditions is correlated to the metabolic 'capacity' of the mold as reflected by its intracellular RNA content. A progressive loss in the penicillin productivity in glucose limited chemostat cultures was correlated to the formation of two mutants. The two mutants were characterized by their sporulation when grown as surface cultures and by Southern dot-tests for delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase (ACVS), isopenicillin-N synthase (IPNS) and acyl-CoA:6-APA acyltransferase (AT). The loss of penicillin productivity was caused by an increasing fraction of mutants which had lost the genes encoding for all three enzymes needed in the penicillin synthesizing pathway.

Comparison of type I and type II Chlamydia psittaci strains infecting koalas (Phascolarctos cinereus)

The native Australian marsupial Phascolarctos cinereus, otherwise known as the koala, is prone to infection by the obligate intracellular parasite Chlamydia psittaci, which causes ocular 'pink eye' and urogenital 'dirty tail' diseases. Several chlamydial DNA probes to both chromosomal and plasmid sequences were used to type by Southern blot analysis 51 samples taken from wild and captive koalas from habitats on the eastern seaboard of Australia as far apart as Queensland and Victoria. Two types of C. psittaci were observed and called types I and II. Type II was found more frequently than type I and occurred in both ocular and urogenital samples, while type I showed a strong but not absolute preference for ocular sites. Cross-hybridization analyses indicated that type I and type II had about 10% DNA sequence identity to each other. DNA analyses showed that type II was very closely related to some ovine and bovine chlamydiae but type I could not be related to any other C. psittaci strain available. Light and electron microscopic analyses of infected BGM monolayers revealed that the two strains were similar in morphological characteristics. The type I strain was considerably more infectious than the type II strain in BGM cells and in the yolk sacs of embryonated eggs. A PCR based assay detected both type I and type II koala chlamydiae in samples that had been negative by Southern blot and tissue culture and provided the first evidence that both types can occur simultaneously at the one site of infection.

A polymerase chain reaction (PCR) protocol for the specific detection of Chlamydia spp

The polymerase chain reaction is an in vitro procedure for primer-directed enzymatic amplification of specific template nucleic acid sequences. This technique was used to detect and differentiate Chlamydia trachomatis and Chlamydia psittaci in laboratory samples of infected McCoy cells. The polymerase chain reaction was shown to be both sensitive, detecting in the order of one chlamydial DNA molecule in 10(5) cells, and specific. No cross reaction (amplified product) was detected when a variety of mammalian cell and bacterial DNAs were used as template with the Chlamydia-specific oligonucleotide primers.

Detection of Chlamydia psittaci in free-ranging koalas (Phascolarctos cinereus): DNA hybridization and immuno-slot blot analyses

DNA-slot hybridization and immuno-slot blot analyses were compared for the detection of Chlamydia psittaci in crude swab material from free-ranging koalas. Immuno-slot blot analysis detected chlamydiae in 43 out of 68 koalas, with the sensitivity of the assay varying from 52 to 73% depending on the site of infection. Gene probe analysis was also used employing a genus-specific probe pCKO-10 isolated from a koala chlamydial gene library (ocular strain) and a plasmid probe pCKU cloned from a urogenital strain. The sensitivity of these two assays was comparable and they were considerably more efficient than the immuno-slot blot method for the detection of chlamydiae. Comparison of these data with a cell-culture method of detection, previously used with the same samples, demonstrated that gene probe analysis detected more positives than observed with cell culture. However, this appears to reflect more on the condition of the swab material rather than the sensitivity of the method.

Nucleic acid analysis by sandwich hybridization

One of the most significant achievements of the biochemist during the past two decades is the use to which immunologically based assays have been put in clinical diagnosis (Hood et al.: Immunology, 1984). The problem faced and surmounted by immunologists in effecting the transition from research tool to routine clinical assay bears a remarkable similarity to that confronting the molecular biologist today; i.e., how can nucleic acid hybridization, a technique of obvious potential (Meinkoth and Wahl: Anal Biochem 138:267-284, 1984; Syvanen: Med Biol 64:313-324, 1986; Matthews and Kricka: Anal Biochem 169:1-25, 1988), be modified in order to fulfill all necessary parameters of a routine diagnostic assay? There are several such requirements, and the importance placed on each depends on the objectives of the assay: the technique must be sensitive, specific, and reproducible. Other advantages would be cost-effectiveness, ease of manipulation, and amenability to automation. Ideally, the signal detection should be based on a non-radioactive system, because of the instability of probes labelled with isotopes like 32p, and the potential hazards involved in their handling and disposal. The sandwich hybridization for the analysis of nucleic acid sequences was first used in 1977 (Dunn and Hassell: Cell 12:23-36, 1977), but its potential as a diagnostic assay was not realized until 1983, when it was applied to the detection of adenovirus DNA in nasopharyngeal aspirates from children with acute respiratory infection (Ranki et al: Gene 21:77-85, 1983). It has since been modified and used not only for the detection of microbial infection (Virtanen et al.: Lancet i:381-383, 1983; Ranki et al.: Cur Top Microbiol Immunol 104:307-318, 1983; Lehtomaki et al.: J Clin Microbiol 24:108-111, 1986; Virtanen et al.: J Clin Microbiol 20:1083-1088, 1984; Palva and Ranki: Clin Lab Med 5:475-490, 1985; Polsky-Cynkin et al.: Clin Chem 31:1438-1443, 1985; Parkkinen et al.: J Med Virol 20:279-288, 1986; Palva: FEMS Microbiol Lett 28:85-91, 1985; Palva et al: FEMS Microbiol Lett 23:83-89, 1984; Zolg et al.: Mol Biochem Parasitol 22:145-151, 1987; Palva: J Clin Microbiol 18:92-100, 1983), but also for the analysis of nucleotide sequence variations (Langdale and Malcolm: Gene 36:201-210, 1985). We will discuss the development of the sandwich technique and the advantages it conveys over the more conventional nucleic acid hybridization formats, together with new developments which will ensure that it earns a place alongside immunoassay in the diagnostic laboratory.

Comparison of DNA-spot hybridization, cell culture and direct immunofluorescence staining for the diagnosis of avian chlamydiae

DNA-spot hybridization, cell culture and direct immunofluorescence staining were compared for the detection of avian Chlamydia psittaci strains in cell culture dilutions and in routine samples submitted for diagnosis. With dilutions of infected cell culture material, growth in BGM cells was by far the most sensitive technique, detecting 0.01 infected cells (20 elementary bodies) ml-1. DNA-spot hybridization and direct immunofluorescence staining were of approximately equal sensitivity, both detecting 16 infected cells (3.2 x 10(4) elementary bodies) per ml-1. When 27 avian liver and spleen samples were assayed, all 3 tests performed similarly (13 positive and 12 negative by all 3 tests). This suggests that in most avian samples presented for diagnosis, sufficient numbers of chlamydiae are present to allow any of the test to the be used. Thus, the direct immunofluorescence staining method is currently the test of choice for routine diagnosis since it is available in kit form, is relatively simple and quick to perform, and like DNA-spot hybridization, detects non-viable as well as viable organisms. However, if low levels of chlamydiae are to be effectively detected, such as in carrier birds or birds with recently acquired infections, then cell culture should be used.

Comparison of Chlamydia psittaci isolates by restriction endonuclease and DNA probe analyses

DNAs from eight Chlamydia psittaci isolates (koala conjunctivitis, avian psittacosis, avian ornithosis, ovine abortion, ovine polyarthritis, sporadic bovine encephalomyelitis, and feline conjunctivitis) and one Chlamydia trachomatis isolate (lymphogranuloma venereum) were compared by restriction endonuclease and DNA probe analyses. Digestion with HindIII yielded a series of discrete fragments which allowed the differentiation of most isolates. A gene probe, pFEN207, which encodes the chlamydia-specific component of the lipopolysaccharide group antigen was used in Southern hybridizations. The probe was chlamydia specific and hybridized to a single BamHI fragment and multiple HindIII fragments in each isolate. The variation in size of the hybridizing fragments allowed easy differentiation of the isolates and may eventually lead to a meaningful subgrouping of the diverse group of disease agents presently included in the species C. psittaci.

Detection of Chlamydia trachomatis by in situ hybridization with sulphonated total DNA

In situ nucleic acid hybridization was applied to the detection of Chlamydia trachomatis on microscope slides by use of sulphonated total DNA as a probe. Visualization of labelled DNA was obtained using a commercial enzyme-linked monoclonal antibody. A mixture of paraformaldehyde and glutaraldehyde was found to be the best fixative. With high probe concentration (10 micrograms/ml), intracellular inclusions were detected as early as 8 h after inoculating the cell culture. Extracellular elementary bodies could also be detected. Five genital specimens were tested by in situ hybridization; the results were in agreement with those observed by culture.

Enzyme immunoassay and enzyme-linked fluoroimmunoassay for detection of Chlamydia trachomatis antigen

An enzyme immunoassay (EIA) and an enzyme-linked fluoroimmunoassay (ELFIA) utilizing monoclonal antibody to major outer membrane protein of Chlamydia trachomatis L2 were developed for rapid detection of chlamydial antigen in clinical samples. The EIA and ELFIA could detect levels of purified chlamydial outer membrane protein as low as 1.0 and 0.2 ng/ml respectively. However, when EIA and ELFIA were compared to chlamydial isolation using 160 patient samples, the sensitivity rate was 68% and 85% respectively. The sensitivity of the antigen detection method might be increased by simply using less diluted samples than in the present study. Chlamydial antigen was also demonstrated by EIA and ELFIA in 15% and 23% of culture-negative samples. The reason for these false-positive findings remains undetermined.

The use of DNA probes in dental diagnosis and therapy

Recombinant DNA technology now allows for the development of genetic probes specific for a growing number of etiologic disease agents, including those suspected pathogens in the oral environment. The increasing refinement of DNA probe methodologies and sensitivities will ultimately permit their commonplace use with clinical samples for the rapid identification of their bacterial compositions. The use of probe technology potentially offers a much more facile, accurate, and less time-consuming mechanism for the identification of fastidious micro-organisms from the oral cavity, many of which are laborious and difficult to cultivate.

Detection of herpes simplex virus in direct specimens by immunofluorescence assay using a monoclonal antibody

A monoclonal antibody (MAb), designated CHA 437, was developed against herpes simplex virus (HSV). This MAb (isotype, immunoglobulin G2b K) reacted with HSV type 1 and HSV type 2. It showed no cross-reactivity with varicella-zoster virus, cytomegalovirus, or Epstein-Barr virus. Direct detection of HSV antigen in clinical specimens using indirect immunofluorescence with this MAb was compared with tissue culture isolation. For the 682 specimens tested, the direct specimen test gave a sensitivity of 84.6% and a specificity of 95.7%.