Selection of an Escherichia coli O157:H7 bacteriophage for persistence in the circulatory system of mice infected experimentally

A bacteriophage lytic for Escherichia coli O157:H7 was isolated from bovine manure. Following in-vivo selection, the phage acquired the capacity to persist in the circulatory system of mice for at least 38 days. When mice were infected experimentally with E. coli O157:H7 (10(7) CFU/mouse), simultaneous injection of the mice with phage (10(8) PFU/mouse) cleared E. coli O157:H7 from the mice within 48 h.

Characterization of the second internal transcribed spacer of ribosomal DNA of Calicophoron daubneyi from various hosts and locations in southern Italy

Isolates of the rumen fluke Calicophoron daubneyi (Digenea: Paramphistomidae) from various hosts and three locations in southern Italy were characterized genetically. The second internal transcribed spacer (ITS-2) of ribosomal DNA (rDNA) plus flanking 5.8S and 28S sequence (ITS-2+) was amplified from individual rumen flukes by PCR. PCR-linked restriction fragment length polymorphism (PCR-RFLP) analysis was performed using four different restriction endonucleases, and PCR products were sequenced. The PCR analyses from all the C. daubneyi specimens produced identical fragments, and the PCR-RFLP analyses did not show, with respect to any of the four restriction endonucleases, any differences between the C. daubneyi specimens. The sequence analyses of the ITS-2+ from each of the C. daubneyi specimens showed them all to be 428 bp, and composed of the entire ITS-2 sequence (282 bp) plus the two partial flanking conserved sequences, 5.8S (99 bp) and 28S (47 bp). No intra-specific variation was observed in the nucleotide composition of the ITS-2+ (homology=100%). There was, however, an observable inter-specific variation between the ITS-2+ of C. daubneyi and the ITS-2+ of both Calicophoron calicophorum (homology=97.2 %) and Calicophoronmicrobothrioides (homology=97.4 %), both previously deposited in the GenBank. The finding of the present study shows that, as has already demonstrated for other parasitic helminths, ITS-2 can serve as an effective genetic marker for the molecular identification of paramphistomes, and as a useful tool for developing molecular epidemiological techniques for the study of C. daubneyi transmission patterns and prevalence in definitive and intermediate hosts.

[Coxiella burnetii: what is the reality?]

After the Second World War, in Italy Q Fever or Coxiellosis has been shown a significant relevance, a recrudescence with an epidemic state for over ten years. Later, the infectious disease occurred as endemic since the 80s, the outbreaks were just isolated. Workflows analysis of some authors has demonstrated the spread out of the infection throughout Italian herds with a prevalence ranging from 1.2 per cent to 10 per cent. Our survey carried out throughout Campania area in cattle has shown a real positivity over 14 per cent performing the IFAT for the detection of IgG antibodies for Coxiella burnetii. Therefore, it has been so important to stress the influence of cattle farming management in stables as a real risk of Coxiellosis. For example, the Relative Risk (RR) has been registrated about 6.84 (2.18<RR<21.4) in comparison with some herds permanently housed than those kept unhoused and about 8.4 (1.8<RR<38.6) in housed herds and those permanently kept at pasture. Therefore, we have detected a seroprevalence of Q Fever about 11.8 per cent within sheep and about 6.3 per cent within goats. The investigations have focused buffaloes too, tested by several authors, especially from India, but in Italy, only Galiero has recorded significant results: the overall seroprevalence (1.2 per cent) was observed within 1012 buffaloes. Other studies have demonstrated that dogs may transmit Q Fever to humans by infected birth fluids and membranes and by urine. Because of this observation, addressed some of our search projects to assess possible relation among other pathogens, such as Leishmania infantum, Rickettsia conori and Ehrlichia canis. The results have confirmed the presence of C. burnetii (seroprevalence about 7 per cent) within tested dogs in southern Italy. There was no direct estimated relationship between C. burnetii and E. canis and R. conori, instead of significant relation has been shown for L. infantum. The investigation focused on the direct interaction between seropositivity and the age of ruminants. For example, the highest prevalence has been observed in cows and sheep ranging from 3-5 years in which the infection risk was higher than in younger herds. In accordance with the workflows serological analysis, C. burnetii is widespread in Italy among housed ruminants. PCR assay was, therefore performed to test cows with clinical signs of abortion and neonatal mortality. All the survey involved 305 animals (267 foeti and 38 stillborn) with 77 positive herds showing DNA of C. burnetii. To detect C. burnetii pathogen in milk samples, two methods have been combined: the immunomagnetic separation (IMS) and PCR assay, obtaining an increasing of sensitivity (10(-17)) more than only PCR technique (10(-8)). The overall analysis of serological and biomolecular results has demonstrated that C. burnetii is really widespread and may have detrimental effects on farm management system.

Single-step method for rapid detection of Brucella spp. in soft cheese by gene-specific polymerase chain reaction

Brucellosis can be transmitted to man by direct contact with infected animals or through contaminated meat, milk and dairy products (Nicoletti, 1989). The analysis of Brucella spp. is carried out in the laboratory by microbiological or serological assays (Alton et al. 1988). The first are more specific but are also time-consuming and expose the analyst to the risk of infection (López-Merino, 1991). However, the latter can result in false positives owing to cross reactivity with other Gram-negative bacteria (Diaz-Aparicio et al. 1994). Because of these limitations, the amplification in vitro of specific DNA regions by the polymerase chain reaction (PCR) could represent a powerful tool for rapid and specific diagnostic analysis. In recent years, several PCR methods have been developed to amplify specific DNA sequences of Brucella strains (Herman & de Ridder, 1992; Romero et al. 1995; Valentino et al. 1997). In addition, direct analysis of Brucella in contaminated abortive tissues (Fekete et al. 1992), milk and blood (Leal-Klevezas et al. 1995; Rijpens et al. 1996) has been reported.

In this paper we describe a method for gene-specific PCR amplification of a 443 base pair (bp) fragment of Brucella DNA that belongs to a gene encoding for a 31 kDa outer membrane protein. This protein (BCSP-31) is a membrane antigen characteristic of the Brucella genus (Mayfield et al. 1988). The PCR method was developed for the analysis of soft cheeses. We focused our attention on Mozzarella, Pecorino and ricotta samples, because such products are not subjected to the natural microbial autopurification process of maturing. They are widely consumed in Italy and a relationship between infected foods and the areas where brucellosis is a human zoonosis is a possibility.

The analysis was performed without purification of DNA from bacteria. Indeed, after homogenization, the sample was subjected to thermal shock by freeze–thaw cycles that lysed bacteria and solubilized nucleic acids for subsequent PCR amplification. Amplified DNA fragments were separated by agarose gel electrophoresis and visualized by ethidium bromide staining. Several brands of soft cheeses and ricotta contaminated at different levels with Brucella cells were analysed by our procedure to evaluate the detection sensitivity and the repeatability of the method.

Simultaneous identification of antibodies to Brucella abortus and Staphylococcus aureus in milk samples by flow cytometry

Two flow cytometric assays are described herein. The single cytometric test (SCT) detects antibodies to either Brucella abortus or Staphylococcus aureus in the serum or milk of a cow or water buffalo. The double cytometric test (DCT) detects both anti-B. abortus and anti-S. aureus antibodies concurrently. In the SCT, the sample to be tested is incubated in succession with the antigen (either B. abortus or S. aureus) and the proper secondary antiserum (fluorescein isothiocyanate-labelled rabbit anti-cow immunoglobulin antiserum or rabbit anti-water buffalo immunoglobulin antiserum). In the DCT, the sample to be tested is incubated first with B. abortus and S. aureus antigens and then with the secondary antiserum. The B. abortus antigen used in the DCT is covalently bound to 3-microm-diameter latex particles. The difference in size between B. abortus and S. aureus permits the establishment of whether the antibodies are directed against one, the other, or both antigens. When compared to the complement fixation test, the SCT and DCT each show a specificity and a sensitivity of 100%. The SCT has been used previously to detect anti-S. aureus antibodies. Here its use is extended to the detection of anti-B. abortus antibodies. The DCT is described here for the first time. The DCT appears to be useful for large-scale brucellosis eradication programs. It offers the possibility of using one test to identify animals that are serologically positive for both B. abortus and S. aureus.

Detection of antibodies to Staphylococcus aureus in water buffalo milk by flow cytometry

An assay has been developed to detect antibodies to Staphylococcus aureus in water buffalo milk by flow cytometry. The method was the protein A-deficient strain Wood 46 of S aureus incubated with milk samples and fluorescein-labelled rabbit anti-water buffalo antiserum. The assay can detect antibodies when the pathogen is not detectable by bacterial tests and can determine the antibody titre directly on undiluted samples.