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Results reveal that low-molecular-weight DNA synthesized by retron reverse transcriptase of Salmonella enterica is double-stranded with single-stranded overhangs unlike the more commonly produced single-stranded DNA by procaryotes. Data indicate that the plasmid containing three open reading frames confers phage resistance onto the host cell independent of double-stranded DNA synthesis.

This study was aimed at determining the prevalence and characterising the strains of Salmonella species in various captive reptiles in the Czech Republic. A total of 211 samples of cloacal swabs from lizards, chelonians and snakes, and 14 swabs from terraria surfaces were collected between November 2014 and July 2015. After isolation according to the reference method (EN ISO), Salmonella spp. isolates were characterised using serotyping and macrorestriction analysis followed by pulsed field gel electrophoresis and antimicrobial susceptibility testing. Altogether, 39 isolates were obtained from 29 (19%) reptiles and from terraria surfaces. Among the different reptilian species, Salmonella spp. were found in 22 (25.6%) lizards, three (17.6%) snakes and four (8%) chelonians with 31 isolates classified as Salmonella enterica subspecies enterica and eight isolates classified as Salmonella enterica subsp. salamae. In total, 14 different serotypes were detected, with the most frequent serotypes being Salmonella Oranienburg, S. Fluntern, S. Tennessee and S. Cotham. Resistance to one antimicrobial agent (ampicillin, tetracycline or streptomycin) was detected in five isolates. The results of the macrorestriction analysis within the serotype groups showed varying level of heterogeneity. This study confirms that reptiles kept as pets can be both carriers and reservoirs of Salmonella spp., and that they can harbour various serotypes with intermittent excretion of the bacteria in faeces. Half of the detected serotypes have been involved in human reptileassociated salmonellosis cases in the past. S. enterica subsp. salamae serotype O:1,13,23;H:z29;H:1,5, monophasic S. enterica subsp. salamae serotype O:40;H:g,t;H:- and its biphasic form (S. enterica subsp. salamae serotype O:40;H:g,t;H:1,5) have apparently been isolated from reptiles for the first time in this study. [ABSTRACT FROM AUTHOR]

A PCR assay with an internal amplification control was developed for Listeria monocytogenes. The assay has a 99% detection probability of seven cells per reaction. When tested against 38 L. monocytogenes strains and 52 nontarget strains, the PCR assay was 100% inclusive (positive signal from target) and 100% exclusive (no positive signal from nontarget). The assay was then evaluated in a collaborative trial involving 12 European laboratories, where it was tested against an additional 14 target and 14 nontarget strains. In that trial, the inclusivity was 100% and the exclusivity was 99.4%, and both the accordance (repeatability) and the concordance (reproducibility) were 99.4%. The assay was incorporated within a method for the detection of L. monocytogenes in raw milk, which involves 24 h of enrichment in half-Fraser broth followed by 16 h of enrichment in a medium that can be added directly into the PCR. The performance characteristics of the PCR-based method were evaluated in a collaborative trial involving 13 European laboratories. In that trial, a specificity value (percentage of correct identification of blank samples) of 81.8% was obtained; the accordance was 87.9%, and the concordance was 68.1%. The sensitivity (correct identification of milk samples inoculated with 20 to 200 L. monocytogenes cells per 25 ml) was 89.4%, the accordance was 81.2%, and the concordance was 80.7%. This method provides a basis for the application of routine PCR-based analysis to dairy products and other foodstuffs and should be appropriate for international standardization. [ABSTRACT FROM AUTHOR]