Validation of direct plating of a stool sample as a method for Listeria monocytogenes detection

The aim of current studies was to validate the direct plating of a stool sample for Listeria monocytogenes detection, using selective medium Palcam agar with Palcam selective supplement. Validation was performed using stool samples collected from healthy humans inoculated with Listeria sp. strains. Stool samples were frozen to determine the influence of freezing on method robustness. The presented research defines the Listeria monocytogenes limit of detection (LOD) as 103 cfu/g of stools for fresh and frozen samples. Repeatability and reproducibility of the method has been confirmed using statistical methods. We show the effectiveness of direct plating of stool samples on Palcam agar with Palcam selective supplement collected for Listeria monocytogenes detection. This method could be useful for this pathogen detection in stool samples collected from patients with diarrhoea

Comparison of Antimicrobial Resistance of Campylobacter jejuni and Campylobacter coli Isolated from Humans and Chicken Carcasses in Poland

Campylobacter-assiociated gastroenteritis remains an important cause of morbidity worldwide, and some evidence suggests that poultry is an important source of this foodborne infection in humans. This study was conducted to analyze the prevalance and genetic background of resistance of 149 Campylobacter jejuni and 54 Campylobacter coli strains isolated from broiler chicken carcasses and from stool samples of infected children in Poland from 2003 through 2005. Nearly all isolates were susceptible to macrolides and aminoglycosides. The highest resistance in both human and chicken strains was observed for ciprofloxacin (more than 40%), followed by ampicillin (13 to 21%), and tetracycline (8 to 29%). Resistance to ampicillin and tetracycline rose significantly between 2003 and 2005. Slight differences in resistance between human and chicken isolates indicate that although chicken meat is not the only source of Campylobacter infection in our population, it can be involved in the transmission of drug-resistant Campylobacter strains to humans

Plasmid diversity in arctic strains of Psychrobacter spp.

Six strains of Psychrobacter spp. isolated from guano of little auks collected on Spitsbergen island (Arctic) carried nine plasmids that were fully sequenced. These replicons (ranging in size from 2917 to 14924 bp) contained either repA (ColE2-type) or repB (iteron-type) replication systems of a relatively narrow host range, limited to Psychrobacter spp. All but one of the plasmids carried predicted mobilization for conjugal transfer systems, encoding relaxases of the MOBQ, MOBV or MOBP families. The plasmids also contained diverse additional genetic load, including a type II restriction-modification system and a gene encoding a putative subunit C of alkyl hydroperoxide reductase (AhpC)-an antioxidant enzyme and major scavenger of reactive oxygen species. Detailed comparative sequence analyses, extended to all plasmids identified so far in psychrophilic bacteria, distinguished groups of the most ubiquitous replicons, which play a key role in horizontal gene transfer in cold environments