Explore the vast range of titles available.

We monitored the presence of Listeria monocytogenes in environmental sources and evaluated phenotypic and molecular characteristics of the isolates recovered. L. monocytogenes was isolated in 12 of the 107 samples from wild and farm environments, and from vegetation. Most isolates (83.3%) were of serotype 1/2a and the remainder (2) were of serotype 4b. All 12 isolates were susceptible to the whole range of antimicrobials tested. These 12 strains were carriers of the virulence genes prfA, hlyA, actA, plcA, plcB, inlA, inlB, inlC, and inlJ. The detection of the inlA gene in 4 strains using the PCR-RFLP suggests the potential of some of these strains to penetrate into epithelial cells of the intestinal barrier. Macrorestriction analysis also confirmed clonal identity of some environmental isolates with food and human isolates. These results indicate that the external environment is a source of potentially pathogenic strains of L. monocytogenes.

The collection of 23 coagulase-positive Staphylococcus aureus strains isolated mainly from food in the Czech Republic were tested on the ability to form biofilms in the presence of ampicillin and vancomycin. The antimicrobial sensitivity (16 antibiotics) was determined in all strains by the standard disc diffusion method on Mueller-Hinton agar plates (NCCLS). The resistance to ampicillin was found in 16 strains (69.5%), all strains being susceptible to vancomycin. The formation of biofilm was conducted in 96-well, polystyrene microtiter plates COSTAR 3797 in tryptic soy broth (TSB) with 1% of glucose for 24 h at 30 deg C. Staining with crystal violet (0.1%) was used for biofilm quantification. Ampicillin (0.5, 2, and 4 mg/l) and vancomycin (32, 64 and 128 mg/l) were added: (i) direct addition of the agent to the well at zero time, (ii) after 24 h to washed well, (iii) after 24 h directly to well with the cell suspension. The tested types of ampicillin treatment did not confirm the impact of resistance on the biofilm production among the strains tested. The addition of vancomycin at zero time of cultivation effectively suppressed the biofilm production. Other types of treatment showed unequal strain dependent response. Planktonic cells demonstrated a higher sensitivity to antibiotics than the biofilm forming cells.

We determined the prevalence and antibiotic resistance of enterococci isolated from raw foods of animal origin (pork, poultry meat, cow milk, ewe milk, ewe cheese). All samples were positive for enterococci. The lowest count of enterococci was found in pork (2.00 log CFU/square cm), while bryndza cheese contained the highest count (4.99 log CFU/g). Among the 349 Enterococcus isolates, 49% were E. faecalis, 29% E. faecium, and 13% Enterococcus spp. Tetracycline and gentamicin resistance were the most common. We found the highest tetracycline resistance levels (91%) in isolates from poultry samples. These isolates also displayed multidrug resistance to all antibiotics tested. The most common vancomycin-resistant species in poultry and milk was E. faecalis. In contrast, pork samples contained vancomycin-resistant E. faecium isolates. It is interesting to note that vancomycin resistance in pork and poultry samples was found only in combination with either four (28%) or all five (14%) of the tested antibiotics. Our results suggest that raw products of animal origin are possible reservoirs of multi-antibiotic resistant enterococci in the food chain.

The assessment of detection sensitivity of five microbial inhibition tests (MITs), STAR (screening test for antibiotic residues) with the test strain Bacillus subtilis BGA, Delvotest SP-NT, Total Antibiotics, Kalidos TB, and Kalidos MP with the test strain Bacillus stearothermophilus var. calidolactis to five aminoglycosides (AMGs), gentamicin, neomycin, streptomycin, kanamycin, and spectinomycin in fortified milk samples were studied. The sensitivity of MITs to AMGs was evaluated on the basis of experimental determination of detection limits (LODs) of MITs for AMGs. The LODs of these tests were compared with the maximum residue limits (MRLs) established for milk by the Commission Regulation (EU) No. 37/2010. LODs of STAR for AMGs in fortified milk samples were at the levels of MRL for neomycin (1.50 microg/g), gentamicin (0.10 microg/g), streptomycin (0.20 microg/g) and kanamycin (0.15 microg/g). Spectinomycin (0.20 microg/g) was not detected at the level of MRL. The LODs determined by Delvotest SP-NT, Total Antibiotics and Kalidos MP were comparable, but only gentamicin and neomycin were reliably detected at the levels of MRL. Kalidos TB was more sensitive to AMGs than Delvotest SP-NT, Total Antibiotics and Kalidos MP. Gentamicin, neomycin and streptomycin were detected at the levels of MRL.

Bacillus anthracis can infect both livestock and humans. The presence of PA and B/C genes (pX01 and pX02 plasmids) as well as susceptibility to several antimicrobial substances was determined in 11 strains of Bacillus anthracis isolated during two recent epizooties of anthrax which occurred in Croatia in 2002 among sheep and in 2006/2007 in cattle. The pX01 plasmid was observed in all of the examined strains, including vaccinal Sterne strains. However, the pX02 plasmid was detected in only eight out of eleven examined field strains of Bacillus anthracis while in vaccinal strains it was not detected at all. Determination of MIC's revealed susceptibility to amoxicillin, amoxicillin with clavulanic acid, ciprofloxacin, gentamicin and tetracycline. All strains were resistant to sulfamethoxazole with trimethoprim and cefotaxime.

Three hundred and ten enterococcal isolates (178 Enterococcus faecium, 68 E. durans, 49 E. faecalis, 8 E. italicus, 3 E. gallinarum, 3 E. casseliflavus, and 1 E. hirae) from Slovak Bryndza cheese were evaluated for susceptibility to nine antimicrobial agents (vancomycin, teicoplanin, ampicillin, streptomycin, gentamicin, erythromycin, rifampicin, nitrofurantoin, and ciprofloxacin). All enterococcal isolates from Bryndza cheese were susceptible to ampicillin, streptomycin, gentamicin, vancomycin, and teicoplanin as determined by the disk diffusion method. Vancomycin resistance genes vanA and vanB were not detected. Resistance rates of enterococcal isolates to rifampicin, erythromycin, ciprofloxacin, and nitrofurantoin were 24, 26, 2, and 1%, respectively. Thirty-six % of E. faecium isolates and 22% of the E. faecalis isolates were resistant to erythromycin. Resistance to rifampicin was similar in E. faecium (31%) and E. faecalis (29%). Both E. faecium and E. faecalis strains showed the same resistance to ciprofloxacin (2%). E. durans isolates showed low levels of resistance to rifampicin, erythromycin, ciprofloxacin, and nitrofurantoin (1-4%). Forty-eight (30 %) of the E. faecium isolates, two (3%) of the E. durans isolates, and six (12%) of the E. faecalis isolates exhibited multidrug resistance. The highest frequency of resistant enterococci was observed in Bryndza produced in winter season.

The antimicrobial susceptibility of 30 clinical and 30 food Bacillus cereus isolates was determined. All isolates were susceptible to streptomycin, ciprofloxacin and gentamicin, 90 % of them to clindamycin and vancomycin, and 67 % to erythromycin. All isolates were resistant to amoxicillin with clavulanic acid, ampicillin, cefotaxime, ciprofloxacin, cloxacillin, cefotaxime with clavulanic acid and penicillin. The MIC values (determined by E-tests) were 48-256 mg/L for ampicillin, 0.19-1.5 mg/L for gentamicin, 0.125-1.0 mg/L for clindamycin, 0.047-4.0 mg/L for erythromycin and 1.5-16 mg/L for vancomycin. The MICs 4.6-18.75 g/L were observed for penicillin using the microdilution method. The presence of metallo-beta-lactamases was detected by E-test for 100 % of strains. Nonhemolytic diarrheal enterotoxin (NHE) was produced by 98.3 % of strains, while 31.7 % of them produced hemolytic diarrheal enterotoxin (HBL). Clinical isolates produced 10 % more HBL than food isolates. The psychrotrophic strains isolated from food samples produced NHE at 6.5 deg C in 73 % of cases.

The study was aimed at the assessment whether foodstuffs contaminated with Bacillus cereus may concurrently be vectors of spreading resistance. The contamination of foodstuffs with B. cereus strains was found in 31 % of dairy and in 28 % of meat products tested. Only one product from skimmed milk was contaminated. High-fat milk products that were heat-treated during the technological process (87 samples), as well as heat-treated meat products (65 samples), were contaminated significantly frequently (63 % and 48 % of the samples, respectively, P0.01). Almost all B. cereus isolates displayed low susceptibility to ampicillin, cephalothin, and to oxacillin. Except for streptomycin (STR) resistance, resistance to other 8 antimicrobial agents occurred sporadically. The STR resistant isolates came particularly from spreading butter (8 samples, P0.05). It was established that the same samples were contaminated with two subpopulations of B. cereus with different STR resistances. The frequent occurrence of B. cereus in foodstuffs with either fat content and/or subject to heat treatment in processing makes these products risky. However, our study did not confirm that foodstuffs contaminated with B. cereus were concurrently vectors of transmissible resistance genes.

Enterotoxigenic Bacillus cereus was detected in a variety of meat stuffs (36), ready-to-cook products (5), and swabs (7). The bacterial colonies isolated from PEMBA agar were identified as B. cereus. The 85 isolates were examined for the enterotoxin production using both TECRA-VIA and BCET-RPLA kits (ELISA - 47, RPLA - 38). Thirty two isolates (66%) were positive for enterotoxin using the ELISA test while only 15 isolates (39%) gave positive results in the RPLA test system. In total, 91.8% and 84% of the strains isolated in our laboratory were enterotoxigenic as determined using TECRA-VIA and BCET-RPLA, respectively. Parallel enterotoxin positive results obtained using both tests were demonstrated in only 9 isolates from 19 assessed. Coincidental negative results from both kits were established for 3 isolates only. The isolates of B.cereus from meat were resistant to cephalothin (57%), clindamycin (14%), oxytetracycline (14%), and erythromycin (7%). The isolates from swabs were resistant to cephalothin (83%), erythromycin (16%), clindamycin (16%) and enrofloxacin (16%).