Explore the vast range of titles available.

The relationship between the structural degradation of veterinary antibiotics, their antimicrobial activity, and possible mutagenicity after heating have not been well investigated sequentially. This study aimed to evaluate the heat stability of 14 veterinary antibiotics under a short-term heating scenario by characterization of their structural degradation and their relationship to resultant changes in antimicrobial activity. Mutagenicity was also examined in four representative antibiotics after 15-min-heat treatments at two temperatures (100 deg C and 121 deg C). Differential heat stabilities of antibiotics between drug classes, between temperature levels, and among the same class of drugs were discovered. Heat treatment resulted in the reduction of the main peak and the production of new peaks in certain antibiotics, contributing to minimum inhibitory concentration increases of 2- to 1,024-fold. Ranking of heat stability by antibiotic classes at 121 deg C was highest for sulfonamides, followed by lincomycin, colistin, tetracyclines and beta-lactams while at 100 deg C sulfonamides equaled lincomycin, but variability was observed within different tetracyclines and beta-lactams. Correlation analysis suggested that except for doxycycline, structural degradation of the drugs was in good agreement with the reduction in antimicrobial activity. Mutagenicity (Ames) tests on heated chlortetracycline resulted in 2- to 6-fold revertant changes in Salmonella typhimurium TA98 and TA100. The combined results suggest that correlation analysis of structural degradation and antimicrobial activity offers dual evaluation of a drug's heat stability but gives little advantage over assessment of the resultant toxicity.

Se presentan 2 casos de Diabetes Insípida Nefrogénica secundaria a la ingestión de demetil - clor- tetraciclina. El mecanismo de acción de este tipo de Diabetes Insípida parece ser un bloqueo parcial de la acción de la hormona antidiurética endógena en el túbulo renal, posiblemente causado por un impedimento en la producción y acción del AMP-cíclico. Este defecto nefronégico depende de la dosis usada y es reversible.

Diarrheagenic E. coli pathotypes are major foodborne pathogens causing gastrointestinal tract infections leading to hemolytic uremic syndrome and hemorrhagic colitis. Consumption of raw vegetables is encouraged due to its nutrient content and antioxidant properties, although their ingestion is linked to a series of foodborne disease outbreaks. The aim of this study was to evaluate the prevalence of Enterotoxigenic, Enteropathogenic, and Shiga toxin-producing E. coli pathotypes in raw vegetables and ready-to-eat salad for the development of better risk management. A total of 260 vegetable and salad mix (cucumber, lettuce, spinach, and carrot) samples were collected from commercial food markets in Southern districts of Khyber Pakhtunkhawa, Pakistan. About 34 % vegetable samples were contaminated with E. coli strains. 32.4 % E. coli strains from vegetable sample were identified as diarrheagenic E. coli pathotypes. Similarly, 26.7 % of salad samples were contaminated with E. coli pathotypes. 15 % [two Enterotoxigenic E. coli and one Enteropathogenic E. coli] were isolated from spinach salad samples. 25 % [three Enterotoxigenic E. coli, one Enteropathogenic E. coli and one Shiga toxin-producing E. coli] were isolated from mixed salad type A. 40 % [four Enterotoxigenic E. coli, two Enteropathogenic E. coli and two Shiga toxin-producing E. coli] were isolated from mixed salad type B. 92 % diarrheagenic E. coli pathotypes showed resistance against Tetracycline and 87 % to Ampicillin. This study showed that fresh vegetable and their products were contaminated with multidrug-resistant E. coli pathotypes.

Acinetobacter baumannii readily developed antimicrobial resistance to clinically available antibiotics. A. baumannii DU202 is a multi-drug resistant strain, and is highly resistant to tetracycline (MIC greater than 1,024 mu/ml). The surface proteome of A. baumannii DU202 in response to the sub-minimal inhibitory concentration (subMIC) of tetracycline was analyzed by 2-DE/MS-MS and 1-DE/LC/MS-MS to understand the pathways that form barriers for tetracycline. Membrane expression of major outer membrane proteins (Omps) was significantly decreased in response to the subMIC of tetracycline. These Omps with sizes of 38, 32, 28, and 21 kDa were identified as OmpA∧38, OmpA∧32, CarO, and OmpW, respectively. However, transcription level of these Omps was not significantly changed. 1-DE/LC/MS-MS analysis of secreted proteins showed that OmpA∧38, CarO, OmpW, and other Omps were increasingly secreted at tetracycline condition. This result suggests that A. baumannii actively regulates the membrane expression and the secretion of Omps to overcome antibiotic stress condition.

The use of antimicrobials has increased the number of resistant bacteria to these drugs; however, the organic production has restricted the use of these compounds. The objectives of this work were to assess counts of tetracycline-resistant bacteria using conventional microbiology, to compare these results with those obtained for tet(A) and tet(B) genes by qPCR and to investigate both genes in conventional and organic meat. Counts of mesophilic aerobic bacteria were higher in organic beef, while chicken meat obtained higher counts for Enterobacteriaceae. Only tet(B) was higher in conventional pork and chicken meat than in their organic counterparts. The tet(A) gene was found in almost 100% of samples and tet(B) gene changed according to the type of meat. The presence of tet genes suggests that they are widely distributed, especially tet(A), in food of animal origin, even in organic meat samples obtained from animals in which the use of antimicrobials is restricted.

The present criteria and rules controlling the approval of the use of probiotics are limited to antibiotic resistance patterns and the presence of antibiotic resistance genes in bacteria. There is little information available in the literature regarding the risk of the usage of probiotics in the presence of antibiotic pressure. In this study we investigated the development and transfer of antibiotic resistance in Bacillus subtilis selected in vitro by chlortetracycline in a stepwise manner. Bacillus subtilis was exposed to increasing concentrations of chlortetracyclineto induce in vitro resistance to chlortetracycline, and the minimal inhibitory concentrations were determinedfor the mutants. Resistant B. subtilis were conjugated with Escherichia coli NK5449 and Enterococcus faecalis JH2-2 using the filter mating. Three B. subtilis tetracycline resistant mutants (namely, BS-1, BS-2, and BS-3) were derived in vitro. A tetracycline resistant gene, tet (K), was found in the plasmids of BS-1 and BS-2. Three conjugates (BS-1N, BS-2N, and BS-3N) were obtained when the resistant B. subtilis was conjugated with E. coli NK5449. The conjugation frequencies for the BS-1N, BS-2N, and BS-3N conjugates were 4.57×10∨-7, 1.4×10∨-7, and 1.3×10∨-8, respectively. The tet(K) gene was found only in the plasmids of BS-1N. These results indicate that long-term use of probiotics under antibiotic selection pressure could cause antibiotic resistance, and the resistance gene could be transferred to other bacteria. The risk arising from the use of probiotics under antibiotic pressure should be considered in the criteria and rules for the safety assessment of probiotics.

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.

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.