Kathleen Andrews

Varied prevalence of Clostridium difficile in an integrated swine operation.

The objectives of this study were to compare the prevalence of Clostridium difficile (Cd) among different age and production groups of swine in a vertically integrated swine operation in Texas in 2006 and to compare our isolates to other animal and human isolates. Results are based on 131 Cd isolates from 1008 swine fecal samples and pork trim samples (overall prevalence of 13%). The prevalence (number positive/number tested in production type) of Cd was different between the groups (P<or=0.001), and was highest among suckling piglets at 50.0% (61/122), followed by 23.8% (34/143) for lactating sows and effluent from the farrowing barn, 8.4% (10/119) for nursery, 6.5% (4/62) for pork products, 3.9% (15/382) for grower-finisher, and 3.9% (7/180) for breeding boars and sows. Of the 131 isolates, 122 were positive by PCR for both toxins A (tcdA) and B (tcdB) genes, 129 isolates harbored a 39 base pair deletion in the tcdC gene, 120 isolates were toxinotype V, and all 131 of the isolates were positive for the binary toxin gene cdtB. All isolates were resistant to cefoxitin, ciprofloxacin, and imipenem, whereas all were sensitive to metronidazole, piperacillin/tazobactam, amoxicillin/clavulanic acid, and vancomycin. The majority of isolates were resistant to clindamycin; resistant or intermediate to ampicillin; and sensitive to tetracycline and chloramphenicol. There was an increased (P</=0.001) number of isolates for the timeframe of September to February compared to March to August.

Clostridium difficile in retail meat and processing plants in Texas

The incidence and severity of disease associated with toxigenic Clostridium difficile have increased in hospitals in North America from the emergence of newer, more virulent strains. Toxigenic C. difficile has been isolated from food animals and retail meat with potential implications of transfer to human beings. The objective of the present study was to determine the prevalence of C. difficile in pork from sausage manufacturing plants and retail meat in Texas. Twenty-three C. difficile isolates were detected from 243 meat samples (9.5%) from 3 sausage-manufacturing plants and 5 retail meat outlets from 2004 to 2009. Twenty-two isolates were positive for toxins A, B, and binary toxin, and were characterized as toxinotype V, PFGE type-NAP7, or “NAP7-variant.” Susceptibilities to 11 antimicrobial agents in the current study were similar to those reported previously for toxinotype V isolates, although the results suggested somewhat reduced resistance than reported for other meat, animal, or human clinical toxinotype V isolates.

Prevalence and Genotypic Characteristics of Clostridium difficile in a Closed and Integrated Human and Swine Population

ABSTRACT Recently, an apparent rise in the number of cases attributed to community-acquired Clostridium difficile infection has led researchers to explore additional sources of infection. The finding of C. difficile in food animals and retail meat has raised concern about potential food-borne and occupational exposures. The objective of this study was to compare C. difficile isolated from a closed population of healthy individuals consisting of both humans and swine in order to investigate possible food safety and occupational risks for exposure. Using a multistep enrichment isolation technique, we identified 11.8% of the human wastewater samples and 8.6% of the swine samples that were positive for C. difficile. The prevalences of C. difficile in swine production groups differed significantly (P < 0.05); however, the prevalences in the two human occupational group cohorts did not differ significantly (P = 0.81). The majority of the human and swine isolates were similar based on multiple typing methods. The similarity in C. difficile prevalence in the human group cohorts suggests a low occupational hazard, while a greatly decreased prevalence of C. difficile in later-stage swine production groups suggests a diminished risk for food-borne exposure. The similarity of strains in the two host species suggests the possibility of a common environmental source for healthy individuals in a community setting.

Characterization of antibiotic and disinfectant susceptibility profiles among Pseudomonas aeruginosa veterinary isolates recovered during 1994-2003

To evaluate susceptibility of Pseudomonas aeruginosa veterinary isolates to antibiotics and disinfectants.

Interaction of T-2 toxin with bovine carrier erythrocytes: effects on cell lysis, permeability, and entrapment.

Hemolysis, morphological changes, binding, and effect on encapsulation of exogenous substances were used as a basis to study the interaction of the trichothecene mycotoxin, T-2 toxin, with erythrocytes. T-2 toxin did not cause hemolysis of bovine erythrocytes but readily hemolyzed rat erythrocytes. T-2 toxin interaction with bovine erythrocytes was minimal because T-2 toxin did not bind appreciably to the erythrocytes. Entrapment of T-2 toxin in carrier erythrocytes was independent of toxin concentration, and interaction of T-2 toxin with erythrocytes did not affect the entrapment of the markers sucrose or inulin. T-2 toxin rapidly diffuses from carrier erythrocytes with less than 20% remaining after 4 hr of incubation. Cross-linking of the erythrocyte membrane with glutaraldehyde prevents T-2 toxin efflux from carrier erythrocytes.

Planktonic and Biofilm Community Characterization and Salmonella Resistance of 14-Day-Old Chicken Cecal Microflora-Derived Continuous-Flow Cultures

This study evaluated the composition of gastrointestinal bacterial communities in birds during an age in which their susceptibility to Salmonella is highly diminished. One of the challenges to developing probiotics is to develop an efficacious culture of minimal diversity that includes bacteria that are vital contributors to protection from pathogens, but excludes unnecessary species. This study used in vitro continuous-flow culture techniques to test the ability of mixed bacterial cultures acquired from in vivo sources, to resist colonization by a marker Salmonella enterica serovar Typhimurium, and then characterized the constituents of both biofilm and planktonic communities by biochemical, phenotypic, and molecular methods. These cultures, initiated from 14-day-old chicks, were all able to restrict colonization by Salmonella in an average of 10 days. Eighteen species of bacteria from 10 different genera were characterized. However, each culture contained a mixture of only 11 species, which included lactic acid bacteria. Biofilms contained less than 50% of the species found in the planktonic communities. Although not adults, the diversity of microbes within the cecal cultures from 14-day-old birds represents a community complex enough to oppose colonization by a nonindigenous bacteria in vitro. These results describe bacterial mixtures containing less diversity than in previously described avian protective cultures.

Survey of Clostridium difficile in retail seafood in College Station, Texas

The incidence and severity of disease associated with toxigenic Clostridium difficile have increased in hospitals in North America with the emergence of newer, more virulent strains. Toxigenic C. difficile has been isolated from food animals and retail meat with potential implications of transfer to humans. The objective of the present study was to investigate the prevalence of C. difficile in retail seafood from grocery stores in College Station, Texas. C. difficile was found in 4.5% (3/67) of shellfish and finfish samples. The positive samples included one each from fresh mussel, frozen salmon and frozen shrimp. The mussel and salmon isolates were characterized as toxinotype V and pulsed-field gel electrophoresis (PFGE) type-NAP7. The shrimp isolate was identified as toxinotype XII, but had an unknown PFGE type. Susceptibilities to 11 antimicrobial agents were identical for the mussel and salmon isolates and were sensitive to eight of 11 antimicrobials (including ampicillin) and intermediate to clindamycin. However, the shrimp isolate was resistant to clindamycin and ampicillin. This study demonstrates that seafood, like other food commodities, can be contaminated by C. difficile.

Planktonic and biofilm communities from 7-day-old chicken cecal microflora cultures: characterization and resistance to Salmonella colonization.

Information implicating bacterial biofilms as contributory factors in the development of environmental bacterial resistance has been increasing. There is a lack of information regarding the role of biofilms within the microbial ecology of the gastrointestinal tract of food animals. This work used a continuous-flow chemostat model derived from the ceca of 7-day-old chicks to characterize these communities and their ability to neutralize invasion by Salmonella enterica serovar Typhimurium. We characterized and compared the biofilm and planktonic communities within these microcosms using automated ribotyping and the Analytical Profile Index biotyping system. Eleven species from eight different genera were identified from six culture systems. Klebsiella pneumoniae was isolated from all planktonic communities and four of the biofilm communities. Three of the communities resisted colonization by Salmonella enterica serovar Typhimurium, two communities suppressed growth, and one community succumbed to colonization. In cultures that resisted colonization, no Salmonella could be isolated from the biofilm; in cultures that succumbed to colonization, Salmonella was consistently found within the biofilms. This study was one of a series that provided a molecular-based characterization of both the biofilm and planktonic communities from continuous-flow culture systems derived from the cecal microflora of chicks, ranging in age from day-of-hatch to 14 days old. The one common factor relating to successful colonization of the culture was the presence of Salmonella within the biofilm. The capacity to sequester the introduced Salmonella into the biofilm appears to be a contributing factor to the inability of these cultures to withstand colonization by the Salmonella.

Characterization of planktonic and biofilm communities of day-of-hatch chicks cecal microflora and their resistance to Salmonella colonization.

Recent concerns about the use of antimicrobials in food animals have increased interest in the microbial ecology and biofilms within their gastrointestinal tract. This work used a continuous-flow chemostat system to model the microbial community within the ceca from day-of-hatch chicks and its ability to resist colonization by Salmonella enterica serovar Typhimurium. We characterized the biofilm and planktonic communities from five cultures by using automated ribotyping. Eight species from six different genera were identified. Overall, the planktonic communities were more diverse, with 40% of the cultures containing four or more bacterial species. Eighty percent of the biofilm communities contained only one or two species of bacteria. Enterococcus faecalis was the only species isolated from all communities. None of the resulting microbial communities was able to resist colonization by S. enterica serovar Typhimurium. This is the first study to provide a molecular-based characterization of the biofilm and planktonic communities found in day-of-hatch chicken cecal microflora cultures.

Use of Fluorescent Probes for Describing the Process of Encapsulation by Hypotonic Dialysis

While drug induced endocytosis in the erythrocyte has been well documented,1–3 the role of endocytosis in encapsulation using hypotonic dialysis has been less understood. Kruse et al.4 reported that the drug methotrexate may be entrapped by endocytosis when carrier erythrocytes are prepared by hypotonic dialysis. Using conditions that favored endocytosis during encapsulation by hypotonic dialysis, DeLoach and co-workers5 were unable to increase the encapsulation of radiolabeled markers thus demonstrating that endocytosis did not play a significant role in the encapsulation process. Additionally, in counting vesicles which appeared within cells on transmission electron micrograph (TEM) sections they were unable to document any increase in endocytosis under those same conditions. Carrier cells with endocytic vesicles did not exceed 25% and were totally absent in cells sampled at the dialyzed cell stage.