Agnes Kilonzo-Nthenge

Prevalence and Antimicrobial Resistance of Pathogenic Bacteria in Chicken and Guinea Fowl

This study was conducted to compare the presence and antimicrobial susceptibility of Campylobacter, Salmonella spp., and other enteric bacteria between chickens and guinea fowls. Birds were reared on enclosed concrete floor housing covered with pine wood shavings litter material. Chicken (n = 40) and guinea fowl (n = 40) carcasses, drinking water (10 mL; n = 40), and litter (10 g; n = 40) were aseptically collected randomly from a poultry farm and analyzed within 1 h of collection. Individual pens served as experimental units and were replicated twice. Campylobacter spp., Salmonella spp., and other enterobactericeae were isolated and identified using standard selective media and biochemical tests. Isolates were tested for sensitivity to tetracycline, ampicillin, streptomycin, kanamycin, nalidixic acid, gentamicin, erythromycin, ciprofloxacin, cefoxitin, and colistin using the Kirby-Bauer disk diffusion test. Campylobacter spp. and Salmonella spp. were isolated from 28 and 35% of whole carcass rinses of chickens and from 18 and 23% of whole carcass rinses of guinea fowl, respectively. Although only Salmonella spp. were recovered from drinking water, both Salmonella and Campylobacter spp. were recovered from litter material. Campylobacter upsaliensis was recovered only in the guinea fowl, whereas Klebsiella oxytoca and Enterobacter sakazakii were recovered only in chickens. Although no antibiotic resistance was determined in Campylobacter upsaliensis, most Campylobacter, Salmonella, and Escherichia coli isolates from both chickens and guinea fowl were resistant to antibiotics such as ampicillin, kanamycin, erythromycin, and nalidixic acid.

Efficacy of home washing methods in controlling surface microbial contamination on fresh produce.

Much effort has been focused on sanitation of fresh produce at the commercial level; however, few options are available to the consumer. The purpose of this study was to determine the efficacy of different cleaning methods in reducing bacterial contamination on fresh produce in a home setting. Lettuce, broccoli, apples, and tomatoes were inoculated with Listeria innocua and then subjected to combinations of the following cleaning procedures: (i) soak for 2 min in tap water, Veggie Wash solution, 5% vinegar solution, or 13% lemon solution and (ii) rinse under running tap water, rinse and rub under running tap water, brush under running tap water, or wipe with wet/dry paper towel. Presoaking in water before rinsing significantly reduced bacteria in apples, tomatoes, and lettuce, but not in broccoli. Wiping apples and tomatoes with wet or dry paper towel showed lower bacterial reductions compared with soaking and rinsing procedures. Blossom ends of apples were more contaminated than the surface after soaking and rinsing; similar results were observed between flower section and stem of broccoli. Reductions of L. innocua in both tomatoes and apples (2.01 to 2.89 log CFU/g) were more than in lettuce and broccoli (1.41 to 1.88 log CFU/g) when subjected to same washing procedures. Reductions of surface contamination of lettuce after soaking in lemon or vinegar solutions were not significantly different (P > 0.05) from lettuce soaking in cold tap water. Therefore, educators and extension workers might consider it appropriate to instruct consumers to rub or brush fresh produce under cold running tap water before consumption.

Evaluation of drug-resistant Enterobacteriaceae in retail poultry and beef

There has been increasing concern on the emergence of multidrug-resistant foodborne pathogens from foods of animal origin, including poultry. The current study aimed to evaluate antibiotic-resistant Enterobacteriaceae from raw retail chicken/turkey parts (thigh, wings, breast, and ground) and beef meat (ground and chunks) in Middle Tennessee. Resistance of the collected Enterobacteriaceae to a panel of antibiotics was determined by the Kirby-Bauer disk diffusion test. Retail meats were also assayed for the presence of Salmonella spp. and Escherichia coli O157:H7. Two hundred thirty-seven samples representing 95.2% of the total of 249 samples tested were positive for Enterobacteriaceae. The level of contamination with Enterobacteriaceae in raw meats ranged from 3.26 log10 cfu/g to 4.94 log10 cfu/g with significant differences in counts among meat types (P < 0.05). Contamination was significantly greater (P < 0.05) in ground beef, beef chucks, ground chicken, chicken breast, and turkey wings (4.92, 4.58, 4.94, 4.75, 4.13 log10 cfu/g, respectively) than ground turkey and chicken wings (3.26 and 3.26 log10 cfu/g, respectively). Klebsiella oxytoca, Serratia spp., E. coli, and Haffnia alvei were most prevalent contaminants at 27.4, 14.3, 12.1, and 11.4%, respectively. Resistance of the Enterobacteriaceae to antimicrobials was most frequent with erythromycin, penicillin, and ampicillin at 100, 89, and 65.8%, respectively. Few (2.7%) of the Enterobacteriaceae were resistant to chloramphenicol. Salmonella spp., E. coli O157:H7, Morganella morganii, Yersinia enterocolitica, and Vibrio parahemolyticus exhibited multiple drug resistance. This investigation demonstrates that raw poultry and beef are potential reservoirs of antibiotic-resistant Enterobacteriaceae.

Occurrence and Antimicrobial Resistance of Enterococci Isolated from Organic and Conventional Retail Chicken

Antibiotic-resistant bacteria existing in agricultural environments may be transferred to humans through food consumption or more multifaceted environmental paths of exposure. Notably, enterococcal infections are becoming more challenging to treat as their resistance to antibiotics intensifies. In this study, the prevalence and antibiotic resistance profiles of enterococci in organic and conventional chicken from retail stores were analyzed. Of the total 343 retail chicken samples evaluated, 282 (82.2%) were contaminated with Enterococcus spp. The prevalence was higher in organic chicken (62.5%) than conventional chicken (37.5%). Enterococcus isolates were submitted to susceptibility tests against 12 antimicrobial agents. Among the isolates tested, streptomycin had the highest frequencies of resistance (69.1 and 100%) followed by erythromycin (38.5 and 80.0%), penicillin (14.1 and 88.5%), and kanamycin (11.3 and 76.9%) for organic and conventional isolates, respectively. Chloramphenicol had the lowest frequency (0.0 and 6.6%, respectively). The predominant species in raw chicken was E. faecium (27.3%), followed by E. gallinarum (6.0%), E. casseliflavus (2.1%), and E. durans (1.4%). These species were also found to be resistant to three or more antibiotics. The data indicated that antibiotic-resistant enterococci isolates were found in chicken whether it was organic or conventional. However, enterococci isolates that were resistant to antibiotics were less common in organic chicken (31.0%) when compared with those isolated from conventional chicken (43.6%). The results of this study suggest that raw retail organic and conventional chickens could be a source of antibiotic-resistant enterococci.

Advances in Soybean and Soybean By-Products in Monogastric Nutrition and Health

Soybean (Glycine max) is a leguminous oilseed and one of the world’s largest and most efficient sources of plant protein. United States holds the largest share of soybean production (32%) followed by Brazil (28%), Argentina (21%), China (7%) and India (4%). Although there are variations based on geographical location, the average crude protein (CP) content of soybean is 38% with a rich and balanced amino acid profile. It is therefore a rich source of protein for humans and food animals besides being a rich source of vegetable oil. Soybean meal is the simplest form of soybean protein and a by-product of the oil milling which by National Research Council standards contains 44-48% CP. It contains higher energy [2,460 metabolizable energy (ME) kcal/kg] and protein than other plant protein sources and has an excellent balance of highly digestible amino acids with the exception of methionine which tends to be low. Soybean meal is however rich in the amino acids lysine, tryptophan, threonine, isoleucine, and valine which are deficient in cereal grains such as corn and sorghum most utilized in poultry and swine diets. These are essential amino acids for monogastric animals such as poultry and swine. Soybeans and soybean meal are also a source of isoflavones which are known to improve growth, promote tissue growth in pigs, and prevent diseases. However, soybean meal possesses anti-nutritional properties which must be overcome to increase its nutritional value. These include antitrypsin inhibitors, oligosaccharides, such as rafinose and stachyose, which are poorly utilized by most food animals. Phytic acid and antigenic factors found in certain soybean proteins cause inflammatory response in the gastrointestinal tract of monogastric animals. Soybeans also contain lectins, compounds that bind with intestinal cells and interfere with nutrient absorption and other compounds such as saponins, lipoxidase, phytoestrogens and goitrogens whose anti-nutritional effects are not known. Soybeans and soybean meal may also be contaminated in the field as a result of using contaminated irrigation water or application of contaminated manure to the growing crop. Since many animal producers use soybean meal as a major constituent of animal feeds, contamination of these feeds with zoonotic foodborne pathogens such as salmonella has increasingly become a global concern. When properly processed for specific purposes, the soybean and soybean by-products can be utilized by all classes of animals ranging from companion animals, monogastric food

Prevalence of Multidrug-Resistant Bacteria from U.S.-Grown and Imported Fresh Produce Retailed in Chain Supermarkets and Ethnic Stores of Davidson County, Tennessee

The aim of this study was to determine whether U.S.-grown and imported fresh produce retailed in ethnic stores and chain supermarkets was a reservoir of antibiotic-resistant bacteria. A total of 360 (129 imported and 231 U.S.-grown) samples of fresh produce were purchased from retail stores and analyzed for Enterobacteriaceae , including three pathogenic bacteria ( Escherichia coli O157:H7, Shigella , and Salmonella ), using standard methods. Presumptive pathogenic isolates were confirmed using PCR. The mean Enterobacteriaceae counts for imported produce were 6.87 ± 0.15 log CFU/g and 7.16 ± 0.11 log CFU/g in ethnic stores and chain supermarkets, respectively. For U.S.-grown produce, the contamination levels were at 8.35 ± 0.17 log CFU/g and 7.52 ± 0.13 log CFU/g in ethnic stores and chain supermarkets, respectively. Salmonella (0 and 0.3%), Shigella (1.7 and 0.6%), E. coli (3.1 and 1.4%), Enterobacter (9.4 and 8.6%), Klebsiella (6.7 and 0.6%), and Serratia (5.8 and 1.4%) were detected in produce from ethnic stores and chain supermarkets, respectively. None of the samples were positive for E. coli O157:H7. Regarding distribution by produce type, leafy vegetables had a significantly (P < 0.05) higher prevalence of Enterobacteriaceae (19.2%) than the other types, followed by root vegetables (6.4%), tomatoes (5.6%), and fruits (3.9%). Antibiotic-resistant Salmonella , Shigella , E. coli , Enterobacter , Klebsiella , and Erwinia bacteria were also isolated from fresh produce. The frequencies of vancomycin resistance (98.1 and 100%) were significantly higher (P < 0.05) than the frequencies of ampicillin resistance (42.3 and 72.9%) for imported and U.S.-grown produce, respectively. Despite the increased attention to the role of imported produce as a source of antimicrobial resistance, this study indicates that U.S.-grown produce is also contaminated with antibiotic-resistant bacteria. Good agricultural practices on the farms and washing of fresh produce before consumption are greatly recommended to avoid possible public health hazards.

A comparative analysis of microbial profile of Guinea fowl and chicken using metagenomic approach

Probiotics are live microbial feed supplements that promote growth and health to the host by minimizing non-essential and pathogenic microorganisms in the host’s gastrointestinal tract (GIT). The campaign to minimize excessive use of antibiotics in poultry production has necessitated development of probiotics with broad application in multiple poultry species. Design of such probiotics requires understanding of the diversity or similarity in microbial profiles among avian species of economic importance. Therefore, the objective of this research was to establish and compare the microbial profiles of the GIT of Guinea fowl and chicken and to establish the microbial diversity or similarity between the two avian species. A metagenomic approach consisting of the amplification and sequence analysis of the hypervariable regions V1-V9 of the 16S rRNA gene was used to identify the GIT microbes. Collectively, we detected more than 150 microbial families. The total number of microbial species detected in the chicken GIT was higher than that found in the Guinea Fowl GIT. Our studies also revealed phylogenetic diversity among the microbial species found in chicken and guinea fowl. The phylum Firmicutes was most abundant in both avian species whereas Phylum Actinobacteria was most abundant in chickens than Guinea fowls. The diversity of the microbial profiles found in broiler chickens and Guinea fowls suggest that the design of effective avian probiotics would require species specificity.

Gamma Irradiation for Fresh Produce

Food irradiation is a promising food safety technology that has a significant potential to control spoilage and eliminate food-borne pathogens. The Food and Agricultural Organization (FAO) has estimated that approximately 25% of all worldwide food production is lost after harvesting due to insects, microbes, and spoilage. As the market for food becomes increasingly global, food products must meet high standards of quality and quarantine in order to move across international borders. The FAO has recommended that member states need to implement irradiation technology for national phytosanitary programs. There is a trend to use food irradiation mainly due to three main factors: the increase of foodborne diseases; high food losses from contamination and spoilage; and increasing global trade in food products. The ever increasing foodborne illness outbreaks associated with fresh produce continue to prove that traditional measures are not sufficient to eliminate food borne pathogens. More effective countermeasures are clearly needed to better manage the foodborne pathogen risks posed by contaminated produce. Fresh produce industries, government regulatory agencies, and consumers all are advocating for new technologies that will eliminate or significantly reduce foodborne pathogens on fresh produce. With increasing awareness of the foodborne idleness linked to fresh produce, gamma irradiation could be applied to mitigate human pathogens in fresh fruits and vegetables. Food irradiation is a safe and effective tool and could be used with other technology to control pathogenic bacteria in fresh produce. Irradiated foods are generally nutritious, better or the same as food treated by convectional methods such as cooking, drying, and freezing. Food irradiation also has other benefits such as delay in repining and sprouting. Further more food irradiation has a significant potential to enhance produce safety and if combined with other anti-microbial treatments; this technology is promising to solve some of the current produce pathogen problems. Although irradiation is safe and has been approved in 40 countries, food irradiation continues to be a debate and slows extensive acceptance and use in the food industries. Several foodborne pathogens have been linked to fresh produce and gamma irradiation could be applied to eliminate microbes before reaching the consumer. There is an urgent need to educate consumer on the principles and benefits of this promising technology.

Kinetics of tropomyosin denaturation as a predictive model for verifying thermal processing of beef products.

An enzyme-linked immunosorbent assay (ELISA) was developed to study thermal denaturation of tropomyosin (Tm) using the time-temperature requirements for cooked beef. The ELISA employed a monoclonal antibody (MAb 2C9) raised against bovine Tm for quantifying residual Tm in muscle extracts. The specificity of MAb 2C9 to bovine Tm was demonstrated by Western blot and the analytical validity of ELISA was confirmed by dot blot. Thermal denaturation of Tm, in the temperature range between 54.4 and 70.0 degrees C, showed first-order dependency. Kinetic parameters of Tm denaturation were derived from isothermal heating of beef muscle extract at 54.4, 57.2, 60.0, and 62.8 degrees C. Temperature dependency of the rate constant (k) was demonstrated by Arrhenius plot; the activation energy (E(a)) of Tm denaturation was determined to be 484 kJ x mol(-1). A mathematic model describing the impact of the heating time-temperature on Tm denaturation was developed. Predicted Tm from the integrated time-temperature model agreed closely with the measured Tm in dynamically heat-processed beef samples. Percent errors between the measured and the predicted values ranged from -5.1 to 5.3%. The kinetic model provides an accurate and reproducible prediction of the impact of actual heating time-temperature on residual Tm in cooked beef. The MAb-based ELISA and kinetic model developed in this study have the potential to be adapted by the meat industry as a quality control tool.