Marlene E. Janes

Antimicrobial Susceptibilities of Vibrio parahaemolyticus and Vibrio vulnificus Isolates from Louisiana Gulf and Retail Raw Oysters

ABSTRACT The antimicrobial susceptibilities of 168 Vibrio parahaemolyticus and 151 Vibrio vulnificus isolates recovered from 82 Louisiana Gulf and retail oysters in 2005 and 2006 were determined. Overall, the two vibrios remained susceptible to the majority of antimicrobials tested; reduced susceptibility was detected only in V. parahaemolyticus for ampicillin (81%; MIC ≥ 16 μg/ml). Additionally, V. parahaemolyticus displayed significantly higher MICs for cefotaxime, ciprofloxacin, and tetracycline than V. vulnificus.

Edible chitosan films on ready-to-eat roast beef for the control of Listeria monocytogenes

The use of chitosan as an edible film was evaluated for its antimicrobial activity against Listeria monocytogenes (LM) on the surface of ready-to-eat (RTE) roast beef. L. monocytogenes, decimally diluted to give an initial inoculation of >6.50logCFU/g, was inoculated onto the surface of RTE roast beef cubes, and air-dried. The samples were dipped into chitosan (high or low molecular weights) solutions dissolved with acetic or lactic acid at 0.5% (w/v) or 1% (w/v) then bagged and refrigerated at 4 degrees C. The bacterial counts were determined on days 0, 7, 14, 21, and 28. The samples were spread plated onto modified Oxford agar plates and incubated at 37 degrees C for 48h. An initial 6.50logCFU/g of L. monocytogenes inoculated onto the surface of the non-coated RTE roast beef increased too >10logCFU/g by day 28. On day 14, L. monocytogenes counts were significantly different for all the chitosan-coated samples from the control counts by 2-3logCFU/g and remained significantly different on day 28. Our results have shown that the acetic acid chitosan coating were more effective in reducing L. monocytogenes counts than the lactic acid chitosan coating. Our study indicated that chitosan coatings could be used to control L. monocytogenes on the surface of RTE roast beef.

Control of Listeria monocytogenes and Salmonella anatum on the Surface of Smoked Salmon Coated with Calcium Alginate Coating containing Oyster Lysozyme and Nisin

This study investigated the antimicrobial effect of oyster lysozyme with or without nisin added to calcium alginate (CaAlg) coated on the surface of smoked salmon against Listeria monocytogenes and Salmonella anatum. L. monocytogenes or S. anatum inoculated smoked salmon samples (1 g) were dipped into CaAlg with either oyster lysozyme (OysL) or hen egg white lysozyme (HEWL), with or without added nisin (N), then stored at 4 degrees C for 35 d. Our results indicated that the effectiveness of oyster lysozyme or hen egg white lysozyme was enhanced when added to calcium alginate coatings. After 35 d at 4 degrees C the growth of L. monocytogenes and S. anatum was suppressed in the range of 2.2 to 2.8 log CFU/g with CaAlgNOysL or CaAlgNHEWL coatings compared to the control nontreated samples. There was no significant difference between oyster lysozyme and hen egg white lysozyme treatments against L. monocytogenes or S. anatum inoculated on the surface of salmon. Calcium alginate coatings containing lysozyme with nisin or without could be used to reduce the growth of L. monocytogenes and S. anatum on the surface of ready-to-eat smoked salmon at refrigerated temperatures.

Identification and characterization of two bacteriocin-producing bacteria isolated from garlic and ginger root.

Two bacteriocin-producing bacterial strains were isolated from garlic and ginger root by the agar overlay method. The bacteria were identified by 16S rRNA sequence analyses and fermentation patterns as Leuconostoc mesenteroides (garlic isolate) and Lactococcus lactis (ginger isolate). The bacteriocins were assigned the names leucocin BC2 and lactocin GI3, respectively. Physiochemical properties and antimicrobial spectra of the bacteriocins were determined by the spot-on-lawn method. Both bacteriocins were inhibited by proteolytic enzymes. Leucocin BC2 exhibited a narrow antimicrobial spectrum, inhibiting only Bacillus, Enterococcus, and Listeria species. Lactocin GI3 had a broader spectrum, inhibiting Bacillus, Clostridium, Listeria, Enterococcus, Leuconostoc, Pediococcus, and Staphylococcus species. Both bacteriocins remained active when heated at 90 degrees C for 15 min or 120 degrees C for 20 min. Leucocin BC2 assayed at 37 degrees C showed an inhibitory activity of 1,600 AU/ml, whereas at 8 degrees C the activity was 12,800 AU/ml. Conversely, lactocin GI3 activity was the same at both assay temperatures. Both bacteriocins remained active over a pH range of 2.0 to 9.0 and in various organic solvents. The activity of leucocin BC2 was increased when treated with 0.5% acetic acid and 0.5% lactic acid, whereas lactocin GI3 activity was decreased with either acid. The molecular mass values were 3.7 kDa for leucocin BC2 and 3.9 kDa for lactocin GI3. These results show that the inhibitory substances produced by the bacteria isolated from garlic and ginger are bacteriocins that appear to be different in some characteristics from previously reported bacteriocins.

Design, synthesis, and biological evaluation of β-lactam antibiotic-based imidazolium- and pyridinium-type ionic liquids.

We herein report the preparation and investigation of antibacterial activity of biocidal ionic liquids (ILs) consisting of cationic imidazolium or pyridinium and an anionic β‐lactam antibiotic. The antibacterial properties were quantified by measuring the minimum inhibitory concentration and minimum bactericidal concentration against Escherichia coli O157:H7, Klebsiella pneumoniae, Staphylococcus aureus, and Enterococcus faecium. In general, the ILs had improved antibacterial activity than their parent materials, whether individually or in combination. In 83% of the experiments, the ampicillin ILs (Amp‐ILs) had better antibacterial activities than their quaternary halide parent materials, whereas in 92% of the experiments, Amp‐ILs outperformed the commercially available sodium ampicillin salt. Amp‐ILs had up to 43 times improved antibacterial activity than sodium ampicillin. Overall, when normalized for ampicillin content, ILs had greater antimicrobial activity against E. coli O157:H7, K. pneumoniae, S. aureus, and E. faecium than sodium ampicillin alone.

Resistant starch from high amylose maize (HAM-RS2) reduces body fat and increases gut bacteria in ovariectomized (OVX) rats†‡

Obesity after menopause is a health concern for older females. Changes in the microbiota are likely to occur with this condition. Modifying the microbiota with a prebiotic is a plausible strategy for improving the health of menopausal females.

Optimization of Ozonated Water Treatment of Wild-Caught and Mechanically Peeled Shrimp Meat

ABSTRACT Ozone is a USFDA and USDA approved food contact sanitizing agent and has been used in the seafood industry in both gaseous and dissolved forms to destroy bacteria. The wild harvest shrimp industry is the most economically important fishery in the U.S. Gulf of Mexico region, and in Louisiana the majority of the harvest is mechanically peeled and frozen. Dissolved ozone was measured in processing water at product application to study the optimization of ozonated water treatment for reducing microbial contamination of peeled shrimp meat. Shrimp samples were either sprayed or soaked in water with 1, 2, and 3 ppm dissolved ozone. Treatment times of 20, 40, and 60 seconds were investigated for all applications and concentrations. Similar volumes of water were applied for all treatments, and soaking showed greater bacterial reduction than spray treatments for all time and concentration combinations studied. Soaking in 3 ppm dissolved ozone for 40 s and 60 s showed the greatest reduction of total aerobic bacteria, and 60 s at 3 ppm resulted in the greatest reduction of Pseudomonas bacteria. Ozonated water treatment did not produce oxidation in the shrimp samples. The optimal treatment of soaking shrimp in 3 ppm dissolved ozone for 60 s will be used for further investigations of refrigerated shelf life extension and Listeria monocytogenes destruction in peeled shrimp meat.

Antimicrobial biocompatible bioscaffolds for orthopaedic implants.

Nationally, nearly 1.5 million patients in the USA suffer from ailments requiring bone grafts and hip and other joint replacements. Infections following internal fixation in orthopaedic trauma can cause osteomyelitis in 22–66% of cases and, if uncontrolled, the mortality rate can be as high as 2%. We characterize a procedure for the synthesis of antimicrobial and biocompatible poly‐l‐lactic acid (PLLA) and poly‐ethyleneglycol (PEG) bioscaffolds designed to degrade and absorb at a controlled rate. The bioscaffold architecture aims to provide a suitable substrate for the controlled release of silver nanoparticles (SNPs) to reduce bacterial growth and to aid the proliferation of human adipose‐derived stem cells (hASCs) for tissue‐engineering applications. The fabricated bioscaffolds were characterized by scanning transmission microscope (SEM) and it showed that the addition of tncreasing concentrations of SNPs results in the formation of dendritic porous channels perpendicular to the axis of precipitation. The antimicrobial properties of these porous bioscaffolds were tested according to a modified ISO 22196 standard across varying concentrations of biomass‐mediated SNPs to determine an efficacious antimicrobial concentration. The bioscaffolds reduced the Staphylococcus aureus and Escherichia coli viable colony‐forming units by 98.85% and 99.9%, respectively, at an antimicrobial SNPs concentration of 2000 ppm. Human ASCs were seeded on bioscaffolds and cultured in vitro for 20 days to study the effect of SNPs concentration on the viability of cells. SEM analysis and the metabolic activity‐based fluorescent dye, AlamarBlue®, demonstrated the growth of cells on the efficacious antimicrobial bioscaffolds. The biocompatibility of in vitro leached silver, quantified by inductively coupled plasma optical emission spectroscopy (ICP‐OES), proved non‐cytotoxic when tested against hASCs, as evaluated by MTT assay. Copyright

Mineral Oil―Chitosan Emulsion Coatings Affect Quality and Shelf-Life of Coated Eggs during Refrigerated and Room Temperature Storage

Effects of mineral oil (MO) and 4 emulsions (prepared with different emulsifier types) of MO and chitosan solution (CH) at a fixed ratio of MO:CH = 25:75 as coating materials in preserving the internal quality of eggs were evaluated during 5 wk at 25 °C and 20 wk at 4 °C. Generally, as storage time increased, Haugh unit and yolk index values decreased whereas weight loss increased. However, MO and/or 4 emulsion coatings minimized the weight loss (<1.5%) and preserved the albumen and yolk quality of eggs (with the final B grade) for at least 3 wk longer than those observed for noncoated eggs at 25 °C. At 4 °C, all coated eggs changed from AA to A grade after 5 wk and they maintained this grade for 10 wk (5 wk longer than that of noncoated eggs). Although refrigeration (4 °C) alone could maintain the B grade of noncoated eggs for up to 20 wk, coating treatments were necessary to keep the weight loss below 2%. Compared with 4 °C, the increasing weight loss showed stronger negative correlation (P < 0.01) with the decreasing Haugh unit (-0.46 to -0.89) and yolk index (-0.36 to -0.89) at 25 °C. The emulsifier type used in this study generally did not affect the internal quality of eggs. Salmonella spp. detection was negative for all coated and noncoated eggs. This study demonstrated that MO and MO:CH emulsion coatings preserved the internal quality, prolonged the shelf-life, and minimized weight loss (<2%) of eggs.

Pathogenic enteric viruses and microbial indicators during secondary treatment of municipal wastewater

ABSTRACT Pathogenic enteric viruses are responsible for a wide range of infections in humans, with diverse symptoms. Raw and partially treated wastewaters are major sources of environmental contamination with enteric viruses. We monitored a municipal secondary wastewater treatment plant (New Orleans, LA) on a monthly basis for norovirus (NoV) GI and GII and enterovirus serotypes using multiplex reverse transcription-quantitative PCR (RT-qPCR) and microbial indicators of fecal contamination using standard plating methods. Densities of indicator bacteria (enterococci, fecal coliforms, and Escherichia coli) did not show monthly or seasonal patterns. Norovirus GII was more abundant than GI and, along with enterovirus serotypes, increased in influent during fall and spring. The highest NoV GI density in influent was in the fall, reaching an average of 4.0 log10 genomic copies/100 ml. Norovirus GI removal (0.95 log10) was lower than that for GII, enterovirus serotypes, and male-specific coliphages (1.48 log10) or for indicator bacteria (4.36 log10), suggesting higher resistance of viruses to treatment. Male-specific coliphages correlated with NoV GII densities in influent and effluent (r = 0.48 and 0.76, respectively) and monthly removal, indicating that male-specific coliphages can be more reliable than indicator bacteria to monitor norovirus GII load and microbial removal. Dominant norovirus genotypes were classified into three GI genotypes (GI.1, GI.3, and GI.4) and four GII genotypes (GII.3, GII.4, GII.13, and GII.21), dominated by GI.1 and GII.4 strains. Some of the seasonal and temporal patterns we observed in the pathogenic enteric viruses were different from those of epidemiological observations.