Mastura Akhtar

Reduction of Escherichia coli O157:H7 viability on leafy green vegetables by treatment with a bacteriophage mixture and trans-cinnamaldehyde

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 has been recognized as a major foodborne pathogen responsible for frequent gastroenteritis outbreaks. Phages and essential oils can be used as a natural antimicrobial method to reduce bacterial pathogens from the food supply. The objective of this study was to determine the effect of a bacteriophage cocktail, BEC8, alone and in combination with the essential oil trans-cinnameldehyde (TC) on the viability of a mixture of EHEC O157:H7 strains applied on whole baby romaine lettuce and baby spinach leaves. The EHEC O157:H7 strains used were Nal(R) mutants of EK27, ATCC 43895, and 472. Exponentially growing cells from tryptic soy (TS) broth cultures were spot inoculated on leaves and dried. EHEC cells were placed at low, medium, and high inoculum levels (10(4), 10(5), and 10(6) CFU/mL, respectively). Appropriate controls, BEC8 (approx. 10(6) PFU/leaf), and TC (0.5% v/v) were applied on treated leaves. The leaves were incubated at 4, 8, 23, and 37 °C in Petri dishes with moistened filter papers. EHEC survival was determined using standard plate count on nalidixic acid (50 μg/mL) Sorbitol MacConkey agar. No survivors were detected when both leaves were treated with BEC8 or TC individually at low inoculum levels after 24 h at 23 and 37 °C. When the EHEC inoculum size increased and/or incubation temperature decreased, the efficacy of BEC8 and TC decreased. However, when the two treatments were combined, no survivors were detected after 10 min at all temperatures and inoculum levels on both leafy greens. These results indicated that the BEC8/TC combination was highly effective against EHEC on both leafy greens. This combination could potentially be used as an antimicrobial to inactivate EHEC O157:H7 and reduce their incidence in the food chain.

Reduction of Escherichia coli O157: H7 viability on hard surfaces by treatment with a bacteriophage mixture

This study determined the effect of a previously characterized phage mixture, referred as BEC8 on enterohemorrhagic Escherichia coli (EHEC) O157:H7 strains applied on materials typically used in food processing surfaces. Sterile stainless steel chips (SSC), ceramic tile chips (CTC), and high density polyethylene chips (HDPEC) were used. Cultures of EHEC O157:H7 strains EK27, ATCC 43895, and 472 were combined, spot inoculated on surfaces, and dried. Chips were inoculated with 10(6), 10(5), and 10(4)CFU/chip, to obtain 1, 10 and 100 multiplicity of infection (MOI) values, respectively. Controls and BEC8 (approx. 10(6) PFU/chip) were applied on inoculated surfaces and incubated at 4, 12, 23, and 37 °C. EHEC survival was determined using standard plate count on tryptic soy agar. At 37 °C and 12 °C on SSC, no survivors were detected (detection limit 10CFU/chip) after BEC8 treatment at MOI of 100 after 10 min and at 23 °C after 1h on SSC. A similar result was obtained on CTC at 37 °C after 10 min, and after 1h at 23 °C. These results indicated that the phage cocktail was effective within an hour against low levels of the EHEC mixture at above room temperature on all 3 hard surfaces.

Green banana reduces clinical severity of childhood shigellosis: a double-blind, randomized, controlled clinical trial.

Background and Aims: Mature green banana (GB) fruit is rich in amylase-resistant starch that stimulates colonic production of short-chain fatty acids (referred to as fatty acid) and is useful in treating diarrheal diseases. We studied therapeutic effects of GB in childhood shigellosis by determining colonic fatty acid production in a double-blind, randomized, controlled, clinical trial. Methods: Seventy-three children aged 6 to 60 months with severe bloody dysentery caused by Shigella infection were either given a rice-based diet (54 kcal/dL), with cooked GB (250 g/L) (n = 34) or without GB (n = 39) for 5 days; all given ciprofloxacin (15 mg/kg, q12 hours). Stool volume, frequency, excretion of blood/mucus, and relevant clinical and laboratory indices were determined. Results: On day 5 (post-treatment), 59% children in GB group had no mucus compared with 36% in controls, fecal blood was completely cleared from 96% in GB group compared with 60% without GB (P < 0.05). GB treatment significantly reduced (P < 0.01) numbers of stools/day compared with controls (70% vs. 50%, P < 0.05). GB-specific reductions of mean fecal volumes (mL/kg) ranged from 25% to 40%; (P < 0.05) during the 5-day observations. Clinical success rates were 85% in GB group compared with 67% in controls (P < 0.05). GB significantly (P < 0.01) reduced fecal myeloperoxidase activity and increased fecal fatty acid concentrations (P < 0.01). Conclusions: GB diet improves clinical severity in childhood shigellosis and could be a simple and useful adjunct for dietary management of this illness.

Isolation and characterization of lytic bacteriophages against enterohaemorrhagic Escherichia coli

Aims:  The objective of this study was to isolate, identify and characterize a collection of lytic bacteriophages capable of infecting enterohaemorrhagic Escherichia coli (EHEC) serotypes.

Antibiotic Resistance of Enterococci in American Bison (Bison bison) from a Nature Preserve Compared to That of Enterococci in Pastured Cattle

ABSTRACT Enterococci isolated from a bison population on a native tall-grass prairie preserve in Kansas were characterized and compared to enterococci isolated from pastured cattle. The species diversity was dominated by Enterococcus casseliflavus in bison (62.4%), while Enterococcus hirae was the most common isolate from cattle (39.7%). Enterococcus faecalis was the second most common species isolated from bison (16%). In cattle, E. faecalis and Enterococcus faecium were isolated at lower percentages (3.2% and 1.6%, respectively). No resistance to ampicillin, chloramphenicol, gentamicin, or high levels of vancomycin was detected from either source. Tetracycline and erythromycin resistance phenotypes, encoded by tetO and ermB, respectively, were common in cattle isolates (42.9% and 12.7%, respectively). A significant percentage of bison isolates (8% and 4%, respectively) were also resistant to these two antibiotics. The tetracycline resistance genes from both bison and cattle isolates resided on mobile genetic elements and showed a transfer frequency of 10−6 per donor, whereas erythromycin resistance was not transferable. Resistance to ciprofloxacin was found to be higher in enterococci from bison (14.4%) than in enterococci isolated from cattle (9.5%). The bison population can serve as a sentinel population for studying the spread and origin of antibiotic resistance.

Antioxidants in detoxification of arsenic-induced oxidative injury in rabbits: preliminary results.

Abstract To assess the oxidative injuries caused by arsenic toxicity in rabbits and evaluate the detoxifying effects of exogenous antioxidants, we administered arsenic trioxide (3–5 mg/kg/day) in rabbits through a feeding tube for seven days. These rabbits were then treated with a recipe of vitamins, zinc, selenium (VZS) or a plant polyphenol or a placebo for the next seven days. Blood samples were collected from ear vein for spectrophotometric assay of reduced glutathione (GSH), thiobarbituric acid reactive substances (TBARS), and nitrite/nitrate (NO x ; index of nitric oxide formation) before arsenic administration, seven days after arsenic administration, and seven days after antioxidant treatment. The total arsenic concentrations in hair and spot urine samples of rabbits before arsenic administration were 0.6 ± 0.21 µg/g and 34.0 ± 5.9 µg/L, respectively. Administration of arsenic trioxide significantly increased arsenic concentrations in hair and in urine to 2.8 ± 0.40 µg/g (p<0.001) and 7372 ± 1392.0 µg/L (p<0.001), respectively. Arsenic administration to rabbits significantly reduced GSH concentration (post-arsenic,17.5 ± 0.81 mg/dL vs. pre-arsenic, 32.0 ± 0.76 mg/dL, p<0.001), increased TBARS concentration (post-arsenic, 8 ± 1.1 µM vs. pre-arsenic, 5 ± 0.7 µM, p<0.05), and NO x concentration (post-arsenic, 465 ± 38.5 µM vs. pre-arsenic, 320 ± 24.7 µM, p<0.001) as compared to the pre-arsenic levels. There was a negative correlation between TBARS and GSH concentrations (r = −0.464, p<0.01) and between NO x and GSH concentrations (r = − 0.381, p<0.05) of intoxicated rabbits. The recovery of the depleted GSH was significantly greater in the polyphenols (77.0 ± 12.0%) or VZS (67.0 ± 17.0%) treatment groups compared with the placebo group (36.0 ± 7.0%). The decrease in NO x level of arsenic-treated rabbits was significantly greater in polyphenols treatment group than the placebo group (60.0 ± 9.0% vs. 17.0 ± 6.0%, p<0.001). These results indicate that arsenic induces toxicity in rabbits associated with an increase in lipid peroxidation. Arsenic toxicity increases nitric oxide production in the body. Exogenous antioxidants such as polyphenols and recipe of vitamins, zinc, and selenium are useful for arsenic detoxification.

Significance and survival of Enterococci during the house fly development.

ABSTRACT House flies are among the most important nonbiting insect pests of medical and veterinary importance. Larvae develop in decaying organic substrates and their survival strictly depends on an active microbial community. House flies have been implicated in the ecology and transmission of enterococci, including multi-antibiotic-resistant and virulent strains of Enterococcus faecalis. In this study, eight American Type Culture Collection type strains of enterococci including Enterococcus avium, Enterococcus casseliflavus, Enterococcus durans, Enterococcus hirae, Enterococcus mundtii, Enterococcus gallinarum, Enterococcus faecalis, and Enterococcus faecium were evaluated for their significance in the development of house flies from eggs to adults in bacterial feeding assays. Furthermore, the bacterial colonization of the gut of teneral flies as well as the importance of several virulence traits of E. faecalis in larval mortality was assessed. Overall survival of house flies (egg to adult) was significantly higher when grown with typically nonpathogenic enterococcal species such as E. hirae (76.0% survival), E. durans (64.0%), and E. avium (64.0%) compared with that with clinically important species E. faecalis (24.0%) and E. faecium (36.0%). However, no significant differences in survival of house fly larvae were detected when grown with E. faecalis strains carrying various virulence traits, including isogenic mutants of the human clinical isolate E. faecalis V583 with in-frame deletions of gelatinase, serine protease, and capsular polysaccharide serotype C. Enterococci were commonly detected in fly puparia (range: 75-100%; concentration: 103–105 CFU/puparium) ; however, the prevalence of enterococci in teneral flies varied greatly: from 25.0 (E. casseliflavus) to 89.5% (E. hirae). In conclusion, depending on the species, enterococci variably support house fly larval development and colonize the gut of teneral adults. The human pathogenic species, E. faecalis and E. faecium, poorly support larval development and are likely acquired in nature by adult flies during feeding. House fly larvae do not appear to be a suitable model organism for assessment of enterococcal virulence traits.