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.

METHODS AND RESULTS

Phages were isolated from dairy and cattle feedlot manure using E. coli O157, O26 and O111 strains as hosts. Phages were enriched from faecal slurries by culture in 10× trypticase soy broth at 37°C overnight. Phage plaques were obtained by mixing the filtered culture supernatant with molten tryptone agar containing the phage E. coli host strain, pouring the inoculated agar on top of cooled TS agar and incubating the culture overnight. Phages were purified from plaques and screened against additional E. coli and EHEC strains by the efficiency of plating method (EOP). Phage CEV2, and five other phages previously isolated, were able to lyse all of the 15 O157 strains tested with EOP values consistently above 0·001. Two phages were found to be highly effective against strains of E. coli O157 through EOP tests and against O26 strains through spot tests, but not against the O serogroup 111 strains. A cocktail of eight phage that lyse E. coli O157 strains resulted in >5 log CFU ml(-1) reductions at 37°C. Multiplex-PCR revealed that none of these eight phages carried stx1, stx2, hlyA or eaeA genes.

CONCLUSIONS

A cocktail of bacteriophages was capable of lysing most strains of two EHEC serotypes.

SIGNIFICANCE AND IMPACT OF THE STUDY

This collection of phages can be combined and potentially used as an antimicrobial cocktail to inactivate E. coli strains from O serogroups 157 and 26 and reduce their incidence in the food chain.

Risk factors associated with the presence of positive reactions in the SCCIT test in water buffalo around two cities in Punjab, Pakistan

The present study was undertaken to find out the association of certain risk factors with the positive SCCIT (single comparative cervical intradermal tuberculin) test in water buffaloes at Faisalabad and Okara, Pakistan. Seventy-six herds (697 buffaloes) at Faisalabad and 56 (395 buffaloes) at Okara were included in the study. The buffaloes were screened through SCCIT Test. Positive reaction to SCCIT test was recorded in 14% of herds and in 3% of buffaloes. The herds positive for this test were 18% when herds with less than 10 animals were excluded from the analysis and these were 19% when herds with less than 10 buffaloes were excluded. The results of logistic analysis (crude and adjusted) revealed the association of lactating status of buffaloes (OR=1.8) and the presence of cattle at the farm (OR=2-4) with positive SCCIT test. After controlling for the farm, the risk of a positive skin test was 1.5 times higher if we change the location of the animal. Similarly, the controlled analysis (for the farm, breed and other variables) revealed an increased risk (OR=1.1) of a positive skin test with the increase in cattle at the farm. The breed controlled stratified analysis showed the association of a number of cattle at the farm with a positive skin test. It can be concluded from the study that the prevalence of tuberculosis on the basis of a positive skin test is higher at herd level and lower at animal level. Further the risk of a positive skin test is higher when cattle are present at the farm.

The conversion of cholest-7-en-3beta-ol into cholesterol. General comments on the mechanism of the introduction of double bonds in enzymic reactions

Convenient syntheses of 6beta-tritiated Delta(7)-cholestenol and 3alpha-tritiated Delta(7)-cholestene-3beta,5alpha-diol are described. It was shown that the conversion of 6beta-tritiated Delta(7)-cholestenol into cholesterol is accompanied by the complete retention of label. It was unambiguously established that the overall reaction leading to the introduction of the double bond in the 5,6-position in cholesterol occurs via a cis-elimination involving the 5alpha- and 6alpha-hydrogen atoms and that during this process the 6beta-hydrogen atom remains completely undisturbed. Metabolic studies with 3alpha-tritiated Delta(7)-cholestene-3beta,5alpha-diol revealed that under anaerobic conditions the compound is not converted into cholesterol. This observation, coupled with the previous work of Slaytor & Bloch (1965), is interpreted to exclude a hydroxylation-dehydration mechanism for the origin of the 5,6-double bond in cholesterol. It was also shown that under aerobic conditions 3alpha-tritiated Delta(7)-cholestene-3beta,5alpha-diol is efficiently converted into cholesterol and that this conversion occurs through the intermediacy of 7-dehydrocholesterol. Cumulative experimental evidence presented in this paper and elsewhere is used to suggest that the 5,6-double bond in cholesterol originates through an oxygen-dependent dehydrogenation process and a hypothetical mechanism for this and related reactions is outlined.

Antiretroviral regimens in pregnancy and breast-feeding in Botswana

BACKGROUND

The most effective highly active antiretroviral therapy (HAART) to prevent mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1) in pregnancy and its efficacy during breast-feeding are unknown.

METHODS

We randomly assigned 560 HIV-1-infected pregnant women (CD4+ count, > or = 200 cells per cubic millimeter) to receive coformulated abacavir, zidovudine, and lamivudine (the nucleoside reverse-transcriptase inhibitor [NRTI] group) or lopinavir-ritonavir plus zidovudine-lamivudine (the protease-inhibitor group) from 26 to 34 weeks' gestation through planned weaning by 6 months post partum. A total of 170 women with CD4+ counts of less than 200 cells per cubic millimeter received nevirapine plus zidovudine-lamivudine (the observational group). Infants received single-dose nevirapine and 4 weeks of zidovudine.

RESULTS

The rate of virologic suppression to less than 400 copies per milliliter was high and did not differ significantly among the three groups at delivery (96% in the NRTI group, 93% in the protease-inhibitor group, and 94% in the observational group) or throughout the breast-feeding period (92% in the NRTI group, 93% in the protease-inhibitor group, and 95% in the observational group). By 6 months of age, 8 of 709 live-born infants (1.1%) were infected (95% confidence interval [CI], 0.5 to 2.2): 6 were infected in utero (4 in the NRTI group, 1 in the protease-inhibitor group, and 1 in the observational group), and 2 were infected during the breast-feeding period (in the NRTI group). Treatment-limiting adverse events occurred in 2% of women in the NRTI group, 2% of women in the protease-inhibitor group, and 11% of women in the observational group.

CONCLUSIONS

All regimens of HAART from pregnancy through 6 months post partum resulted in high rates of virologic suppression, with an overall rate of mother-to-child transmission of 1.1%. (ClinicalTrials.gov number, NCT00270296.)

Comparison of antinociceptive and antidiabetic effects of sertraline and amitriptyline on streptozotocin-induced diabetic rats

Antidepressants (ADs) are frequently used for the treatment of persistent pain associated with diabetic neuropathy. The aim of this study is to investigate the antinociceptive effects of sertraline (Ser) and amitriptyline (Ami) in diabetic rats, and additionally monitoring their effects on grip strength, blood glucose and percentage glycosylated hemoglobin (GHb%) levels. Streptozotocin (STZ; 55 mg/kg, intraperitoneal [ip]) was injected in rats to induce diabetes. After 7 days, Ser (30 mg/kg) or Ami (15 mg/kg) was administered in diabetic rats orally. After 28 days drug treatment, the antinociceptive effects were evaluated using hot plate test both in diabetic and non-diabetic rats. The effects of these drugs on grip strength, blood glucose and GHb% were also measured. Ser and Ami showed antinociceptive effects in diabetic and non-diabetic rats. Both the drugs increased the grip strength reduction in STZ-induced diabetic rats. Ser reduces and Ami increases the serum glucose levels in diabetic and normal rats. Administration of Ami per se increased GHb% levels, while Ser per se has no effects. The effects of Ser (30 mg/kg, per os [po]) on glucose, GHb% and antinociceptive action on hot plate test showed an association between improved blood glucose levels and analgesia. However, the results of Ami treatment are controversial and needs further studies.

Quantitative structure activity relationship and risk analysis of some heavy metal residues in the milk of cattle and goat

Milk of cattle and goat was collected from various localities of Faisalabad, Pakistan. Heavy metal concentration in milk was determined by atomic absorption spectrophotometer. Milk from both of the species was found richly contaminated with cadmium (Cd), chromium (Cr), nickel (Ni), and lead (Pb). Lead concentration in the milk of goat was significantly higher as compared to cattle milk. Quantitative structure activity relationship (QSAR) models were suggested to predict the residues of unknown heavy metals in the milk of cattle and goat using their known physicochemical properties such as molecular weight (MW), melting point (MP), and boiling point (BP) as well as the milk characteristics such as pH, % fat, and specific gravity (SG) of both of these species. The analysis revealed good correlation coefficients ( R2 = 0.759) and ( R2 = 0.876) for cattle and goat QSAR models, respectively. This analysis indicates the need to construct species specific QSAR models for residue prediction. The coefficients for SG for the studied metals were higher in both cattle and goat milk. This suggests that SG is a better determinant for heavy metal residue prediction in the milk of these animals. Risk analysis was conducted based upon the determined heavy metal residues and their provisional tolerable daily intakes. The daily intake of Cd, Cr, and Pb was found to be 1.6, 27, and 116 times higher, respectively, in cattle milk and 1.8, 29, 262 times higher respectively, in goat milk. This intake of heavy metal contaminated milk might pose health hazards to humans in this locality.

Effect of thioperamide on oxidative stress markers in middle cerebral artery occlusion model of focal cerebral ischemia in rats

In view of the recent evidence for the involvement of histamine in cerebral ischemia, the present study evaluated the effect of thioperamide (THP), a selective histamine H3-receptor antagonist, on middle cerebral artery occlusion (MCAO) induced focal cerebral ischemia in rats. The rats were subjected to 2 h of MCAO followed by 22 h reperfusion after which the grip strength, locomotor activity and spontaneous alternation performance were assessed. Animals were then killed and oxidative stress markers were estimated in the whole brain. An elevation of thiobarbituric acid reactive substance (TBARS) and a reduction in glutathione (GSH) and antioxidant enzymes, such as glutathione-S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR) and superoxide dismutase (SOD), was observed following MCAO, the last two being statistically insignificant. Pretreatment with THP (5.5 mg/kg i.p. and 11 mg/kg i.p.) significantly reversed the MCAO-induced increase in TBARS, but could not reverse the other parameters. Paradoxically, it further reduced the levels of GPx, GR and SOD. No significant changes were observed in the catalase levels and in the grip strength and spontaneous alternation behavior of rats. Locomotor activity was reduced slightly, but reversed on pretreatment with THP. The dual effect of THP on oxidative stress requires further investigation and raises doubts on its possible use in cerebral ischemia.

Crystallization and preliminary X-ray diffraction analysis of L-threonine dehydrogenase (TDH) from the hyperthermophilic archaeon Thermococcus kodakaraensis

The enzyme L-threonine dehydrogenase catalyses the NAD(+)-dependent conversion of L-threonine to 2-amino-3-ketobutyrate, which is the first reaction of a two-step biochemical pathway involved in the metabolism of threonine to glycine. Here, the crystallization and preliminary crystallographic analysis of L-threonine dehydrogenase (Tk-TDH) from the hyperthermophilic organism Thermococcus kodakaraensis KOD1 is reported. This threonine dehydrogenase consists of 350 amino acids, with a molecular weight of 38 kDa, and was prepared using an Escherichia coli expression system. The purified native protein was crystallized using the hanging-drop vapour-diffusion method and crystals grew in the tetragonal space group P4(3)2(1)2, with unit-cell parameters a = b = 124.5, c = 271.1 A. Diffraction data were collected to 2.6 A resolution and preliminary analysis indicates that there are four molecules in the asymmetric unit of the crystal.