Manisha Deb Mandal

Plasmid-Mediated Dimethoate Degradation by Bacillus licheniformis Isolated From a Fresh Water Fish Labeo rohita

The Bacillus licheniformis strain isolated from the intestine of Labeo rohita by an enrichment technique showed capability of utilizing dimethoate as the sole source of carbon. The bacterium rapidly utilized dimethoate beyond 0.6 mg/mL and showed prolific growth in a mineral salts medium containing 0.45 mg/mL dimethoate. The isolated B licheniformis exhibited high level of tolerance of dimethoate (3.5 mg/mL) in nutrient broth, while its cured mutant did not tolerate dimethoate beyond 0.45 mg/mL and it was unable to utilize dimethoate. The wild B licheniformis strain transferred dimethoate degradation property to E coli C600 (Nar, F−) strain. The transconjugant harbored a plasmid of the same molecular size (approximately 54 kb) as that of the donor plasmid; the cured strain was plasmid less. Thus a single plasmid of approximately 54 kb was involved in dimethoate degradation. Genes encoding resistance to antibiotic and heavy metal were also located on the plasmid.

Synergism of Ciprofloxacin and Trimethoprim against Salmonella enterica Serovar typhi Isolates Showing Reduced Susceptibility to Ciprofloxacin

The activity of the combination of ciprofloxacin and trimethoprim against 16 Salmonella enterica serovar typhi isolates from blood cultures were tested by agar dilution checkerboard technique. When used in combination, minimum inhibitory concentrations (MICs) of ciprofloxacin and trimethoprim ranged from 0.5 to 1.25 and from 10 to 125 µg/ml, respectively, and fractional inhibitory concentrations (FICs) from 0.025 to 0.125 and from 2.5 to 10 µg/ml, respectively. The FIC index was 0.140–0.483, indicating a marked synergy between ciprofloxacin and trimethoprim against trimethoprim-resistant S. enterica serovar typhi isolates (100%) with high MICs for ciprofloxacin.

Indigenous Probiotic Lactobacillus Isolates Presenting Antibiotic like Activity against Human Pathogenic Bacteria

Background: Indigenous lactic acid bacteria are well known probiotics having antibacterial activity against potentially pathogenic bacteria. This study aims to characterize the curd lactobacilli for their probiotic potentiality and antagonistic activity against clinical bacteria. Methods: Four curd samples were processed microbiologically for the isolation of lactic acid bacteria (LAB). The LAB strains obtained were identified by conventional methods: cultural aspect, gram-staining, biochemical and sugar fermentation tests. The probiotic properties were justified with tolerance to low-pH, bile salt and sodium chloride, and the antagonistic activity of the lactobacilli against human pathogenic bacteria (Escherichia coli, Proteus vulgaris, Acinetobacter baumannii and Salmonella enterica serovar Typhi) was assessed. Hemolytic activity and antibiotic susceptibility were determined for the lactobacilli isolates, and the cumulative probiotic potential (CPP) values were recorded. Result: Four lactobacilli isolates, L. animalis LMEM6, L. plantarum LMEM7, L. acidophilus LMEM8 and L. rhamnosus LMEM9, procured from the curd samples, survived in low-pH and high bile salt conditions, and showed growth inhibitory activity against the indicator bacteria by agar-well (zone diameter of inhibition; ZDIs: 13.67 ± 0.58–29.50 ± 2.10 mm) and agar overlay (ZDIs: 11.33 ± 0.58–35.67 ± 2.52 mm) methods; the average growth inhibitory activity of lactobacilli ranged 233.34 ± 45.54–280.56 ± 83.67 AU/mL, against the test bacterial pathogens. All the lactobacilli were non-hemolytic and sensitive to most of the test antibiotics. The CPP values of the isolated LAB were recorded as 80–100%. Conclusion: The curd lactobacilli procured might be used as the valid candidates of probiotics, and bio-therapeutics against bacterial infection to humans.

ASSESSMENT OF BACTERIAL GROWTH INHIBITION PROPERTY AND PHYTOCHEMICAL ANALYSIS OF OCIMUM SANCTUM L. LEAF EXTRACT

Tulsi plant, Ocimum sanctum L., is famous for its therapeutic potentiality. The present study investigates the antibacterial activity of O. sanctum leaf extracts, and the bioactive components present in the extracts. The antibacterial activity of ethanolic leaf extract of O. sanctum: dark variety; Krishna tulsi (DOSE) and bright variety; Rama tulsi (BOSE), and aqueous leaf extract of dark variety (AqDOS) and bright variety (AqBOS) of O. sanctum was determined by in vitro methods against gram-negative and gram-positive clinical bacterial isolates. Phytochemical screening of the extracts was done qualitatively, and thin layer chromatography (TLC) was performed using n-hexane-ethyl acetate mobile phase. The ethanolic extracts showed more antibacterial activity as compared to aqueous extracts in terms of ZDI (zone diameter of inhibition); the ZDI of DOSE ranged 20 – 28 mm for gram-positive, and 14 – 23 mm for gram-negative bacteria, whereas in case of BOSE the ZDIs ranged 11 – 22 mm and 12 – 18 mm, respectively, for gram-positive and gram-negative bacteria. The Rf values of phytocomponents detected on the TLC plate, ranged 0.06 0.94. The O. sanctum leaf extracts had broad spectrum antibacterial activity and found rich source of phytochemicals, which thus, be utilized against a broad range of bacterial infection.

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY ANALYSIS AND ANTI-METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS ACTIVITY OF OLIVE FRUIT ETHANOLIC EXTRACT

The current study explores the antibacterial activity and HPLC (high performance liquid chromatography) profiles of olive (Elaeocarpus floribundus) fruits. The ethanolic extract of olive fruit parts: seed (OSE) and mesocarp-epicarp (OME), were prepared, and tested for their antibacterial activity, by agar-well diffusion method using 1.875 – 6.25 mg/well, against the clinical isolates of methicillin resistant Staphylococcus aureus (MRSA; n=3). The HPLC profiles of the extracts were prepared. For the test MRSA isolates, the OSE, at concentrations 1.875, 3.125 and 6.25 mg/well, had ZDI (zone diameter of inhibition) values 8  1.73 mm (range: 6 – 9 mm), 9  1.73 mm (range: 7 – 10 mm) and 11.67  1.53 mm (range: 10 – 13 mm), respectively, and the ZDIs for OME recorded were 12.33  2.51 mm (range: 10 – 15 mm), 13.66  2.08 mm (range: 12 – 16 mm) and 16.33  1.53 mm (range: 15 – 18 mm), respectively (when the values expressed as mean  standard deviation). The HPLC chromatograms for both OSE and OME displayed 9 major compounds with retention times 1.54 – 6.14 min and 1.79 – 9.47 min, respectively. Thus, the olive fruit extracts (OME and OSE) possessing various phytochemicals, showed anti-MRSA activity, suggesting the plausible usage of the extracts in the preparation of antibacterial leads in combating various life threatening diseases caused due to S. aureus infection, including MRSA.

LACTATE DEHYDROGENASE ISOENZYME PROFILES IN GROUP A STREPTOCOCCAL INFECTION

The serum lactate dehydrogenase isoforms analysis and estimation are useful in the determination of pathogenic infection. This study explores the possible association between serum lactate dehydrogenase level and group A streptococci (also called Streptococcus pyogenes) infection compared to the healthy controls, and determines the lactate dehydrogenase isoenzyme patterns in group A streptococci infection. The serum samples procured from blood of group A streptococci infection (anti-Streptolysin O positive) cases as well as from the normal individuals were processed for lactate dehydrogenase estimation, and the results were expressed as mean  SD; the lactate dehydrogenase levels of ≤320 IU/L were considered normal. The all serum samples from group A streptococci infection cases and the healthy controls were subjected to polyacrylamide gel electrophoresis analysis for lactate dehydrogenase isoforms. In group A streptococcal infection cases, the lactate dehydrogenase values were 729.86  161.46 IU/L (range: 482 – 862 IU/L) for males, and 455.75  74.60 IU/L (range: 370 – 540 IU/L) for females, while among the normal groups the lactate dehydrogenase values ranged from 152.80  32.46 IU/L (for males) to 160.75  40.33 IU/L (for females). A significant increase in lactate dehydrogenase levels in group A streptococcal infection cases was observed, when compared with healthy controls (p value: <0.01). Based upon the staining intensity, the increased levels of lactate dehydrogenase1, lactate dehydrogenase2 and lactate dehydrogenase3 isoforms have evidently been proved. Therefore, the total serum lactate dehydrogenase and the individual lactate dehydrogenase isoforms might be useful in the diagnosis of group A streptococci infection.