Antibacterial and Antibiofilm Activities of Crude Extract of Lasiodiplodia pseudotheobromae IBRL OS-64 against Foodborne Bacterium, Yersinia enterocolitica

The antibacterial and antibiofilm activities of crude extract of Lasiodiplodia pseudotheobromaeIBRL OS-64 was studied and tested against a foodborne pathogenic bacterium, Yersinia enterocolitica. The ethylacetate extract exhibited favorable antibacterial activity with the zone of inhibition was 20.3±0.6 mm compared to dichloromethane (15.0±0.3 mm) and butanol (9.0±0.3 mm) extracts. Minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) values of the extract were 125 and 250 μg/mL, respectively. Structural degeneration studies through scanning electron microscopy (SEM) and transmission electron microscope (TEM) micrographs exhibited major abnormalities that occurred on thebacterial cells after exposureto the extract were complete alterations in their morphology and collapsed of the cells beyond repair. The findings showed that the extract possesses antibiofilm activity against the initial and preformed biofilm of Y. enterocoliticawith the highest inhibition value of 69.12% and 58.70%, respectively The results also revealed the initial biofilm was more susceptible to the extract as compared to pre-formed biofilm. The light microscopy (LM) and SEM photomicrographs proved that thefungal extract significantly eliminates extracellular polysaccharide (EPS) matrices and hinder the attachment of the bacterial cells for biofilm formation. Therefore, the current study suggested the ethyl acetate crude extract from an endophytic fungus, L. pseudotheobromae IBRL OS-64 may be an effective antibacterial and anti-biofilm agent to treat foodborne pathogens

Antimicrobial and drug-synergistic potential of Alpinia conchigera Griff.-derived phenylpropanoids against Mycobacterium smegmatis

Aims@#This study aimed to evaluate the antimicrobial activity of naturally derived phenylpropanoids from Alpinia conchigera (A. conchigera) Griff. and its synthetic analogues, as well as interactions between selected compounds with first-line tuberculosis (TB) drug, rifampicin, against Mycobacterium smegmatis, a potential opportunistic nontuberculous mycobacterium (NTM) and a surrogate organism for TB. @*Methodology and results@#Twelve phenylpropanoids of A. conchigera were evaluated for antimicrobial activity against M. smegmatis (ATCC 14468). The phenylpropanoid compound from A. conchigera with the lowest minimum inhibitory concentration and bactericidal (MIC, MBC) values were selected for checkerboard tetrazolium microplate assay (TEMA) with rifampicin to determine drug interactions. A majority of the compounds had antimicrobial activity, however, purified natural compound 1'S-1'-acetoxychavicol acetate (ACA) showed the highest antimicrobial activity with an MIC value of 62.5 µg/mL against M. smegmatis. The combination of ACA and rifampicin produced indifferent interaction with fractional inhibition concentration (FIC) index of 1.5, while the combination of rifampicin and ACA synthetic analogue 4-allyl-2,6- methoxyphenyl isobutyrate produced a synergistic interaction effect with FIC index of 0.5. None of the compounds tested were bactericidal but appear to be bacteriostatic.@*Conclusion, significance and impact of study@#This study presents the first report on the antimicrobial potential of natural A. conchigera-derived ACA against M. smegmatis as well as the synergistic interaction of 4-allyl-2,6- methoxyphenyl isobutyrate with rifampicin which warrants further investigation.

Comparative in-vitro efficacy of fluoroquinolones against Streptococcus pneumoniae recovered from bacterial keratitis as determined by E-test.

Background and Objectives: The advent of new fluoroquinolones has drawn the attention for reliable methods on the in-vitro susceptibility testing of Streptococccus pneumoniae. This study attempts to determine the minimum inhibitory concentration (MIC) of second-generation (ciprofloxacin and ofloxacin), third-generation (levofloxacin) and the fourth-generation (moxifloxacin and gatifloxacin) fluoroquinolones against S. pneumoniae recovered from bacterial keratitis. Materials and Methods: In retrospect, the MICs of 50 strains of S. pneumoniae isolated from the corneal scrapes of patients with bacterial keratitis were determined against ciprofloxacin, ofloxacin, levofloxacin, gatifloxacin and moxifloxacin using E-tests. The National Committee of Clinical Laboratory Standards (NCCLS) susceptibility patterns and the potencies of the MICs were statistically compared. Results: The median MIC of ciprofloxacin (0.25μg/ml) was found to be lower than the median MICs of ofloxacin (0.5μg/ml) (P<0.449) and levofloxacin (1.0μg/ml) (P<0.001). The median MICs of gatifloxacin (0.1μg/ml) was lower than the median MICs of ciprofloxacin (0.25μg/ml) (P<0.001), ofloxacin (0.5μg/ml) (P<0.001) and levofloxacin (1.0μg/ml) (P<0.001). Moxifloxacin (0.06μg/ml) had showed lower median MICs than gatifloxacin (0.1μg/ml) (P<0.001) levofloxacin (1.0μg/ml) (P<0.001), ofloxacin (0.5μg/ml) (P<0.001) and ciprofloxacin (0.25μg/ml) (P<0.001). Moxifloxacin (0.06μg/ml) had a lower MIC50 (μg/ml) than gatifloxacin (0.1μg/ml), levofloxacin (1.0μg/ml), ciprofloxacin (0.25μg/ml) and ofloxacin (0.5μg/ml). MIC90 (μg/ml) of moxifloxacin (0.06μg/ml) was found to be lower than the MIC90 (μg/ml) of gatifloxacin (0.5μg/ml), levofloxacin (1.0μg/ml), ofloxacin (0.5μg/ml) and ciprofloxacin (0.5μg/ml). Conclusion: Based on in-vitro testing, the five portrayed fluoroquinolones 100% sensitivity to S. pneumoniae. However, the fourth-generation fluoroquinolone, moxifloxacin appeared to be more effective against S. pneumoniae than gatifloxacin, levofloxacin, ofloxacin and ciprofloxacin.

Minimum inhibitory concentration of drugs against Mycobacterium leprae as determined by an in vitro assay.

The observations that live Mycobacterium leprae after entry into cultured peritoneal macrophages from mice, reduced the EA rosetting macrophages, have been exploited to determine the minimum inhibitory concentration of diamino diphenyl sulphone and rifampicin. Diamino diphenyl sulphone showed a minimum inhibitory concentration of 0·028 μg/ml and rifampicin 0·11 μg/ml when given externally. However, there was accumulation of diamino diphenyl sulphone inside the macrophages. At an external concentration of 0·028 μg/ml the concentration inside the macrophage was 0·5 μg/ml. The minimum inhibitory concentration for diamino diphenyl sulphone in this assay system is higher by several folds and that for rifampicin is slightly lower, than what is reported earlier with mice foot pad experiments. The minimum inhibitory concentration reported in this assay system is quite close to what is observed for in vitro inhibition of Mycobacterium lufu with both the drugs.

Cytotoxic effects of granulysin on Candida albicans / 第二军医大学学报

Objective:To study the cytotoxic effects of granulysin on Candida albicans.Methods: Candida albicans were cultured with different concentrations of granulysin peptides and the colonies of Candida albicans on Sabouraud dextrose agar were calculated.Broth microdilution method was used to determine the minimum inhibitory concentrations(MIC) of granulysin and fluconazole on Candida albicans.Results: When granulysin peptides 2 and 3(corresponding to G2 and G3 peptides) were at 20 ?g/ml,the average colonies of Candida albicans decreased from 838 and 927 to 203 and 218,respectively;G1,G4 and G5 did not reduce the average colony of Candida albicans even at 40 ?g/ml.Three strains of Candida albicans were sensitive to granulysin,with their MICs being 26,22,29 ?g/ml,and their MICs to fluconazole were 4,20 and 128 ?g/ml.Conclusion: Granulysin has cytotoxic effects on Candida albicans and is one of the natural anti-fungi proteins in human body;it has a promising future for anti-fungi drug development.