Green tea and epigallocatechin-3-gallate are bactericidal against Bacillus anthracis.

Bacillus anthracis, the etiological agent of anthrax, is listed as a category A biothreat agent by the United States Centers for Disease Control and Prevention. The virulence of the organism is due to expression of two exotoxins and capsule, which interfere with host cellular signaling, alter host water homeostasis and inhibit phagocytosis of the pathogen, respectively. Concerns regarding the past and possible future use of B. anthracis as a bioterrorism agent have resulted in an impetus to develop more effective protective measures and therapeutics. In this study, green tea was found to inhibit the in vitro growth of B. anthracis. Epigallocatechin-3-gallate (EGCG), a compound found abundantly in green tea, was shown to be responsible for this activity. EGCG was bactericidal against both the attenuated B. anthracis ANR and the virulent encapsulated B. anthracis Ames strain. This study highlights the antimicrobial activity of green tea and EGCG against anthrax and suggests the need for further investigation of EGCG as a therapeutic candidate against B. anthracis.

Improvement of a selective media for the isolation of B. anthracis from soils.

To prove linkage between an environmental sample and an anthrax case, there must be isolates obtained from both that can be compared. Although Bacillus anthracis is easily isolated from powder samples, isolating it from soil is difficult because of the high bacterial count in it. Formulations of PLET were prepared, inoculated with B. anthracis, B. cereus and B. thuringiensis and examined for growth. Two hundred eighty-three isolates including 23 B. anthracis were placed onto one formulation while MICs against trimethoprim-sulfamethoxazole were determined. The media supported B. anthracis growth at 30 degrees C and inhibited almost all other bacterial growth, including closely-related species. Sensitivity for B. anthracis and selectivity against other Bacillus and against non-Bacillus were 96.8%, 100% and 97.2% respectively. Isolates that grew had MICs >4 and >76 microg mL(-1) against trimethoprim and sulfamethoxazole, respectively. Soils spiked with 10(2)B. anthracis spores and suspended in PLET broth yielded a 6-7 log(10) increase in B. anthracis. Other growth was inhibited. PLET supplemented with sulfamethoxazole (38 microg mL(-1)), trimethoprim (2 microg mL(-1)), polymyxin B (15,000 U L(-1)), and lysozyme (150,000 U L(-1)) can successfully select for B. anthracis and will facilitate agricultural, environmental and forensic investigations of B. anthracis isolates.

Is in vitro antibiotic combination more effective than single-drug therapy against anthrax?

Antibiotic combinations are used to enhance antibacterial efficacy and to prevent the development of resistance. We have tested a possible synergistic effect of several antibacterial combinations on Bacillus anthracis. The in vitro activities of antibiotic combinations against two strains of B. anthracis, strain Sterne and the Russian anthrax vaccine strain STi, were tested by the fractional inhibitory concentration (FIC) method, derived from the MICs of the agents in combination, and by measuring the rate of bacterial killing over time by several antibiotic combinations. The FIC results showed that synergism against both B. anthracis strains was observed only with the combination of rifampin and clindamycin. The telithromycin-amoxicillin combination showed synergism against strain Sterne only. All other combinations were either indifferent or antagonistic. The results of the bacterial time-kill study demonstrated indifferent effects for all combinations. These in vitro results demonstrate the difficulties in obtaining synergistic combinations of antibiotics against B. anthracis.

Bacteriocidal activity of garlic powder against Bacillus anthracis.

The antibacterial activity of garlic powder was examined against Bacillus anthracis using agar plate cultivation and test tube methods. On the agar plate test, 1-5% garlic powder inhibited the growth of B. anthracis and Escherichia coli O157 used as references. A 1% water solution of garlic powder in the test tube method killed B. anthracis at 10(7) cfu/mL within 3 h of treatment at room temperature. A number of intestinal bacteria in a BALB/c mouse decreased after the oral administration of 1 mL of 1%, garlic powder solution once a day for 3 d. These results suggest that the oral administration of garlic powder is effective against pathogenic bacteria invasion into the intestine as an infection.

Evaluation of spore extraction and purification methods for selective recovery of viable Bacillus anthracis spores.

AIMS: To investigate methods of improving anthrax spore detection with PLET. METHODS AND RESULTS: Comparisons were made of PLET and blood-supplemented PLET to recover and distinguish spores of a variety of Bacillus species. Heat and ethanol purification of spores, and spore extraction from soil with water and high specific gravity sucrose plus non-ionic detergent, were also carried out. CONCLUSION: PLET was more selective and suitable than blood-supplemented PLET for detection of anthrax spores in the environmental specimens. However, PLET is not an optimal spore recovery medium. Purification of spores with ethanol was as effective as heat purification. High specific gravity sucrose plus detergent extraction solutions may be more sensitive than extraction with water. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights shortcomings with the standard PLET isolation of anthrax spores and describes ways in which the procedure may be improved.