J Vet Sci.  2019 Jan;20(1):58-62. 10.4142/jvs.2019.20.1.58.

Evaluation of in vitro antimicrobial susceptibility of Bacillus anthracis strains isolated during anthrax outbreaks in Italy from 1984 to 2017

• Manzulli V
• Fasanella
• Parisi A
• Serrecchia L
• Donatiello A
• Rondinone
• Caruso M
• Zange S
• Tscherne A
• Decaro N
• Pedarra C
• Galante D

• KMID: 2434778
• DOI: http://doi.org/10.4142/jvs.2019.20.1.58

Abstract

Anthrax, caused by Bacillus anthracis, is a non-contagious infectious disease that affects a wide range of animal species (primarily ruminants) including humans. Due to the often-fatal outcome in humans, quick administration of definitely effective antimicrobials is crucial either as prophylaxis or as a clinical case therapy. In this study, 110 B. anthracis strains, temporally, geographically, and genetically different, isolated during anthrax outbreaks in Italy from 1984 to 2017, were screened using a broth microdilution method to determine their susceptibility to 16 clinically relevant antimicrobial agents. The strains were isolated from various matrices (human, animal, and environmental samples) and were representative of thirty distinct genotypes previously identified by 15-loci multiple-locus variable-number of tandem repeats analysis. The antimicrobials tested were gentamicin, ceftriaxone, streptomycin, penicillin G, clindamycin, chloramphenicol, vancomycin, linezolid, cefotaxime, tetracycline, erythromycin, rifampin, amoxicillin, ciprofloxacin, doxycycline, and trimethoprim. All isolates were susceptible to most of the tested antimicrobials, with the exception of trimethoprim for which all of them showed high minimal inhibitory concentration values. An intermediate level of susceptibility was recorded for ceftriaxone and cefotaxime. Although the Centers for Disease Control and Prevention recommend the use of doxycycline, ciprofloxacin, penicillin G, and amoxicillin for treatment of human cases and for post-exposure prophylaxis to anthrax spores, this study shows a high degree of in vitro susceptibility of B. anthracis to many other antimicrobials, suggesting the possibility of an alternative choice for prophylaxis and therapy.

Keyword

Bacillus anthracis; Antimicrobial susceptibility testing; Anthrax treatment; Minimum inhibitory concentration

MeSH Terms

Amoxicillin
Animals
Anthrax*
Anti-Infective Agents
Bacillus anthracis*
Bacillus*
Cefotaxime
Ceftriaxone
Centers for Disease Control and Prevention (U.S.)
Chloramphenicol
Ciprofloxacin
Clindamycin
Communicable Diseases
Disease Outbreaks*
Doxycycline
Erythromycin
Genotype
Gentamicins
Humans
In Vitro Techniques*
Italy*
Linezolid
Methods
Microbial Sensitivity Tests
Penicillin G
Post-Exposure Prophylaxis
Rifampin
Spores
Streptomycin
Tandem Repeat Sequences
Tetracycline
Trimethoprim
Vancomycin
Amoxicillin
Anti-Infective Agents
Cefotaxime
Ceftriaxone
Chloramphenicol
Ciprofloxacin
Clindamycin
Doxycycline
Erythromycin
Gentamicins
Linezolid
Penicillin G
Rifampin
Streptomycin
Tetracycline
Trimethoprim
Vancomycin

Reference

1. Barrow EW, Bourne PC, Barrow WW. Functional cloning of Bacillus anthracis dihydrofolate reductase and confirmation of natural resistance to trimethoprim. Antimicrob Agents Chemother. 2004; 48:4643–4649.

2. Berger T, Kassirer M, Aran AA. Injectional anthrax - new presentation of an old disease. Euro Surveill. 2014; 19:20877.

3. Cavallo JD, Ramisse F, Giradet M, Vaissaire J, Mock M, Hernandez E. Antibiotic susceptibilities of 96 isolates of Bacillus anthracis isolated in France between 1994 and 2000. Antimicrob Agents Chemother. 2002; 46:2307–2309.

4. Clinical and Laboratory Standards Institute (CLSI). Methods for Antimicrobial Dilution and Disk Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria. CLSI Guideline M45. 3rd ed. Wayne: CLSI;2016.

5. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility Testing. CLSI Supplement M100. 27th ed. Wayne: CLSI;2017.

6. Esel D, Doganay M, Sumerkan B. Antimicrobial susceptibilities of 40 isolates of Bacillus anthracis isolated in Turkey. Int J Antimicrob Agents. 2003; 22:70–72.

7. Fasanella A, Galante D, Garofolo G, Jones MH. Anthrax undervalued zoonosis. Vet Microbiol. 2010; 140:318–331.

8. Fasanella A, Losito S, Trotta T, Adone R, Massa S, Ciuchini F, Chiocco D. Detection of anthrax vaccine virulence factors by polymerase chain reaction. Vaccine. 2001; 19:4214–4218.

9. Fasanella A, Van Ert M, Altamura SA, Garofolo G, Buonavoglia C, Leori G, Huynh L, Zanecki S, Keim P. Molecular diversity of Bacillus anthracis in Italy. J Clin Microbiol. 2005; 43:3398–3401.

10. Hudson MJ, Beyer W, Böhm R, Fasanella A, Garofolo G, Golinski R, Goossens PL, Hahn U, Hallis B, King A, Mock M, Montecucco C, Ozin A, Tonello F, Kaufmann SH. Bacillus anthracis: balancing innocent research with dual-use potential. Int J Med Microbiol. 2008; 298:345–364.

11. Sarker SD, Nahar L, Kumarasamy Y. Microtitre plate-based antibacterial assay incorporating resazurin as an indicator of cell growth, and its application in the in vitro antibacterial screening of phytochemicals. Methods. 2007; 42:321–324.

12. Turnbull PC, Sirianni NM, LeBron CI, Samaan MN, Sutton FN, Reyes AE, Peruski LF Jr. MICs of selected antibiotics for Bacillus anthracis, Bacillus cereus, Bacillus thuringiensis, and Bacillus mycoides from a range of clinical and environmental sources as determined by the Etest. J Clin Microbiol. 2004; 42:3626–3634.

13. Van Ert MN, Easterday WR, Huynh LY, Okinaka RT, Hugh-Jones ME, Ravel J, Zanecki SR, Pearson T, Simonson TS, U'Ren JM, Kachur SM, Leadem-Dougherty RR, Rhoton SD, Zinser G, Farlow J, Coker PR, Smith KL, Wang B, Kenefic LJ, Fraser-Liggett CM, Wagner DM, Keim P. Global genetic population structure of Bacillus anthracis. PLoS One. 2007; 2:e461.