Anthrax is a worldwide distributing zoonotic disease, caused by Bacillus anthracis, which occurs sporadically in Indonesia, particularly in the provinces of East Java, Central Java, and Yogyakarta, which are the working areas of the Disease Investigation Center (DIC) Wates. Penicillin has been the primary antimicrobial treatment recommended for anthrax since there has never been a report of resistance to this antibiotic in Indonesia. The objective of this research was to assess the sensitivity of B. anthracis isolates from Central Java, East Java, and Yogyakarta to penicillin and tetracycline. Sixteen B. anthracis isolates from DIC Wates collected between 1990-2021 recovered from environmental samples were used in this study. All isolates were identified by phenotype, then tested for sensitivity to penicillin and tetracycline by agar diffusion (Kirby-Bauer) and broth dilution method. The data obtained were compared with the standard and analyzed descriptively. The results showed that all isolates were B. anthracis. One of 16 isolates (6,25%) consistently showed resistance to penicillin, but was sensitive to tetracycline, while 15 isolates (93,75%) showed sensitive to both antibiotics. A penicillin-resistant isolate was soil sample from anthrax endemic area. In conclusion, there was B. anthracis isolate that was found resistance to penicillin. Therefore, tetracycline can be used as an alternative for anthrax treatment.

Background and Aim: Anthrax is a non-contagious infectious disease caused by Bacillus anthracis. The bacteria form spores that are resistant to extreme conditions and can contaminate the environment for decades. This study aimed to detect and characterize B. anthracis found in endemic areas of anthrax in Yogyakarta and Central Java province, Indonesia. Materials and Methods: Soil samples were collected from Gunungkidul regency, Yogyakarta province (n=315) and Boyolali regency, Central Java province (n=100). Additional soil samples (n=10) and straw samples (n=5) were obtained from Pati regency, Central Java province. The isolation and identification of B. anthracis were performed using conventional methods: Morphology of bacteria colony in solid media, Gram staining, capsule staining, spores staining, and motility test. Isolates were further identified using polymerase chain reaction (PCR) against Ba813, lef (pXO1), and capC (pXO2) gene. An avirulent vaccine strain of B. anthracis (strain 34F2) was used as a control. Results: Only four samples grew on blood agar with a ground-glass appearance, white-gray colony (Gunungkidul and avirulent strain) or yellowish (Boyolali and Pati). All were Gram-positive, presented chains, square-ended rods, spores, and were then identified as B. anthracis. Boyolali, Pati, and avirulent strain isolates had slightly different characteristics, including the growth of non-mucoid in the bicarbonate agar medium, and their uncapsulated form. The PCR showed two Gunungkidul isolates which amplified three genes, including Ba813, lef, and capC. Contrarily, the other isolates did not amplify the capC gene. Conclusion: Gunungkidul isolates were identified as virulent strains of B. anthracis while Boyolali and Pati isolates were proposed as avirulent strains. This is the first report of isolation and identification of avirulent strains of B. anthracis in Central Java, Indonesia.