survival of multidrug‐resistant bacteria in thermophilic and mesophilic anaerobic co‐digestion of dairy manure and waste milk

• Published in: Animal science journal Vol. 84; no. 5; pp. 426 - 433
• Main Authors: Beneragama, Nilmini, Iwasaki, Masahiro, Lateef, Suraju A, Yamashiro, Takaki, Ihara, Ikko, Umetsu, Kazutaka
• Format: Journal Article
• Language: English
• Published: Australia Japanese Society of Zootechnical Science, Jan. 1999-<Apr. 2003> 01-05-2013; Blackwell Publishing Ltd
• Subjects: agar; ampicillin; anaerobic digestion; Anaerobiosis - physiology; Animals; Anti-Bacterial Agents - pharmacology; antibiotic resistance; Antibiotics; Bacteria; Bacteria - drug effects; Bacteria - growth & development; Cattle; cefazolin; dairy manure; digestion; Drug resistance; Drug Resistance, Multiple, Bacterial; glucose; kanamycin; Manure - microbiology; Manures; mesophilic; Methane; Milk; Milk - microbiology; multi-drug resistant bacteria; multiple drug resistance; neomycin; oxytetracycline; population density; streptomycin; Temperature; thermophilic; thermophilic bacteria; Time Factors; tryptones; vancomycin; Waste materials; waste milk; yeasts
• ISSN: 1344-3941; 1740-0929
• DOI: 10.1111/asj.12017

Anaerobic digestion is considered as a promising method to manage animal waste with antibiotic‐resistant bacteria. Current research was conducted to investigate the survival of multidrug‐resistant bacteria (MDRB) resistant to three groups of antibiotics: (i) cefazolin, neomycin, vancomycin, kanamycin (group 1); (ii) penicillin, oxytetracycline, ampicillin, streptomycin (group 2); and (iii) cefazolin, neomycin, vancomycin, kanamycin, penicillin, oxytetracycline, ampicillin, streptomycin (group 3), in anaerobic digestion of dairy manure and co‐digestion of dairy manure and waste milk at 37°C and 55°C for 22 days, respectively. The population densities of three groups of MDRB on peptone, tryptone, yeast and glucose agar plates incubated at 30°C for 7 days before and after digestion showed 100% destruction in both digestates at thermophilic temperature. Overall reduction of more than 90% of three groups of MDRB was observed in mesophilic digestion with no significant differences (P > 0.05) between manure and milk mixture. Co‐digestion of dairy manure and waste milk always produced significantly (P < 0.05) higher total gas and methane gas than digestion of manure alone at both temperatures. Gas production in each case was significantly (P < 0.05) higher in thermophilic digestion than in mesophilic digestion. The results demonstrate that thermophilic co‐digestion of dairy manure and waste milk offers more benefits in terms of the environment and economy.