title: Analyzing indicator microorganisms, antibiotic resistant Escherichia coli, and regrowth potential of foodborne pathogens in various organic fertilizers.
abstract: This study analyzed various organic fertilizers for indicator microorganisms, pathogens, and antibiotic-resistant Escherichia coli, and evaluated the growth potential of E. coli O157:H7 and Salmonella in fertilizers. A microbiological survey was conducted on 103 organic fertilizers from across the United States. Moisture content ranged from approximately 1% to 86.4%, and the average pH was 7.77. The total aerobic mesophiles ranged from approximately 3 to 9 log colony-forming units (CFU)/g. Enterobacteriaceae populations were in the range of <1 to approximately 7 log CFU/g, while coliform levels varied from <1 to approximately 6 log CFU/g. Thirty samples (29%) were positive for E. coli, with levels reaching approximately 6 log CFU/g. There were no confirmed positives for E. coli O157:H7, Salmonella, or Listeria monocytogenes. The majority of E. coli isolates (n=73), confirmed by glutamate decarboxylase (gad) PCR, were from group B1 (48%) and group A (32%). Resistance to 16 antibiotics was examined for 73 E. coli isolates, with 11 isolates having resistance to at least one antibiotic, 5 isolates to ≥ 2 antibiotics, and 2 isolates to ≥ 10 antibiotics. In the presence of high levels of background aerobic mesophiles, Salmonella and E. coli O157:H7 grew approximately 1 log CFU/g within 1 day of incubation in plant-based compost and fish emulsion-based compost, respectively. With low levels of background aerobic mesophiles, Salmonella grew approximately 2.6, 3.0, 3.0, and 3.2 log CFU/g in blood, bone, and feather meals and the mixed-source fertilizer, respectively, whereas E. coli O157:H7 grew approximately 4.6, 4.0, 4.0, and 4.8 log CFU/g, respectively. Our results revealed that the microbiological quality of organic fertilizers varies greatly, with some fertilizers containing antibiotic resistant E. coli and a few supporting the growth of foodborne pathogens after reintroduction into the fertilizer.
authors.affiliation: Department of Biological Sciences, Clemson University, Clemson, South Carolina, USA.
authors.forename: Cortney
authors.initials: C
authors.lastname: Miller
authors.forename: Spencer
authors.initials: S
authors.lastname: Heringa
authors.forename: Jinkyung
authors.initials: J
authors.lastname: Kim
authors.forename: Xiuping
authors.initials: X
authors.lastname: Jiang
mesh_terms: D000818:Animals; D015169:Colony Count, Microbial; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D004755:Enterobacteriaceae / Q000254:growth & development / Q000302:isolation & purification; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects / Q000254:growth & development* / Q000302:isolation & purification; D019453:Escherichia coli O157 / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005308:Fertilizers / Q000032:analysis / Q000191:economics / Q000382:microbiology*; D005398:Fisheries / Q000191:economics; D005517:Foodborne Diseases / Q000382:microbiology*; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008372:Manure / Q000032:analysis / Q000382:microbiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D058889:Molecular Typing; D058871:Organic Agriculture / Q000191:economics; D012475:Salmonella / Q000254:growth & development* / Q000302:isolation & purification; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D014481:United States; D014866:Waste Products / Q000032:analysis / Q000191:economics; D014867:Water / Q000032:analysis
chemical_list: D029968:Escherichia coli Proteins; D005308:Fertilizers; D008372:Manure; D008565:Membrane Proteins; D012987:Soil; D014866:Waste Products; D014867:Water; C121044:gadA protein, E coli; C584507:gadB protein, E coli; D005968:Glutamate Decarboxylase