A bacterial population study of commercialized wastewater inoculants.
OBJECTIVE
To assess the bacterial diversity and safety of wastewater inoculants, which are commercially available products used to improve the aerobic digestion processes of the domestic waste compost in the septic tank.


RESULTS
Eighteen wastewater inoculants were analysed on nonselective and selective media and the cultivable bacteria were identified. In all wastewater inoculants, the number of CFUs were between 10(4) and 10(7) g(-1) powder on nonselective media and Bacillus was the predominant cultivable genus. Culture-independent molecular methods such as sequencing of 16S rRNA clone libraries and denaturating gradient gel electrophoresis demonstrated the high prevalence of interfering chloroplast 16S rRNA from plant material and the presence of Bacillus spp. Only after selective enrichments and cultivation, the presence of one pathogenic strain (Klebsiella pneumoniae subsp. pneumoniae) and one opportunistic strain of (Enterobacter cloacae) bacteria were detected in six different products.


CONCLUSIONS
The predominant cultivable species of the wastewater inoculants were Bacillus spp. and after enrichment six products were found to contain opportunistic or pathogenic strains.


CONCLUSIONS
The presence of opportunistic pathogenic strains in the inoculants might represent a risk for immunocompromised, the elderly or children. A clear labelling should therefore be displayed on the product.
Vrints
M
M
Bacteriology Division, Scientific Institute of Public Health, Brussels, Belgium. m.vrints@iph.fgov.be
Bertrand
S
S
Collard
J-M
JM
D001407:Bacillus / Q000302:isolation & purification; D001419:Bacteria / Q000235:genetics*; D001483:Base Sequence; D004587:Electrophoresis, Agar Gel; D016972:Enterobacter cloacae / Q000235:genetics / Q000302:isolation & purification; D017343:Genes, Plant; D006795:Household Products / Q000382:microbiology*; D006796:Household Work / Q000379:methods*; D006801:Humans; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000302:isolation & purification; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000032:analysis*; D012722:Sewage / Q000382:microbiology; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*
D012336:RNA, Ribosomal, 16S; D012722:Sewage