ESBL-producing E. coli in Austrian sewage sludge.
The aim of this study was to investigate the degree of contamination of sewage sludge with ESBL-producing Escherichia coli strains and the effectiveness of different sewage sludge treatment methods. Monthly sewage sludge samples were collected between January and September 2009 in 5 different sewage treatment plants and tested for the presence of ESBL E. coli. In addition, the number of colony forming units (CFU) of E. coli and coliform bacteria before and after the different sludge treatment methods (aerobic/anaerobic digestion, lime stabilization, and thermal treatment) was investigated. Of the 72 sewage sludge samples investigated, ESBL-positive E. coli were found in 44 (61.1%) sewage sludge samples. The classification of beta-lactamase groups was carried out in 15 strains resulting in the detection of 2 different groups (CTX-M and TEM) of bla genes. All 15 of them had a CTX-M gene and 4 of these strains furthermore carried a TEM gene. With regard to the CFU of E. coli and coliform bacteria, thermal treatment and lime stabilization following dehydration sufficiently reduced pathogen concentrations. The plants using merely stabilization and dehydration showed an increase of E. coli and coliform bacteria and thus also an increase in ESBL-producing E. coli.
Reinthaler
Franz Ferdinand
FF
Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Universitätsplatz 4, 8010 Graz, Austria. franz.reinthaler@medunigraz.at
Feierl
Gebhard
G
Galler
Herbert
H
Haas
Doris
D
Leitner
Eva
E
Mascher
Franz
F
Melkes
Angelika
A
Posch
Josefa
J
Winter
Ingrid
I
Zarfel
Gernot
G
Marth
Egon
E
D001317:Austria; D015169:Colony Count, Microbial; D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development; D012722:Sewage / Q000382:microbiology*; D018508:Water Purification; D001618:beta-Lactamases / Q000096:biosynthesis*
D012722:Sewage; D001618:beta-Lactamases