Shifts in Extended-Spectrum Beta-Lactamase types with increasing prevalence of Escherichia coli producing ESBL

• Objectives: Contrary to other multidrug-resistant pathogens, the prevalence of bacteria producing extended-spectrum beta-lactamase (ESBL) is increasing rapidly in Sweden. In Europe, ESBL of CTX-M-, TEM-, OXA- and SHV-types are generally associated with E. coli infections, CTX-M being the most predominant. We have investigated how the prevalence of these types has changed during the last five years in the low endemic setting of western Sweden. Methods: Yearly resistance in urinary (approximately 10,000 isolates/year) and blood (approximately 250 isolates/year) E. coli during 2004-2008 were determined. Cephalosporin-resistant isolates were screened for ESBL, using a double-disk assay with clavulanic acid as the inhibitory agent. All ESBL-E. coli isolated in the region during the periods Sept 2003-April 2005 (n=46) and April 2008-March 2009 (n=256) were typed by multiplex-PCR, detecting CTX-M, TEM, OXA and SHV. CTX-M-positive isolates were sub-typed by real time Q-PCR for CTX-M-1, CTX-M-2 and CTXM-9 groups. Results: During 2004-2008, ESBL-producing E. coli strains increased from 0.3-1.5% in urinary and 0-1.4% in blood isolates. Resistance to quinolones and trimethoprim was observed in 60-80% of strains, as compared to less than 8% in non-ESBL-producing E. coli. The majority of the ESBL-E. coli strains possessed the CTX-M gene-type, increasing from 78% (36/46) in 2003-2005 to 93% (238/256) in 2008-2009. Between these time-periods, a marked shift occurred in the distribution of CTX-M types, in that strains with the CTX-M-9 group decreased from 42% (15/36) of isolates to 21% (51/238, p=0.01) and, simultaneously, strains with the CTX-M-1 group increased from 58% (21/36) to 78% (185/238, p= 0.02). Furthermore, strains of CTX-M-type exhibiting also TEM- and/or OXA increased to comprise 86% of cases, as compared to 75% previously. Similar trends were seen for community and hospital detected isolates and with no differences associated with age in affected patients. Conclusion: A steady increase in multidrug-resistant ESBL-E. coli, possessing the genes for multiple ESBL-types, was observed in western Sweden, contrary to the patterns of other multidrug-resistant bacteria. As ESBL has increased during the five-year study period, we detected a shift in the prevalence of ESBL-types, currently dominated by the CTX-M-1 group. These observations suggest that a novel ESBL-producing E. coli clone may have emerged in the area, which will be further investigated and presented.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Mikrobiologi inom det medicinska området (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Microbiology in the medical area (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Infektionsmedicin (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Infectious Medicine (hsv//eng)

Nyckelord

Escherichia coli

ESBL

CTX-M

OXA

SHV

TEM

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