The β-Lacta Test for Direct Detection of Extended-Spectrum-β-Lactamase-Producing Enterobacteriaceae in Urine

Abstract

cWith the ␤-Lacta test, production of extended-spectrum ␤-lactamases (ESBLs) was assayed in 200 urine samples showing Gramnegative bacilli during direct microscopic examination. While 168 samples tested negative, all samples yielding ESBL-producing Enterobacteriaceae after culture gave positive (n ‫؍‬ 30) or uninterpretable (n ‫؍‬ 2) results. The sensitivity and specificity of ESBL detection were 94% and 100%, respectively. A survey conducted from 2002 to 2010 by the French national infection control program demonstrated an increase of 282% in the incidence of extended-spectrum ␤-lactamase-producing Enterobacteriaceae (ESBLE), particularly ESBL-producing Escherichia coli (1). The increasing importance of multiresistant ESBL-producing E. coli strains in the community should make clinicians aware of potential treatment failures associated with serious and potentially life-threatening infections (2). A recent study by Peralta et al., conducted in 19 Spanish hospitals, found that the ESBLE causing bacteremia were mainly from the urinary (55.3%) and biliary (12.7%) tracts. E. coli accounted for 89% of all ESBLE strains, and 45.7% of these were multidrug resistant (e.g., resistant to ␤-lactam-␤-lactamase inhibitor combinations, cephalosporins, quinolones, and aminoglycosides) (3). Furthermore, empirical antibiotic treatment was adequate in only 48.8% of the cases, and the in-hospital mortality was 20.9% (3). ESBL-producing E. coli isolates, particularly those producing CTX-M enzymes, account for a significant number of cases of bacteremia in hospitalized and nonhospitalized patients (4). Moreover, Livermore has reported that, since 2003, 90% of ESBL-producing E. coli isolates in the United Kingdom produce CTX-M-15 (5).Urinary tract infections (UTI) are among the most frequent bacterial infections in the community and in the health care setting (6). Broad-spectrum cephalosporins, ␤-lactam-␤-lactamase inhibitor combinations, or fluoroquinolones are recommended for first-line empirical therapy of sepsis arising from the urinary tract in community-acquired and nosocomially acquired cases (4, 7). These recommendations might be difficult to apply if a significant proportion of such infections is caused by ESBLE (4).A new chromogenic test (␤-Lacta test [BLT]; Bio-Rad, MarnesLa-Coquette, France) was developed for the rapid detection (in less than 15 min) of strains of Enterobacteriaceae with decreased susceptibility or resistance to third-generation cephalosporins (3GC) conferred by enzymes such as ESBLs and carbapenemases. This test provides useful information to guide antibiotic treatment before full results of antimicrobiotic susceptibility testing are available (8). The aim of this study was to highlight the time saved in cases of UTI when the BLT is performed directly with urine rather than bacterial colonies.Urine samples. All urine samples received over a 3-month period and showing Gram-negative bacilli (GNB) upon direct microscopic examination and on Gram stains of uncentrifuged urine were prospectively included. Urin...

Early detection with the β-LACTA™ test of extended-spectrum β-lactamase–producing Enterobacteriaceae in blood cultures

“…Our results are consistent with published data with respect to the low sensitivity of BLT in the detection of plasmid-encoded (CMY, DHA) or overproduced AmpC -lactamases(10,11). In contrast, K. oxytoca isolates with high-level expression of their chromosome-encoded β-lactamase were previously reported as being BLT-positive(10). This discrepancy may be explained by a difference in -lactam hydrolysis rates of OXY-1 and OXY-2 (15) which have not been determined.…”

Evaluation of early antimicrobial therapy adaptation guided by the BetaLACTA® test: a case-control study

“…The BLT showed interesting intrinsic diagnostic performance in laboratory evaluations, notably sensitivity and specificity >95% for ESBL detection on Enterobacteriaceae colonies [14–17]. However, to our knowledge, a BLT-guided antimicrobial adaptation strategy has never been investigated in the clinical setting.…”

Development of a novel chromogenic method, Penta-well test, for rapid prediction of β-lactamase classes produced in clinical Enterobacteriaceae isolates

“…Although these methods are rapid and simple and allow direct assessment of clinical samples (Dortet et al, 2014a(Dortet et al, , 2014bGallah et al, 2014), their visual interpretation may give rise to ambiguity across different microbiology laboratories (Maurer et al, 2015;Simner et al, 2014;Tijet et al, 2013). Simner et al (2014) reported that the degree of color change used to determine positive results varied, while Tijet et al (2013) reported that intermediate color changes caused discrepancies between the interpretations of the findings made by 2 different laboratories.…”