Importance of pre-enrichment for detection of third-generation cephalosporin-resistant Enterobacteriaceae (3GCREB) from rectal swabs

Abstract

Screening for multidrug-resistant Enterobacteriaceae is performed in many institutions as part of infection control measures. However, the sensitivity of current standard diagnostics is modest. Furthermore, patients are usually screened by rectal swabs (mostly rayon based), which have been shown to be sub-optimal for the recovery of Enterobacteriaceae. Therefore, it is likely that many patients colonised with multidrug-resistant Enterobacteriaceae remain undetected. The present study aimed to analyse if the detection of multidrug-resistant Enterobacteriaceae can be improved when screening with rayon swabs is done in combination with an additional pre-enrichment step. The detection of third-generation cephalosporin-resistant Enterobacteriaceae (3GCREB) was assessed in 514 rectal samples by the standard diagnostic approach (direct plating of swabs on selective ESBL agar) and after pre-enrichment in 5 mL of a semi-selective MacConkey broth. The recovery rate of 3GCREB and extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E), patient characteristics and isolate characteristics were evaluated for both diagnostic approaches. Overall, by pre-enrichment, the detection of 3GCREB carriers increased by 22.8% (13/57, p = 0.004) and the detection of ESBL-E carriers by 21.4% (9/42, p = 0.01). This study demonstrates the low sensitivity of rectal screening by direct plating and the improvement by pre-enrichment. We believe that it is no longer acceptable to refrain from pre-enrichment as, with the standard approach, more than 20% of 3GCREB and ESBL-E carriers remain undetected.

Surveillance von Infektionserregern am Beispiel der Erregersurveillance im KISS

“…Es ist schwer, aus solchen Zusammenstellungen einen epidemiologischen Zusammenhang herauszufinden. [12]. Darüber hinaus sollten breite Screeningmaßnahmen zur Surveillance in der endemischen Situation kritisch betrachtet werden, da sowohl für den individuellen Patienten als auch für die Allgemeinheit der Nutzen einer solchen mikrobiologischen Diagnostik ohne Infektionsverdacht fraglich ist [13].…”

Successful control of an extended-spectrum beta-lactamase-producing Klebsiella pneumoniae ST307 outbreak in a neonatal intensive care unit

“…As the systematic microbiological screening was not continued or repeated after reinforcing the IC measures, we cannot be sure if the outbreak had really ended. There might have been undetected cases because the direct plating of rectal swabs has a low sensitivity of detection [31]. In addition, we did not have any cases of non-ESBL KPN during the same period, and therefore we could not perform a risk analysis.…”

Detection of AmpC β-lactamases in Escherichia coli using different screening agars

“…This pre-enrichment step was included to mimic our laboratory algorithm for screening of multiresistant Enterobacterales in rectal samples. Former studies on the screening of third generation cephalosporin resistance have shown that a pre-enrichment strategy results in higher yield compared to direct plating (28–30). We assume that that the use of a pre-enrichment strategy in clinical setting will result in a similar detection range, though inoculum of the original sample may differ.…”