Isolation Procedure for CP E. coli from Caeca Samples under Review towards an Increased Sensitivity

• Published in: Microorganisms (Basel) Vol. 9; no. 5; p. 1105
• Main Authors: Pauly, Natalie, Klaar, Yvonne, Skladnikiewicz-Ziemer, Tanja, Juraschek, Katharina, Grobbel, Mirjam, Hammerl, Jens André, Hemmers, Lukas, Käsbohrer, Annemarie, Schwarz, Stefan, Meemken, Diana, Tenhagen, Bernd-Alois, Irrgang, Alexandra
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 20.05.2021; MDPI
• Subjects: Antiinfectives and antibacterials; Bacteria; Carbapenemase; Cefotaxime; CPE detection; E coli; Enrichment; Feces; Glycerol; Isolation; Laboratories; Livestock; Lysogeny; Meat; Medicine; Meropenem; Microbiota; Minimum inhibitory concentration; Plasmids; Salmonella; selective media; Sensitivity; specificity; Germany
• ISSN: 2076-2607; 2076-2607
• DOI: 10.3390/microorganisms9051105

Due to the increasing reports of carbapenemase-producing Enterobacteriaceae (CPE) from livestock in recent years, the European Reference Laboratory for Antimicrobial Resistances (EURL-AR) provided a protocol for their recovery from caecum and meat samples. This procedure exhibited limitations for the detection of CPE with low carbapenem MIC values. Therefore, it was modified by a second, selective enrichment in lysogeny broth with cefotaxime (CTX 1 mg/L) and with meropenem (MEM 0.125 mg/L) at 37 °C under microaerophilic conditions. By Real-time PCR, these enrichments are pre-screened for the most common carbapenemase genes. Another adaptation was the use of in-house prepared MacConkey agar with MEM and MEM+CTX instead of commercial selective agar. According to the EURL-method, we achieved 100% sensitivity and specificity using the in-house media instead of commercial agar, which decreased the sensitivity to ~75%. Comparing the method with and without the second enrichment, no substantial influence on sensitivity and specificity was detected. Nevertheless, this enrichment has simplified the CPE-isolation regarding the accompanying microbiota and the separation of putative colonies. In conclusion, the sensitivity of the method can be increased with slight modifications.