Influence of Stress Factors Related to Cheese-Making Process and to STEC Detection Procedure on the Induction of Stx Phages from STEC O26:H11.
Shiga toxin-producingEscherichia coli(STEC) are responsible for human infections, ranging from mild watery diarrhea to hemorrhagic colitis (CH) that may be complicated by hemolytic uremic syndrome (HUS). The main STEC virulence factor is Shiga toxin encoded by thestxgene, located in the genome of a bacteriophage integrated into the bacterial chromosome. The serotype O26:H11 is the second HUS-causing serotype worldwide (after O157:H7), and the first found in dairy products such as raw-milk cheeses. A small number of HUS cases identified each year in France are caused by serotype O26:H11. Stx phage induction is known to result in STEC lysis and release of new Stx phages particles. This phenomenon could negatively impact STEC screening in foods based onstxgene detection by PCR. Here, we evaluated the influence of physicochemical parameters related to cheese-making process on the induction rate of Stx phages from STEC O26:H11, including H2O2, NaCl, lactic acid and temperature. In addition, selective agents from the analytical STEC enrichment and detection procedure (XP CEN ISO/TS 13136) were tested, including novobiocin, acrifavin, cefixim-tellurite, and bile salts. An impact of H2O2and NaCl on Stx phage induction was observed. Production of Stx phages was also observed during a real cheese-making process. By contrast, no significant effect could be demonstrated for the chemical agents of the STEC detection procedure when tested separately, except for acriflavin and novobiocin which reduced Stx1 phage production in some cases. In conclusion, these results suggest that the cheese-making process might trigger the production of Stx phages, potentially interfering with the analysis of STEC in food.
Université Paris-Est, Anses, Laboratory for Food SafetyMaisons-Alfort, France; ACTALIA Produits Laitiers, Laboratoire de Microbiologie d'Intérêt LaitierLa Roche sur Foron, France.
Ludivine
L
Bonanno
Université Paris-Est, Anses, Laboratory for Food SafetyMaisons-Alfort, France; ACTALIA Produits Laitiers, Laboratoire de Microbiologie d'Intérêt LaitierLa Roche sur Foron, France.
Benjamin
B
Delubac
ACTALIA Produits Laitiers, Laboratoire de Microbiologie d'Intérêt Laitier La Roche sur Foron, France.
Valérie
V
Michel
Université Paris-Est, Anses, Laboratory for Food Safety Maisons-Alfort, France.
Frédéric
F
Auvray
O26:H11; STEC; Stx phages; cheese; induction