Abstract
Cronobacter spp. has been reported to cause meningitis, necrotizing enterocolitis, and septicemia in a group of infants through the consumption of powder infant formula. These bacteria are reported to withstand various stress conditions such as heating, drying, low water activity, low pH, etc. A local isolate of Cronobacter sakazakii YRt2a was reportedly survived and entered Viable But Non-Culturable (VBNC) conditions during desiccation stress. This study aims to study the behavior of local isolates of Cronobacter spp. in response to acid stress and its resuscitability. C. sakazakii E2 and YRt2a were grown in TSB at pH 3.0±0.2 or 3.5±0.2. The number of culturable cells and viable cells were enumerated by the Total Plate Count and Direct Viable Count methods, respectively. Resuscitation was done by growing the stress or VBNC cells in TSB with or without sodium pyruvate, catalase, Tween 20, or Cronobacter autoinducer. The results showed that C. sakazakii E2 and YRt2a entered VBNC state after 60 mins of exposure to pH 3.0±0.2, while remained culturable after 120 minutes exposure to pH 3.5±0.2. TSB with or without sodium pyruvate, catalase, Tween 20, or Cronobacter autoinducer could resuscitate the stress or VBNC cells of C. sakazakii. Stress or VBNC state experienced by C. sakazakii in response to acid tends to be transient and can be resuscitated. C. sakazakii experiencing stress or VBNC may pose a risk for food safety.
Highlights
Cronobacter spp. is able to cause meningitis, necrotizing enteritis, and septicemia in certain of infants through the consumption of powder infant formula
The bacteria used in this study were C. sakazakii E2 isolated from follow-up formula (Estuningsih et al 2006) and C. sakazakii YRt2a (JF800182) from powder infant formula (Dewanti-Hariyadi et al, 2010)
The results suggested that C. sakazakii E2 and YRt2a exposed to acid for up to 120 mins experienced stress and capable of entering the Viable But Non-Culturable (VBNC) state
Summary
Cronobacter spp. is able to cause meningitis, necrotizing enteritis, and septicemia in certain of infants through the consumption of powder infant formula These pathogenic bacteria are reported to be resistant to various stresses such as heating (Arroyo et al, 2009; Dancer et al, 2009), drying (Breeuwer et al, 2003; Dancer et al, 2009), low water activity (Dancer et al, 2009) and low pH (Dancer et al, 2009). These bacteria grow rapidly at pH 5.0, the range of gastric pH for newborns and infants (Álvarez-Ordóñez et al, 2014) and have a minimum pH for growth at pH 3.9 (Dancer et al, 2009). Exposure of foodborne pathogenic bacteria to stress conditions causes low transcription activity, increased ribosomal RNA degradation, and non-coding RNA regulation (Deng et al, 2012), reduced cytoplasmic membranes fluidity (Yang et al 2014), slow enzymatic reactions and metabolic rate decline (Maserati et al, 2017)
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