Optimization of broth recovery for repair of heat‐injuredSalmonella entericaserovar Typhimurium andEscherichia coliO157:H7

Abstract

Aims The purpose of this research was to determine optimum conditions for broth recovery of heat‐injured Salmonella Typhimurium and Escherichia coli O157:H7. Methods and Results Exposure to 55°C for 15 and 25 min, respectively, induced cellular injury to those pathogens. Comparison was made with the commonly used overlay method using selective medium for recovering sublethally injured cells of S. Typhimurium. For E. coli O157:H7, phenol red agar base with 1% sorbitol was used. After cell suspensions were heated at 55°C for selected time intervals, microbes were 10‐fold diluted with brain heart infusion (BHI), tryptic soy broth (TSB) and TSB with 0·6% yeast extract (TSBYE) and incubated at 37°C for up to 3 h. At hourly intervals, diluents were plated onto selective medium for recovery. Simultaneously, diluents were plated onto tryptic soy agar (TSA) for recovery of sublethally injured cells. For overlays, diluents were plated onto TSA and overlaid with selective agar after a resuscitation interval. Broth recovery conditions for S. Typhimurium and E. coli O157:H7 were determined to be 1 h in any of the following broth media: BHI, TSB or TSBYE. When liquid resuscitation was applied to sublethally injured cells in food samples (milk), 1 h was also sufficient time for recovery. Conclusions The broth recovery method is a convenient alternative to conventional recovery methods. Significance and Impact of the Study Cells sublethally injured by control interventions might not grow on selective medium because they have no resistance to several selective compounds. However, injured cells can recuperate and multiply under conditions sufficient for recovery. To repair and detect heat‐injured cells, the overlay method is commonly used but this method has some limitations. This study confirms the effectiveness of liquid resuscitation method on recovery of injured cells. The broth recovery can replace the overlay method due to greater convenience and timesaving.

Adhesion and bactericidal properties of nanostructured surfaces dependent on bacterial motility

“…It is noted that some population of bacteria inactivated by various methods such as UV and heat treatment to destroy micro-organisms can still survive as injured cells. [27][28][29] Injured cells are dened as cells exposed to physical and chemical stresses. They are not destroyed aer sterilization but their life and death are judged by additional broth condition aer the sterilization.…”

Quercetin mediated antimicrobial photodynamic treatment using blue light on Escherichia coli O157:H7 and Listeria monocytogenes

“…The selective media used were sorbitol MacConkey agar (SMAC) (Difco, Sparks, MD, USA) for E. coli O157:H7 and Oxford agar (MBcell) (Seocho-Gu, Seoul, South Korea) with Oxford agar supplement (MBcell) (Seocho-Gu, Seoul, South Korea) for L. monocytogenes . The occurrence of sublethally injured E. coli O157:H7 and L. monocytogenes in food samplas after aPDT was investigated using the broth recovery method ( Han et al, 2019 ). Treated or untreated sample 1 ml was poured into 9 ml of TSB and incubated at 37 °C for 2 h. After incubation, resuscitated pathogens in TSB was serially diluted 10-fold in 9 ml of 0.2% sterilized PW, and 100 μl or 1 ml of the diluent was spread onto SMAC and Oxford agar.…”

Bacterial pathogen detection by conventional culture‐based and recent alternative (polymerase chain reaction, isothermal amplification, enzyme linked immunosorbent assay, bacteriophage amplification, and gold nanoparticle aggregation) methods in food samples: A review

“…Recently, the conventionally used selective media has been modified to improve cell sensitivity and selectivity. For example, several techniques were combined to detect injured cells on solid media (Wu, 2008), and the liquid medium resuscitation method for the recovery of nonculturable cells has been innovated (Han, Song, & Kang, 2019). Despite these improvements, conventional method has limitation of time‐consuming and laborious, and therefore, several alternative detection methods have been developed to detect microorganisms.…”