Comparison of two commercial preparations of buffered peptone water for the recovery and growth ofSalmonellabacteria from foods

Abstract

E T T S . 2000. This study compared the performance of two commercial preparations of buffered peptone water. Performance was assessed in terms of ability to resuscitate and recover low numbers of stressed cells, buffering capacity, growth of Salmonella bacteria in pure culture and growth of Salmonella in food pre-enrichments. Although both the preparations of BPW had similar chemical compositions, differences in their recovery performance were found. Brand A recovered signi®cantly higher numbers of heat-injured Salmonella (mean 0Á57 log 10 cfu ml À1 difference) in pure culture compared with brand B when dealing with very low inoculum levels. Although brand B had higher buffering capacity, the pH at the end of the pre-enrichment was found to be similar in both media, even in foods such as milk powder which showed the greatest decline in pH. Both brands were comparable in their ability to grow unstressed Salmonella from different food types. In unstressed cell studies, similar cell numbers were recovered at the end of a 24 h incubation period from both media, although brand B yielded a higher biomass. In the food study with unstressed cells, performance was related more to the food type and the likely association between this and the level and type of competitor organisms present, rather than to the brand of medium used.

Evaluation of different buffered peptone water (BPW) based enrichment broths for detection of Gram-negative foodborne pathogens from various food matrices

“…Gram-negative foodborne pathogens are usually present in relatively low numbers, sometimes 60 accompanied by a high number of closely related competitor organisms (Baylis et al, 2000). 61…”

Low tyrosine content of growth media yields aflagellate Salmonella enterica serovar Typhimurium

“…The most common pre-enrichment medium for salmonella enumeration and recovery is buffered peptone water (BPW) comprising salts, phosphate buffers and the complex, undefined ingredient peptone. Performances of commercial preparations of BPW were compared (Baylis et al, 2000), and differences found in their ability to sustain the recovery of injured organisms.…”

Improvement of methods for the detection of Gram-negative foodborne pathogens

“…The pre-enrichment and selective enrichment step are the main time limiting factors in regards to turn around time for rapid methods (62). The usual sequence of enrichment and detection steps in the reference methods can be accelerated by omitting one of the two subsequent enrichment steps.…”

“…in infant formula (ISO/ TS 22964:2006) (60) and STEC in sprouts (ISO/TS 13136:2012) (61). In order to provide conditions for the resuscitation and growth of cells prior to the selective enrichment, BPW buffers the pH of the growth system against changes caused by the growth and metabolism of microorganism and those brought about by the food sample (62). The success of pre-enrichment is also depending on the quality of the medium.…”

“…During a comparison of two commercially available preparations of buffered peptone water with regards to their ability to promote recovery and growth of sub-lethally injured S. enterica, there was a significantly higher recovery rate of stressed cells with one brand of buffered peptone water. However, the performance of BPW in food was mostly dependent on the food type with the type and level of background flora present being the most important influential factors (62). Different studies have investigated the effect of changing the composition of BPW and modification of the incubation conditions during enrichment (temperature, time, etc.)…”