Detection and recovery of sublethally-injured enterotoxigenic Staphylococcus aureus.
OBJECTIVE
To determine whether sublethally-injured (acid- or heat-shocked) Staphylococcus aureus cells are recoverable using selective agar overlays.


RESULTS
Brain Heart Infusion (BHI) Agar overlaid with either Baird-Parker Agar (BPA) or Gram-Positive Agar (GPA) was compared in the ability to resuscitate heat- and acid-shocked enterotoxigenic Staph. aureus. BHI/BPA overlays allowed for greater recovery of both heat- and acid-shocked cells than BHI/GPA, although the former was not selective and allowed growth of bacteria other than Staph. aureus. No significant difference existed in percent recovery of heat- and acid-shocked cells between the two overlay approaches. Significant differences were noted in counts on BHI/GPA plates and straight selective GPA/GPA plates, however. Viability of heat- and acid-shocked Staph. aureus was also examined using fluorescence microscopy, the relative counts of which correlated well to the calculated percent recovery on selective agar overlays.


CONCLUSIONS
This work has shown that an improved agar overlay technique increases the sensitivity of the standard plate count while enumerating sublethally-injured enterotoxigenic Staph. aureus compared with direct plating onto selective media.


CONCLUSIONS
These data emphasize the need to develop practical and cost-effective methods that reliably detect and enumerate sublethally-injured pathogens such as Staph. aureus.
Sandel
M K
MK
School of Biological Sciences, Louisiana Tech University, Ruston, LA 71272, USA. mckillip@latech.edu
Wu
Y-F G
YF
McKillip
J L
JL
D000362:Agar; D001427:Bacterial Toxins; D015169:Colony Count, Microbial; D003470:Culture Media; D004768:Enterotoxins; D006358:Hot Temperature; D019344:Lactic Acid; D008856:Microscopy, Fluorescence; D013211:Staphylococcus aureus / Q000302:isolation & purification*
D001427:Bacterial Toxins; D003470:Culture Media; D004768:Enterotoxins; D019344:Lactic Acid; D000362:Agar