TABLE 2.

Effect of chloramphenicol (200 μg/ml) and ciprofloxacin (20 μg/ml) on survival (CFU) and PCR amplification of P. fluorescens CHA0 (used at 7.7 log CFU/ml) incubated at pH 7 (control) or pH 4 (acidity stress)

Antibiotic and time of exposure	Survival of cells (log CFU/ml)a at pH:		phlA PCRb at pH:		rrs PCR at pH:		D7 RAPD PCR at pH:		GAC RAPD PCR at pH:
	7	4	7	4	7	4	7	4	7	4
None
0.5 h	7.47 ± 0.14	4.92 ± 0.19	+	0	+	+	+	(+)	(+)	0
4 h	6.99 ± 0.14	2.39 ± 0.25	+	(+)	++	+	++	(+)	+	0
1 day	7.41 ± 0.52	BD	+	(+)	++	(+)	++	0	++	0
Chloramphenicol
0.5 h	6.95 ± 0.06	5.92 ± 0.19	+	0	+	(+)	+	(+)	(+)	0
4 h	6.24 ± 0.20	0.92c	+	(+)	++	+	++	(+)	+	0
1 day	7.08 ± 0.03	BD	+	(+)	++	+	++	0	++	0
Ciprofloxacin
0.5 h	BD	BD	+	0	+	(+)	+	0	+	0
4 h	BD	BD	+	(+)	++	(+)	+	0	+	0
1 day	BD	BD	+	(+)	++	(+)	+	0	+	0

^aResults are means ± standard deviations. BD, below detection (detection limit = 0.92 log CFU/ml).

^bEfficiency of PCR amplification methods was rated as follows: 0, no amplification; (+), weak or nonspecific amplification; +, normal amplification; ++, strong amplification.

^cFrom 0 to 2 colonies were recovered per plate.