Zinc protects against shiga-toxigenic Escherichia coli by acting on host tissues as well as on bacteria

BMC Microbiology

Table 2 Effect of zinc on the bacteriophage yield from STEC bacteria by phage plaque assay on E. coli MG1655 as host strain

Experiment number	Donor/source strain for bacteriophage	Growth condition (in DMEM Medium)	Bacterio-phage titer	Fold reduction by zinc
Expt. 1	TSA14; O26:H11, Stx1+; harbors phage H19B	control, no additives	1:10
		+ 0.4 mM Zn	no plaques, < 1:10	> 2-fold decrease
		+ 4 ng/ml cipro	1:640	> 2-fold decrease
		+ 4 cipro + 0.4 mM Zn	1:80	8-fold decrease
Expt. 2	TSA14; O26:H11	control, no additives	1:20
		+ 0.6 mM Zn	no plaques	> 2-fold decrease
		+ 8 ng/ml cipro	1:640
		+ 8 cipro + 0.4 mM Zn	1:160	4-fold decrease
		+ 8 cipro + 0.6 mM Zn	1:80	8-fold decrease
Expt. 3	EDL933; O157:H7; Stx1+, Stx2+;	control	1:80
	EDL933; O157:H7; Stx1+, Stx2+;	+ 0.6 mM Zn	1:40	2-fold decrease
	Harbors phages H19B and 933 W	+ 10 ng/ml cipro	> 1:5120
	Harbors phages H19B and 933 W	+ 10 cipro + 0.6 mM Zn	1:320	≥ 16-fold decrease
Expt. 4	EDL933	control	1:80
		+ 0.6 mM Zn	1:20	4-fold decrease
		+ 10 ng/ml cipro	1:640
		+ 10 cipro + 0.6 mM Zn	1:160	4-fold decrease

All source strains were grown for 5 hours, 4 hours after addition of ciprofloxacin and/or zinc.
Zn, zinc acetate; cipro, ciprofloxacin, usually added at ~ 1/3 of the MIC.

ISSN: 1471-2180