Affiliations: Department of Biochemistry, Lagos State University,
Apapa, Lagos, Nigeria | Department of Microbiology, Lagos State University,
Apapa, Lagos, Nigeria
Note: [] Correspondence: Dr. Bamidele Abiodun Iwalokun, Department of
Biochemistry, Lagos State University, PMB. 1087, Apapa, Lagos, Nigeria. Tel.:
+234 1 8504327; E-mail: [email protected]
Abstract: This study aims to determine the ability of zinc sulphate to inhibit
growth of Shigella in vitro and test the hypothesis that the
isolates recovered from Nigerian children with low plasma zinc concentration
are more sensitive than the marginal plasma zinc isolates. The effect of zinc
sulphate on extracellular protease secretion was also investigated. A total of
15 Shigella isolates recovered from the stool samples of 117 diarrheic
children at various health centers in Lagos, Nigeria were tested for
sensitivity to zinc sulphate in vitro by agar dilution method. Plasma
zinc concentration was determined spectrophotometrically to enable
stratification of the patients into two zinc arms: low (plasma zinc
<9.2 μmol/L) and marginal (plasma
zinc: 9.2–4 μmol/L). The in vitro effect of zinc
sulphate on extracellular protease secretion based on azocasein hydrolysis in
these isolates was also determined. Isolates of Shigella
dysenteriae and Shigella flexneri were found to be more sensitive
to zinc sulphate (minimum inhibitory concentration =
0.89–0.98 ± 0.03–0.06 mg/mL) than the isolates of
Shigella sonnei and Shigella boydii (minimum inhibitory
concentration = 1.13–1.4 ±
0.06–0.1 mg/mL (P < 0.05). The late logarithmic growth
kinetics of these isolates also produced similar response to zinc sulphate
in vitro. The observed zinc sulphate-induced growth inhibition of the
Shigella isolates tested was further found to be associated with a decline in
their extracellular protease secretion in both zinc arms. Zinc sulphate elicits
in vitro inhibition of growth and serogroups-dependent decline in
extracellular protease activity among Shigella isolates from Nigerian
children irrespective of their systemic zinc levels. We conclude that zinc
sulphate may have potentials to be used as a shigellocidal and anti-virulent
agent in the management of shigellosis in children.
