Mg, Mn, and Co Ions Enhance the Formation of Entamoeba histolytica Cyst-Like Structures Resistant to Sodium Dodecyl Sulfate

Abstract Background Entamoeba histolytica forms cyst-like structures (CLS) in PEHPS but not in TYS-33 medium. Sodium dodecyl sulfate [(SDS (0.1%)] dissolves most of them in 10 min, but not natural cysts. Chitin is responsible mainly for cyst wall resistance. Its synthesis depends on Mg 2 +, Mn 2 +, or Co 2 +, whose action is interactive. With the aid of the Simplex method, we analyzed the effect of 20 blends of these cations to find the one that, when added to PEHPS, produced the highest proportion of CLS resistant to 1% SDS (RCLS). Methods The concentration of Mg 2 +, Mn 2 +, and Co 2 + was determined in PEHPS and TYI-S-33 with a flame atomic absorption spectrometer. The proportion of RCLS produced in PEHPS with each ion blend was tested. The CLS and RCLS affinity to fluorescein wheat germ agglutinin (WGA/FITC), which binds chitin, was determined. Results PEHPS contained a similar concentration of Co 2 + (0.52 μM) and 3.4 and 1.6 times more Mg 2 + (798 μM) and Mn 2 + (3.15 μM) than TYI-S-33, respectively. The proportion of RCLS increased gradually in PEHPS until reaching 3.6 ± 1.43% with MgCl 2 1.22 mM, MnCl 2 14.44 mM, and CoCl 2 19.44 mM (ion blend No. 20). Both CLS and RCLS bound WGA/FITC. The RCLS formed in the presence of ion blend No. 20 appeared wrinkled. Conclusions Mg 2 +, Mn 2 +, and Co 2 + enhanced the ability of PEHPS to form RCLS, possibly because these ions stimulated their chitin synthesis. Although ion blend No. 20 produced the highest proportion of RCLS, this high ion concentration may be toxic for encysting amebas.