Antimicrobial Effect of Zn2+ Ions Governs the Microbial Quality of Donor Human Milk

Abstract

Donor human milk (HM) obtained at HM banks is exceptionally crucial for the feeding and treatment of preterm infants. Bacterial contaminations of HM in various stages of its handling are very common and can lead to disqualification of donations or severe infections in worse cases. Hence, HM donations are subject to strict bacteriological evaluations pre- and post-pasteurization. The main contaminating species vary between countries, banks and donors and even exhibit inter-individual variation. We initiated an assessment of the bacteriological composition of HM donated by women hospitalized in a neonatal intensive care unit in Israel. The most common bacterium identified was Staphylococcus epidermidis, found in all but one of the HM samples; the presence of several species of coagulase-negative Staphylococci was also noted. Next, we sought to develop a platform towards antibacterial treatment using Zn2+ ions that have recently been found to be potent against contaminants isolated from bovine milk. Zn2+ efficiently inhibited the growth of viable aerobic population and S. epidermidis in HM. Growth was also inhibited in other Gram-positive bacteria such as Bacillus cereus, a well-known food-borne pathogen. S. epidermidis and B. cereus cells grown in the presence of zinc were taken for microscopic evaluation, aiming to demonstrate zinc’s antimicrobial mode of action morphologically. Images obtained using scanning electron microscopy indicated leakage of cellular content and cell lysis in S. epidermidis. Besides, B. cereus cells showed abnormalities in their cell surface and complete loss of flagella upon treatment with zinc. Along with the above findings, it should be noted that this was a pilot study that tested how high doses of Zn2+ affect breast milk as a product. Further research is likely needed on the safety of consumption of Zn2+-treated HM in infants and older children.

ZIF‐8 Based Active Wound Dressing for pH Modulation and pH‐Responsive Delivery of Curcumin and Zn2+: Effect of Acidity on the Drug Release for Antibacterial and Antioxidant Efficacy

“…This result demonstrates that the release of Zn 2+ by the ZIF‐8 decomposition can be advantageous for antibacterial activity; when Zn 2+ release of ZIF‐8 is induced by acid layer, the released ions can act as an effective antibacterial agent even ZIF‐8 is incorporated in a fibrous structure. Zn 2+ infiltrates the cell membrane of bacteria, intensifying the destruction of the membrane integrity and interfering the enzyme system of bacteria, [ 41,42 ] and this antibacterial action can ultimately inhibit the proliferation of bacteria and resist bacterial infection at the wound site, as the previous study confirmed. [ 43 ] In fact, as the microbial species isolated from infected wounds involves Gram positive bacteria also, additional assay against various bacteria may be needed for the range of practical applications.…”

Design of Laser Activated Antimicrobial Porous Tricalcium Phosphate-Hydroxyapatite Scaffolds for Orthopedic Applications

“…Two of these involve: (i) the production of free Zn 2+ ions from the Zn nanoparticles and (ii) the attachment of ZnO nanoparticles to the external part of the bacteria via electrostatic forces [50]. As an element, zinc has been found to be an important factor in multiple vital intracellular processes occurring in all organisms; however, an increase in its concentration could have a detrimental impact for cells [51]. Particularly in bacterial cells, it has been reported that rising levels of free zinc can result in protein deactivation, disruption in glycolysis, polysaccharide synthesis, acid tolerance and proton translocation [52].…”

Endogenous Antimicrobial‐Immunomodulatory Molecules: Networking Biomolecules of Innate Immunity

“…[82] Zn 2 + has antibacterial activities against Gram-positive (S. epidermidis, Bacillus cereus) and Gram-negative (E. coli) bacteria. [83] Like Cu 2 + , Zn 2+ ions induce the production of H 2 O 2 , OH À , O 2 À and * OH, generating bacterial membrane damage by ROS-mediated oxidative stress. [84] Zn 2 + also achieves antimicrobial effects through direct enzyme inhibition: in viruses (coronavirus, arterivirus) Zn 2 + inhibits RNA polymerase; in Gram-positive bacteria, Zn 2 + inflicts cell wall destruction via inhibition of transglycolase and transpeptidase enzymes.…”

“…Zn 2+ is likewise a broad‐spectrum EAIM [82] . Zn 2+ has antibacterial activities against Gram‐positive ( S. epidermidis , Bacillus cereus ) and Gram‐negative ( E. coli ) bacteria [83] . Like Cu 2+ , Zn 2+ ions induce the production of H 2 O 2 , OH − , O 2 − and ⋅OH, generating bacterial membrane damage by ROS‐mediated oxidative stress [84] .…”