According to a new study reported in the open-access journal PLoS ONE, a human breast milk protein complex called HAMLET can help reverse the antibiotic resistance of bacterial species, including penicillin-resistant Streptococcus pneumoniae and methicillin-resistant Staphylococcus aureus.

In petri dish and animal experiments, HAMLET (Human Alpha-lactalbumin Made Lethal to Tumor Cells) increased bacteria’s sensitivity to multiple classes of antibiotics, such as penicillin and erythromycin.

“The effect was so pronounced that bacteria including penicillin-resistant S. pneumoniae and methicillin-resistant S. aureus (MRSA) regained sensitivity to the antibiotics they were previously able to beat,” said lead author Laura Marks and her colleagues from the University at Buffalo.

In a 2012 study published in PLoS ONE, the team described HAMLET’s effects against S. pneumoniae, also Acinetobacter baumanii and Moraxella catarrhalis. The newly-published PLoS ONE paper details protein’s effects on MRSA.

“HAMLET has the potential minimize the concentrations of antibiotics we need to use to fight infections, and enable us to use well-established antibiotics against resistant strains again,” explained senior author Prof Anders Hakansson.

The findings hold great promise in an era when hospitals are struggling to contain drug-resistant bacteria like MRSA, the culprit behind lethal hospital-acquired staph infections.

Bacteria seem to have difficulty developing resistance to HAMLET, dying in huge numbers even after being exposed to HAMLET for many generations.

“Unlike synthetic drugs, HAMLET is a naturally occurring human milk protein-lipid complex, and so is not associated with the types of toxic side effects that we so frequently see with the high-powered antibiotics needed to kill drug-resistant organisms,” Marks added.

The idea to test HAMLET in combination with other antibiotics was inspired, in part, by a presentation Marks saw on using drug cocktails to treat HIV.

“What really hit home for me in this lecture was the idea of using drug combinations where each drug had a different mechanism that could enhance the action of the other drug as an appealing way to optimize therapy for resistant organisms,” Marks said.

“I was immediately curious to see if using HAMLET together with existing therapies could result in synergistic interactions.”

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Bibliographic information: Marks LR et al. 2013. Sensitization of Staphylococcus aureus to Methicillin and Other Antibiotics In Vitro and In Vivo in the Presence of HAMLET. PLoS ONE 8 (5): e63158; doi: 10.1371/journal.pone.0063158