Disclosed is a pharmaceutical composition to prevent transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pharmaceutical composition comprising: genetically modified bacteria; sequences of small peptides; and pharmaceutical excipients, wherein the genetically modified oral bacteria are modified to translate, produce, and emit the sequences of small peptides which neutralize SARS-CoV-2 against COVID-19, wherein transgenic technology is used to modify the genetically modified oral bacteria to add genes in genetically modified oral bacteria that are transcribed to produce small peptides from the sequences of small peptides so added, wherein the sequences of small peptides show extreme binding and neutralization to SARS-CoV-2 but not to host proteins or processes, and wherein the pharmaceutical excipients aid the oral and/or nasal administration of the pharmaceutical composition.

In the present invention, the influence by flora of the skin on dermatitis is examined by analyzing Tmem79-knockout model mice, and a bacterium having a suppressive effect on dermatitis is identified, and the present invention relates to a pharmaceutical composition derived from such a bacterium, containing as active components one or more substances selected from: (a) a bacterial cell of an ampicillin-sensitive bacterium, or a constituent component of the bacterium; (b) a culture supernatant of an ampicillin-sensitive bacterium, or a purified product from the culture supernatant; (c) an extract of an ampicillin-sensitive bacterium; and (d) a metabolite of an ampicillin-sensitive bacterium.

Described herein is a synergistic combination comprising a quorum-sensing inhibitor and/or postbiotic metabolite and an antibiotic. Typically, the postbiotic metabolite comprises at least one peptide. Related compositions, uses, and methods are also described, including methods for resensitizing resistant bacteria to an antibiotic, and methods of treating antibiotic-resistant infections, such as methicillin-resistant Staphylococcus aureus (MRSA).