The present disclosure is directed to lysin-AMP polypeptide constructs, isolated lysin polypeptides, and pharmaceutical compositions comprising the isolated polypeptides and/or lysin-AMP polypeptide constructs. Methods of using the lysin-AMP polypeptide constructs, isolated lysin polypeptides and pharmaceutical compositions are also herein provided, including methods of treating a bacterial infection of an organ or tissue in which pulmonary surfactant is present or Gram-negative bacterial infections that are associated with a biofilm. In addition, isolated polynucleotides encoding the lysin-AMP polypeptide constructs and isolated lysin polypeptides are disclosed herein.