RANKING OF MAJOR CLASSES OF ANTIBIOTICS FOR ACTIVITY AGAINST STATIONARY PHASE GRAM-NEGATIVE BACTERIA PSEUDOMONAS AERUGINOSA AND CARBAPENEMASE-PRODUCING KLEBSIELLA PNEUMONIAE AND IDENTIFICATION OF DRUG COMBINATIONS THAT ERADICATE THEIR PERSISTENT INFECTIONS

Abstract

From the earliest identification of different bacterial phenotypic states, researchers found under antibiotic exposure, there are some bacteria that can keep dormant in a non-growing state as persister cells. These dormant persister bacteria can revert back to the growing population when the antibiotics are removed. The formation of bacterial persister cells establishes phenotypic heterogeneity within a bacterial population and is important for increasing the chances of successfully adapting to environmental change. Persister cells were first discovered in Staphylococcus sp. in 1944 when penicillin failed to kill a small subpopulation of bacterial cells. In the past several decades, researchers found persisters are present in virtually all bacterial species including Escherichia coli, Pseudomonas aeruginosa, M. tuberculosis, Borrelia burgdorferi and Klebsiella pneumoniae, which can cause hard to eradicate chronic infections clinically. Persisters exhibit temporary antibiotic-tolerant phenotype and the underlying mechanisms involved in the induction and regulation of persister cells formation have been investigated by the previous lab members regarding mechanisms of persistence in Borrelia burgdorferi and with Yin-Yang Model to illustrate persistent infection. This investigation focuses on the optimal treatment for persistent infection. Because current treatments for such chronic persistent infections are not effective and antibiotic phenotypic resistance is a significant issue. The discovery of antibiotics and their widespread use represent a significant milestone in human history since the 20th century. However, their efficacy has declined at an alarming rate due to the spread of antibiotic resistance, and persistence and the evidence is accumulating that persister cells can contribute to the emergence of antibiotic resistance. Effective treatments for bacterial persistent infections can greatly improve patient outcome. A comprehensive overview of anti-persister treatments suggests that development of drug combination treatments may represent a useful therapeutic approach. A typical drug for treating tuberculosis persistent infection includes pyrazinamide (PZA) which is combined with rifampin and isoniazid which kill growing bacteria. PZA is an anti-persister drug that inhibits unconventional drug targets such as proteins involved in energy metabolism and trans-translation. PZA in this triple drug combination therapy demonstrates a strong activity against persister cells, and based on this principle, we screened for pesister drugs like PZA and ranked drugs from six typical classes of antibiotics for their activity against non-growing Pseudomonas aeruginosa. Based on the ranking results, we formulated drug combinations that can effectively kill the heterogeneous population of Gram-negative bacteria in biofilm model. To further evaluate the activity of drug combinations in a relevant mouse model, we established a chronic pulmonary murine infection model. We found that consistent with our findings in vitro, the drug combinations are more effective against the persistent lung infection than the current standard of care treatment. Finally, we conclude that drug combinations consisting of drugs targeting both actively growing bacteria and non-growing persister cells can eradicate the Gram-negative bacteria biofilm related chronic infections. These findings lay the groundwork for possible improved treatment of persistent infections in the clinic