Klebsiella pneumoniae (KP) remains the most prevalent nosocomial pathogen and carries the carbapenemase (KPC) gene which confers resistance towards carbapenem. Thus, it is necessary to discover novel antimicrobials to address the issue of antimicrobial resistance in such pathogens. Natural products such as essential oils are a promising source due to their complex composition. Essential oils have been shown to be effective against pathogens, but the overall mechanisms have yet to be fully explained. Understanding the molecular mechanisms of essential oil towards KPC-KP cells would provide a deeper understanding of their potential use in clinical settings. Therefore, we aimed to investigate the mode of action of essential oil against KPC-KP cells from a proteomic perspective by comparing the overall proteome profile of KPC-KP cells treated with cinnamon bark (Cinnamomum verum J. Presl) essential oil (CBO) at their sub-inhibitory concentration of 0.08% (v/v). A total of 384 proteins were successfully identified from the non-treated cells, whereas only 242 proteins were identified from the CBO-treated cells. Proteins were then categorized based on their biological processes, cellular components and molecular function prior to pathway analysis. Pathway analysis showed that CBO induced oxidative stress in the KPC-KP cells as indicated by the abundance of oxidative stress regulator proteins such as glycyl radical cofactor, catalase peroxidase and DNA mismatch repair protein. Oxidative stress is likely to oxidize and disrupt the bacterial membrane as shown by the loss of major membrane proteins. Several genes selected for qRT-PCR analysis validated the proteomic profile and were congruent with the proteomic abundance profiles. In conclusion, KPC-KP cells exposed to CBO undergo oxidative stress that eventually disrupts the bacterial membrane possibly via interaction with the phospholipid bilayer. Interestingly, several pathways involved in the bacterial membrane repair system were also affected by oxidative stress, contributing to the loss of cells viability.
Doripenem is approved in the Asia-Pacific (APAC) region for treating nosocomial pneumonia (NP) including ventilator-associated pneumonia (VAP), complicated intra-abdominal infections (cIAIs) and complicated urinary tract infections (cUTIs). Clinical usage of doripenem (500mg intravenously, infused over 1h or 4h every 8h for 5-14 days) in APAC was evaluated in a prospective, open-label, non-comparative, multicentre study of inpatients (≥18 years) with NP, VAP, cIAI or cUTI. A total of 216 [intention-to-treat (ITT)] patients received doripenem: 53 NP (24.5%); 77 VAP (35.6%); 67 cIAI (31.0%); and 19 cUTI (8.8%). Doripenem MIC90 values for Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli and Klebsiella pneumoniae were 32, 32, 0.094 and 0.64μg/mL, respectively. Doripenem was used most commonly as monotherapy (86.6%) and as second-line therapy (62.0%). The clinical cure rate in clinically evaluable patients was 86.7% at the end of therapy (EOT) and 87.1% at test of cure (TOC) (7-14 days after EOT). In the ITT population, overall clinical cure rates were 66.2% at EOT and 56.5% at TOC. The median duration of hospital stay, intensive care unit (ICU) stay and mechanical ventilation was 20, 12 and 10 days, respectively. Of 146 discharged patients, 7 were re-admitted within 28 days of EOT; 1 VAP patient was re-admitted to the ICU. The all-cause mortality rate was 22.7% (49/216). The most common treatment-related adverse events were diarrhoea (1.4%) and vomiting (1.4%). Doripenem is a viable option for treating APAC patients with NP, VAP, cIAI or cUTI. [ClinicalTrials.gov: NCT 00986102].