Antimicrobial activity of novel 4H-4-oxoquinolizine compounds against extensively drug-resistant Acinetobacter baumannii strains

Sub-minimum inhibitory concentrations (sub-MICs) of colistin on Acinetobacter baumannii biofilm formation potency, adherence, and invasion to epithelial host cells: an experimental study in an Iranian children's referral hospital

Here, we described the efficacy of colistin sub-minimum inhibitory concentrations (sub-MICs) on biofilm-forming activity, host epithelial cell adherence, and invasion capacity of Acinetobacter baumannii strains collected from children admitted to the Children's Medical Center Hospital. Biofilm formation potency of A. baumannii clinical isolates was measured using a 96-well microtiter plate assay. Distribution of biofilm-related genes, including bap, abaI, ompA, csuE, and blaPER-1, was detected by PCR. The mRNA expression level of ompA and csuE was measured by qPCR in the presence of ¼ and ½ MICs of colistin. A. baumannii adhesion and invasion to eukaryotic host cells were phenotypically assayed at sub-MICs of colistin. Eighty percent (56/70) and 35.7% (25/70) of A. baumannii isolates were multidrug-resistant (MDR) and extensively drug-resistant (XDR) phenotypes, respectively. The strong, moderate, and weak biofilm producers of A. baumannii were 37.1% (26/70), 32.8%, (23/70), and 22.8% (16/70), respectively. The frequencies of biofilm-associated genes were 100% for abaI, ompA, and csuE, followed by 22.8% (16/70) and 24.3% (17/70) for bap and blaPER-1, respectively. The downregulation of csuE and ompA expression levels was observed in the sub-MIC of colistin. In vitro cell culture study showed a decreased capability of A. baumannii to adhere to the human epithelial cells at sub-inhibitory doses of colistin; however, none of the isolates could invade HEp-2 cells. Our study showed that the genes encoding biofilm-associated proteins undergo downregulation in expression levels after exposure to sub-MICs of colistin in A. baumannii. Longitudinal in vivo studies are needed to fully understand the clinical aspects of pathogenicity mechanisms and evolutionary dynamics of drug resistance.IMPORTANCESince the toxicity of colistin is dose dependent, there is a focus on strategies that reduce the dose while maintaining the therapeutic effect of the drug. Our findings about sub-inhibitory doses of colistin provide a novel insight into the logical use of colistin to treat and control Acinetobacter baumannii-related infections in clinical practice.

Halogenated Antimicrobial Agents to Combat Drug-Resistant Pathogens

Antimicrobial resistance presents us with a potential global crisis as it undermines the abilities of conventional antibiotics to combat pathogenic microbes. The history of antimicrobial agents is replete with examples of scaffolds containing halogens. In this review, we discuss the impacts of halogen atoms in various antibiotic types and antimicrobial scaffolds and their modes of action, structure-activity relationships, and the contributions of halogen atoms in antimicrobial activity and drug resistance. Other halogenated molecules, including carbohydrates, peptides, lipids, and polymeric complexes, are also reviewed, and the effects of halogenated scaffolds on pharmacokinetics, pharmacodynamics, and factors affecting antimicrobial and antivirulence activities are presented. Furthermore, the potential of halogenation to circumvent antimicrobial resistance and rejuvenate impotent antibiotics is addressed. This review provides an overview of the significance of halogenation, the abilities of halogens to interact in biomolecular settings and enhance pharmacological properties, and their potential therapeutic usages in preventing a postantibiotic era. SIGNIFICANCE STATEMENT: Antimicrobial resistance and the increasing impotence of antibiotics are critical threats to global health. The roles and importance of halogen atoms in antimicrobial drug scaffolds have been established, but comparatively little is known of their pharmacological impacts on drug resistance and antivirulence activities. This review is the first to extensively evaluate the roles of halogen atoms in various antibiotic classes and pharmacological scaffolds and to provide an overview of their ability to overcome antimicrobial resistance.

Risk Factors and Drug Resistance of the MDR Acinetobacter Baumannii in Pneumonia Patients in ICU

OBJECTIVE

To investigate the risk factors and drug resistance of MDR Acinetobacter baumannii in pneumonia patients.

METHODS

From January 2013 to February 2016, 98 pneumonia patients with MDR Acinetobacter baumannii in our hospital ICU were selected as the observation group, and 49 pneumonia patients with not-MDR Acinetobacter baumannii in our hospital ICU were selected as the control group in accordance with the proportion of 2:1. Sputum samples were collected from the two groups for drug resistance, and the risk factors and prognosis of MDR Acinetobacter baumannii in pneumonia patients were given survey analysis.

RESULTS

The observation group was highly resistant to cefotaxime, piperacillin, imipenem, levofloxacin, gentamicin, tetracycline and ceftazidime, and was only sensitive to polymyxin. In addition to piperacillin, polymyxin B, the other antimicrobial drug resistance rates in the control group was significantly lower than in the observation group (P<0.05). Univariate analysis showed that diabetes, infection before hospitalization, admission 24h score of APACHE II and GCS scores, deep venous catheterization, and mechanical ventilation were related to the MDR Acinetobacter baumannii in pneumonia patients(P<0.05). Non conditional logistic regression analysis showed that diabetes mellitus, infection before hospitalization, admission 24h score of APACHE II and GCS scores were the independent risk factors for the MDR Acinetobacter baumannii in pneumonia patients(P<0.05).

CONCLUSION

MDR Acinetobacter baumannii in pneumonia patients in ICU is common, where diabetes infection before hospitalization, admission 24h score of APACHE II and GCS scores are the main risk factors, and the vast majority of the antibiotics are resistant to the MDR Acinetobacter baumannii that can lead to poorer prognosis and followed-up of patients with increased mortality.

GC-072: A Novel Therapeutic Candidate for Oral Treatment of Melioidosis and Infections Caused by Select Biothreat Pathogens

Burkholderia pseudomallei (B. pseudomallei), the etiological agent of melioidosis, is a Gram-negative bacterium with additional concern as a biothreat pathogen. The mortality rate from B. pseudomallei varies depending on the type of infection and extent of available health care, but in the case of septicemia left untreated it can range from 50 - 90%. Current therapy for melioidosis is biphasic, consisting of parenteral acute-phase treatment for two weeks or longer, followed by oral eradication-phase treatment lasting several months. An effective oral therapeutic for outpatient treatment of acute-phase melioidosis is needed. GC-072 is a potent, 4-oxoquinolizine antibiotic with selective inhibitory activity against bacterial topoisomerases. GC-072 has demonstrated in vitro potency against susceptible and drug-resistant strains of B. pseudomallei and is also active against Burkholderia mallei, Bacillus anthracis, Yersinia pestis, and Francisella tularensis GC-072 is bactericidal both extra- and intracellularly, with rapid killing noted within a few hours and reduced development of resistance compared to ceftazidime. GC-072, delivered intragastrically to mimic oral administration, promoted dose-dependent survival in mice using lethal inhalational models of B. pseudomallei infection following exposure to a 24 or 339 LD50 challenge with B. pseudomallei strain 1026b. Overall, GC-072 appears to be a strong candidate for first-line, oral treatment of melioidosis.