Author Interviews, Hospital Acquired, Infections, Nature / 24.02.2016
Marine Microbial Cahuitamycins as Biofilm Inhibitors For Medical Devices
MedicalResearch.com Interview with:
[caption id="attachment_21986" align="alignleft" width="200"]
Dr. Ashootosh Tripathi[/caption]
Ashootosh Tripathi, PhD
Postdoctoral Research Fellow
Life Sciences Institute I Sherman lab
University of Michigan
Ann Arbor, MI, USA
MedicalResearch: What is the background for this study? What are the main findings?
Dr. Tripathi: Acinetobacter baumannii is a nosocomial opportunistic and resistant pathogen that can spread epidemically among patients causing ventilator-associated pneumonia and bacteremia. The mortality rates associated with it can be as high as 60%, representing a paradigm of pathogenesis, transmission and resistance. In addition, numerous reports have shown the startling emergence of multidrug-resistant A. baumannii in hospitals as well as the identification of pan-drug-resistant strains at some locations. Among the various reasons for the antibiotic resistance of this pathogenic microbe, perhaps the most significant is mediated by its tendency to form biofilms (a highly structured extracellular polymeric matrix), which provide the microbe with the alarming ability to colonize medical devices. Interestingly, despite the well-understood role of bacterial biofilm behind aggravating antimicrobial resistance, there are currently no drugs specifically targeting biofilms in clinical trials to date. The study sought to solve this problem through the development of a biofilm inhibitor as a precision medicine, directed towards vulnerable patients, to avoid potential life-threatening infections.
A crystal-violet based high throughput in vitro screen was developed to identify inhibitors of A. baumannii biofilms against our natural products extract (NPE) library. The vast NPE library of ~42,000 extracts has been under constant development in Prof David H. Sherman laboratory at University of Michigan, Ann Arbor, for over the past decade, from a relatively underexplored marine microbiome collected from different part of world viz., Costa Rica, Panama, Papua New Guinea, etc., and is available for any research group with a robust high-throughput screening (HTS) assay (http://www.lsi.umich.edu/centers/center-for-chemical-genomics). The HTS assay that was queried against a library of 9,831 NPEs aimed to identify extracts inhibiting biofilm formation as a primary screening. Further secondary screening and activity threshold optimization revealed the extract from Streptomyces gandocaensis (collected from Costa Rica) to be of particular interest due to its ability to inhibit biofilm formation and had a limited effect on A. baumannii growth. Activity based chromatographic separation and analysis of extracts derived from S. gandocaensis resulted in the discovery of three peptidic metabolites (cahuitamycins A–C), with cahuitamycin C being the most effective biofilm inhibitor (IC50 =14.5 µM) with negligible A. baumannii growth inhibition (an important trait for ideal biofilm inhibitor). Following up on the exciting discovery, we also completely characterized the biosynthetic machinery involved in making the active molecules by S. gandocaensis, using sophisticated bioinformatics and molecular biology techniques. The knock out analysis revealed that the biosynthesis of cahuitamycin C proceeds via a convergent biosynthetic pathway, with one of the steps apparently being catalyzed by an unlinked gene encoding a 6-methylsalicylate synthase. Efforts to assess starter unit diversification through selective mutasynthesis led to production of unnatural analogues cahuitamycins D and E with increased potency (IC50=8.4 and 10.5 µM) against A. baumannii biofilm.
Dr. Ashootosh Tripathi[/caption]
Ashootosh Tripathi, PhD
Postdoctoral Research Fellow
Life Sciences Institute I Sherman lab
University of Michigan
Ann Arbor, MI, USA
MedicalResearch: What is the background for this study? What are the main findings?
Dr. Tripathi: Acinetobacter baumannii is a nosocomial opportunistic and resistant pathogen that can spread epidemically among patients causing ventilator-associated pneumonia and bacteremia. The mortality rates associated with it can be as high as 60%, representing a paradigm of pathogenesis, transmission and resistance. In addition, numerous reports have shown the startling emergence of multidrug-resistant A. baumannii in hospitals as well as the identification of pan-drug-resistant strains at some locations. Among the various reasons for the antibiotic resistance of this pathogenic microbe, perhaps the most significant is mediated by its tendency to form biofilms (a highly structured extracellular polymeric matrix), which provide the microbe with the alarming ability to colonize medical devices. Interestingly, despite the well-understood role of bacterial biofilm behind aggravating antimicrobial resistance, there are currently no drugs specifically targeting biofilms in clinical trials to date. The study sought to solve this problem through the development of a biofilm inhibitor as a precision medicine, directed towards vulnerable patients, to avoid potential life-threatening infections.
A crystal-violet based high throughput in vitro screen was developed to identify inhibitors of A. baumannii biofilms against our natural products extract (NPE) library. The vast NPE library of ~42,000 extracts has been under constant development in Prof David H. Sherman laboratory at University of Michigan, Ann Arbor, for over the past decade, from a relatively underexplored marine microbiome collected from different part of world viz., Costa Rica, Panama, Papua New Guinea, etc., and is available for any research group with a robust high-throughput screening (HTS) assay (http://www.lsi.umich.edu/centers/center-for-chemical-genomics). The HTS assay that was queried against a library of 9,831 NPEs aimed to identify extracts inhibiting biofilm formation as a primary screening. Further secondary screening and activity threshold optimization revealed the extract from Streptomyces gandocaensis (collected from Costa Rica) to be of particular interest due to its ability to inhibit biofilm formation and had a limited effect on A. baumannii growth. Activity based chromatographic separation and analysis of extracts derived from S. gandocaensis resulted in the discovery of three peptidic metabolites (cahuitamycins A–C), with cahuitamycin C being the most effective biofilm inhibitor (IC50 =14.5 µM) with negligible A. baumannii growth inhibition (an important trait for ideal biofilm inhibitor). Following up on the exciting discovery, we also completely characterized the biosynthetic machinery involved in making the active molecules by S. gandocaensis, using sophisticated bioinformatics and molecular biology techniques. The knock out analysis revealed that the biosynthesis of cahuitamycin C proceeds via a convergent biosynthetic pathway, with one of the steps apparently being catalyzed by an unlinked gene encoding a 6-methylsalicylate synthase. Efforts to assess starter unit diversification through selective mutasynthesis led to production of unnatural analogues cahuitamycins D and E with increased potency (IC50=8.4 and 10.5 µM) against A. baumannii biofilm.


Dr. Casey Theriot[/caption]
MedicalResearch.com Interview with:
Casey M. Theriot, Ph.D.
Assistant Professor Infectious Disease
College of Veterinary Medicine
Department of Population Health and Pathobiology
North Carolina State University
Raleigh, NC 27607
Medical Research: What is the background for this study? What are the main findings?
Dr. Theriot: This study is an extension of the work we did in 2014 in our Nature Communications paper (Theriot et al. Antibiotic-induced shifts in the mouse gut microbiome and metabolome increase susceptibility to Clostridium difficile infection, 2014). We really wanted to know how different antibiotics that varied in their mechanism of action altered the gut microbiota in different ways and also in turn how this altered the bile acids present in the small and large intestine of mice. Primary bile acids are made by the host and are further converted to secondary bile acids by members of the microbiota in the large intestine. We know from previous work that secondary bile acids can inhibit the growth of C. difficile, but no one has looked in depth at the bile acid makeup in the actual gut before in the context of C. difficile. In this study we show that specific antibiotics that significantly alter the large intestinal gut microbiota and deplete all secondary bile acids allow for
Dr. Halwani[/caption]
MedicalResearch.com Interview with:
Muhammad A. Halwani, MSc, PhD
Faculty of Medicine, Al Baha University
Al Baha, Saudi Arabia.
Medical Research: What is the background for this study? What are the main findings?
Response: The study idea was based on examining the current rate of post cesarean section infections that were detected in the hospital at the time. It was hypothesized that the detected infections were actually less than the real number identified. Therefore, we challenged the traditional surveillance method that was applied in the hospital with a new enhanced methodology which is telephone follow-ups for patients who under go C-section operations.
Our main finding proved that this new applied method was able to detect more cases than the traditional one. Using phone calls as a gold standard, the sensitivity of the standard methodology to capture SSI after cesarean increased to 73.3% with the new methodology identifying an extra five cases. These patients represented 26.3% (5 of 19) of all the patients who developed SSI. In other words, for every 100 C-section procedures there were 2.6% missed cases which the new method was able to detect. The duration of the calls ranged from 1 to 5 minutes and were well received by the patients.
Prof. Maillard[/caption]
MedicalResearch.com Interview with:
Prof. Jean-Yves Maillard
Professor of Pharmaceutical Microbiology
College of Biomedical and Life Sciences
Cardiff School of Pharmacy and Pharmaceutical Sciences
Cardiff University
Cardiff United Kingdom
Medical Research: What is the background for this study? What are the main findings?
Prof. Maillard: Environmental surfaces in healthcare and other settings become contaminated with a variety of infectious agents which may survive long enough to infect susceptible hosts, either directly or through secondary vehicles such as hands. Therefore, routine decontamination of environmental surfaces, in particular those that are frequently touched, is crucial to reduce the risk of infections. Such decontamination is often performed by wiping the target surface with disinfectant-soaked or pre-wetted wipes. However, the label claims of wipes marketed for this purpose are often based upon testing that does not reflect their field use, where contact times are frequently no more than a few seconds with wide variations in the pressure applied during wiping. In addition, wipes impregnated with a disinfectant or detergent can potentially transfer microbial contaminants to a wider area, when the same wipe is used on multiple surfaces.
A device called the ‘Wiperator’ was invented to address these issues. It can be used to test wipes with predetermined pressures, wiping times and number of wiping strokes, using a standardized rotary action. It can not only assess the decontaminating efficiency of the test wipe, but also its ability to transfer the acquired contamination to clean surfaces. The test procedure developed using the device is now a standard (E2967) of ASTM International, a highly-respected standards-setting organization.
The Wiperator was used in a multi-laboratory collaborative to test commercially-available wipes for their ability to decontaminate metal disks that had been experimentally-contaminated with vegetative bacteria representing healthcare-associated pathogens. The used wipes were subsequently tested for their potential to transfer viable bacteria to clean surfaces. The contact time for wiping and transfer was 10 seconds. Only one of the wipes tested reduced the contamination to an undetectable level while not transferring any viable bacteria to a clean surface. All others left behind detectable levels of contamination on the wiped disks and transferred the contamination to clean surfaces.











