Antimicrobial resistance is considered by the National Foundation for Infectious Diseases to be the number one infectious disease problem in the USA. Bacteria such as Pseudomonas, Klebsiella, and Acinetobacter are presently resistant to all therapy with the exception of the polymyxins, but polymyxin resistance is now being reported as well. New antibiotics are not being developed fast enough. One approach would be to find synergy with the use of two presently available agents, but doing so would not have practical value in caring for very sick patients unless the synergy can be determined quickly.
The goal of the Infectious Disease Research Laboratory is to develop rapid diagnostic methods for the determination of synergy or antagonism between two or more antimicrobial agents against multi-drug resistant bacteria and fungi. We developed an Etest® methodology that is very promising in this regard.
We have purchased a Vitek® 2 instrument (which performs rapid automated identification and drug susceptibility testing of bacteria and fungi) and a Diversilab® instrument (which provides rapid DNA fingerprinting of bacteria and fungi and ensures that all of the microorganisms studied are genetically unique). Synergy studies are ongoing with polymyxin plus meropenem or rifampin against carbapenemase-producing Klebsiella; televancin plus rifampin against vancomycin- and linezolid-resistant Enterococcus faecium; and fosfomycin plus doxycycline against vancomycin- and linezolid-resistant E. faecium. Our laboratory is also involved in the study of how quickly bacteria are killed by antibiotics, medicinal honey, and molasses.
Candida species are the fourth most common cause of hospital-acquired bloodstream infections in the US (1995-2002), with Candida albicans predominating. However, in 2010-2011 at Ochsner, Candida glabrata was most common. C. glabrata is more resistant to certain antifungals, creating a concern regarding appropriate therapy because susceptibility studies are not performed by the Ochsner microbiology laboratory. Also, it is not known if the Ochsner Candida isolates are genetically similar. Our research laboratory is performing DNA fingerprinting on the C. glabrata isolates and antifungal susceptibility testing on DNA unique strains by two different methods. Synergy studies include: fluconazole plus polymyxin B or doxycycline or tigecycline and caspofungin plus polymyxin B against C. glabrata. Specific aims of the study include determining if there is a trend in Candida species being isolated more frequently from the blood, if any antifungal resistance is developing, and comparing clinical data with in vitro data. We will determine if there is any effect of time of diagnosis and time of initial antifungal therapy on mortality of patients with Candida bloodstream infections. This study will provide useful information that may improve treatments for future patients.
We have obtained a T2MR® instrument (T2Dx®) that will rapidly (in 3-5 hours) detect Candida in the blood. This will enable early and more appropriate treatment decisions, since up to 5 days are required for identification from blood culture.
We are collaborating with the University of Southern Mississippi Gulf Coast Research Lab to study antimicrobial resistance of bacteria isolated from dolphins.
Our laboratory continues to collect and freeze bacterial and fungal isolates from blood cultures—as well as unusual or multi-drug resistant isolates from other specimen sources. Over 15,000 isolates are available for use in future studies. The Infectious Disease Research laboratory serves as a reference laboratory to the Ochsner diagnostic microbiology laboratory to expand testing capabilities on patients’ cultures.