Getting Ahead of Infectious Disease

Culture-based assays are often considered the mainstay of clinical microbiology – but, increasingly, new technologies are offering alternatives that can boost the speed or accuracy of diagnosis. Wendy Szymczak, Director of the Clinical Microbiology Laboratory and Associate Professor of Pathology, Montefiore Health System, Bronx, New York, USA, is exploring these alternatives to bring infectious disease patients faster, more accurate diagnoses and treatment options.

“My colleagues and I began working on a next-generation sequencing (NGS)-based assay to predict antimicrobial resistance to Helicobacter pylori because the organism is very difficult to culture and, even when cultured, grows so slowly that routine phenotypic susceptibility results can take weeks,” says Szymczak. “We were able to show that NGS can accurately predict resistance to clarithromycin and levofloxacin, two antibiotics often used to treat infections.”

But NGS carries challenges of its own – costs, lack of FDA-approved infectious disease assays, the need for bioinformatics expertise, and more. And although Szymczak believes these are surmountable challenges, she and her colleagues are exploring other options.

“We began using MALDI-TOF to identify pathogens directly from blood culture bottles at the end of 2013,” she says. “By using MALDI-TOF as part of the diagnostic workup for two elderly patients with nonspecific clinical presentations, we were able to rapidly identify Listeria monocytogenes from positive blood cultures, which allowed the prompt initiation of pathogen-directed treatment (1).” More recently, the team have adopted multiplex nucleic acid amplification tests (NAAT) to detect pathogens in cerebrospinal fluid (CSF) specimens. “Last month, we had two patients with meningitis caused by L. monocytogenes. The organisms were detected using this NAAT, which provides results in a little over an hour,” says Szymczak. “This is important because blood cultures can take 24 hours or longer before becoming positive, so a NAAT that can be performed directly on CSF can provide a timelier diagnosis.”

To stay at the cutting edge of rapid diagnostics, Szymczak recommends journal clubs, webinars, workshops, and conferences (even virtually). “As these new technologies continue to emerge, we all have a lot to learn, but that’s why I think laboratory medicine is such an exciting field!”