Polymerase chain reaction (PCR) techniques have potential in faster and more accurate diagnosis of infections.
PCR and eye infection
Researchers at the Aravind Eye Hospital and Postgraduate Institute of Ophthalmology, Tamil Nadu, India, have used quantitative real-time PCR (qPCR) for diagnosing postoperative bacterial endophthalmitis, an infection of the interior of the eye that can happen after surgery, including cataract surgery.
Diagnosis relies on microbiology and is time consuming and not very sensitive. As bacterial endophthalmitis is hard to treat and can lead to loss of sight, being able to diagnose patients as early as possible could mean that treatment is more effective, leading to better outcomes for patients and lowering costs for treatment providers.
The researchers looked at 64 patients who had signs of eye infection within one year of cataract surgery. They took samples of the vitreous (the gel-like fluid inside the eye) and sent these for microbiology testing as well as qPCR and sequencing. The team used samples from 50 patients who underwent vitrectomy (surgical removal of some or all of the vitreous) for reasons other than infection or inflammation.
qPCR found bacterial DNA in 37 patients (66%), but microbiology culture only found bacteria in 19 (34%) of patients. The results from sequencing and phenotypic speciation (identifying the species by looking at its appearance and traits) matched in 100% of cases. The results were published in the American Journal of Ophthalmology.
According to the researchers, qPCR produced rapid diagnostic results that were more sensitive than traditional culture and staining, and qPCR could be used to support microbiology in diagnosis of bacterial endophthalmitis, though it will need more and larger studies.
PCR and infections in newborns
In newborn babies, fast diagnosis of infections and meningitis is vital, and researchers at the Health Protection Agency in the UK have found that a realtime PCR (RT-PCR) assay specific for a bacterial gene is faster and more specific than traditional culture, which is time-consuming and unreliable, according to research published in Journal of Medical Microbiology.
A particular strain of Streptococcus, S agalactiae, is the main cause of sepsis (infection leading to an inflammatory response throughout the body), pneumonia, and meningitis in newborn babies. About 20-30% of pregnant women naturally carry this bacterium on or in their bodies. Around half of these will pass the bug onto their babies. For most babies, this is harmless, but about 1-2% of will end up with invasive infections. About 12% of babies with severe disease will die, so fast diagnosis is very important.
The researchers looked at 110 blood and cerebrospinal fluid (CSF) samples from babies with suspected sepsis or meningitis, and found that PCR was more sensitive and specific, and took less than two hours.
“Overall, this real-time PCR assay was shown to be superior to culture methods for detection of GBS [group B streptococcus] from CSF and EDTA blood samples. The method is rapid, sensitive, specific and reproducible,” Aruni de Zoysa and colleagues of the Health Protection Agency said to MedWire News, adding that it “could be an invaluable tool in the rapid diagnosis of GBS and may improve our ability to detect and manage GBS, particularly in intrapartum and neonatal settings.”
Suzanne Elvidge is a freelance science, biopharma, business and health writer with more than 20 years of experience. She is editor of Genome Engineering, a blog that monitors the latest developments in genome engineering and that aims to educate (and sometimes to entertain!) and has written for a range of online and print publications including FierceBiomarkers, FierceDrugDelivery, European Life Science, the Journal of Life Sciences (now the Burrill Report), In Vivo, Life Science Leader, Nature Biotechnology, PR Week and Start-Up. She specialises in writing on pharmaceuticals, biotechnology, healthcare, science, lifestyle and green living, but can write on any topic given enough tea and chocolate biscuits. She lives just beyond the neck end of nowhere in the Peak District with her second-hand bookseller husband and two second-hand cats.