Molecular methods

• there is still a huge role for culture and subsequent identification

• but molecular methods do come in

• DNA homologies are often for analysis after growth: cDNA probes with chemoluminescent tag for early ID of Mycobacteria and fungi

• PCR for direct ID of bacterial nucleic acid from blood or tissue, e.g. PCR ID of gonorrhea from urine. useful because gonorrhea and chlamydia don’t readily grow in culture

• plasmid profiles and RFLP for epidemiology

  • Salmonella epidemics

  • MRSA, hospital-acquired infections

Identification of uncultivable organisms by PCR: Whipple’s disease

• patients present with chronic fever, diarrhea, weight loss

• pathology of bowel show bacilli that can’t be cultured

• using broad-range PCR primers based on rRNA sequences of known bacteria, the bacteria responsible for Whipple’s disease was found and was named Tropheryma whippelii

Localization of T. whippelii

• cDNA probes can identify this bacteria (here colored blue) in the tips of villi

Category: Microbiology Notes