MICROBIOLOGY

• Gram-positive, facultative anaerobic (or microaerophilic) rod [Fig].
  • > 170 species are known.
  • Many clinically familiar “Lactobacillus” probiotics now have updated genus names.
    • In 2020, the genus Lactobacillus was officially reclassified into 25 separate genera (23 novel, plus Lactobacillus and Paralactobacillus) due to extensive phylogenetic and genomic diversity. Key species such as L. plantarum and L. rhamnosus are now known as Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus, respectively[8].
• Normal flora of the GI/GU tract.
• Produces lactic acid from glycogen, providing for a low vaginal pH.
• Species are often used to produce yogurt, cheese, wine and other fermented products.
• Most are inherently resistant to vancomycin.
  • Lactobacilli are typically resistant to aminoglycosides, ciprofloxacin and metronidazole.
    • L. acidophilus is susceptible to both penicillin and vancomycin.
    • L. rhamnosus and L. casei are resistant to metronidazole and vancomycin.