Inflammatory / infectious

Topic Completed: 1 January 2015

Minor changes: 26 March 2020

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PubMed Search: Lactobacillus [title] cervix

John K.S.S. Philip, M.D.
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Cite this page: Philip J. Lactobacillus. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/cervixcytologylactobacillus.html. Accessed October 20th, 2020.
Definition / general
  • Presence of gram positive rods (lactobacilli) with cytolysis of intermediate cells
  • Also known as bacillus vaginalis, bacillus Doderlein
  • Lactobacilli are the most abundant bacteria found in normal vaginal flora which varies from person to person
  • Found in 50% of women with "good" vaginal hygiene versus 20% with "poor" vaginal hygiene and high levels of sexual exposure (Koss' Diagnostic Cytology, 5th Edition, pg 262)
  • Aerobic gram - positive bacilli which produce enzymes that dissolve cell membranes of intermediate cells to utilize their cytoplasmic glycogen
  • Fully mature superficial squamous cells and parabasal cells are less likely to be cytolyses because they have a firm cytoplasmic skeleton
  • Cytolysis is mainly observed when intermediate cells predominate, including premenstrual phase of cycle, pregnancy and early menopause
  • Lactobacillus survives best at vaginal pH of 5, which is maintained by glycolysis
  • Lactobacilli prevent bacterial vaginosis, gonorrhea, Candida or other sexually transmitted diseases by multiple mechanisms, such as lowering pH and producing hydrogen peroxide (FEMS Immunol Med Microbiol 2006;48:424, Microbios 1994:80:125)
Clinical features
  • Normal flora of GI tract, mouth and vagina; more commmonly found in vagina in second half of menstrual cycle, pregnancy and diabetes mellitus
  • Decreased with bacterial vaginosis, antibiotic use and postmenopausal
  • Occasionally, excessive colonization causes marked cytolysis and production of clear vaginal discharge (cytolytic vaginosis / lactobacillus vaginitis) (Indian J Sex Transm Dis 2009;30:48)
Cytology description
  • Slender rod shaped pale blue bacilli (on Papanicolaou stain), arranged singly or in short chains of variable length
  • In conventional smears, found on surface of squamous cells and in background
  • In liquid based preparations, found overlying squamous epithelium or trapped in mucus
  • The background is usually clean
  • Lysis of intermediate cell cytoplasm creates moth eaten appearance and presence of isolated nuclei (bare nuclei)
  • Abundant cytolysis ( > 50%), may be reported as a quality indicator but most of these specimens do not qualify as unsatisfactory
    • Nuclear preservation and visualization are of key importance in determining specimen adequacy
    • Unless nearly all of the nuclei are devoid of cytoplasm, the specimen is considered as satisfactory for evaluation
Cytology images

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Bacilli on surface of squamous cells

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Cytolysis of intermediate cells with bare nuclei

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Lactobacillus in wet mount

Differential diagnosis
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