A single, 30-year-old woman presents to her physician with vaginitis. She complains of a slightly increased, malodorous discharge that is gray-white in color, thin, and homogenous. Clue cells are discovered when the discharge is examined microscopically. Which of the following organisms is the most likely cause of her infection?
Microscopic examination can readily demonstrate clue cells (epithelial cells with Gardnerella bacteria attached) or pseudohyphae (Candida). A wet mount will be needed to demonstrate motile Trichomonas cells. Candida, Trichomonas, and bacterial vaginitis are seen most often. Staphylococcus aureus is involved much less frequently. While E. coli may be a common cause of genitourinary infection, clue cells are usually absent. See the below table for a comparison of these bacteria.GRAM-NEGATIVE RODS ASSOCIATED WITH THE RESPIRATORYTRACTSpeciesMajor DiseasesLaboratory DiagnosisFactors X and V Required for Vaccine GrowthVaccine availableProphylaxis for ContactsHaemophilusinfluenzaeMeningitisa; otitis media, sinusitis, pneumonia, epiglottitisCulture; capsular polysaccharide in serum or spinal fluid++RifampinBordetelhpertussisWhooping cough (pertussis)Fluorescent antibody on secretions; culture-+ErythromycinLegionellapneumophilaPneumoniaSerology; urinary antigen; culture--None aIn countries where the H. influenzae b conjugate vaccine has been deployed, the vaccine has greatly reduced the incidence of meningitis caused by this organism.CLINICAL FEATURES OFVAGINITIS NormalVulvovaginal Candidiasis TrichomoniasisBacterial VaginosisSymptomsNonePruritus SorenessSoreness DyspareuniaOften asymptomatic Occasional abdominal pain DyspareuniaOften asymptomatic DischargeAmountVariableScant/moderateProfuseModerateColorClear/whiteWhiteGreen-yellowWhite/grayConsistencyNonhomogeneous floccularClumped, adherentHomogeneous, frothyHomogeneous adherentVaginal Fluid pH4.0-4.54.0-4.55.0-6.0>4.5Amine test (fish odor)NoneNoneUsually positivePositiveMicroscopySalinePMN:EC ratio < 1 Lactobacilli predominatePMN:EC<1Pseudohyphae ( 40%)PMN:EC>1Motile trichomonads PMNs predominatePMN:EC<1Clue cells Coccobacilli10% KOHNegativePseudohyphae ( 70%)NegativeNegativePMN, polymorphonuclear leukocytes; EC, epithelial cells.
Candida albicans
Trichomonas vaginalis
Escherichia coli
Gardnerella vaginalis
Bacteria