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A 23-year-old woman presents to the emergency room with pelvic pain. A Gram's stain of her cervical discharge reveals multiple polymorphonuclear leukocytes, but none contain gram-negative diplococci. Which of the following statements best describes the two organisms that most commonly cause this disorder?
Options:
A. Both are unlikely to recur because of acquired cell mediated immunity
B. Both are unlikely to recur because of antibody mediated immunity
C. Both induce endocytosis by epithelial cells
D. Both are obligate intracellular parasites
E. Both respond to ß-lactam antibiotics
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D...gardnerella and trichomonas?
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The correct answer is C. In young women, the most likely causes of cervicitis and pelvic inflammatory disease (PID) are Neisseria gonorrhoeae and Chlamydia trachomatis.
Neisseria gonorrhoeae is a gram-negative diplococcus. It is endocytosed by mucus-secreting
epithelia, and is exocytosed into subepithelial tissues leading to necrotizing acute inflammation and destruction of ciliated and non-ciliated cells. Through direct extension, it can lead to PID and infertility in women. It can be detected by visualizing the organism in polymorphonuclear leukocytes (PMNs) in Gram's stained clinical material more easily in men than in women. Therefore, culture onto Thayer-Martin agar is usually required for diagnosis in women. Since the organism can be cultured, it is not an obligate intracellular parasite (compare with choice D). The organism can be killed by PMNs, antibody, and complement, however, many of its outer membrane proteins undergo antigenic or phase variation or cause the production of blocking antibody that interferes with bactericidal activity. Immunity to the organism does not develop (compare with choices A and B). Neisseria gonorrhoeae is resistant to penicillin, a ß-lactam antibiotic (compare to choice E), because of a plasmid-mediated penicillinase and a chromosomally-mediated mutation that decreases the permeability of the outer membrane and decreases the affinity of penicillin binding proteins. It can be treated with ceftriaxone, a cephalosporin, which resists the penicillinase, or with quinolones and azithromycin.
Chlamydia trachomatis is an obligate intracellular parasite (choice D) that induces endocytosis and resides in the phagosome of infected epithelial cells. It possesses a gram-negative envelope but lacks peptidoglycan, and hence is intrinsically resistant to all antibiotics that inhibit peptidoglycan synthesis, such as the β-lactam antibiotics (compare with choice E). Antibodies are ineffective at controlling infection. Cell mediated immunity (choice A) is probably the major means of controlling this infection since a deficiency in cell mediated immunity both increases susceptibility and severity in animal models. Chronic and clinically latent infections cause serious morbidity, including pelvic inflammatory disease, fallopian tube dysfunction and blindness. Chlamydia infection can be treated with macrolides, quinolones and tetracyclines.
