INDIVIDUAL PATHOGENS

INDIVIDUAL PATHOGENS is a topic covered in the Harrison's Manual of Medicine.

To view the entire topic, please or purchase a subscription.

Harrison’s Manual of Medicine 19th edition provides 600+ internal medicine topics in a rapid-access format. Download Harrison’s App to iPhone, iPad, and Android smartphone and tablet. Explore these free sample topics:

Harrison’s Manual of Medicine - App + Web

-- The first section of this topic is shown below --

GONORRHEA

Microbiology

N. gonorrhoeae, the causative agent of gonorrhea, is a gram-negative, nonmotile, non-spore-forming organism that grows singly and in pairs (i.e., as diplococci).

Epidemiology

The ~311,000 cases reported in the United States in 2012 probably represent only half the true number of cases because of underreporting, self-treatment, and nonspecific treatment without a laboratory diagnosis.

  • 60% of reported cases in the United States occur in 15- to 19-year-old women and 20- to 24-year-old men.
  • Gonorrhea is transmitted from males to females more efficiently than in the opposite direction, with 50–70% of women acquiring gonorrhea during a single unprotected sexual encounter with an infected man. Roughly two-thirds of all infected men are asymptomatic.
  • Drug-resistant strains are widespread. Penicillin, ampicillin, and tetracycline are no longer reliable therapeutic agents, and oral cephalosporins and fluoroquinolones are no longer routinely recommended. In addition, strains highly resistant to ceftriaxone have been isolated in Japan and some European countries.

Clinical Manifestations

Except in disseminated disease, the sites of infection typically reflect areas involved in sexual contact.

  • Urethritis and cervicitis have an incubation period of 2–7 days and ~10 days, respectively. See above for details.
  • Anorectal gonorrhea can cause acute proctitis in women (due to the spread of cervical exudate to the rectum) and MSM.
  • Pharyngeal gonorrhea is usually mild or asymptomatic and results from oral–genital sexual exposure (typically fellatio). Pharyngeal infection almost always coexists with genital infection, resolves spontaneously, and is rarely transmitted to sexual contacts.
  • Ocular gonorrhea is typically caused by autoinoculation and presents as a markedly swollen eyelid, hyperemia, chemosis, and profuse purulent discharge.
  • Gonorrhea in pregnancy can have serious consequences for both the mother and the infant.
    • Salpingitis and PID are associated with fetal loss.
    • Third-trimester disease can cause prolonged rupture of membranes, premature delivery, chorioamnionitis, funisitis, and neonatal sepsis.
    • Ophthalmia neonatorum, the most common form of gonorrhea among neonates, is preventable by prophylactic ophthalmic ointments (e.g., containing erythromycin or tetracycline), but treatment requires systemic antibiotics.
  • Gonococcal arthritis results from dissemination of organisms due to gonococcal bacteremia. Pts present during a bacteremic phase (relatively uncommon) or with suppurative arthritis involving one or two joints (most commonly the knees, wrists, ankles, and elbows), with tenosynovitis and skin lesions. Menstruation and complement deficiencies of the membrane attack complex (C5–C9) are risk factors for disseminated disease.

Diagnosis

NAATs, culture, and microscopic examination (for intracellular diplococci) of urogenital samples are used to diagnose gonorrhea; NAAT of urine samples is most sensitive. A single culture of endocervical discharge has a sensitivity of 80–90%.

Treatment

See Table 83-2.

TABLE 83-2: RECOMMENDED TREATMENT FOR GONOCOCCAL INFECTIONS: ADAPTED FROM THE 2010 GUIDELINES OF THE CENTERS FOR DISEASE CONTROL AND PREVENTION
DiagnosisTreatment of Choicea
Uncomplicated gonococcal infection of the cervix, urethra, pharynxb, or rectum 
First-line regimenCeftriaxone (250 mg IM, single dose)
 plus
 Treatment for Chlamydia if chlamydial infection is not ruled out:
 Azithromycin (1 g PO, single dose)
 or
 Doxycycline (100 mg PO bid for 7 days)
Alternative regimenscCefixime (400 mg PO, single dose)
 or
 Ceftizoxime (500 mg IM, single dose)
 or
 Cefotaxime (500 mg IM, single dose)
 or
 Spectinomycin (2 g IM, single dose)d, e
 or
 Cefotetan (1 g IM, single dose) plus probenecid (1 g PO, single dose)d
 or
 Cefoxitin (2 g IM, single dose) plus probenecid (1 g PO, single dose)d
EpididymitisCeftriaxone (250 mg IM once) followed by doxycycline (100 mg PO bid for 10 days) is effective for epididymitis due to Chlamydia trachomatis or Neisseria gonorrhoeae.
Pelvic inflammatory diseaseSee Chap. 163 in HPIM-19
 Outpatient

Ceftriaxone (250 mg IM once)

plus

Doxycycline (100 mg PO bid for 14 days)

plus

Metronidazole (500 mg PO bid for 14 days)

 Inpatient

Cefotetan (2 g IV q12h) or cefoxitin (2 g IV q6h)

plus

doxycycline (100 mg IV/PO q12h)

or

Clindamycin (900 mg IV q8h)

plus

gentamicin (loading dose of 2.0 mg/kg IV/IM followed by 1.5 mg/kg q8h)

Gonococcal conjunctivitis in an adultCeftriaxone (1 g IM, single dose)f
Ophthalmia neonatorumgCeftriaxone (25–50 mg/kg IV, single dose, not to exceed 125 mg)
Disseminated gonococcal infectionh 
 Initial therapyi 
  Pt tolerant of β-lactam drugs    

Ceftriaxone (1 g IM or IV q24h; recommended)

or

Cefotaxime (1 g IV q8h)

or

Ceftizoxime (1 g IV q8h)

  Pts allergic to β-lactam drugsSpectinomycin (2 g IM q12h)d
 Continuation therapyiCefixime (400 mg PO bid)
Meningitis or endocarditisCeftriaxone (1–2 g IV bid) for 10–14 days (meningitis) or ≥4 weeks (endocarditis)j
aTrue failure of treatment with a recommended regimen is rare and should prompt an evaluation for reinfection, infection with a drug-resistant strain, or an alternative diagnosis.
bCeftriaxone is the only agent recommended for treatment of pharyngeal infection.
cPersons given an alternative regimen should return for a test of cure targeting the infected anatomic site, with a culture strongly preferred over a NAAT. All positive cultures for test of cure should undergo antimicrobial susceptibility testing.
dSpectinomycin, cefotetan, and cefoxitin, which are alternative agents, currently are unavailable or in short supply in the United States.
eSpectinomycin may be ineffective for the treatment of pharyngeal gonorrhea.
fPlus lavage of the infected eye with saline solution (once).
gOcular neonatal instillation of a prophylactic agent (e.g., 1% silver nitrate eye drops or ophthalmic preparations containing erythromycin or tetracycline) prevents ophthalmia neonatorum but is not effective for its treatment, which requires systemic antibiotics.
hHospitalization is indicated if the diagnosis is uncertain, if the pt has frank arthritis with an effusion, or if the pt cannot be relied on to adhere to treatment.
iAll initial regimens should be continued for 24–48 h after clinical improvement begins, at which time the switch may be made to an oral agent (e.g., cefixime or a quinolone) if antimicrobial susceptibility can be documented by culture of the causative organism. If no organism is isolated and the diagnosis is secure, then treatment with ceftriaxone should be continued for at least 1 week. Treatment for chlamydial infection (as above) should be given if this infection has not been ruled out.
jHospitalization is indicated to exclude suspected meningitis or endocarditis.

-- To view the remaining sections of this topic, please or purchase a subscription --

Citation

* When formatting your citation, note that all book, journal, and database titles should be italicized* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - INDIVIDUAL PATHOGENS ID - 623644 Y1 - 2017 PB - Harrison's Manual of Medicine UR - https://harrisons.unboundmedicine.com/harrisons/view/Harrisons-Manual-of-Medicine/623644/all/INDIVIDUAL_PATHOGENS ER -