Spread and Dissemination of Microbes

Some microorganisms proliferate locally, at the site of infection, whereas others penetrate the epithelial barrier and spread to other sites via the lymphatics, the blood, or nerves[11] ( Fig.

8-4 ). Some of the superficial pathogens stay confined to the lumen of hollow viscera (e.g., cholera); others adhere to or proliferate exclusively in or on epithelial cells (e.g.,

papillomaviruses, dermatophytes). A variety of pathogenic bacteria, fungi, and helminths are invasive by virtue of their motility or ability to secrete lytic enzymes (e.g., streptococci and

staphylococci secrete hyaluronidase, which degrades the extracellular matrix between host cells). Microbial spread initially follows tissue planes of least resistance and regional lymphatic

and vascular anatomy. For example, staphylococcal infections may progress from a localized abscess or furuncle to regional lymphadenitis that sometimes leads to bacteremia and

colonization of distant organs (heart, liver, brain, kidney, bone). Within the blood, microorganisms may be transported free or within host cells. Some viruses (e.g., poliovirus and HBV),

most bacteria and fungi, some protozoa (e.g., African trypanosomes), and all helminths are transported free in the plasma. Leukocytes can carry herpesviruses, HIV, mycobacteria, and

Leishmania and Toxoplasma organisms. Certain viruses (e.g., Colorado tick fever virus) and parasites (Plasmodium and Babesia) are carried by red blood cells. Viruses also may propagate

Figure 8-4Routes of entry, dissemination, and release of microbes from the body. (Adapted from Mims CA: The Pathogenesis of Infectious Disease, 4th ed. San Diego, CA, Academic

Press, 1996.)

TABLE 8-7-- Classification of Important Sexually Transmitted Diseases

Disease or Syndrome and Population Principally Affected

Pathogens Males Both Females

Viruses

••Herpes simplex virus Primary and recurrent herpes, neonatal herpes

••Hepatitis B virus Hepatitis

••Human papillomavirus Cancer of penis (some cases) Condyloma acuminatum Cervical dysplasia and cancer, vulvar cancer

••Human immunodeficiency virus Acquired immunodeficiency syndrome

Chlamydiae

••Chlamydia trachomatis Urethritis, epididymitis, proctitis Lymphogranuloma venereum Urethral syndrome, cervicitis, bartholinitis,

salpingitis and sequelae

Mycoplasmas

••Ureaplasma urealyticum Urethritis

Bacteria

••Neisseria gonorrhoeae Epididymitis, prostatitis, urethral

stricture

Urethritis, proctitis, pharyngitis, disseminated

gonococcal infection

Cervicitis, endometritis, bartholinitis, salpingitis,

and sequelae (infertility, ectopic pregnancy,

recurrent salpingitis)

Treponema pallidum Syphilis

Haemophilus ducreyi Chancroid

Calymmatobacterium granulomatis Granuloma inguinale (donovanosis)

Shigella * Enterocolitis

Campylobacter * Enterocolitis

ProtozoaVaginitis

••Trichomonas vaginalis Urethritis, balanitis

••Entamoeba histolytica * Amebiasis

••Giardia lamba * Giardiasis

Modified and updated from Krieger JN: Biology of sexually transmitted diseases. Urol Clin North Am 11:15, 1984.

*Most important in homosexual populations.

Syphilis is discussed later in this chapter, and other STIs are described in Chapter 21 and Chapter 22 .

Date: 2016-04-22; view: 839