Institute for Microbiology, Medical Faculty of Masaryk University and St. Anna Faculty Hospital in Brno Miroslav Votava COURSE AND FORMS OF INFECTION – II The 11th lecture for the 2nd-year students, April 27th, 2015 Infection – revision •Definition: •Infection = a relation between the pathogenic microbe and the macroorganism (= ecological point of view) •Infection × colonization: •Infection = situation when an etiological agent 1)penetrates into an organism and multiplies in it, or 2)it settles on bodily surfaces (skin or mucosae) and unfavourably affects them •× Colonization = situation when 1)a non-pathogenic microbe settles on a bodily surface, or 2)a pathogen located there does not cause pathological symptoms Course of infection I – revision •Four components can be distinguished during the course of infection: • •Incubation time •Prodromes •Typical syndrome (= complex of symptoms) of the infectious disease •Convalescence Course of infection II – revision •Incubation time salmonellosis ½–1 day, influenza 1–2 days, tbc 2–8 weeks, hepatitis B 90–100 days •Prodromes not always; nonspecific (  T, headache, feeling ill etc.), several hours to days •Typical syndrome of infectious disease as described in textbooks •Convalescence from subsiding troubles till normalization of laboratory results (except antibodies!) Course of infection III – revision •Relapse the same agent, infection comes on again during the convalescence •Recurrence the agent remains in the body, infection comes on again only after recovery (Brill-Zinsser disease = recurrence of epidemic typhus) •Reinfection new infection by the same agent from outside •Superinfection infection by another agent before recovery from the first infection • • Forms of infection – revision •Inapparent infection (without symptoms) sole consequence: development of immunity (usually by means of antibodies) •Manifest infection (with symptoms) • subclinical: non-characteristic signs only • abortive: only some symptoms or slightly manifested ones • clinical: typical signs as in textbooks • foudroyant, fulminant: very abrupt, with dramatic symptoms • Duration of infection – revision •Acute: days (common cold, salmonellosis) to weeks (majority of infections) •Subacute: months – either as a complication of any infection, or as the rule (some kinds of hepatitis, warts, sepsis lenta) •Chronic: years (tbc, lepra, dermatomycoses, parasitic infections) •Fulminant, foudroyant: very rapid course – hours (meningococcal sepsis) • Extent of infection – revision •Local: portal of entry & regional nodes, or a specific organ (common cold, ringworm, warts, uncomplicated gonorrhoea, abscessus in an organ) •Systemic: whole organ system (influenza, lung tbc, meningitis, extensive pyodermia, pyelonephritis, pelvic inflammatory disease) •Generalized: regularly (exanthematic viroses, typhoid fever, exanthematic typhus), or as a complication (sepsis after injury, during cystitis or cholecystitis, salmonellosis in a newborn) Focal infection I – revision •Focal infection theory: chronic infection limited to a certain focus can result in a systemic illness with symptoms in quite a different site •Concept of focal infection used to be very fashionable formerly in diverse medical branches •In the name of so-called sanation of focuses thousands of patients were bona fide subjected to tooth extractions, tonsillectomies, cholecystectomies and other surgical interventions without proving the usefulness of these procedures by controlled studies Focal infection II – revision •The connection between systemic disease and a local infection has been proved only in •rheumatic fever – inflammation of heart, kidneys and joints after tonsillar infection by Streptococcus pyogenes •Reiter’s syndrome = reactive arthritis after 1. sexually transmitted urogenital infection by Chlamydia trachomatis serotypes D-K, 2. intestinal infection caused by pathogens from genus Salmonella, Shigella, Yersinia or Campylobacter •hemolytic-uremic syndrome after intestinal infection by Escherichia coli serotype e.g. O157:H7 •sterile mykids e.g. on palms during tinea pedis Special types of chronic infections – revision • •Inapparent chronic infections can be clasified as •1. latent: agent hides in a non-infectious form, or it escapes from the infected cell after an activation of infection only • HSV and VZV: nerve ganglia cells, CMV: kidney and salivary glands cells, EBV: lymphocytes •2. persistent: agent can be detected by routine methods, because it is present mostly in an infectious form •Both types are markers of failing immunity •Both types can be activated Examples of persistent infections – revision • •Bacterial: Rickettsia prowazekii (activation of exanthematic typhus = m. Brill-Zinsser), Salmonella Typhi (carriers), Mycob. tbc (lymphatic nodes) •Viral: HBV (hepatocytes), adenoviruses (adenoids), JCV and BKV (kidneys), congenital infections by CMV and rubella virus •Parasitary: hypnozoites of Plasmodium ovale and P. vivax (liver), Toxoplasma gondii bradyzoites (nodes, muscles, brain) •… Primary infections • •primary × secondary infection: before the first (primary) infection is over the secondary infection (superinfection) supersedes caused by another microbe •primary × postprimary infection: in tbc only; in postprimary infection the late hypersensitivity has developed •primary × recurrent infection: during latent infections, e.g. HSV: primary infection = gingivostomatitis aphthosa; recurrent one = herpes labialis Other types of infection – I • •Opportunist infection: infection on a weakened terrain, often secondary one •During AIDS: CMV retinitis, CMV or candidal esophagitis, herpes zoster, cryptococcal meningitis, toxoplasmatic encephalitis, cryptosporidial or microsporidial enteritis, colibacillary and other types of sepsis •Nosocomial (hospital-acquired) infection: in connection with the stay in hospital, often opportunist one •Iatrogenic infection: caused by a medical intervention •Community-acquired infection: infection obtained in common population Other types of infection – II • • •Pyogenic infection: is manifested by suppuration •Specific infection: usually with typical pathology and histology, therefore syphilis or tuberculosis •Exogenous infection: agent enters the body from the outside •Endogenous infection: agent = member of normal microflora (the disease is not contagious, it is not possible to determine the incubation time) Other types of infection – III • •Anthroponoses = infections transmissible among human beings only (typhoid fever, shigelloses, exanthematic viroses, venereal infections etc.) •Zoonoses = infections transmissible from animals to man and vice versa (salmonelloses, tularemia, lyme borreliosis, tick-borne encephalitis, some types of ringworm etc.) •Sapronoses = infections acquired from the environment in which the agent actively multiplies (tetanus, gas gangraene, legionellosis, histoplasmosis, amoebic meningoencephalitis etc.) Other types of infection – IV • •Active infection: still proceeding, possibly even without apparent signs •Subsided infection: without signs of activity, but sequelae or at least antibodies remain •Recent infection: occurred at best several weeks ago • •These attributes are typically used in the interpretation of serologic results Outcome of infection – I •It depends on both participants: •Microorganism: • its pathogenicity virulence dosis portal of entry •Macroorganism: species resistance • individual’s immunity • non-specific (innate) • specific (acquired) • intensity of reaction Outcome of infection – II •Complete recovery (restitutio ad integrum): banal respiratory, urogenital, intestinal and infant generalized infections •Recovery with sequelae: paralysis after encephalitis, deafness after otitis, scar after abscess, cavern after lung tuberculosis •Persistent infection: if the immune system is not able to eliminate the agent •Death (exitus letalis) Outcome of infection – III •Species pathogenicity •Strain virulence •High dosis •Uncommon portal of entry •Exaggerated reaction • • • Death of the • host •High species resistance of the host •High non-specific resistance of the individual • no risk factors no functional or anatomical defects •Specific immunity and its quality • • • Elimination of • the microbe • • • • • • • • • VáhyII V = recovery, or no infection Recommended reading material •Paul de Kruif: Microbe Hunters •Paul de Kruif: Men against Death •Axel Munthe: The Story of San Michele •Sinclair Lewis: Arrowsmith •André Maurois: La vie de Sir Alexander Fleming •Hans Zinsser: Rats, Lice, and History •Michael Crichton: Andromeda Strain •Albert Camus: Peste •Victor Heisser: An American Doctor Odyssey •Richard Preston: The Hot Zone •Mika Waltari: The Egyptian • • • •Please mail me other suggestions at: •mvotava@med.muni.cz •Thank you for your attention • •