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    1) The document discusses host-parasite relationships and how pathogens are able to breach host barriers, replicate, spread infection, and cause disease while the host mounts immune responses to control the pathogen. 2) It defines pathogens as microorganisms capable of causing disease and describes virulence factors like toxins that allow pathogens to establish infection by overcoming host defenses. 3) Specifically, it discusses Enterobacteriaceae, a family of Gram-negative bacteria including E. coli, describing their morphology, growth, metabolism, toxins, epidemiology, diagnosis, and treatment with various antibiotics.

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    1) The document discusses host-parasite relationships and how pathogens are able to breach host barriers, replicate, spread infection, and cause disease while the host mounts immune responses to control the pathogen. 2) It defines pathogens as microorganisms capable of causing disease and describes virulence factors like toxins that allow pathogens to establish infection by overcoming host defenses. 3) Specifically, it discusses Enterobacteriaceae, a family of Gram-negative bacteria including E. coli, describing their morphology, growth, metabolism, toxins, epidemiology, diagnosis, and treatment with various antibiotics.

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    1) The document discusses host-parasite relationships and how pathogens are able to breach host barriers, replicate, spread infection, and cause disease while the host mounts immune responses to control the pathogen. 2) It defines pathogens as microorganisms capable of causing disease and describes virulence factors like toxins that allow pathogens to establish infection by overcoming host defenses. 3) Specifically, it discusses Enterobacteriaceae, a family of Gram-negative bacteria including E. coli, describing their morphology, growth, metabolism, toxins, epidemiology, diagnosis, and treatment with various antibiotics.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    24 views11 pages

    شات

    Uploaded by

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    1) The document discusses host-parasite relationships and how pathogens are able to breach host barriers, replicate, spread infection, and cause disease while the host mounts immune responses to control the pathogen. 2) It defines pathogens as microorganisms capable of causing disease and describes virulence factors like toxins that allow pathogens to establish infection by overcoming host defenses. 3) Specifically, it discusses Enterobacteriaceae, a family of Gram-negative bacteria including E. coli, describing their morphology, growth, metabolism, toxins, epidemiology, diagnosis, and treatment with various antibiotics.

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    of 11

    Bacteriology and Infection

    control course for 1st year


    Nursing students

    Prepared by
    Dr/Sally Abdel-Basset
    The 4th lecture

    Medical part
    Host parasite relationships
    The interaction between host and parasite include the
    followings:
    1. The organisms's ability to breach host barriers and to evade
    destruction by innate local and tissue host defenses.
    2. The organisms's biochemical tactics to replicate, to spread,
    to establish infection, and to cause disease.
    3. The microbes ability to transmit to a new susceptible host.
    4. The body's innate and adaptive immunologic ability to
    control and eliminate the invading parasite.
    What is a pathogen?

     In medicine, we define a pathogen as any microorganism


    capable of causing disease.

     Most human microbes are commensal.

     Some commensal species may be opportunistic pathogen.

     Symptoms of disease can reflect part of the microbes strategy


    for survival within the host. For example, coughing promotes
    the transmission of the tubercle bacillus and influenza virus.
    Virulence factors: toxins

     Microbial virulence factors that permit the establishment of


    the pathogen in the host and permit them to overcome host
    defenses.

     No pathogen possesses all of the classes of virulence factors,


    nor are all virulence factors essential for a pathogen to reach
    its goal of sufficient multiplication to establish itself in host
    or to transmitted to a new susceptible host.
    Exotoxins

     A number of microorganisms synthesize


    protein molecules that are toxic to their
    hosts and are secreted into their
    environment or are found associated with
    the microbial surface.
    Bacterial exotoxins, synthesized by Gram-
    positive or Gram-negative bacteria
    Endotoxin

     In many infections caused by Gram-negative


    organisms, the endotoxin of the outer membrane
    is a significant component of the disease process.

     Endotoxin is a lipopolysaccharide and that the


    lipid portion (lipid A) is the toxic portion.
    Enterobacteriaceae

     Are a large and diverse family of Gram-negative


    rods, members of which are both free-living and
    part of the indigenous flora of humans and animals.

     Grow rapidly under aerobic or anaerobic conditions.

     They are the most common cause of urinary tract


    infection.
    Morphology and structure
    • Are among the largest bacteria, measuring 2 to 4 mm in length
    and 0.4 to 0.6 mm in width, with parallel sides and rounded ends.
     Growth and metabolism
    • Grow on simple media, only a single carbon energy source.
    Growth is rapid under both areobic and anaerobic conditions. All
    Enterobacteriaceae ferment glucose, reduce nitrates to nitrites,
    and are oxidase negative.
    Toxins
    • In addition to LPS endotoxin common to all Gram-negative
    bacteria, some Enterobacteriaceae produe protein exotoxins,
    which act on host cells by damaging membranes, inhibiting
    protein synthesis, or altering metabolic pathways.
    Epidemiology
     Most Eterobacteriaceae are colonizers of the lower
    gastrointestinal tract of humans and animals.
     E.coli is the most common species of Enterobacteriaceae found
    among the indigenous flora.
    Diagnosis
     Culture is the primary method of diagnosis, such as MacConkey
    agar are commonly used in primary isolation.
     Molecular and immunodiagnosis techniques are still too
    expensive for use in clinical laboratories.
    Treatment
     They are resistant to high concentrations of penicillin G,
    erythromycin, but may susceptible to the broader-spectrum
    beta-lactams, aminoglycosides, tetracycline, chloramphenicol
    antibiotics.
    Thank you for
    listening and
    attention

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