Normal Flora - PowerPoint PPT Presentation


PPT – Normal Flora PowerPoint presentation | free to download - id: 45aefa-YjUwN


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation

Normal Flora


Normal Flora What s growing on us? Normal flora (mostly bacteria) In the past Medical Microbiology was largely focused on those organisms that were frankly pathogenic. – PowerPoint PPT presentation

Number of Views:178
Avg rating:3.0/5.0
Slides: 43
Provided by: nmcq


Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Normal Flora

Normal Flora
  • Whats growing on us?

Normal flora (mostly bacteria)
  • In the past Medical Microbiology was largely
    focused on those organisms that were frankly
  • It is now known that those microorganisms that
    normally colonize the human host without disease
    production can play an important role in the
    disease process.
  • Many of those once considered to be innocuous
    members of the normal flora are now known to be
    potentially pathogenic under certain
    circumstances (what circumstances?). Therefore,
    its important to acquire knowledge about our
    normal flora because

Normal Flora
  • An understanding of the different normal flora
    (NF) found at specific body locations provides
    greater insight into the possible infections that
    might result from injury to those body sites.
  • A knowledge of the native organisms in the
    infected part of the body gives the clinician
    perspective on the possible source and/or
    significance of microorganisms isolated from the
    site of infection.

Normal Flora
  • Before a discussion of adult NF begins, a
    discussion of how or when NF is acquired is
  • A healthy fetus, in utero, is essentially free of
  • The infant is exposed to NF from the moms
    vaginal tract during the delivery process and to
    microorganisms in the environment almost
    immediately thereafter.

Normal Flora
  • Within a few hours, the oral and nasopharyngeal
    flora of the neonate are established.
  • Within one day the resident microflora of the
    lower intestinal tract are established.
  • Adult NF refers to microorganisms that normally
    live on or in any part of the body without
    causing disease. There are two basic types of NF

Normal Flora
  • Resident organisms these are organisms that
    normally GROW on or in the indicated body site.
    Their presence becomes fixed in well defined
    distribution patterns.
  • Transient organisms These organisms are only
    temporarily present on or in the indicated body
    site. They usually dont become firmly
    entrenched, but simply die within a few hours.

Normal Flora
  • NF of the skin
  • The actual physiology of the skin varies from one
    part of the body to another and the resident
    microflora reflect these variations.
  • The skin, itself, is not a very favorable
    environment for the colonization of
  • Therefore, there are few resident microorganisms,
    but many transient microorganisms. Why is the
    microenvironment hostile?

Normal Flora
  • The skin is subject to periodic drying. However,
    in certain parts of the body (body folds or areas
    near orifices), there is sufficient moisture to
    support the growth of resident microorganisms
  • Skin has a slightly acidic pH due to organic
    acids produced by normal secretions from the
    sebaceous and sweat glands and by Staphylococcus
    epidermidis that normally resides there. This
    prevents the colonization by many organisms.
  • Sweat contains a high content of NaCl, thus
    producing a hypertonic condition on the skin
    surface that osmotically stresses many

Normal Flora
  • The skin surface contains many inhibitory
    substances that help control colonization,
    overgrowth, and production of infectious disease
    by resident microorganisms. Remember that
    colonization does not necessarily mean infection
    and disease.
  • Lysozyme is produced by the sweat glands and
    acts to lyse G organisms, including Staph.
  • Complex lipids are metabolized by
    Propionobacterium acnes to unsaturated fatty
    acids that have antimicrobial activity. These
    produce a strong odor. Use of deodorants that
    have antibacterial substances to inhibit the
    growth of these G organisms may lead to the
    growth of a preponderance of G- organisms and the
    subsequent development of infection.

Normal Flora
  • Most skin NF are found on the superficial
    squamous epithelium colonizing dead cells or
    closely associated with the sebaceous and sweat
    glands. The secretions from these glands provide
    the environmental conditions and nutrients for
    the growth of

Skin Normal Flora
  • Staph. epidermidis and Staph. aureus

Skin NF
  • Propionibacterium acnes this is an anaerobic G
    branching bacillus

Skin NF
  • P. acnes is usually harmless, but has been
    associated with acne vulgaris (acne),
    particularly during adolescence when there is an
    overproduction of the fluid secreted by the
    sebaceous glands (sebum).
  • This provides the ideal environment for the
    growth of P. acnes and substances produced by
    the organisms may trigger an inflammatory
    response leading to the production of acne.
  • Tetracycline or accutane (prevents sebum
    secretions, but has some severe side effects) may
    be used for treatment of acne.

Skin NF
  • Diphtheroids (aerobic corynebacterium)

Skin NF
  • Streptococcus species

Skin NF
  • Clostridium perfringens

Skin NF
  • Candida albicans

Normal Flora
  • Normal flora of the nose and nasopharynx (part of
    the pharynx above the soft palate)
  • Staph aureus
  • Staph epidermidis
  • Diphtheroids
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Neisseria meningitidis
  • may be causing disease if found in large
    numbers (relative numbers are important)

Nose/nasopharynx NF
  • Neisseria meningitidis

Nose/nasopharynx NF
  • Haemophilus influenzae

Normal Flora
  • Normal flora of the oral cavity and oropharynx
  • Organisms found are those that are able to resist
    mechanical removal by adhering to various
    surfaces such as the gums and teeth.
  • Those bacteria that cant resist the mechanical
    flushing of the oral cavity are swallowed and
    destroyed by the HCl in the stomach.
  • This is a comfortable environment for
    microorganisms due to the availability of water
    and nutrients. The most common NF in this area

Normal oral flora
  • viridans group Streptococcus species
  • Strep. pyogenes
  • Diphtheroids
  • Staph. epidermidis
  • Staph. aureus
  • Neisseria meningitidis
  • Other Neisseria species
  • Haemophilus influenzae
  • Other Haemophilus species

Normal oral flora
  • Candida albicans
  • Actinomycetes sp.
  • Lactobacillus sp.
  • Bacteroides sp.
  • Fusobacterium sp.
  • Enterobacteriaceae
  • these organisms are probably causing infection
    if they are the predominant organism found in
    this area or they are found in large numbers.

Normal oral flora
  • Actinomycetes

Normal oral flora
  • Granules of Actinomycetes

Normal oral flora
  • Bacteroides sp.

Normal oral flora
  • Fusobacterium sp.

Normal oral flora
  • Fusobacterium nucleatum

Normal oral flora
  • Lactobacillus

Normal oral flora
  • E. coli (a member of the Enterobacteriaceae)

Normal oral flora
  • Some of the Strep. species that adhere to the
    teeth (sanguis, mutans, salivarious) contribute
    to the formation of dental plaques and caries

Normal Flora
  • Normal flora of the alimentary tract
  • Because of the high acidic content of the
    stomach, very few organisms are found there.
    They include
  • Candida sp.
  • Lactobacilli
  • A few Strep. sp. (mainly Enterococcus faecalis)
  • The small intestine also has few microorganisms
    because of the combined inhibitory effects of
    stomach acid, bile, and pancreatic secretions.
    Normal flora include

Normal intestinal flora
  • Enterococcus faecalis
  • Lactobacilli
  • Diphtheroids
  • Candida sp.
  • The large intestine has the largest microbial
    population in the body. There are 1012 organisms
    excreted per gram of wet weight feces.
  • Over 300 different species of bacteria are
    normally found in the large intestine

Normal intestinal flora
  • The anaerobic/facultatively anaerobic ratio of
    organisms is 300/1 and includes the following
  • Bacteroides sp.
  • Fusobacterium sp.
  • Lactobacillus
  • Clostridium sp.
  • Peptostreptococcus sp.
  • Staph. sp.
  • Enterococcus faecalis

Normal intestinal flora
  • Other Strep. sp.
  • Pseudomonas species
  • Enterobacteriaceae
  • Candida sp.

Normal intestinal flora
  • Pseudomonas species

Normal intestinal flora
  • Peptostreptococcus species

Normal intestinal flora
  • Normal physiological processes move the
    microorganisms through the colon so that a normal
    adult excretes 3X 1013 microorganisms daily.
  • Under normal conditions the resident flora are
    self-limiting. Competition( for example, colicin
    produced by E. coli) and mutualism between them
    and the host (E.coli produces vitamin K and B for
    the host) maintains the status quo.

Normal intestinal flora
  • Anything the disturbs the intestinal environment
    (stress, altitude change, starvation, diarrhea,
    antibiotics) can serve to greatly alter the
    normal flora leading to gastrointestinal disease
    such as yeast infections and antibiotic
    associated pseudomembraneous colitis.

Normal flora
  • NF of the genitourinary tract
  • NF of the urethra include
  • Staph. epidermidis
  • Enterococcus faecalis
  • Diphtheriods
  • Neisseria sp. (NOT N. gonorrhoeae)
  • Enterobacteriaceae
  • NF of the vaginal tract the microflora present
    on this large, moist surface area changes with
    the menstrual cycle. Organisms include

Normal genitourinary flora
  • Lactobacillus
  • Bacteroides
  • Enterococcus sp.
  • Staph. epidermidis
  • Diphtheroids
  • Strep. agalactiae
  • Clostridium perfringens
  • Peptostreptococcus
  • Enterobacteriaceae
  • Candida albicans

Normal genitourinary flora
  • NF of the external genitalia include
  • Strep. sp.
  • Staph. sp.
  • Diphtheroids
  • Bacteroides
  • Candida sp.