Normal microbiota and

endogenous infections

Prof. dr hab. n. med. Beata Sobieszczańska University of Medicine

Dept. of Microbiology

• Permanent colonization = resident flora:

• Present invariably in a particular site

• Can be reduced by washing but not eliminated

• Transient colonization = transient flora:

• Present briefly, rest on the body surface but do not persist

• Can be eliminated by washing

Normal microbiota

Outcomes of exposure to a microorganisms:

1. Permanentcolonization

2. Transient colonization

3. Disease

• Normal flora is present

in/on

– skin

– upper respiratory tract

– oral cavity

– intestines, especially large

intestine

– vaginal tract

• Very little normal flora in

eyes & stomach

Normal microbiota

Notably absent in all

internal organsAbsent in:

lower respiratory

tract

muscle tissue

blood & tissue

fluid

cerebrospinal

fluid

peritoneum

pericardium

meninges

Conjunctiva

Skin

Oral cavity

Upper respiratory tract

Urinary tract

Genital tract

Gastrointestinal tract

Normal flora changes continuously through out life and

reflects: age of person, nutrition, genetics, environment, sex

Benefits of the normal flora a. Nutrient production/processing e.g. vitamins

K, B production by E. colib. Competition with pathogenic microbes

(competing for attachment sites and fornutrients; produce toxin that are harmful toother bacteria i.e. non specific fatty acids,peroxides and bacteriocins that inhibit or killother bacteria)

c. Normal development of the immune system (stimulate the production of cross-reactiveantibodies)

d. Stimulate the development of certain tissuese.g. the caecum and certain lymphatic tissues (Peyer's patches) in the GI tract

• ca. 2 m2 of skin

• Lysozyme, NaCl (sweat

glans) low pH, sebum,

fatty acids (oil glans)

• Staphylococci -

S. epidermidis >90%

• Micrococcus,

• Corynebacteria =

diphteroids

• Propionibacterium

Skin flora - GP bacteria

Benefit: inhibits fungal growth

Harm: body odour, acne,

opportunistic infections

Neither profuse sweating nor

washing and bathing can

eliminate or significantly

modify the normal resident

flora

• Low number of bacteria

• Blinking, tear (lysozyme)

Conjunctiva flora

S. epidermidis diphteroids

Neisseria

Haemophilus

Oral cavity flora

Oral and systemic diseases associated with the oral microbiome

• URT (nose, nasopharynx)

assorted Streptococci, Staphylococci,

non-pathogenic Neisseria,

nontypeable Haemophilus influenzae

Anaerobes : Actinomycetes, Fusobacterium

• LRT (trachea, bronchi, and pulmonary tissues) are free

of microorganism – protected by ciliary

epithelium, mucus blanket, alveolar macrophages

• If breached - opportunistic infections

Respiratory tract flora

Gastrointestinal tract flora

Many species

ferment waste

material feces,

generating

vitamins (B12, K,

riboflavin and

thiamine)

Bacterial digestive

enzymes that

convert

disaccharides to

monosaccharides

• Kidney, bladder, urine

in bladder are free of

microorganism

• Urethra:

S.epidermidis

Enterococci

Neisseria

Mycoplasma

Urinary tract flora

Urogenital tract

Male anterior urethra – same as skin (enteric,

enterococci)

Vagina – complex microbiota:

• at birth – same as mother (pH 5)

• neonate – same as skin + enteric, strepto. (pH 7)

• at puberty – Lactobacillus + same as skin +

anaerobes+ streptococci (pH 5)

• at menopause – return to prepuberty flora (pH 7)

Benefit: competition with pathogens and production of

lactic acid

Endogenous infection =

an infection caused by

an infectious agent that

is already present in the

body (normal microflora)

Opportunistic and endogenous infections

Opportunistic infection

an infection caused by

a microorganism that

normally does not

cause disease but can

cause the disease

when the body’s

immune system is

impaired and unable to

fight an infection

Predisposing Factors of

Opportunistic Infections

1. Damage of epithelial

barriers:

burn, trauma, decubitus,

operation and

instrumentation

2. Chronic diseases:

diabetes mellitus,

chronic renal failure,

liver cirrhosis, etc.

Opportunistic and endogenous infections

3. Hematologic disorders and

cancer

Leukaemia, malignant

lymphoma, multiple

myeloma, etc.

4. Iatrogenic - drug induced

Steroids

Cytostatic and

immunosuppressive drugs

Antibiotics

Irradiation

Examples:

• Actinomycosis (A. israeli)

• Endocarditis (oral streptococci,

enterococci)

• Prostheses and catheters

colonization = bacteremia

(coagulase-negative)

staphylococci)

• Plaut-Vincent angina Borrelia +

Fusobacterium)

• Ludwig's angina

• Most UTI, many RTI

Opportunistic and endogenous infections

Candidiasis (C. albicans)

Aspergillosis (Aspergillus

fumigatus)

Pneumocystosis

(Pneumocystis jirovecii)

MOTT-associated infections

& tuberculosis

HSV reactivation (sores,

shingles)

Toxoplasmosis

CMV & EBV infections

Non-fermentative rods