Microbial Flora (Normal Human Microbiota) PDF

Microbial Flora (Normal Human Microbiota)  Normal Microbiota ❑ Refers to microorganisms that reside on/in: Skin Conjunctivae Oral Cavity Upper respiratory tract Intestinal tract Genitourinary tract Blood & tissues of every human being.  Normal Fl...

Microbial Flora (Normal Human Microbiota)  Normal Microbiota ❑ Refers to microorganisms that reside on/in: Skin Conjunctivae Oral Cavity Upper respiratory tract Intestinal tract Genitourinary tract Blood & tissues of every human being.  Normal Flora Under normal circumstances they do not cause disease and they are useful for the host (human). Some normal flora members can be opportunistic pathogens. Some of them once they are introduced into blood stream and other tissues (not their orginal habitat/ place).  Normal flora A fetus when they born, they are sterile and does not have flora within their body. The sooner the newborn starts having normal flora from its mother and surrounding environment. In fact normal flora differ from one human to another depending on: - age - diet( nutritional status) - geographic habitat  Normal Flora Sterile sites of human body: – CNS. – Blood(circulatrory system). – Lower bronchi and alveoli. – Liver. – Spleen. – Kidney. – Bladder.  Normal Flora Classified into: A. Resident flora: – Microorganisms which are regularly found in specific sites. B. Transient flora: – Temporary and they can not compete with resident flora. – Derived from environment. – Non-pathogenic or potentially pathogenic. – If resident microbiota is disturbed, then the transient microorganisms may colonize, proliferate, & produce disease.  Normal Flora ▪ The normal flora protect us from disease by: 1) Competing with invaders for space and nutrients. 2) Producing compounds (bacteriocins,fatty acids, peroxides) which kill other bacteria. 3) Lowering the pH so that other bacteria can't grow.  Benefits ▪ Produce vitamins that we are unable to produce such as vitamin B12. ▪ Boost our immune system by contributing to the maturation of the immune system. ▪ Helps in food digestion.  Drawback If the normal flora escape from their normal location, they can cause disease. For example, Escherichia coli, commonly found in the intestine, can cause urinary tract infections if introduced into the bladder. They can cause a disease in immunosuppressed people, such as AIDS pts, people with long use of steroids and immunosuppressant drugs.  Skin Skin is always in contact with the enviroment; – Resident flora. – Transient flora.  Skin Resident microorganisms of the skin: – Aerobic and anaerobic diftheroid bacilli (corynebacterium). – Staphylococci (S.aureus, S.epidermidis). – Streptococci ( viridans streptococci, enterococcus). – Gram (-) bacilli and acinetobacter. – Fungi and yeast (skin fold). – Non-pathogenic mycobacteria occur in areas rich in sebaceous secretions (genitalia,external ear).  Skin Transient flora eliminating of skin by: – Low Ph of skin. – Fatty acids. – Sebaceous secretions. Profuse sweating, washing and bathing can eliminate resident flora, but the flora is replenished from sebaceous and sweat glands, contact with other skin areas and enviroment.  Conjunctiva Diftheroids, S.epidermidis, Non-hemolytic streptococci, Neisseriaea, Moraxella species are present in conjuntiva.  Oral cavity The mucosal membrane of the mouth and the pharynx are often sterile at birth. Within 4-12 hours after birth viridans streptococci become most prominent members of the oral cavity and remain so for life.  Oral cavity Early in life : – Staphylococci. – Neisseriaea. – Moraxella. – Diftheroids. – Lactobacilli are added.  Oral cavity When the teeth erupt : – Anaerobic spirochetes. – Prevotella, Fusobacterium, Rothia. – Vibrios, Lactobacilli. – Actinomycetes. – Yeast. – Various protozoa are added.  Upper Respiratory Tract The flora of the nose is consist of : S.aureus, S.epidermidis, Streptococci, Propinobacterium Pharynx and trachea flora : – Non-hemolytic and alfa-hemolytic streptococci. – Neisseriae, staphylococci, difteroides, pneumonococci. – Mycoplasma and prevotella.  Upper Respiratory Tract Infections of mouth and respiratory tract are usually caused by oronasal flora. Small bronchi and alveoli are normally sterile. Aspiration of saliva may result in pneumoniae, lung abscesses, empyema.  Intestinal Tract At birth intestine is sterile. Breast-fed children intestine colonized with streptococci and lactobacilli. Bottle-fed children intestine colonized with mixed flora. The bowels of newborns (ICU) colonized with enterobactericeae.  Intestinal Tract In normal adult esophagus contains bacteria. Acid Ph of stomach protect against infection with enteric pathogens. Intestinal Ph is alkaline,resident flora increase in bowel.  Intestinal Tract Anatomic location bacteria per gr Adult duodenum: 10³-10⁶ Jejunum and ileum: 10⁵-10⁸ Cecum and transvers colon 10⁸-10⁹ Sigmoid colon and rectum >10¹¹  Intestinal Tract In the upper intestine lactobacili and enterococci predominant. Adult colon %96-99 resident flora consist of anaerobs – Bacteroides. – Fusobacterium. – Anaerobic lactobacilli. – Clostridia. – Anaerob gr(+) cocci.  Intestinal Tract ▪ Adult colon %1-4 flora consist of facultative aerobs – Gr(-) coliform bacteria. – Enterococci. – Pseudomanas. – Lactobaclli. – Candida. ▪ More than 100 distint types of bacteria regularly can occur in fecal flora..  Intestinal Tract Intestinal bacteria are important: – Synthesis of vitamin K. – Conversion of bile pigments and bile acids. – Absorption of nutrients and breakdown products. – Antagonism to microbial pathogen.  Anterior urethra The anterior urethra of both sexes contains small numbers of bacteria, same types with skin and perineum. These organisms regularly appear in voided urine in numbers of 10²-10.⁴ ml.  Vagina Soon after birth, aerobic lactobacilli appear in the vagina, persist several weeks.(Ph acid) When the Ph becomes neutral a mixed flora bacilli and cocci is present (until puberty). In puberty aerobic lactobacilli reappear in large numbers (Ph acid).  Vagina In puberty reappears of lactobacilli is an important mechanism to preventing harmful microorganisms in the vagina. If lactobacilli are supressed, yeast and various bacteria increase in numbers and cause irritation and inflamation After menapouse, lactobacilli decreases and mixed flora return.  Vagina The normal flora includes group B streptococci in as many as 25% of women childbearing age. During the birth baby infected group B streptococci, which subsequently may cause neonatal sepsis and meningitidis.  Blood Occasionally commensals bacteria from mouth, nasophrarynx and GI are carried into the blood. Under normal conditions, they are eliminated – By normal defense mechanisms – Phagocytosis by RES.  Blood Simple manipulations – Chewing – Tooth brushing – Dental work – Genitourinary catheterization – Endoscopic examination ………….bacteremia  Blood This simple manifestations are little consequence in the normal host. In the presence of: – Abnormal heart valves. – Prosthetic heart valves. – Other prosthetic devices. Bacteremia may lead to colonization and infection.