normal floura.pptx

NORMAL FLORA 08/30/2024 1  Introduction Definition Normal microbial flora denotes the population of microorganisms that inhabit the skin and mucous membranes of healthy normal perso...

NORMAL FLORA 08/30/2024 1  Introduction Definition Normal microbial flora denotes the population of microorganisms that inhabit the skin and mucous membranes of healthy normal persons Also called the normal flora or more properly the Indigenous micro biota In humans, the normal flora is located in various sites such as gastrointestinal tract (GIT), respiratory tract, genitourinary tract and skin Humans acquire the normal flora soon after the birth and then continue to harbor until death 08/30/2024 2  Con't… The presence of the normal microbial flora in a given body site depends upon various factors such as: Local temperature Moisture Ph Environmental flora (hospital or community) Immunity Anatomical site (skin or mucosa) 08/30/2024 3  Con't… Most of the normal flora predominantly contain bacteria and to a less extent some fungi and parasites. The existence of viruses as normal flora is recently gained importance The total population of normal flora in humans is roughly about 1014 bacteria which is more than the total number of cells (1013), present in the human body Overall, anaerobic flora dominates over aerobes the ratio of anaerobic/aerobic bacteria varies depending upon the body site GIT is the predominant site of normal flora, where the most common flora is Bacteroides fragilis (anaerobic flora) Escherichia coli (aerobes) 08/30/2024 4  Con't…  Normal flora typically fall into one of the two categories 1.The resident flora are life-long members of the body’s normal microbial community. They are very closely associated with a particular area. When disturbed, they again re-establish themselves. if disturbed, it promptly reestablishes itself They do not cause harm; rather they have beneficiary effect on the host 08/30/2024 5  Con't… The transient flora Consists of microorganisms that inhabit the body surface or mucous membranes temporarily for a short interval. Do not produce disease as long as the resident flora remains intact. If the resident flora gets disturbed due to any reasons, transient flora may colonize and produce disease, e.g. pneumococcus in nasopharynx 08/30/2024 6  Role of the Resident Flora Synthesizes and excretes vitamins E.g. Enteric bacteria secrete Vitamin K and Vitamin B12, and lactic acid. Prevents colonization by pathogens Compete for attachment sites or for essential nutrients. May antagonize other bacteria Intestinal bacteria produce nonspecific fatty acids and peroxides to highly specific bacteriocins, which inhibit or kill other bacteria. 08/30/2024 7  Con't… Stimulates the production of cross-reactive antibodies. Antibodies produced against components of the NF cross react with certain related pathogens, and prevent infection or invasion. Antibodies to NF referred to as "natural" antibodies Prevent allergic diseases (Hygiene hypothesis) It states that a lack of early childhood exposure to symbiotic microorganisms (e.g. gut flora or probiotics), infectious agents and parasites increases susceptibility of the individual to allergic diseases by suppressing the natural development of the immune system 08/30/2024 8  Con't… Disturbed normal flora promote infection When the composition of normal flora is disturbed, it facilitates pathogenic organisms to enter and cause disease. Several mechanisms by which the normal flora is disturbed are as follows: Injudicious use of broad spectrum antimicrobial agent It may completely suppress the normal flora thus permitting the pathogen (exogenous and endogenous) to take the upper hand and cause infection. For example, Clostridioides difficile, causing pseudomembranous colitis 08/30/2024 9  Con't… Host factors such as immune suppression, reduced peristalsis may promote the pathogen to grow Physical destruction of the normal flora by chemicals, burns, irradiations Minor trauma in mouth (e.g. by dental procedure, chewing or vigorous brushing) can promote passage of small numbers of bacteria (e.g. viridians streptococci) transiently into bloodstream, which can cause bacterial endocarditis. 08/30/2024 10  Harmful Effects Normal flora may produce the following harmful effects May be agents of disease: Members of the normal flora may cause various endogenous disease If they enter a wrong site or tissue (e.g. blood, sterile body cavities)—then even the resident flora can produce disease. For example, E. coli which is a resident flora of intestine may cause urinary tract infection if enters into urinary tract. Bacterial synergism Bacterial vitamins and growth factors produced by members of the normal flora may promote the growth of the potential pathogens Competition for host nutrients Bacteria in GIT absorb some of the host’s nutrients for their survival. 08/30/2024 11  Con't… Normal sterile body parts Colonization of one of these sites generally involves a defect or breach in the natural defenses that creates a portal of entry.  Brain; Central nervous system  Blood; Tissues; Organ systems  Sinuses; Inner and Middle Ear  Lower Respiratory Tract: Larynx; Trachea; Bronchioles (bronchi); Lungs; Alveoli  Kidneys; Ureters; Urinary Bladder; Posterior Urethra  Uterus; Endometrium (Inner mucous membrane of uterus ); Fallopian Tubes; Cervix and Endocervix 08/30/2024 12  Con't… Non sterile areas of human body Skin Respiratory tract Nose and Nasopharynx; Mouth and Oropharynx Eye (Conjunctiva) and Outer ear Intestinal tract Stomach Small Intestine Large Intestine Genitourinary tract External Genitalia & Anterior Urethra Vagina 08/30/2024 13 Con't… The microbiological profile of the normal flora in various sites of human body UPPER RESPIRATORY TRACT The upper respiratory tract is colonized with numerous organisms, Most of the common organisms in the upper respiratory tract are relatively avirulent and are rarely associated with disease unless they are introduced into normally sterile sites e.g., sinuses, middle ear, brain The most common aerobic bacteria are: Streptococcus, Haemophilus, and Neisseria spp The most common anaerobic bacteria are: Peptostreptococcus and related anaerobic cocci, Veillonella, Actinomyces, and Fusobacterium spp. 08/30/2024 14  Con't… LOWER RESPIRATORY TRACT The larynx, trachea, bronchioles, and lower airways are generally sterile Although transient colonization with secretions of the upper respiratory tract may occur More virulent bacteria present in the mouth (e.g., S. pneumoniae, S. aureus, members of the family Enterobacteriaceae such as Klebsiella) cause acute disease of the lower airway The presence of the dimorphic fungi (e.g., Histoplasma, Co|ccidioides, and Blastomyces spp.) is diagnostic because asymptomatic colonization with these organisms never occurs. 08/30/2024 15  Con't… EAR The most common organism colonizing the outer ear is coagulase- negative Staphylococcus. Other organisms colonizing the skin have been isolated from this site, as well as potential pathogens such as S. pneumoniae, Pseudomonas aeruginosa, and members of the Enterobacteriaceae family. EYE The surface of the eye is colonized with coagulase-negative staphylococci, as well as rare numbers of organisms found in the nasopharynx (e.g., Haemophilus spp., Neisseria spp., viridans streptococci). 08/30/2024 16  Con't… GASTROINTESTINAL TRACT The gastrointestinal tract is colonized with microbes and remains the home for a diverse population of organisms throughout the life of the host Although the opportunity for colonization with new organisms occurs daily with the ingestion of food and water, the population remains relatively constant, unless exogenous factors such as antibiotic treatment disrupt the balanced flora 08/30/2024 17  Con't… STOMACH Because the stomach contains hydrochloric acid and pepsinogen the only organisms present are small numbers of acid-tolerant bacteria such as Lactobacillus and Streptococcus spp. and Helicobacter pylori SMALL INTESTINE the small intestine is colonized with many different bacteria, fungi, and parasites. Most of these organisms are anaerobes, such as Peptostreptococcus, Porphyromonas, and Prevotella. Common causes of gastroenteritis (e.g., Salmonella and Campylobacter spp.) can be present in small numbers as asymptomatic residents 08/30/2024 18  Con't… LARGE INTESTINE More microbes are present in the large intestine than anywhere else in the human body. It is estimated that more than 1011 bacteria per gram of feces can be found Various yeasts and nonpathogenic parasites can also establish residence in the large intestine. The most common bacteria include Bifidobacterium, Eubacterium, Bacteroides, Enterococcus, and the Enterobacteriaceae family. E. coli is present in virtually all humans from birth until death. 08/30/2024 19  Con't… Genitourinary System The anterior urethra and vagina are the only anatomic areas of the genitourinary system permanently colonized with microbes The other structures of the urinary system should be sterile, except when disease or an anatomic abnormality is present 08/30/2024 20  Con't… ANTERIOR URETHRA The commensal population of the urethra consists of a variety of organisms The most numerous are lactobacilli, streptococci, and coagulase-negative staphylococci In contrast, the urethra can be colonized transiently with fecal organisms such as Enterococcus, Enterobacteriaceae, and Candida-all of which can invade the urinary tract, multiply in urine, and lead to significant disease. 08/30/2024 21 Con't… VAGINA The microbial population of the vagina is more diverse and is dramatically influenced by hormonal factors. Newborn girls are colonized with lactobacilli at birth, and these bacteria predominate for approximately 6 weeks The levels of maternal estrogen have declined, and the vaginal flora changes to include staphylococci, streptococci, and Enterobacteriaceae. When estrogen production is initiated at puberty, the microbial flora again changes. Lactobacilli reemerge as the predominant organisms other organisms are also isolated, including staphylococci (S. aureus less commonly than the coagulase- negative species), streptococci (including group B Streptococcus), Enterococcus, Gardnerella, Mycoplasma, Ureaplasma, Enterobacteriaceae, and a variety of anaerobic bacteria 08/30/2024 22  Con't… Skin Although many organisms come into contact with the skin surface relatively hostile environment does not support the survival of most organisms the most common organisms found on the skin surface are Gram-positive bacteria (e.g., coagulase-negative Staphylococcus and, less commonly, S. aureus, corynebacteria, and propionibacteria). Clostridium perfringens is isolated on the skin of approximately 20% of healthy individuals The fungi Candida and Malassezia are also found on skin surfaces, particularly in moist sites. 08/30/2024 23 Con't… 08/30/2024 24 08/30/2024 25