objectives Define and classify normal microbiological flora of human body Explain the beneficial role of microbial flora Explain endogenous and exogenous diseases in reference to microflora

The term "normal microbial flora" denotes the population of microorganisms that inhabit the skin and mucous membranes of healthy normal persons. The skin and mucous membranes always harbor a variety of microorganisms that can be arranged into two groups:

(1) The resident flora relatively fixed types of microorganisms regularly found in a given area at a given age; if disturbed, it promptly reestablishes itself (2) The transient flora nonpathogenic or potentially pathogenic microorganisms that inhabit the skin or mucous membranes for hours, days, or weeks; it is derived from the environment, does not produce disease, and does not establish itself permanently on the surface. Members of the transient flora are generally of little significance so long as the normal resident flora remains intact. However, if the resident flora is disturbed, transient microorganisms may colonize, proliferate, and produce disease.

Skin Staphylococcus epidermidis Staphylococcus aureus (in small numbers) Micrococcus species Nonpathogenic Neisseria species Alpha-hemolytic and nonhemolytic streptococci Diphtheroids Nasopharynx diphtheroids, nonpathogenic Neisseria,S epidermidis, nonhemolytic streptococci, anaerobes Lesser amounts of the following when accompanied by organisms listed above: yeasts, Haemophilus species, pneumococci, S aureus, GIT Various Enterobacteriaceae except Salmonella, Shigella, Yersinia, Vibrio, and Campylobacter species Enterococci Alpha-hemolytic and nonhemolytic streptococci Diphtheroids S aureus in small numbers Yeasts in small numbers Anaerobes in large numbers (too many species to list) Genitalia Corynebacterium species, Lactobacillus species, -hemolytic and nonhemolytic streptococci, nonpathogenic Neisseria species enterococci, Enterobacteriaceae and other gram-negative rods, S epidermidis, Candida & other yeasts Anaerobes (too many to list); Prevotella, Clostridium, and Peptostreptococcus species

BENEFICIAL FUNCTIONS OF NORMAL FLORA(commensals) 1.Prevent colonization by pathogens 2.Produce antimicrobial substances 3.In newborn it is a powerful stimulus for the development of the immune system 4.Microflora of intestine synthesize vitamin k and several B vitamins 5.Certain bacteria metabolize dietary carcinogens

Haemorrhagic disease of the newborn Haemorrhagic disease of the newborn is a coagulation disturbance in newborns due to vitamin K deficiency Newborns have low vitamin K stores at birth, vitamin K passes the placenta poorly, the levels of vitamin K in breast milk are low and the gut flora has not yet been developed (vitamin K is normally produced by bacteria in the intestines).

Pseudomembranous colitis The harmless normal flora in the GIT protect against colonization by harmful exogenous(coming from outside) bacteria because of nutritional competition Broad spectrum antibiotic usage especially in the hospitals kills this normal flora in the GIT A bacteria called Clostridium difficile which is widespread in the environment and resistant to these antibiotics take the place of normal flora The C. difficile cause the disease known as “Pseudomembranous colitis” or “antibiotic associated diarrhea” Most common symptom is diarrhoea

Vaginal candidiasis Candida vaginitis – Vagina is colonized by a friendly bacteria lactobacillus species that produces lactic acid and lowers the vaginal pH – Lower pH prevents colonization by harmful pathogens as most organism do not grow in acidic pH – Antibiotic usage kill normal flora and colonization with a fungus called candida takes place – 75% of women may have an episode of candidal vaginitis during their lifetime – intense itching of the vulva & thick scanty curdlike discharge, – The vagina and labia are usually very red(erythematous)

Harmful effects of normal flora/DISEASE CAUSING ABILITY OF MICROBIAL FLORA 1.When organisms are displaced from their normal site in the body to an abnormal site For example, streptococci of the viridans group, Bacteroides species are the most common resident bacteria of the large intestine. If introduced into the free peritoneal cavity or into pelvic tissues along with other bacteria as a result of trauma, they cause suppuration and bacteremia. 2. When potential pathogens gain a competitive advantage due to diminished populations of harmless competitors example: by use of antibiotic therapy 3. Immunocompromised individuals 4. Drug resistance

Exogenous and endogenous diseases Endogenous infection is "due to reactivation of organisms present in a dormant focus mainly by normal bacterial flora." Exogenous infection is "caused by organisms not normally present in the body but which have gained entrance from the environment." A prime example of this is when the residential bacterium E. coli of the GI tract enters the urinary tract. This causes a urinary tract infection. Infections caused by exogenous bacteria occurs when microbes that are noncommensal enter a host. These microbes can enter a host via inhalation of aerosolized bacteria, ingestion of contaminated or ill- prepared foods, sexual activity, or the direct contact of a wound with the bacteria

DISEASE CAUSING ABILITY OF MICROBIAL FLORA Urinary tract infection(UTI) in females – UTI is very common in females – Fecal gram negative bacteria inhabit the perianal area – With sexual thursting and very short length of female urethra these perianal gram negative bacteria gain assess to the urinary bladder causing urinary tract infection in females

DISEASE CAUSING ABILITY OF MICROBIAL FLORA Some pathogenic bacteria normally colonize the throat ;e.g Streptococcus pneumoniae, Hemophilus influenze etc. Loss of respiratory defences(e.g cilia damage by viruses,loss of cough reflex etc.)make these organism move to lungs, sinuses and middle ear causing pneumonia,sinusitis, otitis media respectively

DISEASE CAUSING ABILITY OF MICROBIAL FLORA Streptococci of the viridans group are the most common resident organisms of the upper respiratory tract. If large numbers of them are introduced into the bloodstream (eg, following tooth extraction or tonsillectomy), they may settle on deformed or prosthetic heartvalves and produce infective endocarditis.

NORMAL FLORA OF THE SKIN Staphylococcus epidermidis is most important(causes infective endocarditis) Fungi and yeasts are often present in skin folds factors that may be important in eliminating nonresident microorganisms from the skin are the low pH, the fatty acids in sebaceous secretions, and the presence of lysozyme. DISEASES Anaerobes and aerobic bacteria often join to form synergistic infections (gangrene, necrotizing fasciitis, cellulitis) of skin and soft tissues. Propionibacterium and Peptococcus-situated in the deeper follicles in the dermis-cause of acne

NORMAL FLORA OF THE CONJUCTIVA It is relatively free from organisms due to the flushing action of tears. Examples: Diphtheroids Staphylococcus S epidermidis The conjunctival flora is normally held in check by the flow of tears, which contain antibacterial lysozyme.

The Role of the Normal Mouth Flora in Dental Caries Caries is a disintegration of the teeth beginning at the surface and progressing inward. First step: The formation of plaque on the hard, smooth enamel surface. There appears to be a strong correlation between the presence of Streptococcus mutans and caries on specific enamel areas. second step is the formation of large amounts of acid (pH < 5.0) from carbohydrates by streptococci and lactobacilli in the plaque. The development of caries also depends on genetic, hormonal, nutritional, and many other factors

NORMAL FLORA OF THE NOSE, NASOPHARYNX AND ACESSORY SINUSES In the nose: Corynebateria Staphylococcus The nasopharynx of infant is sterile at birth But acquires the common commensal flora and pathogenic flora carried form the mother and hospital staff Examples: Peudomonas E.coli

NORMAL FLORA OF THE MOUTH AND UPPER RESPIRATORY TRACT The flora of the nose consists of prominent corynebacteria, staphylococci ( S epidermidis, S aureus), and streptococci. The mucous membranes of the mouth and pharynx are often sterile at birth but may be contaminated by passage through the birth canal. Within 4–12 hours after birth, viridans streptococci become established as the most prominent members of the resident flora and remain so for life. When teeth begin to erupt, the anaerobic spirochetes, Prevotella species etc establish themselves, along with some anaerobic vibrios and lactobacilli. Actinomyces species are normally present in tonsillar tissue and on the gingivae in adults, and various protozoa may also be present. Yeasts (Candida species) occur in the mouth. Diseases: Periodontal infections, perioral abscesses, sinusitis, and mastoiditis may involve predominantly Prevotella melaninogenica, fusobacteria, and peptostreptococci. Aspiration of saliva (containing up to 10 2 of these organisms and aerobes) may result in necrotizing pneumonia, lung abscess, and empyema

NORMAL FLORA OF THE INTESTINAL TRACT In % newborn infants,the meconium is sterile but in 10-20% a few orrganisms probably acquired through labour may be present. In all cases,within 4-24 hours of birth an intestinal flora is established In bresstfed children the intestine contains lactobacillus while bottle fed babies have enterococci, colon bacilli and stahpylococci Bowels of newborns in intensive care nurseries tend to be colonized by Enterobacteriaceae, eg, klebsiella, citrobacter, enterobacter. The normal acid pH of the stomach markedly protects against infection with some enteric pathogens, eg, cholera. As the pH of intestinal contents becomes alkaline, the resident flora gradually increases.

Minor trauma (eg, sigmoidoscopy, barium enema) may induce transient bacteremia in about 10% of procedures. Intestinal bacteria are important in synthesis of vitamin K, conversion of bile pigments and bile acids, absorption of nutrients and breakdown products, and antagonism to microbial pathogens. Antimicrobial drugs taken orally suppress the drug- susceptible components of the fecal flora The drug-susceptible microorganisms are replaced by drug- resistant ones, particularly staphylococci, enterobacters, enterococci, protei, pseudomonads, Clostridium difficile, and yeasts. The feeding of large quantities of Lactobacillus acidophilus may result in the temporary establishment of this organism in the gut and the concomitant partial suppression of other gut microflora.

Normal Flora of the Vagina At puberty, aerobic and anaerobic lactobacilli reappear in large numbers and contribute to the maintenance of acid pH through the production of acid from carbohydrates, particularly glycogen. This appears to be an important mechanism in preventing the establishment of other, possibly harmful microorganisms in the vagina. If lactobacilli are suppressed by the administration of antimicrobial drugs, yeasts or various bacteria increase in numbers and cause irritation and inflammation. After menopause, lactobacilli again diminish in number and a mixed flora returns The cervical mucus has antibacterial activity and contains lysozyme. In some women, the vaginal introitus contains a heavy flora resembling that of the perineum and perianal area. This may be a predisposing factor in recurrent urinary tract infections. Vaginal organisms present at time of delivery may infect the newborn (eg, group B streptococci).

BACTERIA IN THE BLOOD AND TISSUES Blood is sterile The commensals from the normal flora of the mouth,nasopharynx and intestinal tract may get into the blood and tissues but they are usually quickly eliminated by the normal defence mechanisms

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Self assessment 1. Which of the following sites of the human body does not have indigenous microflora? a. bladder b. colon c. distal urethra d. vagina 2. The indigenous microflora of the external ear canal is most like the indigenous microflora of the: a. colon. b. mouth. c. skin. d. distal urethra. 3.Microbial flora is also known as: Commensals Pathogens Microbes Infectious particles

Muhammad Talha 58-years-old man, smoker presents with shortness of breath, cough, expectoration of rusty colored sputum. His Chest X-rays showed consolidation of right lower lobe of lung. Sputum and blood culture isolated Strep pneumoniae. The most likely source of this pathogen in this patient is a.From another patient in community b.Patient’s own GIT flora c.Patient’s own throat flora d.Ingestion of contaminated water from community e.None of the above Correct Answer: c MCQ

A 25-years-young lady reported with upper respiratory tract infection. General practitioner prescribed Tab Co-amoxiclav for 3 days. On 4 th day, lady experienced itching, thick curdy discharge from vagina. Gram stain of the discharge reveal numerous pus cells and gram positive budding microorganism. The cause of this infection is most likely due to: a.Fecal contamination of vagina b.Recto-vaginal fistula c.Antimicrobial intake d.Catheterization e.Per-vaginal exam Correct Answer: c MCQ

Muhammad 24-years-young met a RTA. He sustained multiple injuries and was hospitalized. At laparotomy, it was found that there was a laceration in ascending colon 50 cm from ceacum. The laceration was stiched but three days later, he experienced pain right side of abdomen and fever. USG revealed pus collection near stitched laceration of ascending colon. The most likely organisms to be isolated will be 1.Vibrio cholerae and Staph aureus 2.Strep pyogenes 3.Mycobacterium tuberculosis 4.Mixed normal gastrointestinal flora 5.Neisseria meningitidis Correct Answer: 4

question: write the harmful effects of normal flora