MedMic Unit 3 Pathogenic bacteria PDF

Medical Microbiology (Course code: CCST4025) Unit 3 Pathogenic bacteria 1  Pathogenic bacteria Part I : Characteristic and classification of bacteria Pathogenic properties of medically important bacteria Part II...

Medical Microbiology (Course code: CCST4025) Unit 3 Pathogenic bacteria 1  Pathogenic bacteria Part I : Characteristic and classification of bacteria Pathogenic properties of medically important bacteria Part II Some examples of medically important bacteria and bacterial diseases 2 Part I: Characteristic and classification of bacteria 3 Bacteria – Introduction to structure  No nucleus (Prokaryote)  Most with one chromosome.  May have plasmids (small, circular molecules of DNA - not part of the bacterial chromosome)  Cell wall present (except Mycoplasma)  Often surrounded by slimy and gelatinous material glycocalyx (a capsule or slime layer) Capsules serve an antiphagocytic function (protein encapsulated bacteria from being phagocytized = eaten up by white blood cells) 4 Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Atypical bacteria without a cell wall  Disease - causing bacteria that  Antibiotics (such as penicillin) do NOT have a cell wall. that target the cell wall of a  Example: Mycoplasma bacterium become useless  Mycoplasma pneumoniae is  Mycoplasma pneumoniae therefore resistant to a range of causes severe lung infections antibiotics. (pneumonia) Penicillin becomes useless 5 http://www.invivogen.com/images/Mycoplasma.gif http://www.antibioticslist.com/images/design/penicillin_img.gif http://www.rayur.com/wp-content/uploads/2012/09/Penicillin-group-M.jpg http://www.invivogen.com/review-mycoplasma How do bacteria move or get themselves attached to a host? Do bacteria have SEX organs?  Many bacteria have flagella to move  Pili are organelles of attachment for bacteria to stick to surfaces.  Sexual reproduction? What for? A sex pilus enables the transfer of genetic material from one bacterial cell (donor cell) to another (recipient cell).  Asexual reproduction? What for? Some produce endospores to enable them to survive adverse conditions. 6 http://en.wikipedia.org/wiki/Pilus#mediaviewer/File:Conjugation.svg http://faculty.ccbcmd.edu/courses/bio141/labmanua/lab7/u1fig15m.html Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins  Bacterial cell Site of protein Enable motility synthesis Serve an antiphagocytic function & used in production of vaccines Provide rigidity, strength & protection Enable bacteria to adhere to surfaces http://torresbioclan.pbworks.com/w/page/22377199/Prokaryotes%20and%20Eukaryotes 7 Bacterial flagellar movement  Bacterial flagellum rotates like a propeller  Counterclockwise rotation causes forward motion  Clockwise rotation disrupts run causing bacterial cell to stop and tumble Spores and sporulation (for survival)  During adverse conditions (e.g. lack of nutrients), some gram- positive rods undergo profound structural and metabolic In fact, sterilization changes procedures are assessed by their  A dormant endospore is formed ability to inactivate spores inside the original cell  Endospore is released when condition becomes favorable  Endospores are the most resistant life forms known resistant to heat (they resistant to high temp. survive boiling), desiccation, ultraviolet light, and bactericidal chemical agents 9 http://si.wsj.net/public/resources/images/BA-AQ717_Steris_NS_20091002222235.jpg Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Characteristics of bacterial growth  By binary fission  Growth slows and ceases entirely (stationary phase) (i.e. one cell splits into two cells = generation/ doubling time) as nutrients are depleted, and toxic waste products accumulate.  Stages of bacterial growth curve:  Most cells in a stationary phase No. of cells increases are not dead (if they are diluted exponentially with time (the into fresh growth medium, exponential or log phase of exponential growth will resume growth) after a lag phase) The minimum doubling time can be as short as 10 min. or as long as several days. E.g. for a rapidly growing species such as E. coli in a nutritionally complete medium, a single cell can give rise to some 10 million cells in 10 just 8 hours Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Identifying bacteria by the way they grow on agar (nutrient)  How is a Surface growth done?  Identification of bacterial species through gross A single bacterial cell is characteristics of colonies, placed on a solid agar namely: (nutrient) surface colour The plate is incubated at 30 – 37 ℃ shape For rapidly growing species adherence produce visible colonies smell (each containing millions of cells) overnight surface texture  Bacterial colony morphology includes size, color, overall shape, elevation, consistency, and the appearance of the margin of the colony. 11 http://www.bacteriainphotos.com/bacteria%20photos.html Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins For reference only Terms to describe gross bacterial colonical morphology How many type of bacterial colonies can you identify?  Two types of bacteria based on oxygen requirement – Aerobes or anaerobes  Aerobes  Anaerobes: They use oxygen to derive They do not need oxygen to energy from glucose to live release energy from glucose and reproduce (The by- during the process of glycolysis. (By-products are CO2 and products are water and CO2 lactic acid) + energy) Obligate anaerobes – lives in Obligate aerobes – air (with absence of O2 2 types of aerobes 20% of oxygen) Aerotolerant anaerobes – do not Microaerophilic aerobes need O2 , but can tolerate the need on 5% of oxygen to presence of O2 (air) thrive Facultative anaerobes –survive in the presence or absence of oxygen  Many bacteria isolated from clinical specimens are facultative 14 anaerobes Two types of bacteria based on oxygen requirement – Aerobes or anaerobes microarephilic  Characteristics of pathogenic bacteria Characteristics Bacterial structures: Flagella: enable flagellated bacteria to invade areas of the body that nonflagellated bacteria cannot reach; may enable bacteria to “escape” from phagocytes Capsules: Serve an antiphagocytic function (they protect encapsulated bacteria from being phagocytized) Pili: Enable bacteria to attach to surfaces Exoenzymes (enable pathogens to evade host defenses, invade, and cause damage to body tissues): Coagulase: Enables bacteria to produce clots Kinase: Enable bacteria to dissolve clots Toxins: Endotoxins: components of the cell walls of Gram-negative bacteria; causes fever and septic shock Exotoxins: poisonous proteins that are released from the cells that produce them Neurotoxins: Cause damage to the central nervous system Enterotoxins: Cause gastrointestinal disease Antigenic variation: Antigenic variation: some pathogens periodically change their surface antigens (antibodies from the host become worthless) 16 http://www.humanillnesses.com/images/hdc_0001_0001_0_img0044.jpg Classification of medically important bacteria  Classification of medically  The three general shapes of important bacteria can be based bacteria are cocci, bacilli (rod), on: and curved or spiral-shaped. Physical properties of cell wall  A bacterial species having cells Morphology of different shapes is said to be pleomorphic. Growth inside or outside host cell Gram reaction Shape Oxygen tolerance  A bacterium’s Gram reaction, basic cell shape, and morphological arrangement are very important clues to its identification. 17 Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Classification of bacteria Gram reaction:  Gram positive bacteria Have thick peptidoglycan cell wall Give blue-purple color  Gram negative bacteria Have more complex cell wall Composed of two membranes Outer membrane: presence of lipopolysaccharide (LPS) that is antigenic and toxic Give pink-red color  Gram-variable bacteria Neither consistently blue to purple nor  Both Gram and acid-fast staining pink to red after Gram staining (are not procedures are “differential staining decolorized by acid-alcohol mixture due to procedures” – to differentiate one waxes in cell walls) group of bacteria from another e.g. Mycobacterium tuberculosis 18 Acid-fast stain is used (acid-fast bacteria are red after staining Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Part II: Examples of medically important bacteria and bacterial diseases 19 Some examples of medically important bacteria Staphylococcus aureus Cocci Gram positive bacteria Streptococcus Bacilli pneumoniae Cocci Escherichia coli Medically important Gram negative Bacilli bacteria bacteria Helicobacter pylori Curved bacilli Vibrio cholerae Gram-variable Bacilli Mycobacterium bacteria tuberculosis 20 Staphylococcus aureus  General features Facultative anaerobic bacteria Round shape (in bunches like grapes) Gram-positive cocci Catalase positive Coagulase positive Non-motile Hardy (resistant to heat and drying) Wash hand before and after contact with food or in contact with potentially infected individuals Can be very difficult to treat (especially those contracted in hospitals) as they become resistant 21 to antibiotics http://microbewiki.kenyon.edu/index.php/Hospital- acquired_Methicillin_Resistant_Staphylococcus_Aureus_(MRSA) http://www.uwyo.edu/molb2210_lect/medmicro/info/biochemical_tests.htm How does S. aureus invade the system?  S. aureus disease may be largely  Diseases caused by S. aureus: or wholly result of : skin and soft tissue infection actual invasive infection - S. aureus infection (small & toxins in the absence of superficial abscesses) infection (e.g. food respiratory infection poisoning) - Pneumonia (important a combination of infection complication of influenza) and toxin production food poisoning - Staphylococcal gastroenteritis 22 Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Boils (S.aureus infection) Food poisoning – Staphylococcal gastroenteritis  Staphylococcal food intoxication  Symptoms: results from consuming food nausea, vomiting, and diarrhea are contaminated with the toxin produced acute following a short incubation by S. aureus period (less than 6 hours)  Contaminating food rich in protein  Short incubation period - because the and/or salty (e.g. egg salad or cream toxin in the food has already been pastry, ham) and improperly formed by the staphylococci before the refrigerated food is ingested  Attack is usually self-limiting  S. aureus multiplies rapidly in food at room temperature and produces toxin  Toxin is (= an enterotoxin ) causes  Prevention: gastroenteritis or inflammation of the Proper hand washing techniques lining of the intestinal tract. when handling food.  Thorough cooking destroys the Proper sanitation of food contact bacteria, but the toxin is very resistant surfaces and utensils. to heat, refrigeration, and freezing. Refrigerate and hold foods at 4ºC or below. 24  Heat-resistant toxins are able to withstand subsequent reheating Chill food to 4ºC within 4 hours.  Treating Staphylococcus aureus infection is NOT easy  Serious S. aureus infections require aggressive Two new antibiotic was used treatment: instead of penicillin G, Resistant to penicillin G and others methicillin or oxacillin. due to transposons The increased use of these antibiotics has caused them to Transposons (as internal mutagenic become resistant agents): mobile genetic elements have ability to move from place to place on These strains are known as methicillin-resistant S. aureus the chromosome and into and out of (MRSA). plasmids responsible for most of the genetic variability in natural bacterial populations and for the spread of antibiotic resistance genes Choice of antibiotics is complicated by the frequent presence of acquired 26 antibiotic resistance determinants Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Methicillin-resistant S. aureus (MRSA)  Hospital-acquired MRSA (HA-  Community-acquired MRSA (CA- MRSA) MRSA) In recent decades, a high percentage Infections were documented in the (often 50%) of hospital S. aureus mid-1990s, occurring in individuals isolates are resistant to methicillin or who had no previous risk factors for oxacillin MRSA infections (e.g. exposure to hospital) MRSA infections are associated with worse outcomes: Most common clinical manifestations: skin and soft tissue – longer hospital and intensive infections e.g. abscesses or cellulitis care unit stays Emerging antibiotic-resistant strains – longer durations of mechanical of S. aureus that infect otherwise ventilation healthy individuals (community- – higher mortality rates acquired infections) are often more HA-MRSA strains are also virulent than the more common frequently resistant to many other strains that originate in hospitals. antibiotics, some being sensitive only to glycopeptides such as 27 vancomycin. Comparison of HA-MRSA and CA-MRSA HA-MRSA (hospital strain) CA-MRSA (community strain) Patients Typically elderly, Typically young and chronically ill healthy Infection site No obvious infection site. Often occur in skin and Infection of surgical soft tissues wounds, open ulcer and intravenous line Medical More likely in patients with No significant medical history a history of MRSA history or health care infections, recent surgery, contact admission to a hospital or nursing home Transmission Occurs in health care Occurs in the community. settings May spread in families & sport teams Antibiotic Multidrug antibiotic More virulent than HA- susceptibility resistance often occurs MRSA. Sensitive to 28 many antibiotics microareophilic Streptococcus pneumoniae (pneumococcus)  General features Aerotolerant anaerobic bacteria Ovoid to spherical in shape, occurring as pairs or chains Gram-positive diplococci Catalase negative Non-motile 30 http://www.cs-tele.com/product-images/strap/hand/hand-strap1.jpg http://www.sciencephoto.com/image/13022/530wm/B2360145-Streptococcus_bacteria-SPL.jpg Streptococcus pneumoniae Diseases caused by S. pneumoniae :  Pneumonia (infections of lung):  Meningitis (infection of the brain membranes): fever, shortness of breath, chill, cough Death in old Fever, stiff neck, confusion, adults especially cancer hearing loss, high mortality patients with low immunity rate  Bacteremia (blood stream  Otitis media (middle ear infection): infections): Symptoms similar to Often in children, ear pain, pneumonia and meningitis, fever, discharge, leads to joint pain and chills hearing loss 31 http://drpaul.com/oldsite/illnesses/images/midear.gif http://www.drugs.com/health-guide/images/204872.jpg http://www.searchhomeremedy.com/wp-content/uploads/2013/09/Meningitis.jpg Streptococcus pneumoniae  Infection can be:  Mainly spread through droplets endogenous (in a carrier via: who develops impaired coughing resistance to the organism) sneezing exogenous (by droplets from the nose of a carrier) close contact with the patient serious or even life- threatening contact with materials soiled with the bacteria  Pneumococci are commonly found in the nose and throat of  Treatment by antibiotics: healthy people, particularly in Penicillin G children vancomycin and ceftrixone (for Penicillin G resistant strains) 32 Streptococcus pneumoniae Prevention:  Maintain good hygiene practices  Have vaccination to prevent the spread of disease A 23-valent pneumococcal Wash hands frequently to polysaccharide vaccine keep the hands clean. (23vPPV) can protect against Cover your mouth and/or 23 pneumococcal serotypes nose with tissue paper when for the high-risk individuals coughing or sneezing. over age 2 years (e.g. elderly) Dispose of the soiled tissues A 13-valent vaccine has properly, e.g. into a rubbish recently been approved for bin with lid, and then wash use in infants over the age of hands thoroughly. 6 weeks Maintain good ventilation in indoor areas. If having respiratory tract infection symptoms, put on a surgical mask. 33 Escherichia coli  E. coli are commonly found in our large intestine as part of the normal flora When does it become a BAD bacteria? Commensal E. coli Deletion, point mutation, rearrangement  Pathogenic E.coli The “virotype” differs from Dysentary Meningitis the normal flora E. coli by acquiring genes that encode new virulence factors Diarrhoea UTI allowing for toxin production and attachment HUS to or invasion of host cells. 36 http://www.nature.com/nrmicro/journal/v2/n2/images/nrmicro818-f5.gif Escherichia coli  General features Facultative anaerobic bacteria Rod shape Gram-negative Catalase positive Oxidase negative (lack cytochrome c oxidase)  E. coli is part of the normal flora in the colon of humans and other animals  Can be found in fecal contaminated food or water  Can be pathogenic both within and outside the gastrointestinal tract (e.g. urinary tract)  E.coli species possess three types of antigens : O, K, and H.  Pili facilitate the attachment of the bacterium to 37 human epithelial surfaces. Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Escherichia coli  Pathogenic E.coli  Clinical significance: intestinal disease “virotypes” differ from the Commonly transmitted by the fecal–oral normal flora E. coli by the route, with contaminated food and water acquisition of genes that serving as vehicles for transmission encode new virulence Five types of intestinal infections (differ in factors allowing for toxin pathogenic mechanisms): production and attachment 1. enterotoxigenic E.coli (ETEC) to or invasion of host cells. 2. enteropathogenic E.coli (EPEC) 3. enterohemorrhagic E.coli (EHEC)  Common cause of: 4. enteroinvasive E.coli (EIEC) Diarrhea (intestinal 5. enteroaggregative E.coli (EAEC) diseases) E.coli all are basically the same organism, Urinary tract infections differing only by the acquisition of specific (UTI) pathogenic traits. Neonatal meningitis EHEC infection should be suspected in all patients with acute bloody diarrhea, 38 particularly if associated with abdominal tenderness and absence of fever. Traveler’s diarrhea  Foodborne illness (ETEC & EHEC)  Enterotoxigenic E. coli (ETEC): Infects only humans From infected food/water Person-to-person contact  ETEC colonizes the small intestine and produces a heat resisting enterotoxin (= toxin of the intestine) Toxin stimulates increased in cAMP production and cause prolonged hypersecretion of chloride ions and water while inhibiting the reabsorption of Action of E. coli LT (heat-labile toxin) sodium. 39 Result: diarrhea Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins http://callisto.ggsrv.com/imgsrv/Fetch?recordID=fdic_0001_0002_0_img0273&contentSet=GALE&banner =53c2d1d4&digest=293307a9cfa028265e0d55b7120f1c00 http://travelertips.org/tips/wp-content/uploads/2013/02/eating_india.jpg Causes of diarrhoea Severe diarrhea with blood in stool Enterohemorrhagic E. coli (EHEC):  EHEC binds to cells in the large  Reduce risk of infection by: intestine, and produces toxins thoroughly cooking ground that destroy microvilli beef and pasteurizing milk Causes a severe form of discarding the outer leaves bloody diarrhea (hemorrhagic of leafy vegetables before colitis) and acute renal failure washing (hemolytic uremic immersing fresh vegetables syndrome – HUS) and sudden in water and washing kidney failure thoroughly with running water to remove dirt and e.g. EHEC O157:H7 surface microorganisms  Primary reservoir of EHEC: thoroughly cooking cattle vegetables (including sprouts, cucumbers, tomatoes and lettuce) before consumption 41  Hygiene! Clean food! http://en.ria.ru/images/16441/98/164419823.jpg Causes of diarrhoea  43 http://en.ria.ru/images/16441/98/164419823.jpg Extraintestinal disease by E. Coli  Clinical significance: extraintestinal disease  Symptoms: Source of infection: frequently the patient's own Urinary frequency flora (own E. coli is non-pathogenic in the intestine) Hematuria (blood in urine) However, it causes disease in that individual Dysuria (difficulty or pain on when the organism is found, e.g. in the bladder urination) or bloodstream (normally sterile sites). Pyuria (high white blood cells E.coli is the top isolate from blood and urine in in urine) Hong Kong in 2021. Fever can indicate infection of  Urinary tract infections (UTI) kidney E. coli is the most common cause of UTIs, UTI: one or more parts of the urinary system (kidneys, ureters, bladder, and urethra) become infected Fecal contamination can lead to entry of E. coli  Neonatal meningitis (most common facultative organisms found in stool) into the urethra In infants, E. coli K1 and group B streptococci are the These bacteria then move up into the bladder 45 leading causes of neonatal (and sometimes ascend into the kidney), meningitis. http://umm.edu/system-hospital- producing infection. sites/uchs/health/medical/reports/articles/urinary-tract-infection Escherichia coli Treatment: Prevention:  Intestinal diseases:  No vaccine or preventive drug is available. maintenance of fluid and electrolyte balance  Diarrhea can best be prevented by care in selection, preparation, and antibiotics may shorten consumption of food and water. duration of symptoms (but  Spread of infection between resistance is nevertheless people can be controlled by hand widespread) washing and disinfection.  Extraintestinal diseases: require antibiotic treatment antibiotic sensitivity testing of isolates is necessary to determine the appropriate choice of drugs. 46 Helicobacter pylori Before 1982 stomach problems were blamed on inflammation of the stomach wall Patients were required to keep a low acidity in the stomach (using anti-acid tablet), eat soft and warm food, no spicy food And hope for the best Two Australian scientists Barry Marshall and Robin Warren followed by British scientist Stewart Goodwin found that a bacteria was the cause of chronic stomach ache and gastric and duodenal ulcers and even cancer of the stomach. How would you now treat stomach ulcer due to H. pylori? 47 http://www.wakegastro.com/wp-content/uploads/2012/02/Peptic-Ulcer2.gif Helicobacter pylori  General features Microaerophilic bacteria Curved or spiral rod Gram-negative Multiple polar flagella give the organism rapid, corkscrew motility Urease positive 48 Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Helicobacter pylori  Commonly causes:  H. pylori colonizes gastric mucosal cells in the stomach acute gastritis (last about 1  Cause a chronic inflammation of the week) mucosa duodenal and gastric ulcers  Secretes enzyme urease, producing  H. pylori is unusual in its ability ammonium ions that neutralize to colonize the stomach (low pH stomach acid (favor bacterial normally protects against multiplication) bacterial infection)  Ammonia can damage the gastric  H. pylori infections are relatively mucosa, and may also potentiate the common and worldwide in effects of a cytotoxin produced by H. distribution. pylori.  Transmission is thought to be  H. pylori appears to be a risk factor from person to person (the for development of gastric organism has not been isolated carcinoma and gastric B-cell from food or water) lymphoma.  Untreated, infections tend to be chronic and lifelong. 49 Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Helicobacter pylori  Symptoms:  Treatment: Pain or discomfort, burning Combination therapy with usually in the upper abdomen two or more antibiotics due to rapid appearance of Sensation of swelling in the resistant strains belly A typical regimen includes Fast satiation (usually after tetracycline plus eating only a small amount of metronidazole plus a proton food) pump inhibitor omeprazole. Nausea or vomiting  Prevention: Dark stool No vaccine or preventive Anemia drug is available. Duodenal ulcerStomach ulcer Duodenitis Stoma ch cancer 51 http://www.tabletsmanual.com/wiki/read/helicobacter_pylori Vibrio cholerae  General features  Vibrio are the most common bacterial causative agents in Facultative anaerobic bacteria food poisoning resulting from the consumption of shellfish Short curved or spiral rod  Vibro cholera, serogroup O1 strains are associated with Gram-negative epidemic cholera Rapidly motile due to single polar  Outbreaks of V. cholerae flagellum infection have been associated with raw or undercooked Growth of many Vibrio species seafood harvested from contaminated waters. requires or is stimulated by NaCl  Vibrio are abundant in the aquatic environment.  Most of them require 2 to 3% NaCl or a seawater base for optimal growth.  Vibrio are associated with live seafood as they form part of the indigenous microflora of the environment at the 53 time of seafood capture or harvest. Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Vibrio cholerae  Following ingestion, V. cholerae  Treatment: infects the small intestine. Replacement of fluids  V. cholerae secrete a toxin and electrolytes ( prevent (enterotoxin -cholera toxin) shock) cause cholera  Chlorea toxin casue an Antibiotics (e.g. outflowing of fluid (ions and doxycycline) can shorten water) into the intestine. the duration of diarrhea  Cause massive loss of fluid and and excretion of the electrolytes from the body organism  After an incubation period (from  Prevention: hours to a few days), profuse Reduce fecal watery diarrhea (rice-water stools) begins. contamination of water supplies and food  Untreated, death from shock may occur in hours to days (Death Adequate cooking of rate may exceed 50 %) foods  V. cholerae is transmitted by drinking water and eating food that has been contaminated by 54 the feces of an infected person. For reference only Flesh-eating infection caused by Vibrio vulnificus Mycobacterium tuberculosis  General features  Distinguished characteristics: Strictly aerobic Acid-fast Long rod (filamentous) Slow growth Lipid-rich cell wall Not stained by Gram stain Stained with acid-fast stain (appear pink) Non-motile Resistant to drying but not to heat or ultraviolet irradiation Grow slowly with generation time of 8-24 hrs 56 Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins http://www.michigan.gov/images/mdch/TB_CXR_191643_7.jpg http://www.newskarnataka.com/uploaded/tb.jpg Symptoms of active TB  Signs and symptoms of active pulmonary TB include: Coughing that lasts three or more weeks Coughing up blood Chest pain, or pain with breathing or coughing Unintentional weight loss Fatigue Fever Night sweats Chills Loss of appetite  Extrapulmonary TB includes meningitis, kidneys infection, spine infection, bones infections, etc Mycobacterium tuberculosis  Mycobacterium tuberculosis is  Most people control the initial one of most successful pathogens infection by mounting a cell- of mankind, infecting one-third mediated immune response that of the global population and prevents disease but can leave a claiming two million lives every residual population of viable mycobacteria. year.  The ability of the bacteria to persist in the form of a long-term asymptomatic infection, referred to as latent tuberculosis  Approximately eight million people develop active tuberculosis (TB) every year, with two million dying from the disease.  It is estimated that up to two billion people have been infected with the causative agent, Mycobacterium tuberculosis. 58 Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Mycobacterium tuberculosis  Between 5 - 10% of individuals who  Patients with active pulmonary become infected subsequently tuberculosis shed large numbers of develop clinical disease. organisms by coughing, creating aerosol droplet nuclei.  Primary TB develops within 1 or 2 years after an initial infection and,  Because of resistance to particularly in children, is often dessication, the organisms can associated with disseminated remain viable as droplet nuclei disease. suspended in room air for at least 30 minutes.  Post-primary TB develops later in life, and can be caused either by  The principal mode of contagion is reactivation of bacteria remaining person-to-person transmission by from the initial infection or by inhalation of the aerosol. failure to control a subsequent reinfection.  A single infected person can pass the organism to numerous people in  Post-primary TB is predominantly a an exposed group, such as a family, pulmonary disease, involving classroom, or hospital ward without extensive damage to the lungs and proper isolation. efficient aerosol transmission of bacteria.  The risk of disease is highly dependent on the immune status of the host; coinfection with HIV 59 markedly increases the incidence of both forms of disease Development of tuberculosis in the lungs Mycobacterium tuberculosis https://desmondtutuhealthfoundation.org.za/blog_post/tuberculo sis-vaccine-bcg/ Mycobacterium tuberculosis  Transmission occurs  Prevention - public health measures: via airborne droplets produced by Chest radiographs infected people during coughing, sneezing and even talking or singing Case registries Contact tracing usually following prolonged direct contact with infected individuals  Treatment: Several chemotherapeutic agents are effective against M. tuberculosis. Multiple drug therapy is used to delay or prevent emergence.  Duration of treatment for tuberculosis Standard therapy: 12-18 months Short therapy: (6 months) effective in some patients with uncomplicated tuberculosis 62 Images from ebook: Lippincott’s illustrated reviews: Microbiology (3 rd Ed.), Lippincott Williams & Wilkins Latent Tuberculosis Infection (LTBI)  A state of persistent immune  TST (Tuberculin Skin Test) response to stimulation and IGRAs (Interferon-Gamma by Mycobacterium Release Assays) are the main tests tuberculosis antigens without currently available for the diagnosis evidence of clinically manifested of LTBI. active TB.  LTBI can be effectively treated in  One-third of the world’s population order to prevent progression to is estimated to have LTBI: they do active TB, thus resulting in a not have active TB disease but may substantial benefit for both the develop it in the near or remote individual and the community. future, a process called “TB Currently available treatment reactivation”. options allow to reduce by at least 60% the risk of developing active TB. 63 Latent Tuberculosis Infection (LTBI) Victory is always possible for the person who refuses to stop fighting. Napoleon Hill Exercise 3