Human Diseases Caused by Bacteria PDF

39 Human Diseases Caused by Bacteria 1 Bacterial Pathogens Of the bacterial species, only a few are pathogenic to humans – some pathogens have been known since antiquity – others have been recently recognized as disease producers 2 Airborne Diseases Most involve the respiratory system Some are skin...

39 Human Diseases Caused by Bacteria 1 Bacterial Pathogens Of the bacterial species, only a few are pathogenic to humans – some pathogens have been known since antiquity – others have been recently recognized as disease producers 2 Airborne Diseases Most involve the respiratory system Some are skin diseases 3 4 Diphtheria Caused by Corynebacterium diphtheriae – Gram-positive – lysogenized strains produce an exotoxin that inhibits protein synthesis and is responsible for pathogenesis – resistant to drying Airborne transmission by nasopharyngeal secretions – crowding increases likelihood of transmission 5 Diphtheria Usually observed in individuals >30 years old with weakened immunity to diphtheria toxin and living in tropical areas Cutaneous diphtheria – infection at a wound or skin lesion – slow-healing ulceration 6 Diphtheria Diagnosis – observation of pseudomembrane in throat – bacterial culture Treatment, prevention, and control – antitoxin neutralizes unabsorbed exotoxin in patient’s tissues – antibiotic therapy – immunization with DPT or acellular DTap vaccine 7 Legionnaires’ Disease and Pontiac Fever Caused by Legionella pneumophila – fastidious, Gram-negative rod – harbored by free-living amoebae and ciliated protozoa Spread by airborne transmission from environmental reservoir to human host – soil, aquatic ecosystems, air-conditioning systems, and shower stalls 8 Legionnaires’ Disease (Legionellosis) Reproduction of bacterium in alveolar macrophages causes localized tissue destruction – produce cytotoxic exoprotease Clinical manifestations – fever, cough, headache, neuralgia, and bronchopneumonia – severe in immunocompromised Treatment, prevention, and control – isolation of bacteria and immunodiagnostics – symptomatic/supportive therapy and antibiotic therapy – eliminate nosocomial spread – Identification/elimination of environmental source 9 Meningitis Inflammation the brain or spinal cord meninges Many causes including bacterial – bacterial may be diagnosed by Gram stain of cerebrospinal fluid (CSF) – culture of CSF may or may not grow bacteria Major bacterial causes include – Streptococcus pneumoniae, Neisseria meningitidis (serotypes), and Haemophilus influenza (serotype b) – may be endogenous infection (normal biota) N. meningitidis (meningococcus) causes epidemic meningitis 10 Aseptic Meningitis Syndrome Clinical manifestations similar to bacterial meningitis but show no microbial agent in gram-stained specimen and in culture Treatment, prevention, and control – must rule out bacterial diagnosis – treatment difficult 11 Meningitis Transmitted by respiratory droplets Clinical manifestations – initial respiratory illness or sore throat interrupted by one of following: vomiting, headache, lethargy, confusion, and stiffness in neck and back may be fatal 12 Meningitidis Treatment, prevention, and control – N. meningitidis antibiotics (also prophylactic), vaccine recommended for college students, others – H. influenzae pneumonia and meningitis kill 3 million worldwide/year vaccine (Hib) reduced cases to 1/100,000 – S. pneumoniae vaccine and antibiotics 13 Streptococcal Diseases Caused by strep, group of Gram-positive bacteria – Streptococcus pyogenes one of most important pathogens group A β-hemolytic streptococci (GAS) – virulence factors extracellular enzymes that break down host molecules streptokinases – dissolve clots streptolysin O and S – kill host leukocytes capsules and M protein for attachment 14 Streptococcal Diseases S. pyogenes – widely distributed, some carriers – transmission respiratory droplets, direct or indirect contact Diagnosis – based on clinical and laboratory findings – rapid diagnostic tests available 15 Streptococcal Pharyngitis Common infection called strep throat Spread by droplets of saliva or nasal secretions Infection in throat (pharyngitis) or tonsils (tonsillitis) Signs and symptoms of disease not diagnostic because many viral infections have similar presentation Physical manifestations – redness, edema, exudate in 50% and lymph node enlargement in throat 16 Streptococcal Pharyngitis Diagnosis – rapid kits Treatment and control – antibiotics important for children to lessen chance of complications such as rheumatic fever and glomerulonephritis – control by preventing contact with contaminated materials or discharges from infected individuals 17 Poststreptococcal Diseases Glomerulonephritis (Bright’s disease) and rheumatic fever 1–4 weeks after an acute streptococcal infection Non-supporative (nonpus-producing) Most serious problems associated with streptococcal infections in U.S. 18 19 Glomerulonephritis Inflammatory disease of renal glomeruli – a type III hypersensitivity Clinical manifestations – edema, fever, hypertension, and hematuria – may spontaneously heal or may become chronic Diagnosis – clinical history, physical findings, and confirmatory evidence of prior streptococcal infection Treatment, prevention, and control – antibiotic therapy (to kill residual bacteria), otherwise no specific therapy 20 Rheumatic Fever Autoimmune disease involving heart valves, joints, subcutaneous tissues, and central nervous system Clinical manifestations – vary widely, making diagnosis difficult Treatment, prevention, and control – therapy directed at decreasing inflammation and fever, and controlling cardiac failure – treatment with salicylates and corticosteroids 21 Arthropod-Borne Diseases Generally rare Some are of historical interest (such as plague and typhus) Some newly emerged (such as Lyme disease and erlichiosis) 22 Lyme Disease LD or Lyme borreliosis Most common tick-borne disease in the U.S. Caused by Borrelia burgdorferi (most common in U.S.), B. garinii, and B. afzelii (most common in Europe and Asia) 23 Lyme Disease Transmitted from animal reservoirs by ticks (Ixodes scapularis and I. pacificus) – deer, field mice, and woodrats Complex disease – clinical manifestations vary with three stages of disease – initial, disseminated, late stage 24 Plague Yersinia pestis – Gram-negative Transmission rodent to human – bite of infected flea, direct contact with infected animal or product, inhalation contaminated airborne droplets In body, multiply in blood and lymph – survive and proliferate in phagocytic cells – enlarged lymph nodes (buboes) 25 Peptic Ulcer Disease and Gastritis Caused by Gram-negative Helicobacter pylori – colonizes gastric mucus-secreting cells – produces urease, which acts to increase pH – releases toxins that damage epithelial mucosal cells Class I carcinogen 26 Sexually Transmitted Diseases Major worldwide public health problem (~300 million new cases/year) Some also transmitted by nonsexual means Some cured easily, others difficult or impossible to cure Most frequent in 15–30-year age group but also others sexually active 27 28 Chlamydial diseases Chlamydia is the most frequently reported sexually transmitted bacterial disease – 1.3 million cases in US in 2010 – number underestimated due to asymptomatic cases – Chlamydia trachomatis is the most commonly isolated species – transmitted through anal, oral, and vaginal sex; can also be transmitted from mother to child during delivery 29 Caused by Neisseria gonorrhoeae Gonorrhea – Gram-negative, oxidasepositive diplococcus – referred to as gonococcus – attaches to microvilli; phagocytosed by mucosal cells Disease of mucous membranes of the genitourinary tract, eye, rectum, and throat Can also be transmitted from mother to child during birth, causing – ophthalmia neonatorum (conjunctivitis of the newborn) 30 Gonorrhea Opthalmia neonatorum (conjunctivitis of the newborn) – newborns’ eyes infected as they pass the birth canal of an infected mother – also caused by Chlamydia – prevention is by antibiotic eye drops or silver nitrate in newborns at birth 31 Syphilis Caused by Treponema pallidum subsp. pallidum Venereal syphilis – sexually transmitted Congenital syphilis – acquired in utero 32 33 And very many others … check out Med 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