Air Microbiology


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Air Microbiology by Saad Farooqi

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Air Microbiology

  1. 1. Air Microbiology Saad Farooqi Department of Environmental Sciences University of Swat
  2. 2. Air Microbiology • Aerobiology is defined as the study of life present in the air. • Aeromicrobiology relates to the study of environmentally relevant microorganisms. • Microorganisms exist within 300-1000 feet of earth’s surface that have become attached to fragments of dried leaves, straw or dust particles light enough to be blown by wind. • In dry whether the microbial load of air is high while in wet weather the rain washes the microorganisms from the air.
  3. 3. • Air is a poor medium for microbial growth – too dry and no nutrients • Spore forming and Gram- positive bacteria are resistant to drying • Dust, water droplets in air carry microbial populations from one place to another • Sneezing, coughing, talking are efficient methods of transferring microbes from one respiratory tract to another 100 m/sec, 10000 – 100000 bacteria
  4. 4. • Liquid and dust particles settle in the respiratory tract depending on their velocity and size • Microorganisms colonize specific locations in the respiratory tract
  5. 5. Streptococcal diseases • S. pyogenes, S. pneumoniae •Nonsporulating, fermentive, anaerobic gram-positive cocci • S. pyogenes accounts for about half of sore throat cases, causes ‘Strep throat’ – enlarged tonsils, mild fever, tender cervical lymph nodes • S. pyogenes lysogenized with bacteriophage produce an erythrotoxin – small blood vessels are damaged, diffuse rash and fever called ‘scarlet fever’ • Systemic infection leads to necrotizing fasciitis – ‘flesh eating disease’ Streptococcus pyogenes
  6. 6. Hemolysis of blood agar • Diagnosis of S. pyogenes infection from throat swab includes fluorescent Ab staining, or culturing on blood agar for hemolysis • S. pneumoniae causes difficult lung infections (pneumonia) due to the bacterial capsule • Infection can spread to inner ear,, heart with mortality rate around 10% • Vaccination is possible with capsule polysaccharide, treatment with antibiotics
  7. 7. Diptheria • Childhood respiratory illness caused by Cornyebacterium diptheriae infection. • Gram-positive non-motile aerobic rods • Spread via fluid droplets entering the lung • Bacterial enzyme called neuraminidase interacts with epithelial glycoproteins for successful invasion • Inflammatory response in throat tissues causes characteristic ‘pseudomembrane’ of damaged host cells, leukocytes and C. diptheriae. • Death can occur from obstructed breathing and the effects of the diptheria exotoxin pseudomembrane
  8. 8. • Treatment includes antibiotic therapy in conjunction with diptheria antitoxin – neutralizing antibodies against the toxin • Diptheria toxoid (formalin treated exotoxin) is part of the
  9. 9. Whooping cough (pertussis) • Infection by Bordetella pertussis •Small, gram-negative, aerobic coccobacillus • Attaches to epithelial cells of upper respiratory tract using an adherence protein called filamentous hemagglutinin antigen •Produces an exotoxin that induces cAMP production, and an endotoxin that may induce the cough •Recurring spasmodic coughing that lasts up to 6 weeks • Nasopharyngeal aspirate is plated on blood- glycerol-potato extract agar to diagnose
  10. 10. • Vaccine consists of killed whole cells or purified proteins derived from Bortedella pertussis • Rise in the incidence of whooping cough. Why?
  11. 11. Tuberculosis (consumption) Lung tubercles • Infection by gram-positive bacillus Mycobacterium tuberculosis • Extremely contagious by respiration • Primary infection usually occurs by inhalation – bacteria are usually engulfed but survive within activated macrophages of the lung – structures called tubercles • Primary infection is diagnosed using the tuberculin test, and usually provides cell-based immunity
  12. 12. • Secondary infection or reactivation of dormant bacteria can cause extensive lung tissue damage • Pathology most often occurs in very young, elderly, malnourished, immune- compromised people 1.5 million deaths annually Treatment includes streptomycin antibiotic, as well as the growth factor analog isoniazid Isoniazid is an analogue of nicotinimide, required For mycolic acid synthesis in Mycobacterium
  13. 13. Leprosy (Hansen’s disease) lepromatous lesion tubercular lesion • Infection by Mycobacterium leprae, can not be cultured in the lab • Intracellular parasite grows in macrophages • Folded, bulblike lesions on the body containing a billion bacteria/gram of tissue • Severe form is lepromatous leprosy which can also affect peripheral nerves and motor function • Milder form is tubercular leprosy, in which fewer bacteria can be recovered • As, many as 12 million cases
  14. 14. Meningitis and meningococcemia • Infection by Neisseria meningitidis • Gram-negative, aerobic encapsulated • Infection starts via the airborne route, spreads to blood and can cause 1) meningococcemia – sepsis, coagulation, shock, 17% mortality 2) meningitis – inflammation of membranes lining the central nervous system, sudden headache, vomiting, stiff neck • Treated by penicillin G or chloramphenicol
  15. 15. Measles, Mumps, Rubella • Measles caused by a paramyxovirus, nasal discharge, sore throat, fever, characteristic rash. Now occurs in isolated outbreaks • Mumps caused by a different paramyxovirus, inflammation of salivary glands, can spread through bloodstream to testis and brain • Rubella caused by a togavirus, generally milder than measles but can be transmitted congenitally • All three are effectively managed by the MMR vaccine
  16. 16. Chickenpox and shingles • Both caused by the same herpes virus • Chickenpox is transmitted by respiration and disseminated in bloodstream causing characteristic rash • Dormant virus in nerve cells can migrate to surface skin causing shingles (zoster). Usually strikes elderly and immune-compromised •Decreased incidence due to new vaccine
  17. 17. Common cold rhinovirus adenovirus • 85% caused by ssRNA viruses, especially rhinovirus and coronavirus, 15% caused by DNA viruses such as adenovirus • Average person gets 3/year • Nasal inflammation and obstruction, general malaise but no fever • Aerosol transmission • Vaccination is extremely unlikely. Why? • Specific anti-rhinoviral drugs are under development: Block viral coat protein to prevent virus-cell recognition
  18. 18. Influenza • ssRNA orhomyxovirus, types A,B,C • Low grade fever, chills, fatigue, headache • Segmented RNA genome – infection by more than one strain leads to gene reassortment called antigenic shift • Mutations in important genes encoding the haemagglutinin and neuraminidase result in antigenic drift • Immunity generally comes from IgA to Ha and Neu antigens
  19. 19. • Severe localized epidemics occur every 2-3 years due to antigenic drift • Worldwide pandemics occur every 10-40 years due to antigenic shift • Vaccines are created using mixed population of strains from the previous year
  20. 20. Staphylococcus infections • gram-positive and nonsporulating, but resistant to drying. Therefore found on skin and mucus membranes • Infection often occurs at wound sites – especially nosocomial (hospital) infections • S. aureus produces a hemolysin exotoxin – lyses red blood cells, an enterotoxin - causing food poisoning, coagulase – blood clots around bacteria mask it from immune system, leukocydin – kills white blood cells • Toxic shock syndrome can be caused by inadequate feminine hygiene
  21. 21. Gastric ulcers and cancers • Infection by Helicobacter pylori in the non acid secreting mucosa of stomach • gram-negative motile, polar flagella • 80% of gastric ulcer patients are infected • Perhaps transmitted from contaminated food or water, or person-to person contact in unknown fashion • Mucosal layer protects from stomach acid, how it causes ulcers is unknown • Treated with a combination of antibiotics
  22. 22. Hepatitis • Infection of hepatocytes (liver cells) leading to inflammation, cirrhosis and sometimes cancer • Jaundice, hepatomegaly • Caused by a number of unrelated viruses: • A – person to person, vaccine • B – parenteral, vaccine, fatal, vaccine • D – defective virus requires B coat • C – parenteral, chronic • E – enteric, acute • G - perhaps asymptomatic • Universal precaution against blood-borne and sexually transmitted infections
  23. 23. Sexually transmitted infections • Fallacy – there is a technological solution to every problem • “The sex drive in some individuals is so strong that it will suppress the fear of disease, even AIDS”
  24. 24. Acquired immunodeficiency syndrome (AIDS) • Suite of disorders as a secondary consequence to infection by human immunodeficiency virus (HIV) • First recognized in 1981, now 50 million infected • HIV is a ssRNA retrovirus: reverse transcriptase enzyme generates a cDNA that integrates into host cell genome • HIV infects macrophages and TH cells
  25. 25. • An individual has AIDS if: 1) Tests positive for HIV AND 2) Has a drastically reduced number of TH cells OR 3) At least one unusual opportunistic infection or cancer such as Pneumocystis carinii pneumonia, toxoplasmosis, or Kaposi’s sarcoma (cancer of blood vessel
  26. 26. • HIV first infects macrophages expressing CD4 and CCR5 coreceptors • HIV next infects T cells expressing CD4 and CXCR4 coreceptors • HIV can exist in latent state as a provirus for long periods • Infected T cells express gp120 on their surface and fuse with uninfected T cells • Death of CD4 T cells leads to complete loss of cytokine production, cellular and humoral immunity is destroyed
  27. 27. • Typical course of a poor-prognosis HIV infection • Presence of HIV in the blood is routinely done by screening for anti-HIV antibodies • More sensitive technique is reverse-transcription PCR (RTPCR) • Blood products are screened using enzyme-linked immunosorbent assay (ELISA)
  28. 28. • Pharmaceutical therapy for AIDS: • 1) Nucleoside analogs such as AZT inhibit reverse transcription • 2) Non-nucleoside Rt inhibitors • 3) Protease inhibitors specifically inhibit maturation of HIV proteins • Intensive vaccination research
  29. 29. • Majority of HIV infections are in people who can not afford treatment • Is this an ethical problem?
  30. 30. Bacteria Disease Streptococcus pyogenes Sore throat Corynebacterium diphtheriae Diphtheria Mycobacterium tuberculosis Tuberculosis Streptococcus pneumoniae Pneumococcal pneumonia Klebsiella pneumoniae atypical pneumonia Neisseria meningitidis Meningococcal meningitis Yersinia pestis Bubonic plaque Bordetella pertussis Whooping cough Haemophilus influenzae Influenza Nocardia asteroids Nocardiosis Air-borne human diseases of importance and their causative agent
  31. 31. Virus Disease Influenza virus Influenza Hantavirus Pulmonary syndrome Hepatitis virus Hepatitis Herpes virus Chicken pox Picorna virus Common cold Flavivirus Dengue fever Rubella virus Rubella Measles virus Measles Influenza virus Influenza Hantavirus pulmonary syndrome
  32. 32. Fungi Disease Aspergillus fumigatus Aspergillosis Blastomyces dermatiridi Blastomycosis Coccidioides immitis Coccidioidomyosis Cryptococcus neoformans Cryptococcosis Histoplasma capsulatum Histoplasmosis Pneumocystis carinii Pneumocystitis