Human Diseases

1

• Human Diseases
• Caused Primarily by Gram-Positive and
  Gram-Negative Bacteria  
• The Airborne Diseases Part I

2

• Airborne Diseases

3
Diphtheria
4

• Diphtheria - Corynebacterium diphtheriae
• General features
• Club shaped (coryne club in Greek)
  pleomorphic V-shaped rods
• Gram positive, non-sporing, non-motile
• Refractile granules give rise to heterogeneous
  staining
• Accumulate in stationary phase phosphate
  storage
• Metachromatic granules
• Volutin
• Babes-Ernst bodies
• Only humans serve as a reservoir for this
  microorganism

5

• Acute, contagious disease
• Affects mainly poor people living in crowded
  conditions unvaccinated
• Acute infection of the respiratory tract ?
  usually invading the tonsilar area
• Spread via respiratory route and contaminated
  milk (unpasteurized)

6

• Virulence factors/pathogenicity
• Exotoxin diphtheria toxin (AB exotoxin)
• Tox gene encoded by bacteriophage that integrates
  into bacteriums genome ? Prophage b (lysogenic)
• Protein synthesis inhibition (involving EF-2 and
  translocase)
• Can disseminate through bloodstream (toxemia) and
  affect nervous system, heart and kidneys
• Cord factor
• Glycolipid containing trehalose

7

• Symptoms/Presentation
• Dead tissue cells, WBC and RBC and bacterial
  cells form a dull gray exudate referred to as a
  pseudomembrane
• Can block airway in trachea suffocation
• Tracheotomy may be required
• Thick mucopurulant (mucous and pus) nasal
  discharge
• Fever
• Cough, sore throat
• Malaise (vague feeling of physical discomfort)
• Enlarged and tender cervical lymph nodes

8

• Laboratory culture swab the tonsilar area
• Tellurite added to medium (chocolate or blood
  agar)
• Enriches for C. diphtheriae and restricts growth
  of normal flora of the throat
• Tellurite is reduced to tellurium metal
  precipitate (dark gray to black colonies)

9

• Diagnosis
• Detection of toxin
• In vitro virulence test ELEK test
• Streak bacteria out on agar in lines
• Lay a paper strip containing anti-toxin antitoxin
  antibodies
• Include a positive control in parallel to
  patients sample
• Incubate and look for line of identity
  (precipitate caused by immune complexes)
• Inject guinea pig ? morbid symptoms/mortality

10

• Susceptibility test
• SCHICK Test (rarely used anymore)
• Diphtheria toxoid inject subcutaneously
• Wait 48 hours and note formation of induration in
  the absence of antibodies susceptible ?
  immunity not present
• If antibodies are present (immune) then toxin is
  neutralized ? no induration
• DTH response

11

• Treatment
• Antitoxin administered to neutralize the toxin
• Immediate administration based on symptoms rather
  than waiting for laboratory results
• Also administer penicillin or erythromycin

12

• Prevention
• Immunization (vaccination)
• Has protected USA from this disease
• Toxoid made from diphtheria toxin
• Part of DPT vaccine
• Diphtheria
• Pertussis
• Tetanus
• Administered at 2, 4, 6, and 15-18 months, and
  again at 4-6 years with boosters every 10 years
  recommended (especially if traveling to areas
  where diphtheria is endemic Asia, Africa,
  Central and South America and Russia)

13
Legionnaires Disease (Legionellosis)
14

• General Features
• Caused by Legionella pneumophila
• Gram negative rods
• This organism also causes Pontiac Fever (no
  pneumonia, self-limiting)
• 1976 American Legion convention in Philadelphia
  in one of the citys largest hotels
• 29 fatalities (182 participants)
• 1985 Stafford, England
• Cooling system
• 39 fatalities out of 163 people exposed

15

• Not spread person-to-person
• Bacteria normally found in soil and aquatic
  ecosystems
• Bacteria also found in air-conditioning systems
  and shower stalls
• Infection causes cytotoxic damage to lung alveoli

16

• Virulence factors/pathogenicity
• Mist inhaled from poor water cooling systems and
  mist machines in supermarkets
• Soil ? dust??
• Whirlpool filters, shower heads, nebulizers and
  hot water systems

17

• Endotoxin in cell wall
• Hemolysin generated
• Cytotoxin produced
• Bacteria divide within alveolar macrophages
• Inhibition of fusion of phagosome with lysosome
• Mediated by mip gene product (macrophage
  infectivity potentiator)
• Important in establishing pneumonia

18

• Symptoms
• Chest pain, dry (non-productive) cough
• Fever
• Headache
• Neuralgia
• Atypical pneumonia (bronchopneumonia)
• Abdominal cramping and gastrointestinal symptoms
  may also occur

19

• Laboratory culture
• Mueller-Hinton agar
• 1 Hemoglobin 1 Isovitalex (vitamins)
• 5 CO2
• Cell culture
• Grown in animals
• Guinea pigs
• Chick embryos
• Can survive in free-living amoebae (another
  potential source)

20

• Increased susceptibility
• Smokers
• Alcoholism
• Endotracheal intubation
• Chronic pulmonary diseases
• Patients on immunosuppressive therapy
• Transplant patients
• Autoimmune patients
• Anesthesia

21

• Diagnosis and treatment
• Isolation and serological identification needed
• Direct immunofluorescence (organisms cultured or
  obtained from sputum)
• Indirect immunofluorescence (patients serum
  antibodies to organism)
• Agglutination tests
• ELISA
• RIA on urine
• Erythromycin and/or rifampin

22
MeningitisNeisseria meningitidis, Streptococcus
pneumoniae, Haemophilus influenzae, Salmonella
choleraesuis (invades from GI tracts), Listeria
monocytogenes
23

• Meningitis - caused by a variety of organisms and
  conditions
• Bacterial (septic) meningitis is diagnosed by the
  presence of bacteria in the cerebrospinal fluid
• Bacterial meningitis is treated with various
  antibiotics, depending on the specific bacterium
  involved
• Aseptic (nonbacterial) meningitis syndrome is
  more difficult to treat but the mortality is
  generally low

24
Neisseria meningitidis(epidemic meningitis)
25

• General features
• Gram negative dipolococci (meningococci)
• Non-motile
• Oxidase positive
• Can oxidize dimethyl (and tetramethyl)
  para-phenylene diamine hydrochloride)
• Must be grown gt30oC
• Require special media ? sensitive to trace metals
  and fatty acids
• Chocolate agar (blood agar treated at 80oC for
  10)
• Decreases inhibitory effects of trace metals and
  fatty acids
• Incubated with 10 CO2
• Causes 2000-3000 cases of meningitis annually in
  USA

26

• Classification
• Serotypes based on common antigens
• Polysaccharide capsule
• Outermembrane proteins
• A-D, X-Z, L, W135 and 29E
• A,B an C are primarily responsible for meningitis
  outbreaks

27

• Virulence characteristics
• Obligate parasite of humans
• Often found in nasopharynx of asymptomatic
  carriers
• Spread via respiratory route
• Pili enable attachment to host cells
• Capsule resists phagocytosis
• Release large amount of endotoxin
• IgA1 protease produced

28

• Three stages
• First stage nasopharyngeal infection
• Minor inflammation or asymptomatic
• Lasts days to months
• Protective antibodies made
• Second state memingococcemia
• Microbes enter bloodstream
• Can be acute and rapid (death in 6-8 hours!)
• May take longer to ensue with fever, malaise and
  rash

29

• Sometimes lesion in joints, lungs, skin, internal
  organs and adrenal glands develop
• Endotoxin induced (TNF-alpha produced)
• Disseminated intravascular coagulation (DIC) may
  develop (Hageman factor)
• Clots disrupt circulation
• Amputation may be necessary

30

• Third stage meninges infected following
  invasion of the blood brain barrier (BBB)
• Headache, stiff neck, vomiting, delerium
• TNF-alpha found in CSF
• Concentration correlates with degree of BBB
  disruption and severity of the disease
• Most severe form of meningococcemia is the life
  threatening Waterhouse-Friderichsen syndrome
• High fever, shock, widespread purpura,
  disseminated intravascular coagulation and
  adrenal insufficiency, seeding of multiple organs
  including the meninges

31
Bleeding into the skin (petechiae and purpura),
and the tissue in these areas may die (become
necrotic or gangrenous).
32

• Diagnosis of Meningococcal infections
• Microscopy smears
• Culturing CSF, blood, skin lesion, nasopharyngeal
  secretions
• Chocolate agar
• Blood agar
• Thayer-Martin medium
• Nystatin, Polymyxin, Vancomycin Antibioitics
  inhibit contaminants while favoring pathogenic
  Neisseria
• 5-10 CO2 (candle jar or CO2 incubator)

33

• Serology
• Group-specific antisera agglutination of
  bacteria
• Sugar fermentation tests (Glucose, Maltose)
• Counterimmunoelectrophoresis
• At the pH used the anti-capsule antibodies have a
  positive charge and moves toward the anode while
  the capsular polysaccharides have a negative
  charge and moves toward the cathode
• Electrophoresed for 30-60 minutes
• A precipitate line forms if positive

34

• Quellung reaction
• Antibodies to capsular components swelling of
  capsule occurs
• Latex bead agglutination (group-specific
  polysaccharide adsorbed to beads incubated with
  patients serum)

35

• Treatment
• Penicillin or erythromycin
• Prevention
• Quadravalent vaccine A, C, Y W135
  polysaccharide antigens
• Used in epidemics and for military personnel
• Prophylactic rifampin used for those exposed

36
Haemophilus influenzae - Meningitis
37

• General features and growth requirements
• Small, Gram negative rod/coccobacillus
  (pleomorphic)
• Non-motile, aerobic
• Associated with bacterial meningitis in children
  and epiglottis infection (can block airway)
• Leading cause of invasive bacterial disease in
  children

38

• Six capsular types
• Type b significant in human infections
• Primary virulence factor - antiphagocytic
• Composed of PRP
• Polymer of ribose phosphate or ribulose phosphate
• Polysaccharide capsule
• Non-encapsulated forms in majority of
  asymptomatic carriers
• Can cause secondary bacterial pneumoni after
  viral infections (influenzae0

39

• Require chocolate agar supplemented with X and V
  factors
• X factor heat stable hematin (reguired for
  cytochromes and catalase)
• V factor heat labile, can be substituted with
  NAD

40

• Virulence factors/pathogenicity
• Respiratory route of infection/transmission
• Menintigitis in children
• 1000-3000 cases annually in USA
• Mortality rate of 3-7
• Enters blood via nasopharynx, then meninges
• CSF resembles meningococcal infection
• PMNLs and elevated sugar concentration

41

• Other diseases caused by HIB
• Epiglottitis in children
• Airway obstruction owing to inflmmation, edema
• Can lead to suffocation if not treated
• Otitis media with effusion (OME)
• Within first 3 years of life, 60-70 of children
  are affected (40 more than once)
• Usually the unencapsulated form is responsible
• Can also cause septic arthritis in children lt2
  years old (joint inflammation)
• Elderly infections pneumonia, meningitis,
  epiglottitis and female genital tract

42

• Diagnosis, treatment and prevention
• Centrifuge the CSF
• Gram stain pleomorphic Gram negative rods
• Quellung reaction with type b antiserum
• Fluorescent antibodies
• Countercurrent electrophoresis of CSF versus
  antiserum
• ELISA

43

• Latex bead agglutination (beads coated with
  antibodies to type b capsule)
• Culture CSF and blood ? chocolate agar, 350C
  CO2 or TSA X,V or XV discs
• Both X and V required for growth

44

• Treatment of meningitis must be immediate!
• Relatively high mortality rate (3-7)
• High level of complications (in 30 of survivors)
• Convulsions
• Hydrocephalus
• Mental retardation
• Blindness
• Ampicillin or if ampicillin resistant then
  chloramphenicol or cephalosporins
• Rifampin used as prophylactic for those exposed

45

• Prevention
• Vaccine for type b capsular antigens
• Early vaccines were inefective in children lt2
  years
• Improved vaccine
• Conjugate vaccine
• Polysaccharide of type b conjugated to large
  proteins which serve as carriers
• Tetanus toxoid carrier
• Diphtheria toxoid carrier
• Administered at 2 months of age, 3 doses, 2
  months apart, then a booster at 12-15 months
• Tetramune DPT HbOC
• Case Study

46
Listeria monocytoenes - Listeriosis
47

• General features
• Small, Gram positive, motile, pleomorphic rod
  (club shaped)
• Facultative anaerobes
• Beta hemolytic on blood agar plates (narrow band)
• 11 serotypes
• Most prevalent forms include types 1a, 1b and 4b

48

• Pathogenicity
• Transmitted by
• Animals
• Contaminated water
• Soil
• Fecal-oral route
• Poultry (major reservoir)
• Unpasteurized milk
• Coleslaw (raw vegetables not cleaned,
  contaminated with manure)

49

• Even pastueurized milk can be a potential source
  intracellular microbes in leukocytes in milk are
  resistant to heat
• Meningitis occurs in gt75 of infections (most
  common feature/manifestation in adults)
• Also causes endocarditis, urethritis,
  conjunctivitis and abortions (miscarriage)
• Most susceptible
• Immunocompromised and immunosuppressed
• Newborns
• Neonatal listeriosis

50

• Neonatal listeriosis
• Early and late onset
• Early onset Transplacental or transvaginal
  acquisition
• Acutely ill at birth or shortly thereafter
• Pneumonia common
• Believed to be a result of decreased
  cell-mediated IRs in pregnancy
• Growth of bacteria within placental cells
• Late onset
• 1-4 weeks after birth
• Meningitis usually
• Probably acquired after birth as a result of
  person-to-person contact

51

• Listerolysin O (LLO)
• Hemolytic cytolysin responsible for intracellular
  growth in macrophages and epithelial cells
• Permits escape of phagocytosed L. monocytoges
  from phagosome ? into the cytosol

52

• Treatment
• Penicillin
• Ampicillin
• Or tetracycline (preferred)

53
Atypical Mycobacteria
54

• Mycobacterium avium - M. intracellulaire
  pneumonia
• Organisms are normal soil and water inhabitants
  especially in Southern USA
• Both the respiratory and the gastrointestinal
  tracts have been proposed as portals of entry
• The gastrointestinal tract is thought to be the
  most common site of colonization and dissemination

55

• Pulmonary infection is similar to tuberculosis
  but usually milder
• Most often seen in elderly patients with
  preexisting pulmonary disease
• Occurs in 15 to 40 of AIDS patients is becoming
  a severe problem
• Symptoms include fever, malaise, weight loss, and
  diarrhea
• Treatment is usually multiple drug therapy

56
Bordetella pertussis Whooping Cough
57

• Pertussis (whooping cough) - Bordetella pertussis
• Highly contagious disease that primarily affects
  children
• Transmission is by droplet inhalation
• Toxins are responsible for most of the symptoms

58

• General features
• Small, Gram negative cocco-bacillus
• Non-motile
• Non-spore forming
• Often encapsulated
• Source
• Respiratory discharge (microdroplets)
• Direct or indirect

59

• Virulence characteristics (non-invasive)
• The disease progresses in stages
• Catarrhal stage
• Inflamed mucous membranes
• Resembles a cold (sneezing, coughing)
• Follows infection of ciliated epithelium of RT
• Lasts 7-10 days

60

• Spasmodic/Paroxysmal stage
• After 1-2 weeks
• Prolonged coughing sieges with inspiratory whoop
• Exhaustive
• Vomiting
• Conovulsions
• Lasts 2 weeks
• Convalescent stage
• Lasts a further 2 weeks or sometimes longer
• Some fatalities

61

• Virulence factors
• Pertussis toxin (AB exotoxin)
• Increased cAMP
• Activated protein kinases in cell
• Anaphylaxis sensitivity (histemine-sensitizing
  effect)
• Increased insulin hypoglycemia
• Increased lymphocytes n blood
• Aids in adherence to host cells
• Extracytoplasmic adenylate cyclase (bacterial
  enzyme)
• Increased cAMP
• Inhibition of neutrophils, macrophages and NK
  cells

62

• Filamentous Hemagglutinin
• Binding to epithelium
• Pertactin
• Binding to epithelium
• Tracheal cytotoxin
• Causes mucous and inflammatory debris to build up
  in the lungs
• PTG degradation product
• Induces IL-1 peroduction
• Ciliated epithelial cells are killed

63

• Spontaneous mutations in lab cultures of
  virulence factors ? can lead to phase changes
  (phase 1,2,3,4)
• Phase 1 most virulent
• Phase 4 avirulent
• Reversible process
• Colony morphology may change
• Loss of virulence factors

64

• Treatment and prevention
• Culture
• Push swab in back of nose to posterior nares and
  ask patient to cough
• Swab (not cotton) coated with penicillin
• Cultured on Bordet-Gengou medium
• Potato blood glycerol agar (high blood, 20-30)
• 3-4 days

65

• Detection
• Agglutination tests
• Fluorescent antibodies
• Antibiotics
• Erythromycin or tetracyclines or chloramphenicol
• Not always helpful, but important in limiting
  secondary infections (bronchitis and pneumonia
  caused by other organisms)

66

• Vaccination
• Effective but there are complications
• 5-20 deaths 50 cases of brain damage in USA per
  year over last 10 years
• Post vaccine encephalopathy
• DPT vaccine
• 2,4,6 and 12-15 mos
• Killed Bordetella pertussis
• Results of vaccination
• 1934 265,000 cases ? 7500 deaths
• 1998 6000 cases ? 3-5 deaths