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Bacterial Agents of Disease

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Bacterial Enteritis. Salmonellosis-Salmonella enteriditis. Enterocolitis- S. typhimurium ... E. coli O157:H7 is the most notable EHEC strain. produces Shiga toxin ... – PowerPoint PPT presentation

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Title: Bacterial Agents of Disease


1
Bacterial Agents of Disease
2
Gram-Positive Group
  • Traditionally, this group was based on Gram stain
    procedure
  • Now the grouping is based on Genetic similarity
  • Group is divided into two taxa based on GC
    content
  • High GC Gram positives (gt50)
  • Low GC Gram positives (lt50)
  • Acid fast species such as the Mycobacterium spp.
    are in this group even though they do not always
    stain positive with Gram stain
  • Mycoplasmas are included in this group even
    though they lack a cell wall structure

3
Staphylococcus aureus
  • Diseases
  • Folliculitis, Abscesses, Furuncles (boils), sty
  • Pneumonia, meningitis, empyema, endocarditis,
    sepsis
  • Scalded skin syndrome-exfoliative
    exotoxin-producing strain
  • Toxic shock syndrome
  • Food poisoning by enterotoxin production in food
  • Transmitted by contact and airborne routes
  • Notes
  • MRSA-Methecillin Resistant Staphylococcus aureus

4
Other Staph. species
  • S. epidermidis
  • Normal flora of skin, opportunistic pathogen
  • Sepsis
  • UTI
  • S. saprophyticus
  • Normal flora of skin and genitourinary mucosa
  • UTI

5
Streptococci
  • Classified by group-specific antisera
  • Important groups include
  • A -S. pyogenes, produce many toxins and enzymes
  • B -S. algalactiae
  • D S. bovis, Enterococcus spp.(now a separate
    genus)

6
Streptococcus pyogenes
  • Beta hemolytic, many other virulence factors
  • Diseases
  • Wound infections
  • Impetigo
  • Necrotizing fasciitis flesh-eating
  • Strep throat,
  • Scarlet fever caused only by streps infected with
    temperate phage
  • pneumonia, meningitis, endocarditis
  • Puerperal (childbed fever), rheumatic fever

7
S. pneumoniae
  • Alpha hemolytic
  • Diseases
  • Bronchitis
  • Classic Pneumonia
  • Streptococcal Meningitis
  • Conjunctivitis (Pink eye)
  • Otitis

8
Other streptococcal infections
  • S. algalactiae -Group B strep disease
  • S. mutans -Dental caries

9
Enterococcus spp.
  • Enterococcus faecalis, and E. faecium
  • Virulence factors not well understood
  • Indicators of fecal pollution
  • Diseases
  • Cholicystitis
  • Endocarditis
  • Septicemia
  • UTI
  • some strains are resistant to vancomycin (VRE)

10
Bacillus spp.
  • Rod-shaped often in chains
  • Many species, most are found naturally in soil
  • Endospore formers resistant to environmental
    extremes
  • Non-hemolytic forms are generally more dangerous
  • Produce a variety of toxins
  • Bacillus cereus
  • Heat-stable exotoxin can result in food poisoning
    giving rise to vomiting w/in hours after
    ingesting
  • Enterotoxin can cause diarrhea 10-12 hrs after
    ingestion

11
Bacillus anthracis
  • Anthrax can be
  • Pulmonary -Usually only ca. 5 of cases but most
    severe form
  • Skin/cutaneous
  • Gastrointestinal
  • Toxin producer
  • Zoonosis, primarily affecting ungulates and
    occasionally predators
  • Vaccine widely used in livestock but not humans

12
Clostridium spp.
  • Anaerobic, endospore-forming rods
  • Found in soil, water and animals
  • Clostridium perfringens
  • Gas gangrene, tissue destruction by toxin and
    enzymes
  • Food poisoning through ingestion of toxins
  • C. difficile
  • Produces enterotoxin
  • causes pseudomembranous colitis
  • Causes antibiotic associated diarrhea

13
Clostridium tetani
  • Causes tetanus, spastic paralysis
  • Infections result when endospores enter host
    through wounds (or umbilical stump in neonates)
    and germinate under anaerobic conditions
  • Produces toxin called tetanospasmin
  • Toxin blocks release of inhibitory mediators
    (GABA and Glycine) from vesicles in spinal and
    sympathetic NS synapses causing spasms
  • Life cycle includes periods in intestines of
    animals and soil
  • Vaccine commonly administered in U.S.
  • .

14
Clostridium botulinum
  • Causes food poisoning, flaccid paralysis, Infant
    botulism
  • One of the most potent toxins known
  • Endospores germinate under anaerobic conditions,
    especially in improperly-packaged foods of humans
    or animals
  • Produces botulinum toxin (BT, Botox) which
    inhibits the release of acetylcholine at
    neuromuscular junction resulting in flaccid
    paralysis

15
Mycobacterium spp.
  • Closely related to Gram positive organisms but do
    not always stain as such using Gram procedure due
    to the lipid mycolic acid in cell wall
  • Intracellular parasites that resist digestion
    within phagosomes
  • Several species can cause disease in humans and
    animals
  • Some species are found in the environment

16
Mycobacterium tuberculosis
  • Causes tuberculosis (consumption)
  • Infection leads to tissue necrosis and chronic
    granulomas, mainly lungs but also other tissues
    including bones
  • Infection leads to hypersensitivity in host
    (positive PPD), but not necessarily active
    disease
  • Most cases in US are reactivation of initial
    infections
  • Increasingly resistant to antibiotics

17
Mycobacterium leprae
  • Hansens disease (leprosy)
  • Mainly a human disease however, armadillos are
    also known to contract the disease
  • Infection gives rise to lesions on the
    extremities
  • Incubation is slow (2-10 yrs)
  • Endemic to Asia and Africa

18
Mycobacterium ulcerans
  • Causes Buruli Ulcer
  • An emerging disease in Africa and other tropical
    countries
  • Results in necrotic lesion that can cause
    significant disfigurement

19
Other diseases involving mycobacteria
  • Mycobacterium (avium) ssp. paratuberculosis
    causes Johnes disease in ungulates (hoofed
    animals), an intestinal wasting disease
  • Some evidence to implicate as a cofactor for
    Irritable bowel syndrome or Crohnes disease

20
Actinomyces isrealii
  • Anaerobic, filamentous, branching rods
  • Normal flora that can be opportunistic pathogen
  • Causes hard lesions mostly around face, neck
    abdominal lesions after surgery , and uterine
    infections after IUD use

21
Corynebacterium diptheriae
  • Cell structure similar to Mycobacterium
  • Some strains cause Diptheria
  • Tox gene which is needed to cause the disease is
    introduced into genome by phage
  • Diptheria toxin can damage to heart, kidneys and
    NS
  • Can cause formation of pseudomembrane

22
Listeria monocytogenes
  • Short rods or coccobacilli
  • Listeriosis
  • Food borne (processed meats, milk, soft cheeses,
    and veggies)
  • Threat to fetus of pregnant women
  • Can grow in the refrigerator

23
Proprionibacterium acnes
  • Cofactor/proximate cause for acne
  • Clinical impact of treatment
  • Antibiotic use may increase resistance
  • Acutane (isotretinoin) strongly interferes with
    developmental processes may have severe side
    effects on tissues

24
Proteobacteria
25
Alphaproteobacteria
26
Brucella spp.
  • Cause Brucellosis, Malta fever
  • Several species that are genotypically similar,
    are differentiated by the primary host and cell
    surface antigens
  • B. abortus (cows)
  • B. melitensis (goat)
  • B. suis (pig)
  • they are highly infectious and considered to be
    potential agents of biowarfare/bioterrorism

27
Rickettsial Pathogens
  • Cat scratch fever- Bartonella henslae
  • Oroya fever/Verrugia Peruana- Bartonella
    bacilliformes
  • Trench fever- Rochalimaea (Bartonella) quintana
  • Epidemic typhus- Rickettsia prowazekii
  • RMSF- Rickettsia riskettsii
  • Scrub typhus- Rickettsia tsutsugamishi
  • Endemic typhus- Rickettsia typhi
  • Rickettsial pox- Rickettsia akari
  • HME- Ehrlichia chaffeensis
  • HGE-Anaplasma (Ehrlichia) phagocytophilum

28
Rickettsia spp.
29
Other rickettsial pathogens
30
Betaproteobacteria
  • Neisseria
  • Burkholderia
  • Bordetella

31
Bordetella pertussis
  • Whooping Cough (Pertussis)
  • Gram (-) coccobacillus
  • Non-invasive, toxin producing

32
Neisseria gonorrhoeae
  • Gonorrhea (the clap)
  • Gram (-) diploccocci
  • Endotoxin damages mucosa
  • Can spread to other systems, PID
  • Pus-filled discharge
  • 1 communicable disease

33
Neisseria menigitidis
  • Meningococcal meningitis
  • Waterhouse-Friderichsen syndrome (endotoxic shock)

34
Gammaproteobacteria
  • Extremely diverse group
  • Contains many of the Gram negative enteric
    organisms

35
Bacterial Enteritis
  • Salmonellosis-Salmonella enteriditis
  • Enterocolitis- S. typhimurium
  • Typhoid fever- Salmonella typhi
  • Shigellosis- Shigella spp.
  • Cholera- Vibrio cholerae
  • Vibriosis- Vibrio parahemolyticus and Vibrio
    vulnificus
  • Campylobacter jejuni
  • Yersinia enterocolitica

36
Salmonella typhi
  • Typhoid fever, nervous fever
  • Transmitted by fecal contamination
  • Several clinical stages last for weeks

37
Salmonella enterica
  • Salmonellosis food poisoning
  • Produce enterotoxins and cytotoxins
  • One species is divided into several serovars-
    different types that are distinguished only by
    antigens
  • Serovars that commonly cause salmonellosis are
    typhimurium and enteritidis
  • May be found in intestines of many vertebrates
    including birds, reptiles and mammals

38
Shigella spp
  • Shigellosis, dysentery
  • Endotoxin irritates bowel
  • Endotoxin affects intestine and nervous system

39
Escherichia coli
  • Most strains are non-pathogenic
  • Various genes increase virulence
  • Enteroinvasive E. coli
  • Enterotoxogenic E. coli
  • Enterohemorrhagic
  • E. coli O157H7 is the most notable EHEC strain
  • produces Shiga toxin
  • Cattle may be primary reservoir
  • Opportunistic infections
  • Traveler's diarrhea
  • Cholecystitis, cholangitis (infalmmation of
    gallbladder , bile ducts)
  • Prostatitis, UTI, kidney infections, septicemia

40
Pseudomonas aeruginosa
  • Burn infections
  • Eye infections associated with contact lenses

41
Yersinia pestis
  • Diseases Bubonic, pneumonic and septicemic
    plague
  • Transmitted to humans by fleas such as Xenopsylla
    cheopis as well as through aerosolized fluids
    from infected hosts
  • Reservoirs rodents
  • Sporadic, isolated outbreaks occur around the
    world

42
Vibrio cholerae
  • causes Cholera
  • Worldwide distribution, especially common in the
    tropics
  • Lives in environmental waters
  • Copepods and shellfish are reservoirs and can
    also be considered as vectors if swallowing them
    results in the disease
  • Infectivity is enhanced when organisms pass
    through human intestine
  • Route of transmission is usually through food or
    water contaminated with feces
  • Serogroups 0139 and 01 are most capable of
    producing epidemics

43
Other important Vibrio spp.
  • Vibrio vulnificus- wound infection, septicemia,
    endometritis, food poisoning
  • Mortality rate of around 40
  • Acquired by eating raw oysters or swimming in
    ocean where organism lives naturally
  • Organisms invade through wounds, GI tract, and
    give rise to septicemia
  • 1 case report of endometritis
  • Vibrio parahemolyticus- food poisoning

44
Haemophilus spp.
  • Haemophilus ducreyi Chancroid
  • Haemophilus influenzae
  • Found on mucous membrane of upper respiratory
    tract infections
  • Can cause meningitis in children
  • Encapsulated forms resist phagocytosis
  • Hib vaccine

45
  • Legionella pneumophila
  • Pontiac Fever is mild form
  • Legionnaire's Disease
  • Several protozoan reservoirs
  • Reside in phagocytes of human host

46
Others
  • Francisella tularensis -Tuleremia (rabbit fever)
  • Coxiella burnetii -Q fever
  • Pasteurella multocida -animal bite infections
  • Spirillum minor- rat bite fever

47
Epsilonproteobacteria
48
Helicobacter pylori
  • Lives in gastric mucosa
  • Produce urease and break down urea into ammonia
    to neutralize stomach acids
  • High infection prevalence, especially in
    developing countries
  • Cofactor for peptic ulcers and stomach cancer
  • Route of transmission may be fecal-oral but
    details unknown
  • One of the most common bacteria in humans (50
    infection rate worldwide, some populations 100)

49
Campylobacter jejuni
  • Common cause of diarrhea
  • Can cause septicemia
  • Transmitted through food and water contaminated
    with feces

50
Spirochaetes and other bacteria
51
Spirochetes
  • Borrelia spp.
  • Treponema pallidum
  • Leptospira interrogans

52
Borrelia spp.
  • Relapsing fever- Borrelia recurrentis
  • Lice and argasid ticks are vectors
  • Lyme disease- Borrelia burgdorferi (sensu lato)
  • Worldwide in distribution
  • Vectors include several species of Ixodes ticks
  • Produces characteristic rash, erythema chronicum
    migrans.

53
Lyme Borreliosis
  • Several genospecies of B. burgdorferi are
    recognized around the world and cause similar
    diseases
  • Reservoirs Rodents, and other wild mammals
  • Dogs and Livestock may also become infected
  • Severity of disease may vary by strain, higher
    genetic variability of B. burgdorferi in Southern
    U.S.
  • Primary vector the black-legged tick (deer tick)
    Ixodes scapularis (Eastern U.S.) Ixodes pacificus
    (Western U.S.)
  • Higher prevalence of infection in New England and
    Upper Midwest

54
Leptospira interrogans
  • Causes Leptospirosis
  • Zoonosis
  • Carried by many wild and domestic mammals
  • Acquired through contact with water/soil

55
Treponema pallidum
  • Diseases syphilis, yaws, bejel, pinta
  • Lesions called chancre
  • Disease consists of primary, secondary and
    tertiary stages that increase in severity,
    sporadic symptoms after latent periods
  • Immunopathology can cause serious nervous
    degeneration and insanity
  • STD, also transmitted through saliva
  • Congenital syphilis trans-placental transmission
  • Recent (ca. last 10000 years) co-evolution with
    changing human lifestyles

56
Chlamydia spp.
  • Chlamydia trachomatis
  • Obligate intracellular parasites
  • Nongonococcal urethritis in men
  • PID in women
  • Lymphogranuloma venereum (LGV) caused by a
    particular strain
  • Self-inoculation of eyes leading to
    conjunctivitis
  • Trachoma, a leading cause of blindness
  • Chlamydia psittaci causes Psitticosis/Ornithosis,
    a respiratory zoonosis
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