Download Chapter 11: Bacteria Bacterial Groups

Bacterial Groups
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Most widely accepted taxonomic classification for
bacteria is Bergey’s Manual of Systematic Bacteriology.
Bacteriology.
Chapter 11: Bacteria
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5000 bacterial species identified, 3100 classified.
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Bacteria are divided into four divisions (phyla) according
to the characteristics of their cell walls.
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Each division is divided into sections according to:
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Gram stain reaction
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Cell shape
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Cell arrangements
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Oxygen requirements
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Motility
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Nutritional and metabolic properties
Each section contains several genera
genera..
Four Divisions of Bacteria
Classification of Bacteria
Procaryotes
Gram-Negative
Bacteria
Division II
Bacteria
Wall-Less
Bacteria
Archaea
Bacteria
(Gracilicutes)
(Firmicutes)
(Tenericutes)
(Mendosicutes)
Thin Cell Walls
Thick cell Walls
Lack cell walls
Unusual cell walls
Division I. GramGram-Negative Bacteria
Gram Negative Bacteria
Spirochetes
1. Spirochetes
Helical shape. Flexible.
Contain two or more axial filaments
( endoflagella
endoflagella).
).
u Move in corkscrew pattern.
u Medically important members:
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F
Treponema pallidum:
pallidum: Syphilis
F
Borrelia spp
spp.:
.: Lyme disease, relapsing fever
Leptospira:: Leptospirosis
Leptospira
F
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Syphilis is Caused by a Spirochete
Primary syphilitic chancre and secondary rash.
Source: Tropical Medicine and Parasitology, 1997
2. Aerobic, Motile, Helical/Vibroid
Helical/Vibroid Gram
Gram-Negative Bacteria
Rigid helical shape or curved rods.
Lack axial filaments (endoflagella
(endoflagella);
); have polar
flagella instead.
u Most are harmless aquatic organisms.
u Genus Azospirillum fixes nitrogen in soil.
u Genus Bdellovibrio attacks other bacteria.
u Important pathogens include:
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F
Campylobacter jejuni : Most common bacterial foodfoodborne intestinal disease in the United States (2 million
cases/year). Associated with undercooked chicken.
F
Helicobacter pylori:
pylori: Causes most gastric ulcers in
humans.
F
Campylobacter fetus : Abortions in domestic animals.
Helicobacter pylori causes Gastric Ulcers
Lyme Disease is Caused by a Spirochete
Lyme Disease early lesion at tick bite site.
Source: Medical Microbiology, 1998
Gram Negative Bacteria
Aerobic, Motile, Helical/Vibroid
Gram-Negative Bacteria
4. GramGram-Negative Aerobic Rods and Cocci
Contains many medically significant groups.
F
Genus Pseudomonas
Pseudomonas:: Rods with polar flagella.
Many secrete pigments in media.
• Pseudomonas aeruginosa
aeruginosa:: Urinary tract infections (UTIs
(UTIs),
),
septicemia, abcesses
abcesses,, burns, pulmonary infections in cystic
fibrosis patients, and meningitis.
F
Genus Legionella
Legionella:: Rods that live in natural waters.
Frequently found in air conditioning systems,
humidifiers, showers, spas, and fountains.
• Legionella pneumophila:
pneumophila: Legionnaires’ disease
(pneumonia, 1976) and Pontiac fever.
F
Genus Neisseria
Neisseria:: Diplococci
Diplococci.. Frequently found on
human mucous membranes. Only grow well around
body temperature.
• Neisseria gonorrhea
gonorrhea:: Gonorrhea.
• Neisseria meningitidis
meningitidis:: Meningitis.
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Neisseria gonorrhea Causes Salpingitis
Neisseria gonorrhea Causes Neonatal Blindness
Ophtalmia neonatorum caused by Neisseria gonorrheae
Source: Microbiology Perspectives, 1999
4. GramGram-Negative Aerobic Rods and Cocci
(Continued)
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Genus Moraxella
Moraxella:: Aerobic eggegg -shaped cocco
cocco--bacilli.
• Moraxella lacunata:
lacunata: Conjunctivitis.
F
Genus Brucella
Brucella:: Small nonmotile coccobacilli.
coccobacilli.
All species are obligate parasites of mammals.
Cause brucellosis
brucellosis.. Can survive phagocytosis .
F Genus Bordetella
Bordetella:: Nonmotile rods. Virulent forms
have capsules.
5. Facultative Anaerobic GramGram-Negative
Rods
Many cause diseases of gastrointestinal tract.
Contains three medically significant families.
I. Family Enterobacteriaceae ( Enterics
Enterics))
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Many have fimbriae for attachment to mucous membranes
and sex pili for exchange of DNA (antibiotic resistance
genes)
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Most ferment glucose and other sugars.
F Genus Escherichia
Escherichia:: E. coli is common inhabitant of
human intestinal tract. Most strains are not pathogenic,
but others can cause UTIs (urinary tract infections),
traveler’s diarrhea, and foodfood-borne disease.
• Bordetella pertussis:
pertussis: Whooping cough (P
(P in DPT vaccine).
vaccine ).
F
Genus Francisella
Francisella:: Small pleomorphic bacteria.
• Francisella tularensis:
tularensis: Tularemia
F
Genera Rhizobium and Bradyrhizobium
Bradyrhizobium:: Form
nodules on legume roots and fix nitrogen in soil.
I. Family Enterobacteriaceae (Continued)
F
Genus Salmonella
Salmonella:: Almost all members are potential
pathogens. Common inhabitants of animal GI tract. Can
contaminate food (eggs, meat).
• Salmonella typhi
typhi:: Typhoid fever, severe illness.
• S. enteritidis
enteritidis:: Causes salmonellosis
salmonellosis,, the second most common
bacterial foodfood- borne disease.
Over 1.3 million cases/year in the U.S.
F
Genus Shigella : Only found in humans. Second most
common cause of traveler’s diarrhea.
F
Genus Klebsiella
Klebsiella:: Cause respiratory and UTIs
UTIs..
Inhabit intestinal tracts of animals.
Motile bacteria with peritrichous flagella or nonmotile
nonmotile..
I. Family Enterobacteriaceae (Continued)
Genus Proteus : Actively motile. Cause UTIs
UTIs,, wound
infections, and infant diarrhea (nosocomial
(nosocomial).
).
F Genus Yersinia
Yersinia::
F
• Yersinia pestis:
pestis: Causes bubonic plague (black death).
Transmitted by fleas, respiratory droplet, and contact with
animals.
F
F
Genus Erwinia
Erwinia:: Important plant pathogens.
Genus Enterobacter
Enterobacter:: Cause UTIs and nosocomial
infections.
• Klebsiella pneumoniae
pneumoniae:: Antibiotic resistant strains cause
pneumonia and nosocomial infections.
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Genus Serratia
Serratia:: Opportunistic respiratory and urinary
tract infections.
• Serratia marcescens:
marcescens: Produces a red pigment. Important
cause of nosocomial infections.
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5. Facultative Anaerobic GramGram-Negative
Rods
Cholera is Caused by Vibrio cholerae
II. Family Vibrionaceae
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Found in aquatic habitats.
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Straight or slightly curved rods
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Genus Vibrio
Vibrio:: Slightly curved rods.
• Vibrio cholerae:
cholerae: Cholera, profuse & watery diarrhea.
• Vibrio parahaemolyticus
parahaemolyticus:: Gastroenteritis. Shellfish.
Rice-water stool of cholera.
Source: Tropical Medicine andParasitology, 1995
5. Facultative Anaerobic GramGram-Negative
Rods
III. Family Pasterellaceae
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Found in aquatic habitats.
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Straight or slightly curved rods
Genus Pasteurella : Pathogens of domestic animals.
F Genus Hemophilus : Important pathogens that inhabit
mucous membranes of upper respiratory tract, mouth,
vagina, and intestinal tract. Require blood in culture.
F
• Hemophilus influenzae:
influenzae: Causes meningitis, ear infections,
bronchitis, arthritis, and pneumonia in children.
• H. ducreyi: Cause of sexually transmitted chancroid
chancroid..
F
Genus Gardnerella : Not assigned to any family.
• G. vaginalis causes common form of vaginitis
vaginitis..
8. Anaerobic GramGram-Negative Cocci
Nonmotile cocci typically found in pairs.
u Genus Veillonella
Veillonella:: Cause dental plaque.
9. Rickettsias and Chlamydias
Gram negative bacteria.
Obligate intracellular parasites.
Rickettsias:: Rod shaped bacteria or coccobacilli
Rickettsias
coccobacilli,,
highly pleomorphic
pleomorphic.. Transmitted to humans by
insects and ticks (except for Coxiella burnetti which
causes Q fever).
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Genus Ehrlichiae
Ehrlichiae:: Live in white blood cells .
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Genus Rickettsia
Rickettsia:: Cause spotted group fevers (Rocky
mountain spotted fever, endemic typhus).
6. Anaerobic GramGram-Negative Rods
May be straight, helical, or curved.
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Genus Bacteroides
Bacteroides:: Nonmotile
Nonmotile.. Live in human intestinal
tract (1 billion/gram of feces) and gum crevices. Cause
peritonitis, abscesses, and deep tissue infections.
Genus Fusobacterium
Fusobacterium:: Long slender rods with pointed
tips. Found in gingival crevices, cause dental abscesses.
7. SulfurSulfur -Reducing Bacteria
Obligate anaerobes that release H2 S into the
atmosphere.
Found in soil and intestinal tract of animals.
Ecologically important.
Chlamydias: Cocci shaped bacteria. Transmitted to
Chlamydias:
humans by interpersonal contact or by airborne
respiratory routes.
Unique life cycle:
cycle: Form a reticulate and elementary
bodies in infected cells.
Three species:
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Chlamydia trachomatis
trachomatis:: Causes blindness in humans and
nongonococcal urethritis (most common STD in U.S.).
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C. psittaci : Parrot fever.
C. pneumoniae
pneumoniae:: Mild pneumonia.
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Division II. GramGram-Positive Bacteria
17. GramGram-Positive Cocci
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Non--spore forming cocci
Non
cocci..
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Aerobic to strictly anaerobic.
Pyogenic (pus
(pus--forming)
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Diseases Caused by Staphylococcus
aureus
Genus Staphylococcus : Tend to form grapegrape-like clusters.
Grow well under high osmotic pressure and low moisture.
Very common infections, because almost always found on
skin and in nasal mucous membranes.
F
Staphylococcus aureus
aureus:: (aureus
(aureus = golden) Yellow pigmented
colonies. Produce several toxins. Cause pimples, sties, skin
abscesses, toxic shock syndrome, food poisoning, and nosocomial
infections.
Antibiotic resistance is big problem.
Vancomycin is last line of defense against antibiotic resistant
strains.
17. GramGram-Positive Cocci
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Genus Streptococcus : Most are pathogens. Tend to
appear in chains or pairs. Do not use oxygen, but most
are aerotolerant
aerotolerant.. Classified based on their effect on red
blood cells (hemolysis
( hemolysis).
).
Scalded
Skin Syndrome
Sty
Toxic Shock
Syndrome
Scarlet Fever is Caused by a Strain of
Streptococcus pyogenes
Cause a wide range of diseases: Strep throat, respiratory
infections, abscesses, puerperal fever, and opportunistic
infections.
A flesh eating Streptococcus strain emerged in 1994 and
1998. After initial infection, bacteria live on dead flesh,
produce toxins, and are not treatable by antibiotics.
F
F
Streptococcus pneumoniae
pneumoniae:: Bacterial pneumonia, ear infections,
meningitis, and sinus infections.
Streptococcus pyogenes: Strep throat, scarlet fever, rheumatic
fever, impetigo, skin infections, erysipelas, puerperal fever,
glomerulonephritis..
glomerulonephritis
Flesh-Eating Streptococcus pyogenes
Necrotizing fasciitis with blood filled vesicles.
Source: Perspectives in Microbiology, 1995
Erysipelas is Caused by Strep. pyogenes
Erysipelas on face due to S. pyogenes infection
Source: Color Guide to Infectious Diseases, 1992
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18. Endospore
Endospore--Forming GramGram-Positive Rods
and Cocci
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Aerobic to strictly anaerobic.
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Motile and nonmotile
nonmotile..
Survive harsh environmental conditions.
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Genus Bacillus : Rod shaped bacteria.
F
F
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Tetanus is Caused by Clostridium tetani
Bacillus anthracis
anthracis:: Causes anthrax a disease of cattle. Large (4 8 um) nonmotile facultative anaerobe.
Bacillus thuringiensis
thuringiensis:: Kills insects, used by gardeners.
Genus Clostridium
Clostridium:: Rod shaped bacteria, obligate
anaerobes.
F
F
F
Clostridium tetani
tetani:: Causes tetanus ( T in DPT vaccine ).
Clostridium botulinum
botulinum:: Causes botulism.
Clostridium perfringens
perfringens:: Causes gas gangrene and foodborne
diarrhea.
Gangrene Caused by Clostridium perfringens
Neonatal Tetanus (Wrinkled brow and risus sardonicus)
Source: Color Guide to Infectious Diseases, 1992
19. Regular Nonsporing Gram
Gram--Positive Rods
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Genus Lactobacillus
Lactobacillus:: Produce lactic acid which inhibits
the growth of other bacteria. In humans live in vagina,
intestinal tract, and mouth. Used commercially to make
yogurt, pickles, sauerkraut, and buttermilk.
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Genus Listeria : Contaminates dairy products.
F
Listeria monocytogenes: Survives in phagocytic cells and grows
in refrigerators.
Causes listeriosis
listeriosis..
Infection of pregnant women can cause stillbirth or severe
damage to fetus.
Severe gangrene caused by Clostridium perfringens.
Source: Tropical Medicine and Parasitology, 1997
20. Irregular Nonsporing Gram
Gram--Positive
Rods
Club shaped (Corynebacteria
(Corynebacteria),
), pleomorphic
pleomorphic..
May be anaerobic or aerobic.
21. Mycobacteria
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Aerobic, nonnon -spore
spore--forming rods.
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Stain GramGram-positive, but cell wall structure is more similar to
Gram--negative bacteria.
Gram
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Waxy cell wall with mycolic acids (instead of
peptidoglycan).
peptidoglycan
).
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Acid -fast, drug resistant, resistant to drying, and pathogenic
Aciddue to waxy cell wall.
Grow very slowly.
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Tend to cause chronic infections.
Important pathogens:
F
F
Corynebacterium diphtheriae:
diphtheriae: Cause diphtheria ( D in DPT
vaccine).
vaccine
).
Propionibacterium acnes
acnes:: Causes acne.
Important pathogens:
F
F
Mycobacterium tuberculosis
tuberculosis:: Causes tuberculosis.
Mycobacterium leprae
leprae:: Causes leprosy.
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Mycobacterium leprae Causes Leprosy
Source: Tropical Medicine andParasitology, 1995
22. Nocardioforms
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Gram--positive, filamentous, aerobic.
Gram
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Many are acid fast.
Common in soil.
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Genus Nocardia
Nocardia:: Form filaments which fragment into
short rods to reproduce.
F
Nocardia asteroides: Pulmonary infections, mycetoma
mycetoma,,
abscesses.
25. Actinomycetes
Mycobacterium leprae Causes Leprosy
Severe bone destruction in advanced leprosy
Source: Diagnostic Pictures in Infectious Diseases, 1995
Division III. WallWall-Less Bacteria
30. Mycoplasmas
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Gram--positive, filamentous, resemble molds.
Gram
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Common in soil.
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Genus Streptomyces
Streptomyces:: Live in soil. Give soil its musty
odor. Produce hundreds of antibiotics.
Do not form cell walls.
Most are aerobes or facultative anaerobes.
Highly pleomorphic
pleomorphic..
Can produce filaments that resemble fungi.
Produce very small colonies (1 nm in diameter).
Very small cells: 0.1 to 0.25 µm in diameter.
Can pass through bacterial filters.
Most important human pathogen:
Mycoplasma pneumoniae:
pneumoniae: Walking pneumonia.
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