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Bacterial Groups u Most widely accepted taxonomic classification for bacteria is Bergey’s Manual of Systematic Bacteriology. Bacteriology. Chapter 11: Bacteria u 5000 bacterial species identified, 3100 classified. u Bacteria are divided into four divisions (phyla) according to the characteristics of their cell walls. u u Each division is divided into sections according to: u Gram stain reaction u Cell shape u Cell arrangements u Oxygen requirements u Motility u 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: u u F Treponema pallidum: pallidum: Syphilis F Borrelia spp spp.: .: Lyme disease, relapsing fever Leptospira:: Leptospirosis Leptospira F 1 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: u u 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. 2 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) F 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)) l l l Many have fimbriae for attachment to mucous membranes and sex pili for exchange of DNA (antibiotic resistance genes) l 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. F Genus Serratia Serratia:: Opportunistic respiratory and urinary tract infections. • Serratia marcescens: marcescens: Produces a red pigment. Important cause of nosocomial infections. 3 5. Facultative Anaerobic GramGram-Negative Rods Cholera is Caused by Vibrio cholerae II. Family Vibrionaceae l Found in aquatic habitats. l Straight or slightly curved rods F 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 l Found in aquatic habitats. l 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). u Genus Ehrlichiae Ehrlichiae:: Live in white blood cells . u Genus Rickettsia Rickettsia:: Cause spotted group fevers (Rocky mountain spotted fever, endemic typhus). 6. Anaerobic GramGram-Negative Rods May be straight, helical, or curved. u u 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: u Chlamydia trachomatis trachomatis:: Causes blindness in humans and nongonococcal urethritis (most common STD in U.S.). u C. psittaci : Parrot fever. C. pneumoniae pneumoniae:: Mild pneumonia. u 4 Division II. GramGram-Positive Bacteria 17. GramGram-Positive Cocci l Non--spore forming cocci Non cocci.. l Aerobic to strictly anaerobic. Pyogenic (pus (pus--forming) l u 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 u 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 5 18. Endospore Endospore--Forming GramGram-Positive Rods and Cocci l Aerobic to strictly anaerobic. l l Motile and nonmotile nonmotile.. Survive harsh environmental conditions. u Genus Bacillus : Rod shaped bacteria. F F u 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 u 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. u 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 l Aerobic, nonnon -spore spore--forming rods. l Stain GramGram-positive, but cell wall structure is more similar to Gram--negative bacteria. Gram l Waxy cell wall with mycolic acids (instead of peptidoglycan). peptidoglycan ). l l Acid -fast, drug resistant, resistant to drying, and pathogenic Aciddue to waxy cell wall. Grow very slowly. l 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. 6 Mycobacterium leprae Causes Leprosy Source: Tropical Medicine andParasitology, 1995 22. Nocardioforms l Gram--positive, filamentous, aerobic. Gram l Many are acid fast. Common in soil. l u 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 l l l l l l Gram--positive, filamentous, resemble molds. Gram l l Common in soil. l u 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. 7