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Foundations in Microbiology Sixth Edition Chapter 20 The Gram-Negative Bacilli of Medical Importance Lecture PowerPoint to accompany Talaro Copyright ©

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Presentation on theme: "Foundations in Microbiology Sixth Edition Chapter 20 The Gram-Negative Bacilli of Medical Importance Lecture PowerPoint to accompany Talaro Copyright ©"— Presentation transcript:

1 Foundations in Microbiology Sixth Edition Chapter 20 The Gram-Negative Bacilli of Medical Importance Lecture PowerPoint to accompany Talaro Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 2 Large, diverse group of non-spore-forming bacteria Wide range of habitats – large intestines (enteric), zoonotic, respiratory, soil, water Most are not medically important; some are true pathogens, some are opportunists. All have a lipopolysaccharide outer membrane of cell wall – endotoxin.

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4 4 Aerobic Gram-Negative Nonenteric Bacilli Pseudomonas and Burkholderia – an opportunistic pathogen Brucella and Francisella – zoonotic pathogens Bordetella and Legionella – mainly human pathogens Alcaligenes – opportunistic pathogen

5 5 Pseudomonas: The Pseudomonads Small Gram-negative rods with a single polar flagellum Free living –primarily in soil, sea water, and fresh water; also colonize plants and animals Important decomposers and bioremediators Frequent contaminants in homes and clinical settings Use aerobic respiration; do not ferment carbohydrates Produce oxidase and catalase Many produce water soluble pigments.

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7 7 Pseudomonas aeruginosa Common inhabitant of soil and water Intestinal resident in 10% normal people Resistant to soaps, dyes, quaternary ammonium disinfectants, drugs, drying Frequent contaminant of ventilators, IV solutions, anesthesia equipment Opportunistic pathogen

8 8 Pseudomonas aeruginosa Common cause of nosocomial infections in hosts with burns, neoplastic disease, cystic fibrosis Complications include pneumonia, UTI, abscesses, otitis, and corneal disease Endocarditis, meningitis, bronchopneumonia Grapelike odor Greenish-blue pigment (pyocyanin) Multidrug resistant Cephalosporins, aminoglycosides, carbenicillin, polymixin, quinolones, and monobactams

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10 10 Other Gram-Negative Aerobic Rods Genera Burkholderia, Acinetobacter, Stenotrophomonas Similar to pseudomonads Wide variety of habitats in soil, water, and related environments Obligate aerobes; do not ferment sugars Motile, oxidase positive Opportunistic

11 11 Burkholderia Burkholderia cepacia – active in biodegradation of a variety of substances; opportunistic agent in respiratory tract, urinary tract, and occasionally skin infections; drug resistant B. pseudomallei – generally acquired through penetrating injury or inhalation from environmental reservoir; wound infections, bronchitis and pneumonia, septicemia

12 12 Acinetobacter and Stenotrophomonas Acinetobacter baumanii – nosocomial and community acquired infections; wounds, lungs, urinary tract, burns, blood; extremely resistant – treatment with combination antimicrobials Stenotrophomonas maltophilia – forms biofilms; contaminant of disinfectants dialysis equipment, respiratory equipment, water dispensers, and catheters; clinical isolate in respiratory soft tissue, blood,CSF; high resistance to multidrugs

13 13 Brucella and Brucellosis Tiny Gram-negative coccobacilli 2 species: –Brucella abortus (cattle) –Brucella suis (pigs) Brucellosis, malta fever, undulant fever, and Bang disease – a zoonosis transmitted to humans from infected animals Fluctuating pattern of fever –weeks to a year Combination of tetracycline and rifampin or streptomycin Animal vaccine available Potential bioweapon

14 14 Francisella tularensis and Tularemia Causes tularemia, a zoonotic disease of mammals endemic to the northern hemisphere, particularly rabbits Transmitted by contact with infected animals, water and dust or bites by vectors Headache, backache, fever, chills, malaise and weakness 10% death rate in systemic and pulmonic forms Intracellular persistence can lead to relapse gentamicin or tetracycline Attenuated vaccine Potential bioterrorism agent

15 15 Bordetella pertussis Minute, encapsulated coccobacillus Causes pertussis or whooping cough, a communicable childhood affliction Acute respiratory syndrome Often severe, life-threatening complications in babies Reservoir – apparently healthy carriers Transmission by direct contact or inhalation of aerosols

16 16 Bordetella pertussis Virulence factors –receptors that recognize and bind to ciliated respiratory epithelial cells –toxins that destroy and dislodge ciliated cells Loss of ciliary mechanism leads to buildup of mucus and blockage of the airways. Vaccine – DTaP- acellular vaccine contains toxoid and other Ags

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18 18 Alcaligenes Live primarily in soil and water May become normal flora A. faecalis – most common clinical species –isolated from feces, sputum, and urine –occasionally associated with opportunistic infections – pneumonia, septicemia, and meningitis

19 19 Legionella pneumophila and Legionellosis Widely distributed in water Live in close association with amebas 1976 epidemic of pneumonia afflicted 200 American Legion members attending a convention in Philadelphia and killed 29 Legionnaires disease and Pontiac fever Prevalent in males over 50 Nosocomial disease in elderly patients Fever, cough, diarrhea, abdominal pain, pneumonia fatality rate of 3-30% Azithromycin

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21 21 Enterobacteriaceae Family Enterics Large family of small, non-spore-forming Gram-negative rods Many members inhabit soil, water, decaying matter, and are common occupants of large bowel of animals including humans. Most frequent cause of diarrhea through enterotoxins Enterics, along with Pseudomonas sp., account for almost 50% of nosocomial infections.

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23 23 Facultative anaerobes, grow best in air All ferment glucose, reduce nitrates to nitrites, oxidase negative, and catalase positive. Divided into coliforms (lactose fermenters) and non-coliforms (non-lactose fermenters) Enrichment, selective and differential media utilized for screening samples for pathogens

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26 26 Antigenic Structures and Virulence Factors Complex surface antigens contribute to pathogenicity and trigger immune response: H – flagellar Ag K – capsule and/or fimbrial Ag O – somatic or cell wall Ag – all have Endotoxin Exotoxins

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28 28 Coliform Organisms and Diseases

29 29 Escherichia coli: The Most Prevalent Enteric Bacillus Most common aerobic and non-fastidious bacterium in gut 150 strains Some have developed virulence through plasmid transfer, others are opportunists.

30 30 Pathogenic Strains of E. coli Enterotoxigenic E. coli causes severe diarrhea due to heat-labile toxin and heat-stable toxin – stimulate secretion and fluid loss; also has fimbriae Enteroinvasive E. coli causes inflammatory disease of the large intestine. Enteropathogenic E. coli linked to wasting form infantile diarrhea Enterohemorrhagic E. coli, O157:H7 strain, causes hemorrhagic syndrome and kidney damage; ID 100 cells

31 31 Escherichia coli Pathogenic strains frequent agents of infantile diarrhea – greatest cause of mortality among babies Causes ~70% of traveler’s diarrhea Causes 50-80% UTI Coliform count - indicator of fecal contamination in water

32 32 Other Coliforms Clinically important mainly as opportunists Klebsiella pneumoniae– normal inhabitant of respiratory tract, has large capsule, cause of nosocomial pneumonia, meningitis, bacteremia, wound infections and UTIs Enterobacter sp. – UTIs, surgical wounds Serratia marcescens – produces a red pigment; causes pneumonia, burn and wound infections, septicemia and meningitis Citrobacter sp. – opportunistic UTIs and bacteremia

33 33 Noncoliform Lactose-Negative Enterics Proteus, Morganella, Providencia Salmonella and Shigella

34 34 Opportunists: Proteus and Its Relatives Proteus, Morganella, Providencia – ordinarily harmless saprobes in soil, manure, sewage, polluted water, commensals of humans and animals –Proteus sp. - swarm on surface of moist agar in a concentric pattern –involved in UTI, wound infections, pneumonia, septicemia, and infant diarrhea –Morganella morganii and Providencia sp. involved in similar infections All demonstrate resistance to several antimicrobials.

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36 36 Salmonella and Shigella Well-developed virulence factors, primary pathogens, not normal human flora Salmonelloses and Shigelloses –some gastrointestinal involvement and diarrhea but often affect other systems

37 37 Typhoid Fever and Other Salmonelloses Salmonella typhi – most serious pathogen of the genus; cause of typhoid fever; human host S. cholerae-suis – zoonosis of swine S. enteritidis – includes 1,700 different serotypes based on variation on O, H, and capsular antigen Flagellated; ferments glucose Resistant to chemicals –bile and dyes

38 38 Typhoid Fever Bacillus enters with ingestion of fecally contaminated food or water; occasionally spread by close personal contact; ID 1,000-10,000 cells Asymptomatic carriers; some chronic carriers shed bacilli from gallbladder Bacilli adhere to small intestine, cause invasive diarrhea that leads to septicemia Treat chronic infections with chloramphenicol or sulfa-trimethoprim 2 vaccines for temporary protection

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40 40 Animal Salmonelloses Salmonelloses other than typhoid fever are called enteric fevers, Salmonella food poisoning, and gastroenteritis. Usually less severe than typhoid fever but more prevalent Caused by one of many serotypes of Salmonella enteritidis; all zoonotic in origin but humans can become carriers –cattle, poultry, rodents, reptiles, animal and dairy products –fomites contaminated with animal intestinal flora

41 41 Shigella and Bacillary Dysentery Shigellosis – incapacitating dysentery S. dysenteriae, S. sonnei, S. flexneri and S. boydii Human parasites Invades villus of large intestine, can perforate intestine or invade blood Enters Peyer’s patches instigate inflammatory response; endotoxin and exotoxins Treatment – fluid replacement and ciprofloxacin and sulfa-trimethoprim

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43 43 The Enteric Yersinia Pathogens Yersinia enterocolitica – domestic and wild animals, fish, fruits, vegetables, and water –bacteria enter small intestinal mucosa, some enter lymphatic and survive in phagocytes; inflammation of ileum can mimic appendicitis Y. pseudotuberculosis – infection similar to Y. enterocolitica, more lymph node inflammation

44 44 Nonenteric Yersinia pestis and Plague Nonenteric Tiny, Gram-negative rod, unusual bipolar staining and capsules Virulence factors – capsular and envelope proteins protect against phagocytosis and foster intracellular growth –coagulase, endotoxin, murine toxin

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46 46 Yersinia pestis Humans develop plague through contact with wild animals (sylvatic plague) or domestic or semidomestic animals (urban plague) or infected humans. Found in 200 species of mammals – rodents, without causing disease Flea vectors – bacteria replicates in gut, coagulase causes blood clotting that blocks the esophagus; flea becomes ravenous

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48 48 Pathology of Plague ID 3-50 bacilli Bubonic – bacillus multiplies in flea bite, enters lymph, causes necrosis and swelling called a bubo in groin or axilla Septicemic – progression to massive bacterial growth; virulence factors cause intravascular coagulation subcutaneous hemorrhage and purpura – black plague Pneumonic – infection localized to lungs, highly contagious; fatal without treatment

49 49 Diagnosis depends on history, symptoms, and lab findings from aspiration of buboes. Treatment: streptomycin, tetracycline or chloramphenicol Killed or attenuated vaccine available Prevention by quarantine and control of rodent population in human habitats

50 50 Oxidase-Positive Nonenteric Pathogens Pasteurella multocida Haemophilus influenzae H. aegyptius H. ducreyi H. parainfluenzae H. aphrophilus

51 51 Pasteruella multocida Zoonotic genus; normal flora in animals Opportunistic infections Animal bites or scratches cause local abscess that can spread to joints, bones, and lymph nodes. Immunocompromised are at risk for septicemia and complications. Treatment: penicillin and tetracycline

52 52 Haemophilus Tiny Gram-negative pleomorphic rods Fastidious, sensitive to drying, temperature extremes, and disinfectants None can grow on blood agar without special techniques – chocolate agar. Require hemin, NAD or NADP Some species are normal colonists of upper respiratory tract or vagina (H. aegyptius, H. parainfluenzae, H ducreyi). Others are virulent species responsible for conjunctivitis, childhood meningitis, and chancroid.

53 53 Haemophilus H. influenzae – acute bacterial meningitis, epiglottitis, otitis media, sinusitis, pneumonia, and bronchitis –subunit vaccine Hib H. aegyptius –conjunctivitis, pink eye H. ducreyi – chancroid STD H. parainfluenzae and H. aphrophilus – normal oral and nasopharyngeal flora; infective endocarditis

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