Chapter 20 The Gram-Negative Bacilli of Medical Importance

1. Chapter 20The Gram-Negative Bacilli of Medical Importance Aerobic Gram-Negative Nonenteric Bacilli -Pseudomonas aeruginosa -Burkholderia cepacia -Acinetobacter baumanii -Other Gram-Negative Nonenteric bacterium Enterobacteriaceae Family(Enteric bacteria)

3. General Characteristics of Gram-Negative Bacilli • Large, diverse metabolism and pathogenicity • Non-spore-forming bacteria • Wide range of habitats – large intestines (enteric), zoonotic, respiratory, soil, water, plants. • Most are not medically important; some are true pathogens(Samonella, Yersinia pestis, E.coli O-157etc), some are opportunists(P.aeruginosa, Burkholderia etc). • All have a lipopolysaccharide(LPS) outer membrane of cell wall- endotoxin,which induces a strong response from normal cells.

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 • Non-fermenting bacterium

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, even in sterile water • Important decomposers and bioremediators(clean oil contamination etc) • Frequent contaminants in homes and clinical settings • Use aerobic respiration; do not ferment carbohydrates • Produce oxidase and catalase • Many produce water soluble pigments. including pyocyanin (blue-green), fluorescein (yellow-green and fluorescent, now also known as pyoverdin), and pyorubin (red-brown), these can be used to identify Pseudomonas.

6. www.nasa.gov/.../content/155845main_microbe5.jpgwww.shroomery.org/.../P.aeruginosa_colonies.jpgwww.nasa.gov/.../content/155845main_microbe5.jpgwww.shroomery.org/.../P.aeruginosa_colonies.jpg 162.129.70.33/images/Pseudomonas_Aeruginosa_i...

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. Pseudomonas aeruginosa • Common cause of nosocomial infections in hosts with burns, neoplastic disease, cystic fibrosis, AIDS,cancer. P.aeruginosa is responsible for 16% of nosocomial pneumonia cases, 12% of hospital-acquired urinary tract infections, 8% of surgical wound infections, and 10% of bloodstream infections. • Complications include pneumonia, UTI, abscesses, otitis, and corneal disease (high mortality, 60%burn wounds infection, 30% bloodstream infection ) • Endocarditis, meningitis, bronchopneumonia • Grapelike odor • Greenish-blue pigment (pyocyanin) • Multidrug resistant bacteria • Cephalosporins, aminoglycosides, carbenicillin, polymixin, quinolones, and monobactams, Vaccine

9. Symptoms of Pseudomonas Infections As with other infections, symptoms include fever, chills, and the production of purulent matter in infected wounds. • Diagnosis of Pseudomonas Infections Diagnosis of pseudomonas infection is established by culturing the organism from infection sites

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. 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

12. 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

13. 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 antigens • Antibiotics (macrolides), erythromycin and azithromycin are useful.

14. 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

15. P.605

16. Enterobacteriaceae Family • Enterics (Facultative anaerobes) • 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.

17. General Characteristics • 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

18. Classification of Enterics • Coliforms in Normal flora: (lactose fermenters) E.coli, Klebsiella, Enterobacter, Hafnia, Serratia, Citrobacter • Noncoliforms in Normal Flora(lactose negative) Proteus, Morganella, Providencia, Edwardsiella • True pathogenic Enterics: Salmonella typhi, S.cholerae-suis, S. enteritidis, Shigella dysenteriae, S.flexneri, S. boydii, S. sonnei, Yersinia enterocolitica, Y. pseudotuberculosis • True pathogenic Nonenterics: Yersinia pestis

19. p.607. Procedure for Isolating and identifying selected enteric genera

21. 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.

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

23. 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

24. 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 • Serratiamarcescens – produces a red pigment; causes pneumonia, burn and wound infections, septicemia and meningitis • Citrobacter sp. – opportunistic UTIs and bacteremia

25. Noncoliform Lactose-Negative Enterics • Proteus, Morganella, Providencia • Salmonella and Shigella

26. 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.

28. 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

29. 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

30. 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

32. Animal Salmonelloses • Salmonelloses other than typhoid fever are called enteric fevers, Salmonellafood 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

33. 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

35. 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

36. 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

37. 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

39. 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

40. 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

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

42. 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.

43. 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

44. Chapter 21Miscellaneous Bacterial Agents of Disease Treponema and Syphilis Nonsyphilitic Treponematoses Leptospira and Leptospirosis Lyme disease and Borrelia burgodorferi Vibrio cholerae and Cholerae Campylobacter and diseases

45. The Spirochetes Common characteristics: • helical form • typical gram-negative cell wall • Periplasmic space that encloses the flagella • Most of are saprobes or commensals of animals. • Gram negative human pathogens: • Treponema • Leptospira • Borrelia

46. Typical spirochetes p.627, Fig21.1

47. Genus Treponema • Thin, regular, coiled cells • Live in the oral cavity, intestinal tract, and perigenital regions of humans and animals • Pathogens are strict parasites with complex growth requirements. • Require live cells for cultivation Disease caused by Treptonema are called treptonematoses

48. Treponema pallidum: The Spirochete of Syphilis • Human is the natural host • Extremely fastidious and sensitive; cannot survive long outside of the host • Sexually transmitted and transplacental (coinfection with AIDs and other STDs) • Infectious dose is 57 organisms

50. Primary syphilis – appearance of hard chancre at site of inoculation; chancre heals spontaneously • Secondary syphilis – fever, headache, sore throat, red or brown rash on skin, palms and soles; rash disappears spontaneously • Tertiary syphilis – about 30% of infections enter in tertiary stage; can last for 20 years or longer; numerous pathologic complications occur in susceptible tissues and organs • neural, cardiovascular symptoms, gummas develop • Congenital syphilis – nasal discharge, skin eruptions, bone deformation, nervous system abnormalities(can be carried to the fetal tissue)