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

2. 20.1 Aerobic Gram-Negative Nonenteric Bacilli
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

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

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

6. Figure 20.1 Pseudomonas aeruginosa

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. Figure 20.2 Skin rash from Pseudomonas

9. 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

10. Figure 20.3 Pseudomonas (left) and Staphylococcus (right)

11. 20.2 Related 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

12. 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

13. 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

14. 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

15. Figure 20.5 Agglutination titer test for brucellosis

16. 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

17. 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

18. 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

19. Figure 20.7 Prevalence of pertussis in the United States

20. 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

21. Legionella Pneumophila and Legionellosis
Widely distributed in water
Live in close association with amoebas
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

22. Figure 20.8 Appearance of Legionella pneumophila

23. 20.3 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

24. Figure 20.9 Bacteria that account for the majority of hospital infections

25. 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

26. Figure 20.10 Biochemical traits for separating enteric genera

27. Figure 20.11 Isolation media for enterics

28. Figure 20.12 BBL Enterotube II, rapid biochemical testing of enterics

29. 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

30. Figure 20.13 Antigenic structures in gram-negative enteric rods

31. 20.4 Coliform Organisms and Diseases

32. 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

33. 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

34. 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

35. Figure 20.14 Rapid identification of E. coli O157:H7

36. 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
Citrobacter sp. – opportunistic UTIs and bacteremia
Serratia marcescens – produces a red pigment; causes pneumonia, burn and wound infections, septicemia and meningitis

37. Figure 20.15 A capsule stain of Klebsiella pneumoniae

38. Figure 20.16 Serratia marcescens

39. 20.5 Noncoliform Lactose-Negative Enterics
Proteus, Morganella, Providencia
Salmonella and Shigella

40. 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

41. Figure 20.17 Wavelike, swarming pattern of Proteus vulgaris

42. 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

43. 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 Vi
Flagellated; survive outside the host
Resistant to chemicals – bile and dyes

44. 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 sulfatrimethoprim
2 vaccines for temporary protection

45. Figure 20.18 Prevalence of salmonelloses

46. Figure 20.19
The phases of typhoid fever

47. 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

48. Shigella and Bacillary Dysentery
Shigellosis – incapacitating dysentery
S. dysenteriae, S. sonnei, S. flexneri, and S. boydii
Human parasites
Invades villus of large intestine, does not perforate intestine or invade blood
Enters Peyer’s patches instigate inflammatory response; endotoxin and exotoxins
Treatment – fluid replacement and ciprofloxacin and sulfatrimethoprim

49. Figure 20.20 The appearance of the large intestinal mucosa in Shigella

50. 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

51. Nonenteric Yersinia Pestis and Plague
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

52. Figure 20.21 Gram-stain of Yersinia pestis

53. 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

54. Figure 20.22 Infection cycle of Yersinia pestis

55. 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

56. Figure 20.23 The bubo, classic sign of bubonic plague

57. 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

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

59. Pasteurella 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

60. 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. parainfluenzae, H. ducreyi)
Others are virulent species responsible for childhood meningitis, and chancroid

61. 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

62. Figure 20.25 Meningitis in the United States

63. Figure 20.26 Acute conjunctivitis