The document discusses several gram-negative bacteria including Vibrios, Pseudomonas, Campylobacter, Helicobacter, Haemophilus, Bordetella, and Brucella. It describes their characteristics, habitats, mechanisms of infection, diseases caused, methods of diagnosis and treatment. Key points covered include that Vibrio cholerae causes cholera, Pseudomonas aeruginosa causes opportunistic infections, Campylobacter jejuni is a common cause of food poisoning, and Haemophilus influenzae was a major cause of childhood meningitis prior to vaccination.

1. Vibrios, Pseudomonas, Campylobacter, Helicobacter Other gram-negative bacilli

2. VIBRIOS Among the most common bacteria in surface waters worldwide Curved, aerobic rods; motile with polar flagella oxidase (+) grow best on alkaline media Often found in brackish water

3. Vibrio cholerae Classified based on somatic O antigen: V. cholerae O1 – most common cause of epidemic & pandemic cholera V. cholerae O139 (Bengal strain) – epidemic Non-O1 group Two biotypes (based on differences in biochemical reactions): El Tor – most common cause of epidemics and cause of 7 th pandemic Cholerae or classical Three serotypes (based on antigenic differences): Ogawa, Inaba, Hikojima

4. Vibrio cholerae MOT: fecal-oral Sources of infection: humans, marine shellfish (shrimp and oysters) Sensitive to gastric acid  high infective dose Virulence factors: Mucinase – cause adherence to cells of the brush border of the gut Choleragen – stimulate adenylyl cyclase

5. Vibrio cholerae

6. Vibrio cholerae Cholera Toxin B subunit A subunit Binds GM1 ganglioside (surface of epithelial cells) Carried to ER (retrograde transport) Endocytosis Reduced by protein disulfide isomerase in ER Cytosol Unfolding Refolding Interact with cytosolic ADP ribosylation factors Activate G protein Stimulate adenylate cyclase Inc. cAMP Open CFTR Cl released in lumen; secretion of HCO 3 , Na + & water

7. Vibrio cholerae Clinical findings: Voluminous watery diarrhea – hallmark; “rice water” stool Loss of fluid and electrolytes – marked dehydration “ washerwoman” hands Cardiac and renal failure Hypovolemic shock

8. Vibrio cholerae Diagnosis: Culture on MacConkey’s agar (slow lactose fermenter) or TCBS (Thiosulfate citrate bile salt sucrose) agar plate for selective isolation Oxidase (+) – distinguished from the family Enterobacteriaceae Serology Treatment: Prompt and rapid fluid and electrolyte replacement Tetracycline – shorten duration

9. Growth on TCBS agar plate

10. Vibrio parahaemolyticus Halophilic – grows on 8% NaCl solution MOT: ingestion of raw or undercooked seafood, especially shellfish such as oysters Mild to severe watery diarrhea, nausea and vomiting, abdominal cramps, fever  self-limited No specific treatment indicated

12. Vibrio vulnificus Found in warm salt waters Causes severe skin and soft tissue infections (cellulitis), especially in shellfish handlers Rapid, fatal septicemia in immunocompromised people who have eaten raw shellfish Treatment: doxycycline

14. Pseudomonas aeruginosa Gram-negative rods that resemble the Enterobacteriaceae but are strict aerobes Derive energy by oxidation of sugars rather than fermentation Oxidase (+) Able to grow in water containing only traces of nutrients

15. Pseudomonas aeruginosa Produce two pigments: Pyocyanin (blue) Pyoverdin (fluorescein) – yellow green pigments that fluoresce under UVL Found chiefly in soil and water Found on the skin in moist areas Primarily opportunistic

16. Pseudomonas aeruginosa Virulence factors: Endotoxins – cause sepsis and shock Exotoxin A – cause tissue necrosis; inhibits eukaryotic protein synthesis similar to diphtheria exotoxin Enzymes Elastases and proteases Pyocyanin – damages the cilia and mucosal cells of respiratory tract

17. Pseudomonas aeruginosa Clinical: Urinary tract infections Pneumonia in cystic fibrosis patients Burn wound infection Sepsis Ecthyma gangrenosum – black necrotic lesions on skin Malignant external otitis Folliculitis Osteochondritis of the foot due to punctured wounds through the soles of gym shoes - most common cause

19. Ecthyma gangrenosum

21. Osteochondritis of foot

23. Pseudomonas aeruginosa Diagnosis: Culture – non-lactose fermenting Oxidase production Biochemical reactions – confirmatory Treatment: Resistant to many antibiotics Ticarcillin or piperacillin + aminoglycoside (gentamicin or amikacin)

24. Production of pyocyanin, water-soluble green pigment of Pseudomonas aeruginosa. (left tube)

25. Campylobacter jejuni Comma- or S-shaped rods Microaerophilic (5% oxygen) Grows well at 42 0 C Sources of infection: domestic animals MOT: fecal-oral (poultry, meat, unpasteurized milk common sources)

27. Campylobacter jejuni Clinical: Enterocolitis – begins as watery, foul-smelling diarrhea  bloody stools Associated with Guillain-Barre syndrome Most common cause of acute neuro-muscular paralysis Autoimmune disease Reactive arthritis Reiter’s syndrome

28. Campylobacter jejuni Diagnosis: Culture Oxidase (+); sensitive to nalidixic acid Treatment: erythromycin or ciprofloxacin

29. Helicobacter pylori Curved; gram-negative; similar in appearance to Campylobacter Strongly urease positive  convert urea to ammonia  neutralize gastric acid Rapidly motile – allow organism to penetrate protective mucus layer

34. Helicobacter pylori Most common cause of chronic gastritis Most common cause of duodenal ulcers Second most common cause of gastric ulcer Associated with development of gastric CA and gastric lymphoma

35. Helicobacter pylori Diagnosis: Culture Urease production  urea breath test

38. Helicobacter pylori Treatment: Proton pump inhibitors (Omeprazole) Antibiotics – amoxicillin, metronidazole, tetracycline Bismuth salts

39. HAEMOPHILUS Family Pasteurellaceae Small, gram negative, pleomorphic Require enriched media containing blood or its derivatives Facultative anaerobes Obligate parasites

40. Haemophilus influenzae (Pfeiffer’s Bacilli) Found on mucus membrane of URT in humans (non-capsular form)  encapsulated species uncommon members of normal flora Short, coccoid bacilli in pairs or chains

41. Haemophilus influenzae Classification: Serotype – based on capsular antigen Biotype – based on biochemical properties a. indole production b. urease activity c. ornithine decarboxylase activity Biogroup – useful for clinical purposes

42. Haemophilus influenzae: Culture Chocolate agar – flat, grayish brown colonies after 24 hrs incubation Does not grow on sheep blood agar except around colonies of Staphylococci  “satellite phenomenon”

43. Haemophilus influenzae Growth Characteristics: Requires X factor (hemin) and V factor (NAD) Ferments carbohydrates poorly and irregularly

44. Haemophilus influenzae Characteristics & Growth Requirements: Species X Factor V Factor Hemolysis H. influenzae H. parainfluenzae H. ducreyi H. haemolyticus H. parahaemolyticus H. aprophilus + - + + - - + + - + + - - - - + + -

45. Haemophilus influenzae: Virulence Factors Capsule Antiphagocytic; impair ciliary function Main virulence factor With capsular polysaccharides (a to f) Type b – polyribose-ribitol phosphate (PRP)

46. Somatic antigen Outer membrane proteins  lipooligo-saccharides (endotoxin) IgA1 proteases Haemophilus influenzae: Virulence Factors

47. Haemophilus influenzae: Clinical Features H. influenzae type b Most common serotype causing systemic disease Meningitis Pneumonia & empyema Epiglottitis Cellulitis Septic arthritis

48. Non-typable (non-encapsulated) H. influenzae opportunistic Chronic bronchitis Otitis media Sinusitis Conjunctivitis Haemophilus influenzae: Clinical Features

49. Meningitis 2 0 to bacteremic spread from nasopharynx Peak incidence: 3 – 18 mos. old Epiglottitis Cellulitis & swelling of supraglottic tissues Pharyngitis, fever & dyspnea  complete airway obstruction  death

50. Cellulitis Reddish blue patches on cheeks or periorbital areas

51. Arthritis Infection of a single large joint Children < 2 y/o or immunocompromised patients or those with previously damaged joints Conjunctivitis Epidemic and endemic H. influenzae biogroup aegypticus

52. Haemophilus influenzae Clinical Features: Sepsis with gangrene

53. Haemophilus influenzae: Prevention Chemoprophylaxis with Rifampicin for non-immune children < 4 y/o who are close contacts Hib conjugate vaccine > 2 mos. old  Hib conjugated with C. diphtheriae toxin protein or N. meningitidis outer membrane complex > 15 mos. old  Hib conjugated with diphtheria toxoid

54. Haemophilus aegypticus H. influenzae biotype III Koch-Weeks bacillus Resembles H. influenzae closely Diseases: Conjunctivitis – highly communicable Brazilian purpuric fever – fever, purpura, shock and death

55. Haemophilus ducreyi Causes chancroid (soft chancre) Ragged ulcer on genitalia with marked swelling and tenderness Lymph nodes enlarged and painful Organism grows best on chocolate agar incubated in 10% CO 2 No permanent immunity

56. Haemophilus ducreyi

57. Bordetella pertussis Small, coccobacillary, encapsulated, gram (-) With bipolar metachromatic granules (toluidine blue stain) Non-motile; strict aerobe Forms acid from glucose and lactose

58. Bordetella pertussis Requires enriched media Bordet-Gengou medium (potato-blood-glycerol agar) Contains Pen G 0.5 ug/mL Virulence genes – bvgA and bvgS

59. Bordetella pertussis Gram stain Culture on chocolate agar

60. Bordetella pertussis: Virulence Factors Filamentous hemagglutinin Protein on pili; adhesion to ciliated epithelial cells Pertussis toxin promote lymphocytosis via inhibition of signal transduction by chemokine receptors  lymphocytes do not enter lymphoid tissues promote sensitization to histamine enhance insulin secretion stimulate adenylate cyclase via ADP-ribosylation

61. Adenylyl cyclase toxin – inhibit phagocytosis Tracheal cytotoxin Fragment of bacterial peptidoglycan Induce nitric oxide  destroy ciliated epithelium Dermonecrotic toxin Hemolysin Bordetella pertussis: Virulence Factors

62. Adheres to and multiplies rapidly on epithelial surface of trachea and bronchi  interfere with ciliary action No invasion of blood Bordetella pertussis: Pathogenesis

63. MOT: airborne droplets Source of infection: patients in early catarrhal stage Disease: Pertussis or Whooping Cough  acute tracheobronchitis Incubation period: approx. 2 weeks Bordetella pertussis: Pathogenesis

64. Clinical: Stages of Disease Catarrhal Mild coughing and sneezing Highly infectious but not very ill Paroxysmal (1-4 weeks) Series of hacking coughs, accompanied by copious amts. of mucus, ending with inspiratory “whoop”  exhaustion, vomiting, cyanosis and convulsions High wbc count (16,000-30,000/uL) with absolute lymphocytosis Convalescence - slow

65. Specimen: saline nasal wash (preferred) or nasopharyngeal swab Direct fluorescence antibody test – 50% sensitivity Culture of saline nasal wash fluid PCR – most sensitive Serology – (+) only on third week of illness  of little diagnostic value Bordetella pertussis: Diagnosis

66. First defense is antibody that prevents attachment Recovery from disease or immunization is followed by immunity Second infection may occur but is mild Re-infection occurring years later in adults may be severe Vaccine-induced immunity not completely protective

67. Chemoprophylaxis – Erythromycin  for exposed, unimmunized individuals OR exposed, immunized children < 4 years old Vaccine – two vaccines available: acellular vaccine – contains 5 purified antigens  main immunogen is inactivated pertussis toxin; first vaccine to contain a genetically inactivated toxoid  ADP-ribosylating activity removed DPT x 3 doses

68. BRUCELLA Zoonotic  obligate parasite of animals & humans Intracellular organism Gram negative coccobacilli Aerobic; non-motile; non-spore-forming

69. BRUCELLA Catalase (+); oxidase (+) Produces H 2 S Culture: trypticase soy agar OR blood culture media; B. abortus requires 5-10% CO 2 for growth

70. Route of infection in humans: Intestinal tract – ingestion of infected milk & contaminated dairy products (cheese from unpasteurized goat’s milk) Mucous membranes – droplets Skin – contact with infected tissues of animals Pathogenesis: endotoxin – O antigen polysaccharide

71. Species Animal Pathology B. melitensis Goats Acute and severe infection B. suis Swine Chronic with suppurative lesions; caseating granulomas B. abortus Cattle Mild disease without suppuration; Non-caseating granulomas of the RES (LN, liver, spleen, BM) B. canis Dogs Mild disease

72. Clinical: Brucellosis (Undulant or Malta Fever) Acute Malaise, fever, weakness, aches & sweats Fever rises in the afternoon  fall during the night with drenching sweats (+) lymphadenopathy w/ palpable spleen; + hepatitis with jaundice Chronic With psychoneurotic symptoms Weakness, aches & pains, low grade fever

73. Diagnosis: Culture BM & blood – commonly used specimen Brucella agar, trypticase soy medium, brain heart infusion medium, chocolate agar Serology – inc. IgM during 1 st week of illness; peak at 3 months