1. The Gram-Positive Bacilli of Medical Importance
Chapter 19

4. Bacillus gram-positive, endospore-forming, motile rods mostly saprobic
aerobic & catalase positive
source of antibiotics
primary habitat is soil
three species of medical importance
B. anthracis
B. cereus
B. subtillis

5. Bacillus spore

6. Bacillus anthracis 1877 – Robert Koch Anthrac is Greek for coal
Large (one of the largest), block shaped rods
central spores that develop under all conditions, except in the living body
virulence factors – capsule & exotoxins
3 types of human anthrax
Cutaneous – spores enter through skin, black sore- eschar; least dangerous
Pulmonary –inhalation of spores, most dangerous
Bacteremia, speen, dies quickly
Gastrointestinal – ingested spores in contaminated meat

7. Zoonotic disease (cattle/sheep)
Affected animals must be burned
Problems with leather jackets, violin bows and shaving bristles
Very low incidence : 27 cases in
Russia 1979—66 died
treated with penicillin or tetracycline
vaccine – toxoid 6X over 1.5 years; annual boosters (side effects?)
Very easy to grow in lab
Bio-terrorist threat
After 9/11 6 people died from Anthrax

8. Anthrax

9. Anthrax Spore

11. Cutaneous Anthrax

12. Cutaneous Anthrax - Eschar

15. Bacillus cereus common airborne & dustborne
grows in foods, spores survive cooking & reheating
ingestion of toxin-containing food causes nausea, vomiting, abdominal cramps & diarrhea
Begin ½ half to six hours after eating
24 hour duration usually self-limiting
no treatment
spores abundant in the environment

16. Bacillus cereus
Very common in certain foods that are being reheated a number of times
Potatoes, meat, rice
Nausea, vomiting, cramps, diarrhea
24 hour food poisoning
Self-limiting

17. B. cereus

18. Bacillus cereus

19. Culprit?

20. B. subtillis Used in lab research Usually opportunistic
Can be used as a probiotic
Eye infections
Lung and blood infections
Can get into spoiled bread dough and cause “ropiness”

21. B. subtillis

22. Clostridium gram-positive, spore-forming rods
anaerobic & catalase negative
120 species
oval or spherical spores produced only under anaerobic conditions
synthesize organic acids & alcohols & exotoxins
cause wound & tissue infections & food intoxications

23. Clostridium perfringens
Found in intestinal tracts
Causes gas gangrene in damaged or dead tissues
Produces a gas that putrifies muscle protein (fermentation of carbohydrates)
2nd most common cause of food poisoning, worldwide (meat, poultry, beans)
Symptoms develop 6 to 72 hours
Pain, swelling, dark yellow-green then black, foul odor
virulence factors
toxins – alpha toxin – causes RBC rupture, edema & tissue destruction
collagenase
hyaluronidase
DNase

25. Warning!
Graphic Pictures!

31. Frostbite (dry gangrene)

32. Clostridium perfringens
Consumption of large amount of vegetative cells produces enterotoxin—clostridial food poisoning
Meat, poultry, and beans

33. Clostridium tetani common resident of soil & GI tracts of animals
causes tetanus or lockjaw, a neuromuscular disease
spores usually enter through accidental puncture wounds, burns, umbilical stumps, frostbite, & crushed body parts
tetanospasmin – neurotoxin causes paralysis
vaccine booster needed every 10 years

38. Clostridium botulinum
Causes 3 diseases
food poisoning -spores are in soil, may contaminate vegetables; improper canning does not kill spores & they germinate in the can producing botulinum toxin
toxin causes paralysis by preventing release of acetylcholine
infant botulism – caused by ingested spores that germinate & release toxin
wound botulism – spores enter wound & cause food poisoning symptoms

40. Clostridium difficile
normal resident of colon, in low numbers
causes antibiotic-associated colitis
treatment with broad-spectrum antibiotics kills the other bacteria, allowing C. difficile to overgrow
produces entertoxins that damage intestine
major cause of diarrhea in hospitals

41. Listeria monocytogenes
non-spore-forming gram-positive
ranging from coccobacilli to long filaments
1-4 flagella
no capsules
resistant to cold, heat, salt, pH extremes & bile
primary reservoir is soil & water
can contaminate foods & grow during refrigeration
Cheese, milk products, fruit
Listerosis in immunocompromised patients, fetuses & neonates affects brain & meninges
20% death rate
ampicillin & trimethoprimsulfamethoxazole 
Prevention – pasteurization & cooking

42. Listeriosis Cases as of Feb. 2015 (carmalized apples)

43. Erysipelothrix rhusiopathiae
gram-positive rod widely distributed in animals & the environment
primary reservoir – tonsils of healthy pigs
enters through skin abrasion, multiples to produce erysipeloid, dark red lesions
penicillin or erythromycin
vaccine for pigs

44. Erysipeloid

46. Corynbacterium diptheriae
gram-positive irregular bacilli (palisade)
Aerobic, produces catalase
possess mycolic acids & a unique type of peptidoglycan
Have metachromatic granules stain as spots
Club shaped
2 stages of disease
local infection –upper respiratory tract
Slow healing ulceration called cutaneous diphtheria
diptherotoxin production & toxemia

47. Pseudo-membrane formation can cause asphyxiation
whitish- green gray film will develop in the throat
Symptoms: sore throat, fever, fatigue, malaise, swelling in neck
Death results from heart and kidney failure due to spread of toxin
Treatment: anti-toxin to neutralize the exotoxin, penicillin
Vaccine: 3 shots- DPT
Humans only reservoir

48. C. diphtheriae

51. Propionibacterium acnes
gram-positive rods
aerotolerant or anaerobic
nontoxigenic
common resident of sebaceous glands
causes acne

52. Propionibacterium acnes

54. Mycobacteria gram-positive irregular bacilli
acid-fast staining (stain must be heated)
strict aerobes
produce catalase
possess mycolic acids & a unique type of peptidoglycan
do not form capsules, flagella or spores
grow slowly
Mycobacterium tuberculosis
Mycobacterium leprae

55. Mycobacterium tuberculosis
Isolated in 1882 by Robert Koch
produces no exotoxins or enzymes that contribute to infectiousness
contain complex waxes & cord factor that prevent destruction by lysosomes of macrophages
transmitted by airborne respiratory droplets
Turn of 20th century leading cause of death in world (1/7)
only 5% infected people develop clinical disease

57. Primary TB Minimum infectious dose 10 cells
20% no infection (-)/ 80% infection (+)
phagocytosed by alveolar macrophages & multiply intracellularly
after 3-4 weeks immune system attacks, forming tubercles, granulomas consisting of a central core containing bacilli surrounded by WBCs
The disease usually stops here

58. Tubercle

59. Tubercle Granuloma

60. Secondary TB Bacilli can be latent for years
Reactivation (re-exposure) of bacilli
tubercles expand & drain into the bronchial tubes & upper respiratory tract
gradually patient experiences more severe symptoms
violent coughing, greenish or bloody sputum, fever, anorexia, weight loss, fatigue, chest pain
untreated 60% mortality rate

61. Extrapulmonary TB
during secondary TB, bacilli disseminate to regional lymph nodes, kidneys, long bones, genital tract, brain, meninges
Obviously, not a good outcome

62. Diagnosis in vivo or tuberculin testing X rays
direct identification of acid-fast bacilli in specimen
cultural isolation and biochemical testing

70. Treatment of TB 20-25 million worldwide active TB 3 million die/year
6-24 months of at least 2 drugs from a list of 11
one pill regimen called Rifater (isoniazid, rifampin, pyrazinamide)
vaccine based on attenuated bacilli Calmet-Guerin strain of M. bovis used in other countries

72. Mycobacterium leprae Hansen’s bacillus
strict parasite – has not been grown on artificial media or tissue culture
slowest growing of all species
multiplies within host cells in large packets called globi
causes leprosy, a chronic disease that begins in the skin & mucous membranes & progresses into nerves

73. Leprosy – Hansen’s Disease
endemic regions throughout the world
spread through direct inoculation from leprotics
2 forms
tuberculoid – superficial infection without skin disfigurement which damages nerves and causes loss of pain perception
lepromatous – a deeply nodular infection that causes severe disfigurement of the face & extremities
treatment by long-term combined therapy

83. Actinomycetes
Genera Actinomyces & Nocardia are nonmotile filamentous bacteria related to mycobacteria
may cause chronic infection of skin and soft tissues
Actinomyces sp – responsible for diseases of the oral cavity & intestines
Nocardia brasiliensis causes pulmonary disease similar to TB