1. Major Pathogens: Bacteria

2. Bacterial Pathogens
Pathogens = disease-causing bacteria
• Gram-positive cocci
• Gram-negative cocci
• Gram-positive rods
• Gram-negative rods
• Mycobacteria
• Walls too thick to stain for gram
• Mycoplasma
• Spirochetes
• Obligate intracellular parasites

3. Gram-Positive Cocci
Staphylococcus
(grape-like clusters)
Genus includes 33 species mostly harmless
Likes high osmotic pressure, low moisture
Staphylococcus aureus
Facultative anaerobe, golden yellow pigmented colonies
Skin infections (abscesses), impetigo
Conjunctivitis
Food poisoning
Toxic shock syndrome
Staphylococcal scalded skin syndrome (SSSS)
Nosocomial sepsis

4. Staphylococcus aureus

5. MOT and Pathology
 Normal habitat: Skin, nose, vagina
 33% are carriers
 Exotoxins:
 Enterotoxins: Food poisoning
 Toxic shock syndrome toxin
 Scalded skin syndrome toxin

6. Food poisoning
1-6 hoursIntoxication: infection by digestion

7. Impetigo
Skin infection caused by
Staphylococcus aureus

8. Scalded Skin Syndrome
Staphylococcus aureus
Usually in babies

9. Diagnosis, Prevention, Treatment
 Coagulase-positive; Catalase-positive
 MSA plate
 Hand-washing; proper food storage; frequent
tampon changes
 Penicillin (80% resistant)
 Oxacillin; (methicillin)
 Vancomycin
Rabbit
plasma

10. Streptococcus = cocci that grow in chains
Streptococcus pyogenes (Group A - GAS)
Pharyngitis (Strep. throat)
Scarlet fever
Rheumatic fever
Necrotizing fasciitis (flesh-eating disease)
Puerperal sepsis.

11. MOT and Pathology
 Droplet infection: Pharyngitis/ Strep throat
 Exotoxins:
 Scarlet fever
 Erythematous rash over body
 Hemolytic enzymes: necrotizing fasciitis
 Capsule
 Composed of hyaluronic acid
 Evades phagocytosis

12. Streptococcal
Pharyngitis

13. Scarlet Fever Rash caused by
Streptococcus pyogenes
Streptococcus epidemitis: normal flora (non pathogenic) on the
body that is opportunistic, can cause UTI’s.

14. Necrotizing Fasciitis due to
Streptococcus pyogenes
http://emedical-help.com/necrotizing-fasciitis-flesh-eating-disease/
Puerperal Sepsis: “Child Fever”

15. Diagnosis, Prevention, Treatment
 Culture swabs from lesions
 Beta-hemolytic on Blood Agar plates
 Antibody titer
 Proper hygiene during wound care
 Prolonged treatment with penicillin (Rheumatic
fever patients)
 Penicillin
 Debridement of infected tissues

16. Streptococcus agalactiae/dysgalactiae (Group B)
Neonatal meningitis and sepsis
Streptococcus mutans
Dental caries
Streptococcus viridans
Bacterial endocarditis
Streptococcus pneumoniae
Pneumonia
Adult bacterial meningitis

17. Streptococcus agalactiae/dysgalactiae (Group B)
Neonatal meningitis and sepsis
MOT and Pathology
Normal vaginal flora: Can colonize genital tract and cause
neonatal meningitis and sepsis
Prevention
Prophylactic Ampicillin (mother)
And Treatment
Penicillin (newborn)

18. Streptococcus mutans = facultative anaerobe
Dental caries (cavities)
• Metabolizes sugars to lactic acid  decays enamel
• Excretes a sticky polysaccharide for adhesion to
surfaces and each other  plaque
• Biofilm protects from extreme and changing
environment of the mouth
• Biofilm plaque best removed mechanically (floss)
• Oral Hygiene is important
• Treatment: Fill cavities

19. Streptococcus viridans
 Bacterial endocarditis
 Prevention
 Prophylactic
amoxicillin

20. Streptococcus pneumoniae
 Pneumonia, meningitis
 MOT
 Droplet
 Diagnosis
 Direct sputum culture
 Prevention
 Vaccination
 Treatment
 Penicillin or erythromycin

21. Gram-Negative Cocci
Neisseria: aerobic, found in mucous
membranes, release endotoxins
• Neisseria gonorrhea
Ophthalmic gonorrhea
Genital gonorrhea
• Neisseria meningitidis:
Adult bacterial meningitis (Meningococcal
meningitis)

22. Pus Discharge in
Gonorrhea

23. N. gonorrhea MOT & Pathology
 STD/STI
 PID (pelvic infl.
Disease)
 Diagnosis
 Culture (Gram-
negative
intracellular
diplococci
 Prevention
 Safe sex
 Treatment
 Ceftriaxone

24. Neisseria meningitidis
 MOT & Pathology
 Droplet: meningitis
 Stiff neck, fever, headache,
vomiting
 Diagnosis
 CSF Culture
 Prevention
 Vaccine
 Treatment: Penicillin,
Rifampicin

25. Gram-Positive Bacilli
• Spore-forming Gram-positive Bacilli
Bacillus anthracis: Anthrax
Bacillus cereus: Food poisoning
Clostridium botulinum: Botulism
Clostridium tetani: Tetanus (lockjaw)
Clostridium perfringens: Gas gangrene
Clostridium difficile: Pseudomembranous
enterocolitis

26. B. anthracis MOT & Pathology
 Spores (facultative anaerobe)
 Diagnosis
 Culture
 Prevention
 PPE
 Prophylaxis
 Vaccine (only for risk groups)
 Treatment
 Ciprofloxacin

27. Bacillus cereus: soil dwelling aerobe
 MOT and Pathology
 Spores ingested: food
poisoning
 Enterotoxin
 Prevention
 Proper food handling
 Treatment
 self-limiting

28. Clostridium botulinum: anaerobe
 MOT and Pathology
 Food contaminated with spores
 Vegetables, Honey
 Neurotoxin: very toxic
 Acetylcholine blocked:
paralysis of face/limbs
 Prevention
 Proper sterilization of food before
canning
 Treatment: Antitoxin

29. Clostridium tetani

30. C. tetani: anaerobe
 MOT and Pathology
 Spores enter wound
 Exotoxins
 Muscle spasms, lockjaw
 Diagnosis
 Direct observation
 Prevention
 Vaccine: DTaP/ Tdap
 Treatment: Tetanus immune globulin; antibiotics

31. Clostridium perfringens: anerobe

32. C. perfringens
 MOT & Pathology
 Spores enter wound after trauma
 Toxins and gas
 Tissue necrosis
 Diagnostics
 Foul smell
 Crepitation
 Prevention
 Clean wound thoroughly
 Treatment: Penicillin & Wound
debridement

33. Clostridium difficile
Pseudomembranous enterocolitis
 MOT & Pathology
 Fecal-Oral – usually nosocomial
 Broad-spectrum antibiotics allow C. difficile to
flourish
 Exotoxins: severe diarrhea
 Treatment
 Stop the antibiotic
 Re-hydration therapy
 Prevention
 Aseptic technique

34. Non-spore-forming Gram-positive
Bacilli
Corynebacterium diphtheriae
Diphtheria
Listeria monocytogenes
Gastroenteritis

35. Corynebacterium diphtheriae
• MOT & Pathology
• Sore Throat, fever, trouble
breathing
• Droplet infection
• Toxin: heart/ kidney damage
• Diagnosis
• Throat exam
• pseudomembrane
• Prevention
• DTaP contains toxoid
• Treatment: Antitoxin,
Penicillin

36. Listeria monocytogenes
• MOT & Pathology
• Ingestion of contaminated food
• Psychrophilic
• Spontaneous abortion
• Prevention
• Proper food handling
• Pasteurization
• Treatment
• Ampicillin

37. Gram-Negative Bacilli
Enteric Gram-negative Bacilli: facultative anaerobes
Escherichia coli: UTI, gastroenteritis
(Traveler’s diarrhea), hemolytic-uremic
syndrome.
Salmonella enteritidis: Gastroenteritis
Salmonella typhi: Typhoid fever
Shigella dysenteriae: Gastroenteritis
Campylobacter jejuni: Gastroenteritis
Helicobacter pylori: Gastric ulcer,
carcinoma of the stomach
Vibrio cholerae: Cholera
Vibrio parahemolyticus: Food toxicity

38. Enterobacteriaceae
• Large family of gram-negative rods
• Found primarily in colon
• Common features
• Facultative anaerobe, non-spore forming

39. Escherichia coli
• MOT & Pathology
• Normal Flora of human colon
• UTI (most common cause)
• Fecal-oral
• O157:H7 toxin: hemolytic-uremic syndrome
• Treatment
• Quinolones
• Self limiting
• Prevention
• Remove urinary catheters, ♀ wipe front to back,
water and food handling, handwashing

40. Salmonella enteritidis
• MOT & Pathology
• Fecal-oral (human and animal)
• Eggs and poultry
• Reptiles
• Treatment
• Self-limiting
• Rehydration therapy
• Prevention
• Public health
• Personal hygiene

41. Salmonella typhi
• MOT & Pathology
• Fecal-oral (human only)
• Typhoid fever
• Treatment
• Ciprofloxacin
• Prevention
• Personal hygiene
• Vaccine available (for travelers only)

42. Shigella dysenteriae
• MOT & Pathology
• Fecal-oral (human only)
• ID50 =10
• The four Fs: fingers, flies, food, and feces
• Treatment
• Rehydration/Ciprofloxacin
• Prevention
• Public health
• Personal hygiene

43. Campylobacter jejuni
• MOT & Pathology
• Fecal-oral (human and animal)
• Food or water contamination
• Treatment
• Ciprofloxacin
• Prevention
• Public health
• Personal hygiene

44. pH – Neutrophiles
& Acidophiles
As with temperature, bacteria have minimum, optimum and
maximum pH ranges.
Neutrophiles
• Protozoans and most bacteria have an optimum pH range of
6.5 to 7.5.
• pH range of human organs and tissues.
Acidophiles
• Most fungi & some bacteria grow best in acid niches.
• Example: Chemoautotrophic bacteria that live in mines and
in water that runs off from waste rock around mines.
• Obligate acidophiles have to live in an acidic environment.
• Acid-tolerant Microbes will survive in an acid environment, but
do not prefer that.
Images: HelicobacterPylori : Electron micrograph of H. pylori possessing multiple flagella.
Yutaka Tsutsumi, M.D. Professor Department of Pathology Fujita Health University School of
Medicine
Helicobacter
pylori
• Gram-negative, microaerophilic, and
acidophilic bacterium.
• Infects various areas of the stomach and
duodenum.
• Many cases of peptic ulcers, gastritis,
duodenitis, and perhaps some cancers are
caused by H. pylori infections.
• However, many who are infected do not
show any symptoms.
• Helicobacter spp. only known
microorganisms to thrive in highly acidic
environment of stomach.

45. Helicobacter pylori
• MOT and Pathology
– Ingestion, produce
ammonia
– Gastric ulcer
– Carcinoma
• Treatment
– Antibiotics
• Prevention
– None

46. pH : Cholera (Alkalinophiles)
Alkilinophiles
• Can live in water as well as soil with pH’s around
11.5 (14 is max alkilinity)!
• Example: Vibrio cholera (Cholera) will grow
outside the body at a pH of 9.0.
• Infectious gastroenteritis caused by the bacterium
Vibrio cholerae.
• Transmission occurs through ingesting contaminated
water or food.
• Major reservoir for cholera long assumed to be
humans, but considerable evidence exists that aquatic
environments can serve as reservoirs of the bacteria.
• Gram-negative bacterium that produces cholera
Alkilinophiles
• Action on mucosal epithelium lining of the small
intestine responsible for the characteristic massive
diarrhea.
• One of the most rapidly fatal illnesses known.
Progresses from first liquid stool to shock in 4 to 12
hours, with death quickly following without rehydration
treatment.

47. Vibrio cholerae
• MOT and Pathology
– Fecal-oral
– Contaminated H2O
– Enterotoxin
– Watery stools
• Treatment
– Rehydration therapy
• Prevention
– Public health
– Personal hygiene

48. Vibrio parahemolyticus
• MOT and Pathology
– Lives in warm seawater
– Ingestion of raw/undercooked seafood
• Treatment
– Self limiting (three days)
• Prevention
– Proper refrigeration and cooking of seafood

49. Nosocomial Gram-negative Bacilli
Klebsiella pneumoniae: Pneumonia and UTI
Proteus vulgaris: UTI especially hospital acquired
Pseudomonas aeruginosa: Burn sepsis and UTI and
more
Serratia marcescens: Burn sepsis

50. Klebsiella pneumoniae
• MOT & Pathology
– Respiratory tract and intestinal tract
– Droplet
– Catheter
• Treatment
– Antibiotics
• Prevention
– Prompt removal of urinary catheter

51. Proteus vulgaris
• MOT & Pathology
– Human colon
– Soil and H2O
– Highly motile, colonizes urethra, leads to
ascending infection
• Treatment/Prevention
– Antibiotics
– Prompt removal of catheters

52. Nail Infection with Pseudomonas
aeruginosa

53. Psuedomonas aeruginosa
• MOT & Pathology
– Soil, H2O, NF colon/skin
– Aqueous solutions
– Withstand disinfectants
– Burn wounds
– Purulent blue-green
discharge/fruity odor
• Treatment/Prevention
– Antibiotics
– Highly resistant
– Sterilization

54. Burn Infection with Pseudomonas
aeruginosa

55. Respiratory Gram-negative Bacilli
Bordetella pertussis: Whooping cough
Haemophilus influenza: Pediatric meningitis,
Otitis media, sinusitis, and epiglottitis
Legionella pneumophilia: Pneumonia

56. Bordetella pertussis
• MOT & Pathology
– Whooping cough
– Droplet infection
– Complications: pneumonia or CNS
• Treatment
– Erythromycin
• Prevention
– DTaP

57. Haemophilus influenza
• MOT & Pathology
– Droplet infection
– Type B encapsulated (Hib)
– Meningitis, otitis media, sinusitis, epiglottitis
• Treatment/Prevention
– Ceftriaxone
– Hib vaccine (Hemophilus influenza type B)

58. Legionella pneumophilia
• MOT & Pathology
– Inhalation of aerosols from infected H2O
– Grows best in warm waters
– Air conditioners, water-cooling towers
– Legionnaire’s disease: Pneumonia
• Treatment/Prevention
– Erythromycin
– Reduce aerosols
– Water treatment

59. Arthropod-borne disease:
Yersinia pestis: Plague
Borelia burgdorferi: Lyme disease (Spirochete)
Rickettsia rickettsii: Rocky mountain spotted fever
(Obligate intracellular parasite)

60. Yersinia pestis
• Plague (black death)
• Killed one quarter of the population of Europe
in the middle ages
• Fleas transmit
• Bubos: inflammed
lymphnodes
• Droplet = pneumonic plague

61. Lyme disease
Causative agent:
Borrelia burgdorferi
• Reservoir: Deer
• Vector: Ticks
• First symptom:
Bull's-eye rash
• Second phase:
Irregular heartbeat,
encephalitis
• Third phase: Arthritis

63. Obligate Intracellular Parasites
• Chlamydia trachomatis: NGU, pelvic
inflammatory disease (PID), eye infection
• Rickettsia rickettsii: Rocky mountain spotted
fever (RMSF)
• Rickettsia prowazeki: Typhus
• Lack ability to produce enough ATP to grow
independently

64. Chlamydia trachomatis
• Most common bacterial STI in USA
• Eye infection, fomites, birth canal
• PID
• Infertility
• Erythromycin

66. Rickettsia rickettsii: Rocky mountain
Spotted Fever
• Dogs and rodents are reservoir
• Tick-borne transmission
• Tetracycline
• Insect repellent/tick inspection

67. Rickettsia prowazeki
• Typhus
– Fever, chills, rash, meningitis, death
• Louse-borne
• Disease of poverty and wartime
• Control of body lice

68. Syphilis: Spirochaete Infection

69. Treponema pallidum
• STI
• Chancres
• Neurosyphilis: 10%; dementia
• Penicillin to treat; safe sex to prevent

70. Mycobacteria
• Aerobic acid-fast bacilli
• Mycobacterium tuberculosis:
• Pulmonary TB
– Droplet
– 90% asymptomatic: Skin Test
– Hemoptysis
• Mycobacterium avium: indistinguishable
from TB
– Widespread in environment

71. Mycobacterium leprae
• Leprosy
• Direct contact
• Nasal or skin secretions
• Replicates in skin
• Anesthesia, bone re-absorption
• Loss of digits or tip of nose
• Antibiotics
• Isolation of patients

72. Mycoplasma
• Smallest bacteria
• Lack cell wall
• Fluorescent stains to visualize
• Mycoplasma pneumoniae: walking pneumonia
– Droplet infection
– Common on campuses
– May be self-limiting or require antibiotics

73. Question
Staphylococcus and Streptococcus can be easily
differentiated in a lab by which of the following?
a) Cell shape
b) Gram stain reaction
c) Growth in high salt concentration
d) Ability to cause disease
e) Glucose fermentation