Bacterial Agents of Disease

1. Bacterial Agents of Disease

2. Gram-Positive Group • Traditionally, this group was based on Gram stain procedure • Now the grouping is based on Genetic similarity • Group is divided into two taxa based on GC content • High GC Gram positives (>50%) • Low GC Gram positives (<50%) • Acid fast species such as the Mycobacterium spp. are in this group even though they do not always stain positive with Gram stain • Mycoplasmas are included in this group even though they lack a cell wall structure

3. Staphylococcus aureus Diseases • Folliculitis, Abscesses, Furuncles (boils), sty • Pneumonia, meningitis, empyema, endocarditis, sepsis • Scalded skin syndrome-exfoliative exotoxin-producing strain • Toxic shock syndrome • Food poisoning by enterotoxin production in food Transmitted by contact and airborne routes Notes • MRSA-Methecillin Resistant Staphylococcus aureus

4. Other Staph. species • S. epidermidis • Normal flora of skin, opportunistic pathogen • Sepsis • UTI • S. saprophyticus • Normal flora of skin and genitourinary mucosa • UTI

5. Streptococci • Classified by group-specific antisera • Important groups include • A -S. pyogenes, produce many toxins and enzymes • B -S. algalactiae • D –S. bovis, Enterococcus spp.(now a separate genus)

6. Streptococcus pyogenes • Beta hemolytic, many other virulence factors Diseases • Wound infections • Impetigo • Necrotizing fasciitis ‘flesh-eating’ • Strep throat, • Scarlet fever caused only by streps infected with temperate phage • pneumonia, meningitis, endocarditis • Puerperal (childbed fever), rheumatic fever

7. S. pneumoniae • Alpha hemolytic Diseases • Bronchitis • Classic Pneumonia • Streptococcal Meningitis • Conjunctivitis (Pink eye) • Otitis

8. Other streptococcal infections • S. algalactiae -Group B strep disease • S. mutans -Dental caries

9. Enterococcus spp. • Enterococcus faecalis, and E. faecium • Virulence factors not well understood • Indicators of fecal pollution Diseases • Cholicystitis • Endocarditis • Septicemia • UTI • some strains are resistant to vancomycin (VRE)

10. Bacillus spp. • Rod-shaped often in chains • Many species, most are found naturally in soil • Endospore formers resistant to environmental extremes • Non-hemolytic forms are generally more dangerous • Produce a variety of toxins • Bacillus cereus • Heat-stable exotoxin can result in food poisoning giving rise to vomiting w/in hours after ingesting • Enterotoxin can cause diarrhea 10-12 hrs after ingestion

11. Bacillus anthracis • Anthrax can be: • Pulmonary -Usually only ca. 5% of cases but most severe form • Skin/cutaneous • Gastrointestinal • Toxin producer • Zoonosis, primarily affecting ungulates and occasionally predators • Vaccine widely used in livestock but not humans

12. Clostridium spp. • Anaerobic, endospore-forming rods • Found in soil, water and animals • Clostridium perfringens • Gas gangrene, tissue destruction by toxin and enzymes • Food poisoningthrough ingestion of toxins • C. difficile • Produces enterotoxin • causes pseudomembranous colitis • Causes antibiotic associated diarrhea

13. Clostridium tetani • Causes tetanus, spastic paralysis • Infections result when endospores enter host through wounds (or umbilical stump in neonates) and germinate under anaerobic conditions • Produces toxin called tetanospasmin • Toxin blocks release of inhibitory mediators (GABA and Glycine) from vesicles in spinal and sympathetic NS synapses causing spasms • Life cycle includes periods in intestines of animals and soil • Vaccine commonly administered in U.S. • .

14. Clostridium botulinum • Causes food poisoning, flaccid paralysis, Infant botulism • One of the most potent toxins known • Endospores germinate under anaerobic conditions, especially in improperly-packaged foods of humans or animals • Produces botulinum toxin (BT, Botox) which inhibits the release of acetylcholine at neuromuscular junction resulting in flaccid paralysis

15. Mycobacterium spp. • Closely related to Gram positive organisms but do not always stain as such using Gram procedure due to the lipid mycolic acid in cell wall • Intracellular parasites that resist digestion within phagosomes • Several species can cause disease in humans and animals • Some species are found in the environment

16. Mycobacterium tuberculosis • Causes tuberculosis (consumption) • Infection leads to tissue necrosis and chronic granulomas, mainly lungs but also other tissues including bones • Infection leads to hypersensitivity in host (positive PPD), but not necessarily active disease • Most cases in US are reactivation of initial infections • Increasingly resistant to antibiotics

17. Mycobacterium leprae • Hansen’s disease (leprosy) • Mainly a human disease; however, armadillos are also known to contract the disease • Infection gives rise to lesions on the extremities • Incubation is slow (2-10 yrs) • Endemic to Asia and Africa

18. Mycobacterium ulcerans • Causes Buruli Ulcer • An emerging disease in Africa and other tropical countries • Results in necrotic lesion that can cause significant disfigurement

19. Other diseases involving mycobacteria • Mycobacterium (avium) ssp. paratuberculosis causes Johnes disease in ungulates (hoofed animals), an intestinal wasting disease • Some evidence to implicate as a cofactor for Irritable bowel syndrome or Crohne’s disease

20. Actinomyces isrealii • Anaerobic, filamentous, branching rods • Normal flora that can be opportunistic pathogen • Causes hard lesions mostly around face, neck abdominal lesions after surgery , and uterine infections after IUD use

21. Corynebacterium diptheriae • Cell structure similar to Mycobacterium • Some strains cause Diptheria • Tox gene which is needed to cause the disease is introduced into genome by phage • Diptheria toxin can damage to heart, kidneys and NS • Can cause formation of pseudomembrane

22. Listeria monocytogenes • Short rods or coccobacilli • Listeriosis • Food borne (processed meats, milk, soft cheeses, and veggies) • Threat to fetus of pregnant women • Can grow in the refrigerator

23. Proprionibacterium acnes • Cofactor/proximate cause for acne • Clinical impact of treatment • Antibiotic use may increase resistance • Acutane (isotretinoin): strongly interferes with developmental processes may have severe side effects on tissues

24. Proteobacteria

25. Alphaproteobacteria

26. Brucella spp. • Cause Brucellosis, Malta fever • Several species that are genotypically similar, are differentiated by the primary host and cell surface antigens • B. abortus (cows) • B. melitensis (goat) • B. suis (pig) • they are highly infectious and considered to be potential agents of biowarfare/bioterrorism

27. Rickettsial Pathogens • Cat scratch fever- Bartonella henslae • Oroya fever/Verrugia Peruana- Bartonella bacilliformes • Trench fever- Rochalimaea (Bartonella) quintana • Epidemic typhus- Rickettsia prowazekii • RMSF- Rickettsia riskettsii • Scrub typhus- Rickettsia tsutsugamishi • Endemic typhus- Rickettsia typhi • Rickettsial pox- Rickettsia akari • HME- Ehrlichia chaffeensis • HGE-Anaplasma (Ehrlichia) phagocytophilum

28. Rickettsia spp.

29. Other rickettsial pathogens

30. Betaproteobacteria • Neisseria • Burkholderia • Bordetella

31. Bordetella pertussis • Whooping Cough (Pertussis) • Gram (-) coccobacillus • Non-invasive, toxin producing

32. Neisseria gonorrhoeae • Gonorrhea (the clap) • Gram (-) diploccocci • Endotoxin damages mucosa • Can spread to other systems, PID • Pus-filled discharge • # 1 communicable disease

33. Neisseria menigitidis • Meningococcal meningitis • Waterhouse-Friderichsen syndrome (endotoxic shock)

34. Gammaproteobacteria • Extremely diverse group • Contains many of the Gram negative enteric organisms

35. Bacterial Enteritis • Salmonellosis-Salmonellaenteriditis • Enterocolitis- S. typhimurium • Typhoid fever- Salmonella typhi • Shigellosis- Shigella spp. • Cholera- Vibrio cholerae • Vibriosis- Vibrio parahemolyticus and Vibrio vulnificus • Campylobacter jejuni • Yersinia enterocolitica

36. Salmonella typhi • Typhoid fever, nervous fever • Transmitted by fecal contamination • Several clinical stages last for weeks

37. Salmonella enterica • Salmonellosis “food poisoning” • Produce enterotoxins and cytotoxins • One species is divided into several serovars- different types that are distinguished only by antigens • Serovars that commonly cause salmonellosis are typhimurium and enteritidis • May be found in intestines of many vertebrates including birds, reptiles and mammals

38. Shigella spp • Shigellosis, dysentery • Endotoxin irritates bowel • Endotoxin affects intestine and nervous system

39. Escherichia coli • Most strains are non-pathogenic • Various genes increase virulence • Enteroinvasive E. coli • Enterotoxogenic E. coli • Enterohemorrhagic • E. coli O157:H7 is the most notable EHEC strain • produces Shiga toxin • Cattle may be primary reservoir Opportunistic infections • Traveler's diarrhea • Cholecystitis, cholangitis (infalmmation of gallbladder , bile ducts) • Prostatitis, UTI, kidney infections, septicemia

40. Pseudomonas aeruginosa • Burn infections • Eye infections associated with contact lenses

41. Yersinia pestis • Diseases: Bubonic, pneumonic and septicemic plague • Transmitted to humans by fleas such as Xenopsylla cheopis as well asthrough aerosolized fluids from infected hosts • Reservoirs: rodents • Sporadic, isolated outbreaks occur around the world

42. Vibrio cholerae • causes Cholera • Worldwide distribution, especially common in the tropics • Lives in environmental waters • Copepods and shellfish are reservoirs and can also be considered as vectors if swallowing them results in the disease • Infectivity is enhanced when organisms pass through human intestine • Route of transmission is usually through food or water contaminated with feces • Serogroups 0139 and 01 are most capable of producing epidemics

43. Other important Vibrio spp. • Vibrio vulnificus- wound infection, septicemia, endometritis, food “poisoning” • Mortality rate of around 40% • Acquired by eating raw oysters or swimming in ocean where organism lives naturally • Organisms invade through wounds, GI tract, and give rise to septicemia • 1 case report of endometritis • Vibrio parahemolyticus- food “poisoning”

44. Haemophilus spp. • Haemophilus ducreyi –Chancroid • Haemophilus influenzae • Found on mucous membrane of upper respiratory tract infections • Can cause meningitis in children • Encapsulated forms resist phagocytosis • Hib vaccine

45. Legionella pneumophila • Pontiac Fever is mild form • Legionnaire's Disease • Several protozoan reservoirs • Reside in phagocytes of human host

46. Others • Francisella tularensis -Tuleremia (rabbit fever) • Coxiella burnetii -Q fever • Pasteurella multocida -animal bite infections • Spirillum minor- rat bite fever

47. Epsilonproteobacteria

48. Helicobacter pylori • Lives in gastric mucosa • Produce urease and break down urea into ammonia to neutralize stomach acids • High infection prevalence, especially in developing countries • Cofactor for peptic ulcers and stomach cancer • Route of transmission may be fecal-oral but details unknown • One of the most common bacteria in humans (50% infection rate worldwide, some populations 100%)

49. Campylobacterjejuni • Common cause of diarrhea • Can cause septicemia • Transmitted through food and water contaminated with feces

50. Spirochaetes and other bacteria