1. © 2015 Pearson Education, Inc. I. Normal Human-Microbial Interactions 23.1 Beneficial Human–Microbial Interactions 23.2 Microflora of the Skin 23.4 Microflora of the Gastrointestinal Tract 23.5 Microflora of Mucosal Tissues

2. © 2015 Pearson Education, Inc. 23.1 Beneficial Human–Microbial Interactions Most microorganisms are benign Few contribute to health, and fewer pose direct threats to health Normal microbial flora (“microflora” or “microbiome”) Microorganisms usually found associated with human body tissue Humans are colonized by microorganisms at birth

3. © 2015 Pearson Education, Inc. 23.1 Beneficial Human–Microbial Interactions Humans are colonized by microorganisms at birth Acquire microbes via birth canal-lactobacillus Scientists swab C-section babies with mothers' microbes Newborns were exposed experimentally to vaginal microbes to restore the microbiomes they missed. Trends Mol Med. Author manuscript; available in PMC 2015 Jun 13. Published in final edited form as: Trends Mol Med. 2015 Feb; 21(2): 109–117. Published online 2014 Dec 11. doi: 10.1016/j.molmed.2014.12.00210.1016/j.molmed.2014.12.002 PMCID: PMC4464665 NIHMSID: NIHMS695563 The infant microbiome development: mom matters Noel T. MuellerNoel T. Mueller, 1,2 Elizabeth Bakacs, 3 Joan Combellick, 4 Zoya Grigoryan, 3 and Maria G. Dominguez- Bello 3Elizabeth BakacsJoan CombellickZoya GrigoryanMaria G. Dominguez- Bello Author information ►Author information ► Copyright and License information ►Copyright and License information ►

4. © 2015 Pearson Education, Inc. 23.1 Beneficial Human–Microbial Interactions Continued exposure throughout life Evolutionary perspective??? Clin Exp Immunol. 2010 Apr; 160(1): 1–9. The ‘hygiene hypothesis’ for autoimmune and allergic diseases: an update H OkadaH Okada, C Kuhn, H Feillet, and J-F BachC KuhnH FeilletJ-F Bach Gut. 2005 Mar; 54(3): 317–320. Microbes, immunoregulation, and the gut G A W RookG A W Rook and L R BrunetL R Brunet ‘old friends hypothesis’

5. © 2015 Pearson Education, Inc. 23.2 Microflora of the Skin The skin surface varies greatly in chemical composition and moisture content Three microenvironments Dry skin Moist skin Sebaceous skin Skin microflora examined by genomic methods 19 phyla detected Each microenvironment shows a unique microbiota (Figure 23.2)

6. © 2015 Pearson Education, Inc. Bacteroidetes 6.3% Others 1% Gram negative Proteobacteria 16.5% Actinobacteria 51.8% Gram positive Firmicutes 24.4% Other Flavobacteriales Betaproteobacteria Corynebacteria Staphylococci Propionibacteria Figure 23.2

7. © 2015 Pearson Education, Inc. Distribution of microflora on surface of human body

8. © 2015 Pearson Education, Inc. 23.4 Microflora of the Gastrointestinal Tract The human gastrointestinal (GI) tract (Figure 23.5) Consists of stomach, small intestine, and large intestine Responsible for digestion of food, absorption of nutrients, and production of nutrients by the indigenous microbial flora Contains 10 13 to 10 14 microbial cells

9. © 2015 Pearson Education, Inc. Major bacteria present Prevotella Streptococcus Veillonella Helicobacter Proteobacteria Bacteroidetes Actinobacteria Fusobacteria Enterococci Lactobacilli Bacteroides Bifidobacterium Clostridium Enterobacteria Enterococcus Escherichia Eubacterium Klebsiella Lactobacillus Methanobrevibacter (Archaea) Peptococcus Peptostreptococcus Proteus Ruminococcus Staphylococcus Streptococcus Anus Colon IIeum Jejunum Duodenum Large intestine Small intestine Stomach Esophagus Organ Esophagus Major physiological processes Secretion of acid (HCI) Digestion of macromolecules pH 2 Continued digestion Absorption of monosaccharides, amino acids, fatty acids, water pH 4–5 Absorption of bile acids, vitamin B 12 pH 7 Figure 23.5

10. © 2015 Pearson Education, Inc. 23.4 Microflora of the Gastrointestinal Tract Functions and products of intestinal flora Intestinal microorganisms carry out a variety of essential metabolic reactions that produce various compounds The type and amount produced are influenced by the composition of the intestinal flora and the diet Compounds produced include: Vitamins Gas, organic acids, and odor Enzymes

11. © 2015 Pearson Education, Inc. 23.5 Microflora of Mucosal Tissues A restricted group of organisms colonizes the upper respiratory tract (Figure 23.7) Examples: staphylococci, streptococci, diphtheroid bacilli, and gram-negative cocci The lower respiratory tract lacks microflora in healthy individuals

12. © 2015 Pearson Education, Inc. 23.5 Microflora of Mucosal Tissues Urogenital tract (Figure 23.8a) The bladder is typically sterile in both males and females Altered conditions (such as change in pH) can cause potential pathogens in the urethra (such as Escherichia coli and Proteus mirabilis) to multiply and become pathogenic E. coli and P. mirabilis frequently cause urinary tract infections in women

13. © 2015 Pearson Education, Inc. 23.5 Microflora of Mucosal Tissues The vagina of the adult female is weakly acidic and contains significant amounts of glycogen Lactobacillus acidophilus, a resident organism in the vagina, ferments the glycogen, producing lactic acid (Figure 23.8b) Lactic acid maintains a local acidic environment

14. © 2015 Pearson Education, Inc. II. Pathogenesis 23.6 Pathogenicity and Virulence 23.7 Adherence 23.8 Invasion, Infection, and Virulence Factors 23.9 Exotoxins 23.10 Endotoxins

15. © 2015 Pearson Education, Inc. 23.6 Pathogenicity and Virulence Pathogen-a disease-causing microbe Pathogenicity-the ability of a pathogen to inflict damage on the host Virulence is the relative ability of a pathogen to cause disease Measure of pathogenicity variable Pathogens use various strategies to establish virulence (Figure 23.9) Opportunistic pathogen-causes disease only in the absence of normal host resistance

16. © 2015 Pearson Education, Inc. 23.6 Pathogenicity and Virulence Measuring virulence Virulence can be estimated from experimental studies of the LD 50 (lethal dose 50 ) The amount of an agent that kills 50% of the animals in a test group (Figure 23.10) Highly virulent pathogens show little difference in the number of cells required to kill 100% of the population as compared to 50% of the population

17. © 2015 Pearson Education, Inc. 23.6 Pathogenicity and Virulence Attenuation The decrease or loss of virulence Toxicity Organism causes disease by means of a toxin that inhibits host cell function or kills host cells Toxins can travel to sites within host not inhabited by pathogen Exo-, endo-, entero- toxins

18. © 2015 Pearson Education, Inc. 23.6 Pathogenicity and Virulence Invasiveness Ability of a pathogen to grow in host tissue at densities that inhibit host function Can cause damage without producing a toxin Many pathogens use a cocktail of adherence, toxins, invasiveness, and other virulence factors to enhance pathogenicity

19. © 2015 Pearson Education, Inc. 23.7 Adherence First step in disease Adherence is ability of microbe to stick to a surface Pathogenic bacteria that initiate infection must adhere to epithelial cells through interactions between molecules on the surfaces of the pathogen and the host cell (Figure 23.12)

20. © 2015 Pearson Education, Inc. 23.7 Adherence Bacterial adherence can be facilitated by Extracellular macromolecules that are not covalently attached to the bacterial cell surface Examples: slime layer, capsule (Figure 23.13) Fimbriae and pili (Figure 23.14) Examples: pathogenic strains of E. coli, Neisseria gonorrheae, Shigella spp. “adherence factors” or “adhesins”

21. © 2015 Pearson Education, Inc. Figure 23.12

22. © 2015 Pearson Education, Inc. 23.8 Invasion, Infection, and Virulence Factors The initial inoculum of a pathogen is insufficient to cause host damage The pathogen must multiply and colonize the tissue The availability of nutrients is most important in affecting pathogen growth Pathogens may grow locally at the original site or invade throughout the body

23. © 2015 Pearson Education, Inc. 23.8 Invasion, Infection, and Virulence Factors Infection: any situation in which a microorganism (not a member of the local flora) is established and growing in a host Bacteremia: the presence of bacteria in the bloodstream Septicemia: bloodborne systemic infection May lead to massive inflammation, septic shock, and death

24. © 2015 Pearson Education, Inc. 23.8 Invasion, Infection, and Virulence Factors Virulence factor: any microbial substance that enhances pathogenicity Virulence factors may be: Antibiotic resistance compounds Enzymes that enhance virulence by breaking down or altering host tissue to provide access to nutrients Example: hyaluronidase Enzymes that protect the pathogen by interfering with normal host defense mechanisms Example: coagulase Toxic substances released outside the pathogen: exotoxins Example: neurotoxins

25. © 2015 Pearson Education, Inc. 23.8 Invasion, Infection, and Virulence Factors Example of enzyme as virulence factor: streptokinase Produced by Streptococcus pyogenes Strep throat, scarlet fever, impetigo, others Streptokinase is an enzyme released by the pathogen It initiates a cascade that leads to the breakdown of fibrin in blood clots Enhances invasiveness of pathogen Was used as medication to help dissolve blood clots

26. © 2015 Pearson Education, Inc. 23.9 Exotoxins Exotoxins Proteins released from the pathogen cell as it grows Three categories based on mechanism of action Cytotoxins AB toxins Superantigen toxins

27. © 2015 Pearson Education, Inc. 23.9 Exotoxins Cytotoxins (cytolytic toxins) Work by degrading cytoplasmic membrane integrity, causing cell lysis and death Toxins that lyse red blood cells are called hemolysins (Figure 23.18) Staphylococcal α-toxin induces apoptosis and lyses erythrocytes (Figure 23.19)

28. © 2015 Pearson Education, Inc. RCSB PDB 3ANZ Cytoplasmic membrane Influx of extracellular components Efflux of cytoplasmic components α-Toxin pore Out In

29. © 2015 Pearson Education, Inc. Clostridium perfringens alpha toxin Degrades plasma membrane Leads to cell and tissue death “gas gangrene” Zone of hemolysis

30. © 2015 Pearson Education, Inc. 23.9 Exotoxins AB toxins Consist of two subunits, A and B Work by binding to host cell receptor (B subunit) and transferring damaging agent (A subunit) across the cell membrane (Figure 23.20) Examples: diphtheria toxin, tetanus toxin, botulinum toxin

31. © 2015 Pearson Education, Inc. 23.9 Exotoxins Clostridium tetani and Clostridium botulinum produce potent AB exotoxins that affect nervous tissue “botulism” food poisoning due to anaerobic production of toxin-often in home canned foods Botulinum toxin or Botox consists of several related AB toxins that are the most potent biological toxins known (Figure 23.21); tetanus toxin is also an AB protein neurotoxin (Figure 23.22)

32. © 2015 Pearson Education, Inc. Excitation signals from the central nervous system A A AA A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A Muscle Normal Acetylcholine (A) induces contraction of muscle fibers Botulism Botulinum toxin,, blocks release of A, inhibiting contraction A A A A A A A A A A A A Figure 23.21 BTX is the most lethal toxin known

33. © 2015 Pearson Education, Inc. 23.9 Exotoxins Enterotoxins Exotoxins whose activity affects the small intestine Generally cause massive secretion of fluid into the intestinal lumen, resulting in vomiting and diarrhea Example: cholera toxin (Figure 23.23) Causative agent-Vibrio cholera in contaminated food or water

34. © 2015 Pearson Education, Inc. 1. Normal ion movement, Na+ from lumen to blood, no net Cl – movement Blood Intestinal epithelial cells Lumen of small intestine GM1 2. Infection and toxin production by V. cholerae Cholera toxin AB form GM1 Vibrio cholerae cell Cholera toxin B subunit A B 3. Activation of epithelial adenylate cyclase by cholera toxin A subunits Adenylate cyclase ATP Cyclic AMP 4. Na + movement blocked, net Cl – movement to lumen 5. Massive water movement to the lumen; cholera symptoms Figure 23.23

35. © 2015 Pearson Education, Inc.

36. 23.9 Exotoxins Superantigens An antigen is a substance that can provoke a response by by the immune system Act by hyperstimulation of immune system Promiscuous binding to immune cell receptors Staphylococcus, Streptococcus S. aureus food poisoning - more than just GI tract

37. © 2015 Pearson Education, Inc. 23.10 Endotoxins Endotoxin The lipopolysaccharide portion of the cell envelope of certain gram-negative Bacteria, which is a toxin when solubilized Not secreted but released upon cell breakdown Generally less toxic than exotoxins Neisseria gonorrheae lipo-oligo-saccharides

38. © 2015 Pearson Education, Inc. 23.8 Invasion, Infection, and Virulence Factors Salmonella species encode a large number of virulence factors of many types (Figure 23.17) Several genes that direct invasion are clustered together on the chromosome as pathogenicity islands Another Salmonella pathogenicity island contains genes that promote a more systemic disease Salmonella also contains resistance plasmids (R plasmids)

39. © 2015 Pearson Education, Inc. Injectisome (inv and prg products form complex) Endotoxin in LPS layer (fever) Anti- phagocytic proteins induced by oxyR O antigen (inhibits phagocyte killing) Pathogenicity islands on chromosome Flagellum (motility) H antigen (adherence; inhibits phagocyte killing) Vi capsule antigen; inhibits complement binding Cytotoxin (inhibits host cell protein synthesis; Ca 2+ efflux from host cell; adherence) Virulence plasmid Type Ι fimbriae (adherence) Siderophores (iron uptake) Enterotoxin (diarrhea) SPΙ2 SPΙ1 Figure 23.17