1 Chapter 19

2 How Do Bacteria Cause Disease?Adherence and colonization factors Factors that prevent activation of complement Factors that enable escape from phagocytosis by white blood cells Factors that prevent destruction within phagocytes Factors that suppress the host immune system (i.e., factors that cause immunosuppression) Endotoxin (a component of the cell walls of Gram-negative bacteria) Production of exotoxins (e.g., cytotoxins, enterotoxins, neurotoxins) Production of necrotic and other types of destructive enzymes

3 Bacterial Infections of the SkinAcne Propionibacterium acnes and other Propionibacterium spp.; anaerobic Gram + bacilli Anthrax, Woolsorter Disease Bacillus anthracis; a spore- forming, Gram + bacillus Gas gangrene (myonecrosis) Anaerobic bacteria in the genus Clostridium, especially C. perfringens Leprosy (Hansen disease) Mycobacterium leprae; an acid- fast bacillus Staphylococcal skin infections (folliculitis, furuncles, abscesses, etc.) Staphylococcus aureus, a Gram + coccus Streptococcal skin infections (scarlet fever, erysipelas, etc.) Streptococcus pyogenes, a Gram + coccus

6 Bacterial Infections of the Skin (cont.)Wound infections Result when protective skin barrier is broken as a result of burns, punctures, surgical procedures, or bites Opportunistic indigenous microbiota and environmental bacteria can invade and cause local or deep tissue infections. Pathogens may spread through blood or lymph, causing serious systemic infections.

7 Viral and Bacterial Ear InfectionsOtitis externa (external otitis, ear canal infection, swimmer’s ear) Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Staphylococcus aureus; less commonly caused by a fungus such as Aspergillus Otitis media (middle ear infection) Bacterial causes: S. pneumoniae, a Gram + diplococcus; Haemophilus influenzae, a Gram  bacillus; and Moraxella catarrhalis, a Gram  diplococcus Viral causes: measles, parainfluenza, and respiratory syncytial (RSV) viruses (RSV)

8 Bacterial Infections of the EyesBacterial conjunctivitis (pinkeye) Haemophilus influenzae biogroup aegyptius and S. pneumoniae are the most common causes Chlamydial conjunctivitis (inclusion conjunctivitis, paratrachoma) Certain serotypes (serovars) of Chlamydia trachomatis Trachoma (chlamydia keratoconjunctivitis) Certain serotypes of Chlamydia trachomatis Gonococcal conjunctivitis (gonorrheal ophthalmia neonatorum) Neisseria gonorrhoeae; a Gram  diplococcus; also called gonococcus or GC

9 Bacterial Infections of the Upper Respiratory TractDiphtheria Corynebacterium diphtheriae; a pleomorophic, Gram + bacillus Transmission occurs via airborne droplets, direct contact, contaminated fomites, and raw milk. Streptococcal pharyngitis (strep throat) Streptococcus pyogenes; beta-hemolytic, catalase-negative, Gram + cocci in chains Transmission is human-to-human by direct contact, usually hands; also via aerosol droplets.

10 Infections of the Lower Respiratory Tract Having Multiple CausesPneumonia May be caused by Gram + or Gram  bacteria, mycoplasmas, chlamydias, viruses, fungi, or protozoa Community-acquired bacterial pneumonia is most frequently caused by S. pneumoniae. S. pneumoniae is the most common cause of pneumonia in the world Transmission, in most cases, occurs via infected humans.

11 Bacterial Infections of the Lower Respiratory Tract (cont.)Tuberculosis (TB) Primarily Mycobacterium tuberculosis (a slow-growing, acid-fast, Gram-positive to Gram-variable bacillus), occasionally other Mycobacterium spp.; transmission occurs primarily via infected humans (airborne droplets). Whooping cough (pertussis) Bordetella pertussis, a small, encapsulated, nonmotile, Gram  coccobacillus that produces endotoxin and exotoxins; transmission occurs via infected humans (i.e., droplets by coughing).

12 Bacterial Infections of the Oral CavityTerms relating to infectious diseases of the oral cavity: dental caries, periodontal disease, gingivitis, periodontitis Acute Necrotizing Ulcerative Gingivitis (ANUG); also known as Vincent’s Angina and Trench Mouth A synergistic infection involving two or more species of anaerobic bacteria of the indigenous oral microbiota; most commonly, Fusobacterium nucleatum and Treponema vincentii

13 Bacterial Infections of the GI TractBacterial gastritis and ulcers Helicobacter pylori, a curved, microaerophilic, capnophilic, Gram  bacillus Transmission occurs via infected humans; probably by ingestion; presumed to be either oral-oral or fecal-oral. Campylobacter enteritis Campylobacter jejuni (less common, C. coli), curved, S-shaped or spiral Gram  bacillus Transmission occurs via animals, including poultry, cattle, sheep, swine, rodents, birds, kittens, puppies, and other pets.

14 Bacterial Infections of the GI Tract (cont.)Cholera Certain biotypes of Vibrio cholerae serogroup 01, curved, Gram  bacillus that secretes enterotoxin Transmission occurs via infected humans and aquatic reservoirs; fecal-oral route. Salmonellosis Salmonella spp.; members of the family Enterobacteriaceae, Gram - bacilli that invade intestinal cells, release endotoxin, and produce cytotoxins and enterotoxins Transmission occurs via domestic and wild animals; contaminated food, fecal-oral, food handlers, contaminated water

15 Bacterial Infections of the GI Tract (cont.)Typhoid fever (enteric fever) Salmonella typhi, a Gram  bacillus that releases endotoxin and produce exotoxins Transmission occurs via infected humans for typhoid and paratyphoid; some people become carriers after infection (e.g., “Typhoid Mary”). Shigellosis (bacillary dysentery) Shigella dysenteriae, S. flexneri, S. boydii, and S. sonnei; nonmotile, Gram  bacilli, members of the family Enterobacteriaceae Transmission occurs via infected humans.

16 Urinary Tract Infections (UTIs)The most common causes of UTIs are E. coli and other members of the family Enterobacteriaceae (especially Proteus and Klebsiella). Other common causes of UTIs are Enterococcus spp., Staphylococcus spp. (especially S. aureus, S. epidermidis, and S. saprophyticus), and Pseudomonas aeruginosa. UTIs may be acquired either within a healthcare setting (called healthcare-associated UTIs) or elsewhere (called community- acquired UTIs). UTIs are the most common type of healthcare-associated infection.

17 Bacterial STDs Genital chlamydial infections (genital chlamydiasis)Certain serotypes of Chlamydia trachomatis; obligate intracellular Gram - bacteria Transmission via infected humans, direct sexual contact, or mother-to-neonate during birth Gonorrhea Neisseria gonorrhoeae; a Gram  diplococcus Transmission via infected humans, usually sexual contact or direct mucous membrane-to- mucous membrane contact Syphilis Treponema pallidum; Gram- variable, tightly-coiled spirochete; too thin to be seen by brightfield microscopy; can be seen by darkfield microscopy Transmission via infected humans, by direct contact with lesions, body secretions, mucous membranes, blood, semen, etc.; usually sexual contact; also blood transfusions and transplacentally from mother to fetus

18 Other Bacterial STDs Bacterial STDs that occur more frequently in parts of the world other than the United States: Chancroid—caused by Haemophilus ducreyi; a Gram  bacterium Granuloma inguinale—caused by Calymmatobacterium granulomatis; a Gram  bacterium Lymphogranuloma venereum—caused by certain serotypes of Chlamydia trachomatis STDs may be transmitted simultaneously; if a patient is diagnosed with one particular type of STD, other types should be sought.

19 Rickettsial and Ehrlichial Diseases of the Cardiovascular SystemSpotted fever rickettsiosis (tickborne typhus fever) Rickettsia rickettsii; a Gram  bacterium; an obligate intracellular pathogen Transmission occurs via infected ticks on dogs, rodents, and other animals Endemic typhus fever (murine typus fever, fleaborne typhus) Rickettsia typhi; a Gram  bacterium; an obligate intracellular pathogen Transmission occurs via rats, mice, possibly other mammals, infected rat fleas.

20 Rickettsial and Ehrlichial Diseases of the Cardiovascular System, cont.Epidemic typhus fever (louseborne typhus) Rickettsia prowazekii; a Gram  bacterium; an obligate intracellular pathogen Reservoirs are infected humans and body lice. Erlichiosis Gram-negative coccobacilli, closely related to rickettsias; obligate intraleukocytic pathogens Reservoir unknown; transmission is via tick bite

21 Other Bacterial Infections of the Cardiovascular SystemLyme disease (Lyme borreliosis) Borrelia burgdorferi; a Gram , loosely coiled spirochete Transmission is via tick bite. Plague (“black death,” bubonic plague, pneumonic plague, septicemic plague) Yersinia pestis; a nonmotile, bipolar-staining, Gram  coccobacillus Transmission is via wild rodents and their fleas (flea bite). Tularemia (Rabbit Fever) Francisella tularensis; a pleomophic, Gram  coccobacillus Transmission is via tick bite; associated with rabbits.

22 Bacterial Infections of the CNSListeriosis Listeria monocytogenes; a Gram + coccobacillus Transmission occurs via ingestion of raw or contaminated milk, soft cheeses, and vegetables. Tetanus (lockjaw) Clostridium tetani; a motile, Gram + anaerobic, spore- forming bacillus Transmission occurs via spores of C. tetani entering a puncture wound, burn, or needlestick by contamination with soil, dust, or feces.