Transcript Chapter 20 - HCC Learning Web

PowerPoint® Lecture
Presentations prepared by
Mindy Miller-Kittrell,
North Carolina
State University
CHAPTER
20
Pathogenic
Gram-Negative
Cocci and
Bacilli
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Gram-Negative Bacteria
• Constitute largest group of human bacterial
pathogens
• Due in part to lipid A in the bacterial cell wall
• Fever, vasodilation, inflammation, shock
• Most Gram-negative bacteria that breach skin or
mucous membranes, grow at 37C, and evade the
immune system can cause disease in humans
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Pathogenic Gram-Negative Cocci: Neisseria
• Structure and Physiology of Neisseria
• Only genus of Gram-negative cocci that regularly
causes disease in humans
• Aerobic, nonmotile, arranged as diplococci
• Oxidase positive
• Distinguishes from many other Gram-negative pathogens
• Pathogenic strains have a polysaccharide capsule, and
a cell wall containing lipid A
• Two species pathogenic to humans
• N. gonorrhoeae
• N. meningitidis
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Figure 20.1 Artist's rendition of diplococci of Neisseria gonorrhoeae.
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Pathogenic Gram-Negative Cocci: Neisseria
• The Gonococcus: Neisseria gonorrhoeae
• Pathogenesis, epidemiology, and disease
• Causes gonorrhea
• Only occurs in humans
• Sexually transmitted disease
• Increased risk of infection with increasing sexual
encounters
• Most cases in the United States occur in adolescents
• Cases have declined over the past decades
• More common in females than in males
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Pathogenic Gram-Negative Cocci: Neisseria
• The Gonococcus: Neisseria gonorrhoeae
• Pathogenesis, epidemiology, and disease
• Gonococci adhere to the genital, urinary, and digestive
tract
• Gonococci can evade the immune system
• Secrete protease that cleaves secretory IgA
• Survive within neutrophils
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Pathogenic Gram-Negative Cocci: Neisseria
• The Gonococcus: Neisseria gonorrhoeae
• Pathogenesis, epidemiology, and disease
• Gonorrhea in men
• Inflammation causes painful urination and pus-filled
discharge
• Gonorrhea in women
• Often asymptomatic
• Can trigger pelvic inflammatory disease
• Infections can occur outside the reproductive tract
• Cause proctitis, pharyngitis, and gingivitis
• Infection of the cornea or respiratory tract of newborns
can occur during childbirth
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Pathogenic Gram-Negative Cocci: Neisseria
• The Gonococcus: Neisseria gonorrhoeae
• Diagnosis, treatment, and prevention
• Diagnosis
• Asymptomatic cases identified with genetic probes
• Gram-negative diplococci in pus from inflamed penis
• Treatment
• Complicated due to resistant strains
• Broad-spectrum intramuscular cephalosporins
• Prevention
• Sexual abstinence, monogamy, and proper condom use
• Eye infections in newborns prevented with
antimicrobials
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Pathogenic Gram-Negative Cocci: Neisseria
• The Meningococcus: Neisseria meningitidis
• Pathogenicity, epidemiology, and disease
• Most common cause of meningitis in individuals under 20
• Can be normal microbiota of the upper respiratory tract
• Bacteria transmitted by respiratory droplets among people
living in close contact
• Meningitis can cause death within 6 hours of symptoms
• Meningococcal septicemia can also be life threatening
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Figure 20.3 Petechiae in meningococcal septicemia.
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Pathogenic Gram-Negative Cocci: Neisseria
• The Meningococcus: Neisseria meningitidis
• Diagnosis, treatment, and prevention
• Diagnosis
• Rapid diagnosis critical
• Gram-negative diplococci in phagocytes of the CNS
• Treatment
• Immediate administration of intravenous penicillin
• Prevention
• Asymptomatic carriers make eradication unlikely
• Vaccine against some meningococcal strains is
available
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Two families contain most human pathogens
• Enterobacteriaceae
• Pasteurellaceae
• Oxidase test distinguishes between these families
• Includes important nosocomial pathogens
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Figure 20.5 Relative causes of nosocomial infections in the United States.
Gram-positive
bacteria
Gram-negative
bacteria
Yeast
Enterobacteriaceae: coliforms
Escherichia
Klebsiella
Serratia
Enterobacter
Citrobacter
Enterobacteriaceae: noncoliforms
Proteus
Salmonella
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Pseudomonas
(not in family Enterobacteriaceae)
Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• The Enterobacteriaceae: An Overview
• Intestinal microbiota of most animals and humans
• Ubiquitous in water, soil, and decaying vegetation
• Enteric bacteria are the most common Gram-negative
pathogens of humans
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• The Enterobacteriaceae: An Overview
• Structure and physiology of the Enterobacteriaceae
• Motile bacilli and coccobacilli
• All reduce nitrate to nitrite and ferment glucose
• Grow best in aerobic environments
• Species distinguished based on biochemical properties,
motility, and colony characteristics
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• The Enterobacteriaceae: An Overview
• Diagnosis
• Enteric bacteria in urine, blood, cerebrospinal fluid
• Biochemical tests rapidly identify enteric bacteria
• Treatment
• Diarrhea is typically self-limited
• Internal infections treated with antimicrobials
• Prevention
• Good personal hygiene and proper sewage control
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• The Enterobacteriaceae: An Overview
• Pathogenic Enterobacteriaceae classified into three
groups
• Coliforms
• Rapidly ferment lactose
• Normal microbiota but may be opportunistic
pathogens
• Noncoliform opportunists
• Do not ferment lactose
• True pathogens
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Coliform Opportunistic Enterobacteriaceae
• Coliforms
• Aerobic or facultatively anaerobic, Gram-negative,
rod-shaped bacteria that ferment lactose to form gas
in lactose broth
• Commonly found in soil, on plants, and on decaying
vegetation
• Colonize the intestinal tracts of animals and humans
• Coliforms in water indicate impure water and poor
sewage treatment
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Coliform Opportunistic Enterobacteriaceae
• Escherichia coli
• Most common and important of the coliforms
• E. coli antigens used to identify particular strains
• Virulent strains have virulence plasmids
• Have genes for fimbriae, adhesins, exotoxins
• Causes several diseases
• Gastroenteritis is most common disease
• Produces diarrhea, cramps, nausea, and vomiting
• Often mediated by enterotoxins
• Major cause of pediatric diarrhea in developing countries
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Coliform Opportunistic Enterobacteriaceae
• Escherichia coli
• Common cause of non-nosocomial urinary tract infections
• Occur more often in women than men
• E. coli O157:H7
• Most prevalent pathogenic E. coli in developed countries
• Causes diarrhea, hemorrhagic colitis, hemolytic uremic
syndrome
• Associated with consumption of undercooked ground beef
or contaminated milk or fruit juice
• Produces type III secretion system and Shiga-like toxin
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Coliform Opportunistic Enterobacteriaceae
• Klebsiella
• In digestive and respiratory systems of humans and
animals
• Capsule protects the bacteria from phagocytosis
• Can cause opportunistic infections
• K. pneumoniae
• Most commonly isolated pathogenic species
• Causes pneumonia
• May be involved in bacteremia, meningitis, wound
infections.
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Figure 20.10 The prominent capsule of Klebsiella pneumoniae.
Capsules
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Coliform Opportunistic Enterobacteriaceae
• Serratia
• Produce a red pigment when grown at room temperature
• Can grow on catheters, in saline solutions, and on other
hospital supplies
• Can cause life-threatening opportunistic infections in
immunocompromised patients
• Frequently resistant to antimicrobial drugs
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Coliform Opportunistic Enterobacteriaceae
• Enterobacter, Hafnia, and Citrobacter
• Found in soil, water, decaying vegetation, and sewage
• Reside in the digestive tracts of animals and humans
• Enterobacter can contaminate dairy products
• All can be opportunistic pathogens
• Cause nosocomial infections in immunocompromised
patients
• Difficult to treat due to resistance to antimicrobial drugs
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Noncoliform Opportunistic Enterobacteriaceae
• Proteus
• Facultative anaerobe
• Proteus mirabilis
• Most commonly associated with human disease
• Associated with urinary tract infections in patients with
long-term urinary catheters
• Infection-induced kidney stones can develop
• Resistant to many antimicrobial drugs
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Figure 20.12 The wavelike concentric rings of the swarming Proteus microbilis.
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Noncoliform Opportunistic Enterobacteriaceae
• Morganella, Providencia, and Edwardsiella
• Nosocomial infections in immunocompromised patients
• Primarily involved in urinary tract infections
• Providencia may cause kidney stones
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Truly Pathogenic Enterobacteriaceae
• Include Salmonella, Shigella, Yersinia
• Almost always pathogenic due to numerous virulence
factors
• Produce type III secretion systems
• Introduce proteins into host cells
• Inhibit phagocytosis
• Rearrange the cytoskeletons of eukaryotic cells
• Induce apoptosis
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Truly Pathogenic Enterobacteriaceae
• Salmonella
• Motile, peritrichous bacilli
• Live in the intestines of birds, reptiles, and mammals
• Most human infections due to consuming food
contaminated with animal feces
• Poultry and eggs are also common sources of Salmonella
• Can cause salmonellosis and typhoid fever
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Truly Pathogenic Enterobacteriaceae
• Salmonella
• Typhoid fever
• Caused by Salmonella enterica serotype Typhi
• Humans are the only host
• Carriers are often asymptomatic
• Bacteria ingested in contaminated food or water
• Bacteria pass through intestines into the bloodstream
• Phagocytic cells ingest the bacteria and carry
them to various organs
• Causes gastroenteritis, bacteremia, and peritonitis
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Figure 20.14 The incidences of diseases caused by Salmonella in the United States.
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Truly Pathogenic Enterobacteriaceae
• Salmonella
• Salmonellosis treated with fluid and electrolyte
replacement
• Typhoid fever treated with antimicrobial drugs
• Gallbladder may be removed from carriers to prevent
infection of others
• Vaccines provide temporary protection to travelers
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Truly Pathogenic Enterobacteriaceae
• Shigella
• Oxidase-negative, nonmotile pathogens
• Primarily a parasite of the digestive tract of humans
• Produce diarrhea-inducing enterotoxin
• Four well-defined species
• S. dysenteriae
• S. flexneri
• S. boydii
• S. sonnei
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Truly Pathogenic Enterobacteriaceae
• Shigella
• Shigellosis
• Severe form of dysentery
• S. sonnei is predominant cause in industrialized nations
• S. flexneri predominates in developing countries
• Associated with poor hygiene and sewage treatment
• People ingest bacteria on their own contaminated
hands or in contaminated food
• Person-to-person spread is possible
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Truly Pathogenic Enterobacteriaceae
• Yersinia
• Normal pathogen of animals
• Three important species
• All contain virulence plasmids
• Adhesins
• Allow attachment to human cells
• Type III secretion systems
• Injection of proteins that causes apotosis of
macrophage and neutrophils
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Truly Pathogenic Enterobacteriaceae
• Yersinia
• Y. enterocolitica
• Acquired by consumption of contaminated food or
water
• Causes inflammation of the intestinal tract
• Y. pseudotuberculosis
• Causes less severe inflammation of the intestines
• Y. pestis
• Highly virulent, nonenteric pathogen
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• Causes bubonic and pneumonic plague
Figure 20.16 The natural history and transmission of Yersinia pestis.
Direct contact
Airborne
transmission
Natural endemic
reservoir hosts (rodents)
Flea bite
Amplifying hosts
(most mammals)
Normal
lymph
nodes
Bubo
Bubonic plague
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Pneumonic plague
Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• Truly Pathogenic Enterobacteriaceae
• Yersinia
• Y. pestis
• Diagnosis and treatment must be rapid
• Fast progression and deadliness of the plague
• Characteristic symptoms are usually diagnostic
• Many antibacterial drugs are effective
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Figure 20.18 Sites of infection by some common members of the Enterobacteriaceae.
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• The Pasteurellaceae
• Most are small, nonmotile, facultative anaerobes
• Require heme or cytochromes for growth
• Two genera contain most human pathogens of this family
• Pasteurella
• Haemophilus
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• The Pasteurellaceae
• Pasteurella
• Normal microbiota in oral and nasopharyngeal cavities of
animals
• Humans infected via animal bites or inhalation of aerosols
• Most cases produce localized inflammation
• Widespread infection and bacteremia can occur in
immunosuppressed individuals
• Diagnosis is by identification of bacteria in patient
specimens
• Antibacterial drugs are effective treatment
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• The Pasteurellaceae
• Haemophilus
• Small, pleomorphic bacilli
• Require heme and NAD+ for growth
• Colonize mucous membranes of humans and some
animals
• Some species cause opportunistic infections
• H. ducreyi causes sexually transmitted disease
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Pathogenic, Gram-Negative, Facultatively
Anaerobic Bacilli
• The Pasteurellaceae
• Haemophilus
• Haemophilus influenzae
• Most strains have capsule that resists phagocytosis
• H. influenzae type b is most significant strain
• Common cause of meningitis prior to vaccination
• Hib vaccine has eliminated most disease by
H. influenzae in the United States
• Other H. influenzae strains cause a variety of diseases
• Conjunctivitis, sinusitis, dental abscesses,
meningitis
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Bartonella
• Aerobic bacilli
• Found in animals but only causes disease in humans
• Three species are pathogenic
• Bartonella bacilliformis
• Bartonellosis
• Causes fever, anemia, headache, muscle and joint
pain, and chronic skin infections
• Often fatal
• Transmitted by bloodsucking sand flies
• Endemic in Peru, Ecuador, and Columbia
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Bartonella
• Bartonella quintana
• Trench fever
• Common during World War I
• Transmitted by human body lice
• Causes headaches, fever, pain in the long bones
• Causes two diseases in immunocompromised patients
• Bacillary angiomatosis
• Bacillary peliosis hepatis
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Bartonella
• Bartonella henselae
• Cat-scratch disease
• Transmitted through cat scratches and bites
• Common disease in children in the United States
• Causes fever, malaise, and swelling at infection site
• Bartonella infections are treated with various antimicrobials
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Figure 20.20 Cat scratch disease.
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Brucella
• Small, nonmotile, aerobic coccobacilli
• Can infect animals or humans
• Brucella melitensis responsible for all disease in humans
• Causes brucellosis
• Often an asymptomatic or mild disease
• Illness is characterized by a fluctuating fever
• Human infection due to contact with contaminated dairy
products or infected animal parts
• Characterized by fluctuating fever
• Vaccine available for use in domesticated animals
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Bordetella
• Pathogenesis, epidemiology, and disease
• Small, aerobic, nonmotile coccobacillus
• B. pertussis is the most important
• Causes pertussis (whooping cough)
• Most cases of disease are in children
• Adhesins and toxins mediate the disease
• Pertussis toxin
• Adenylate cyclase toxin
• Dermonecrotic toxin
• Tracheal cytotoxin
• Bacteria inhaled in aerosols multiply in epithelial cells
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Bordetella
• Diagnosis, treatment, and prevention
• Diagnosis
• Pertussis symptoms usually diagnostic
• Treatment
• Primarily supportive
• Prevention
• Immunization with DTaP or Tdap vaccine
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Burkholderia
• Burkholderia cepacia
• Aerobic, flagellated betaproteobacterium
• Can decompose a broad range of organic molecules
• Assists in cleanup of contaminated environmental sites
• Used by farmers to reduce fungal infection of plant crops
• Opportunistic pathogen of cystic fibrosis patients
• Resistant to many antimicrobial drugs
• Burkholderia pseudomallei
• Causes melioidosis
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Pseudomonads
• Aerobic bacilli
• Ubiquitous in soil, decaying organic matter, moist
environments
• Problematic in hospitals
• Opportunistic pathogens
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Pseudomonads
• Pseudomonas aeruginosa
• Rarely part of normal human microbiota
• Rarely causes disease
• Despite producing various virulence factors
• Fimbriae, adhesins, capsule, toxins, and enzymes
• Opportunistic infections in immunocompromised patients
• Can colonize almost any organ or system
• Also infects the lungs of cystic fibrosis patients
• Biofilm protects bacteria from phagocytosis
• Treatment is difficult due to drug resistance
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Figure 20.25 A Pseudomonas aeruginosa infection.
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Pseudomonads
• Moraxella and Acinetobacter
• Aerobic, short, plump bacilli
• Rarely cause disease in humans
• Moraxella catarrhalis
• Opportunistic infections of the sinuses, bronchi, ears,
and lungs
• Acinetobacter
• Grows in soil, water, and sewage
• Opportunistic infections of the respiratory, urinary, and
central nervous systems
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Pseudomonads
• Francisella tularensis
• Nonmotile, strictly aerobic coccobacillus
• Intracellular parasite of animals and amoebae in water
• Diverse range of hosts
• Reservoirs in the United States include rabbits, muskrats,
and ticks
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Pseudomonads
• Francisella tularensis
• Tularemia
• Zoonotic disease
• Spread through bite of an infected tick or contact with an
infected animal
• Also spread by bacteria in meat, water, and in aerosols
• The bacteria is highly infectious
• Tularemia may be misdiagnosed
• Symptoms are similar to other diseases
• Treated with antimicrobial drugs
• Infection prevented by avoiding reservoirs of Francisella
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Pseudomonads
• Legionella
• Pathogenesis, epidemiology, and disease
• Aerobic, slender, pleomorphic bacteria
• Universal inhabitants of water
• Humans inhale bacteria in aerosols from water sources
• Intracellular parasites
• L. pneumophila causes most disease in humans
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Pseudomonads
• Legionella
• Pathogenesis, epidemiology, and disease
• Legionnaires' disease
• Results in pneumonia
• Can be fatal
• Particularly immunocompromised individuals
• Pontiac fever
• Similar to Legionnaires' disease
• Doesn't produce pneumonia and is not fatal
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Pseudomonads
• Legionella
• Diagnosis, treatment, and prevention
• Diagnosis
• Identification of Legionella by antibody staining or
other serological tests
• Treatment
• Pontiac fever is self-limiting
• Fluoroquinolone and azithromycin used to treat
Legionnaires' disease
• Prevention
• Elimination of the bacteria is not feasible
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Pseudomonads
• Coxiella
• Coxiella burnetii
• Extremely small, aerobic bacteria
• Obligate intracellular parasite
• Originally thought to be a virus
• Infective body enables survival in harsh environment
• Human disease associated with farm animals and pets
• Transmitted mainly by inhalation of the infective bodies
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Pathogenic, Gram-Negative, Aerobic Bacilli
• Pseudomonads
• Coxiella
• Coxiella burnetii
• Q fever
• Causes fever, headache, chills, muscle pain, mild
pneumonia
• Chronic Q fever can cause endocarditis years later
• Chronic Q fever treated with long-term antimicrobials
• Vaccine developed but not available in the United
States
• Prevent by avoiding inhalation of contaminated dust
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Pathogenic, Gram-Negative, Anaerobic Bacilli
• Predominant microbiota of the gastrointestinal,
urinary, reproductive, and lower respiratory tracts
• Important for human health
• Inhibit the growth of most pathogens
• Synthesize vitamins and vitamin precursors
• Aid in digestion of food
• Cause disease when introduced into other parts of
the body
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Pathogenic, Gram-Negative, Anaerobic Bacilli
• Bacteroides
• Normal microbiota of the intestinal and upper respiratory
tracts
• Bacteroides fragilis
• Most important pathogen of this genus
• Produces various virulence factors
• Involved in a variety of conditions
• Abdominal infections
• Genital infections in women
• Wound infections of the skin
• Infections can be treated with metronidazole
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Pathogenic, Gram-Negative, Anaerobic Bacilli
• Prevotella
• Normal microbiota of urinary, genital, and upper respiratory
tracts
• Differ from Bacteroides in their sensitivity to bile
• Produce several virulence factors
• Involved in various conditions
• Sinus and ear infections
• Almost all periodontal infections
• Gynecological infections
• Brain abscesses
• Abdominal infections
• Treat by surgical removal of infected tissue and carbapenem
© 2014 Pearson Education, Inc.