Chapter 20: Objectives Flashcards
List three structural features of Neisseria that contribute to its pathogenicity.
- Fimbriae
- Capsules
- Variable cell wall antigens composed of lipooligosaccharide
Compare and contrast the symptoms of gonorrhea in men and women.
Gonorrhea in men:
- Painful urination and pus filled discharge
Gonorrhea in women:
- Often asymptomatic
- Can trigger pelvic inflammatory disease, proctitis, gingivitis, pharyngitis
Infection of children can result during childbirth (ophthalmia neonatorum)
Gonorrhea in men
- Painful urination
- Pus filled charge
Gonorrhea in women
- Often asymptomatic
- Can trigger pelvic inflammatory disease, proctitis, gingivitis, pharyngitis
Discuss the difficulties researchers face in developing an effective vaccine
against Neisseria gonorrhoeae
- Treatment is complicated due to resistant strains
- Broad spectrum antimicrobial drugs like cephalosporins
- Long term immunity does not develop due to variable surface antigens
What is cultured in Thayer-Martin agar
Neisseria gonorrhoeae
Diagnosis of Neisseria gonorrhoeae
- Asymptomatic cases identified with genetic probes
- Gram negative diplococci in pus
- Can be cultured in Thayer-Martin agar
Describe how meningococci: Neisseria meningitidis survive and thrive in humans
- 13 antigenic strains cause disease; A, B, C, and W135
- Can survive in neutrophils and macrophages
- Polysaccharide capsules resists lytic enzymes of phagocytes
- Neisseria meningitidis causes blebbing - a process of shedding outer membrane
What is blebbing
- A process in which the bacterium sheds extrusions of outer membrane
- Much of the damage caused by N. meningitidis results from blebbing
How is meningococcus: Neisseria meningitis transmitted?
- By respiratory droplets
- Bacteria transmitted among people living in close contact
- Most common cause of meningitis in individuals under 20 years
Meningococcal meningitis
Can cause death within 6 hours of symptoms:
- Abrupt sore throat
- Fever
- Headache
- Stiff neck
- Vomiting
- Convulsions
Petechiae
- Minute hemorrhagic skin lesions on the trunk and lower extremities, can combine together to form large black lesions
- Caused by Meningococcal
Meningococcal septicemia
- Also known as blood poisoning can also be life threatening
- LOS may trigger shock
- Petechiae - minute hemorrhagic skin lesions on the trunk and lower extremities, can combine together to form large black lesions
Discuss the epidemiology of meningococcal diseases
- Most common cause of meningitis in individuals under 20 years
- Respiratory droplets transmit the bacteria among people living in close contact, especially families, soldiers living in barracks, prisoners, and college students living in dormitories
Diagnosis of Neisseria meningitidis
- Gram negative diplococci in phagocytes of the cerebrospinal fluid
- Physician obtain a sample of cerebrospinal fluid using a needle inserted into the lower spinal canal; spinal tap
How to distinguish between Neisseria gonorrhoeae and N meningitidis
- N. gonorrhoeae is cultured on Thayer-Martin agar
- N. meningitidis can oxidize maltose in laboratory culture
Neisseria meningitidis treatment
- Intravenous antibiotics like ceftraxone, a cephalosporin
Prevention of Neisseria meningitidis
- Asymptomatic carriers are common which make eradication of meningococcal disease is unlikely
- Vaccination against strains A, C, Y, and W135
Describe how members of the family Enterobacteriaceae are distinguished from
members of the family Pasteurellaceae.
- Distinguish between members of the two families by preforming an oxidase test;
- Enterobacteriaceae are oxidase negative
- Pasteurellaceae are oxidase positive
Discuss how to distinguish between members of the family Enterobacteriaceae in the laboratory
- Biochemical tests
- Motility
- Colonial characteristics on a variety of selective and non-selective media (EX. MacConkey agar and blood agar)
All enterobacteriaceae bacteria are:
- Also known as enteric bacteria
- Gram negative
- Oxidase negative
- Able to metabolize nitrate to nitrite
Outer membrane that contains lipopolysaccharide:
- A core polysaccharide (common antigen)
- O polysaccharide
- Lipid A
Six virulence factors found in members of the family Enterobacteriaceae
- Fimbria
- Exotoxin
- Adhesin
- Plasmid (virulence genes)
- Iron-binding protein
- Hemolysin
Enterobacteriaceae virulence factor: Exotoxin
Exotoxins that cause a variety of symptoms such as diarrhea frequently located on plasmids, which increases the likelihood that they will be transferred among bacteria
Enterobacteriaceae virulence factor: Adhesin
Fimbriae and proteins called adhesins enable the bacteria to attach tightly to human cells
Enterobacteriaceae virulence factor: Plasmid
Plasmid-encoded enzymes that degrade antimicrobial drugs conveying drug resistance
Enterobacteriaceae virulence factor: Iron-binding protein
Also called siderophores that capture iron and make it available to the bacteria
Enterobacteriaceae virulence factor: Hemolysins
Release nutrients such as iron by lysing red blood cells
Four antigen factors found in members of the family Enterobacteriaceae
- Outer membrane: common antigen, O antigen, lipid A
- Type III secretion system
- Capsular antigens (K, Vi in Salmonella)
- Flagellar antigens (H)
Antigen factor of Enterobacteriaceae: Type III secretion system
- A complex structure composed of 20 different polypeptides that is synthesized by several pathogenic enteric species
- Like a hypodermic needle, the system spans the two membranes and peptidoglycan of the bacterial cell and inserts through a host cell’s cytoplasmic membrane
Diagnosis of Enterobacteriaceae
- Enteric bacteria in urine, blood, and cerebrospinal fluid
- Biochemical tests rapidly identify enteric bacteria
Culturing members of Enterobacteriaceae from clinical specimen
- Eosin methylene blue (EMB) agar
- MacConkey agar
Treatment of Enterobacteriaceae
- Diarrhea typically self limited, expulsion of the organisms from the body is often more effective, which involves treating the symptoms with fluid and electrolyte replacement
- Internal infections treated with antimicrobials
Treatment of Enterobacteriaceae: Diarrhea
- Self limited: Expulsion of the organisms from the body is often more effective
- Involves treating the symptoms with fluid and electrolyte replacement
Treatment of Enterobacteriaceae: Internal infections
Antimicrobials
Prevention of Enterobacteriaceae
- Good personal hygiene
- Proper sewage control
Compare and contrast Enterobacter, Hafnia, and Citrobacter
- Coliforms
- Reside in digestive tracts of animals, humans, soil, water, decaying vegetation and sewage
- Involved in healthcare-associated infections of blood, wounds, surgical incisions, and urinary tracts of immunocompromised patients
- Enterobacter can be a contaminant of dairy products
Escherichia coli can cause:
- Septicemia
- Urinary tract infections (UTIs - urethritis, cystitis, pyelonephritis)
- Meningitis
- Gastroenteritis (most common)
