Chapter 20: pathogenic gram negative cocci and bacilli

Question 1

What are the largest group of bacterial pathogens

Answer 1

pathogenic gram negative cocci and bacilli
-about 30 genera are included

Question 2

Why are there so many negative mesophiles pathogenic? What is it about the cell wall

Answer 2

-the cell wall can cause fever, vasodilation, inflammation, circulatory shock and disseminated intravascular coagulation (blood clots in vessels)

Question 3

Neisseria

Answer 3

-the only genus of gram negative cocci that regularly cause diseases in humans
-non-motile, aerobic diplococcal bacteria
-distinguished from others by being cytochrome oxidase positive
-fastidious so cultured on chocolate agar
-pathogenic strains except N. meningitides, usually are unable to ferment maltose, sucrose, or lactose

Question 4

What two species of Neisseria are pathogenic to humans

Answer 4

1. gonococcus (N. gonorrhoeae)
2. meningococcus (N. meningitides)

Question 5

Neisseria gonorrhoeae

Answer 5

-gonorrhea means flow of seed, because it is a sexually transmitted infection known as the clap (clapoir-brothel)
-both men and women are affected but women contract it with higher incidence (20% in males vs 50% in females)
-gonococci adhere to epithelial cells of the mucous membranes lining the genital, urinary, and digestive tract spreading to deeper tissue before multiplying
-they live, multiply, and are transported within phagocytes allowing them to be pathogenic

Question 6

Who has the symptoms of gonorrhea usually

Answer 6

-men do producing inflammation that causes painful urination and a pus filled discharge
-women are often asymptomatic or symptoms are mistaken for a UTI or yeast infection
-can infect cervix and fallopian tubes by hitch hiking on sperm does not attach to vaginal walls
-can cause PID (Pelvic inflammatory disease) where chronic infection can cause ectopic pregnancy or sterility

Question 7

Diagnosis for gonorrhea?

Answer 7

-in mean identified by the presence of gram negative diplococci in pus discharge
-in women from a swab culture

Question 8

Treatment for gonorrhea

Answer 8

mostly resistant to penicillin, tetracycline, so broad-spectrum cephalosporins are recommended

Question 9

Prevention for gonorrhea

Answer 9

same for other STI (safe sex practices)

Question 10

Neisseria meningitidis

Answer 10

-humans are natural carriers of this
-it can be a member of normal microbiota of upper respiratory tract also cause life threatening disease if gets into the blood or CSF
-most common cause of meningitis in people under 20
-respiratory droplets transmit bacteria among people, especially college students living in dorms
-meningococcal meningitis can result in death as early as 6 hours after initial symptoms from blebbing

Question 11

what is blebbing

Answer 11

mass shedding of the outer membrane (gram neg cells dying at once)

Question 12

meningococcal septicemia

Answer 12

can be life threatening as it can produce blood coagulation and the formation of minute hemorrhagic lesions which can coalesce

Question 13

diagnosis of Neisseria meningitidis

Answer 13

presence of gram negative diplococci in phagocytes of CNS which are maltose fermenting confirms meningococcal meningitis

Question 14

Treatment of Neisseria meningitidis

Answer 14

penicillin administered by IV for active cases and cephalosporins for prophylaxis cases are drug of choice

Question 15

prevention of Neisseria meningitidis

Answer 15

eradication is unlikely due to asymptotic carriers but when exposed prophylactic antibiotics are used

Question 16

Enterobacteriaceae (enteric bacteria)

Answer 16

-are most common members of the intestinal microbiota of most animals and humans they are found in water, soil, and decaying vegetation
-morphology: bacilli or coccobacilli
-most common gram negative pathogens of humans causing intestinal diseases
-treatment involves fluids if you got diarrhea

Question 17

diagnosis of Enterobacteriaceae (enteric bacteria)

Answer 17

are cultured using selective and differential media like EMB or MaConkey’s
-some commercially available biochemical test can identify species in 4-24 hours

Question 18

treatment of Enterobacteriaceae (enteric bacteria)

Answer 18

antimicrobial drugs are not usually needed unless infection disseminates

Question 19

prevention of Enterobacteriaceae (enteric bacteria)

Answer 19

almost impossible as they are a major component of normal microbiota
-have good personal hygiene, proper sewage control, and degerming

Question 20

Three groups of pathogenic Enterobacteriaceae

Answer 20

1. coliforms
2. non-coliform opportunists
3. true pathogens

Question 21

coliforms

Answer 21

-rapidly ferment lactose and are part of normal microbiota but may be opportunistic
-aerobic or facultatively anaerobic, gram negative rods, that form gas in broth
-presence in water indicates impure water and poor sewage treatment
-
ex: e.coli, klebsiella, serratia, hafnia, citrobacter, enterobacter

Question 22

non-coliform opportunists

Answer 22

-do not ferment lactose
ex: proteus, morganella, providencia, and edwardsiella

Question 23

true pathogens

Answer 23

ex: salmonella, shigella, and yersinia

Question 24

What is the most important coliform

Answer 24

e.coli
-virulent strains have virulence plasmids that allow bacteria to colonize human tissue
-most common cause of non-nosocomial UTI

Question 25

what is the most common disease associated with e.coli

Answer 25

gastroenteritis
-often mediated by exotoxins that produce symptoms associated with gastroenteritis

Question 26

Escherichia coli O157:H7

Answer 26

-most prevalent strain of pathogenic E.coli in developed countries
-infection can cause diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome
-mot epidemics have been associated with undercooked beef or unpasteurized milk/juice, most recently veggies
-produces a type III secretion system and shiga like toxin that aid in virulence

Question 27

klebsiella

Answer 27

-found in digestive and respiratory tract of humans and animals
-it produces a capsule that protects the bacteria from phagocytosis
-klebsiella pneumonia is the most common pathogenic species
-can cause pneumonia or involved in bacteriemia, meningitis, wound infections or UTI

Question 28

Serratia marcescens

Answer 28

-produce a red pigment if grown at room temperature
-can also grow on catheters or saline solution
-can cause life threatening infections in urinary and reparatory tract of immunocompromised patients

Question 29

Enterobacter, Hafnia, and Citrobacter

Answer 29

cause nosocomial infections blood, surgical wounds or UTI
-all three are difficult to treat b/c of resistance

Question 30

what are some truly pathogenic Enterobacteriaceae

Answer 30

1. salmonella
2. shigella
3. yersinia