Chapter 20: pathogenic gram negative cocci and bacilli Flashcards
What are the largest group of bacterial pathogens
pathogenic gram negative cocci and bacilli
-about 30 genera are included
Why are there so many negative mesophiles pathogenic? What is it about the cell wall
-the cell wall can cause fever, vasodilation, inflammation, circulatory shock and disseminated intravascular coagulation (blood clots in vessels)
Neisseria
-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
What two species of Neisseria are pathogenic to humans
- gonococcus (N. gonorrhoeae)
- meningococcus (N. meningitides)
Neisseria gonorrhoeae
-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
Who has the symptoms of gonorrhea usually
-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
Diagnosis for gonorrhea?
-in mean identified by the presence of gram negative diplococci in pus discharge
-in women from a swab culture
Treatment for gonorrhea
mostly resistant to penicillin, tetracycline, so broad-spectrum cephalosporins are recommended
Prevention for gonorrhea
same for other STI (safe sex practices)
Neisseria meningitidis
-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
what is blebbing
mass shedding of the outer membrane (gram neg cells dying at once)
meningococcal septicemia
can be life threatening as it can produce blood coagulation and the formation of minute hemorrhagic lesions which can coalesce
diagnosis of Neisseria meningitidis
presence of gram negative diplococci in phagocytes of CNS which are maltose fermenting confirms meningococcal meningitis
Treatment of Neisseria meningitidis
penicillin administered by IV for active cases and cephalosporins for prophylaxis cases are drug of choice
prevention of Neisseria meningitidis
eradication is unlikely due to asymptotic carriers but when exposed prophylactic antibiotics are used
Enterobacteriaceae (enteric bacteria)
-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
diagnosis of Enterobacteriaceae (enteric bacteria)
are cultured using selective and differential media like EMB or MaConkey’s
-some commercially available biochemical test can identify species in 4-24 hours
treatment of Enterobacteriaceae (enteric bacteria)
antimicrobial drugs are not usually needed unless infection disseminates
prevention of Enterobacteriaceae (enteric bacteria)
almost impossible as they are a major component of normal microbiota
-have good personal hygiene, proper sewage control, and degerming
Three groups of pathogenic Enterobacteriaceae
- coliforms
- non-coliform opportunists
- true pathogens
coliforms
-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
non-coliform opportunists
-do not ferment lactose
ex: proteus, morganella, providencia, and edwardsiella
true pathogens
ex: salmonella, shigella, and yersinia
What is the most important coliform
e.coli
-virulent strains have virulence plasmids that allow bacteria to colonize human tissue
-most common cause of non-nosocomial UTI
