Gram Negative Bacteria Flashcards
Neisseria meningitidis is transmitted by ____
Neisseria meningitidis is transmitted by respiratory droplets (nasopharynx)
____ is the most common cause of acute pyogenic meningitis in adolescents and young adults
Neisseria meningitidis is the most common cause of acute pyogenic meningitis in adolescents and young adults
describe clinical features of meningitis
- fever, headache, photophobia, cloudy consciousness, neck stiffness (nuchal rigidity)
- signs:
- neck rigidity = pain in touching chin to chest
- Kernig sign = pain when flexing leg (meninges)
- Brudzinski sign
describe the lab investigations in meningitis and other causes of meningitis
the most common organism producing meningitis in neonates is _____
the most common organism producing meningitis in neonates is group B streptococci and E. coli
the most common organism producing meningitis in adolescence and younger adults is _____
the most common organism producing meningitis in adolescents and younger adults is Neisseria meningtidis
the most common organism producing meningitis in older adults is _____
the most common organism producing meningitis in older adults is Strep. pneumoniae and Listeria monocytogenes
the most common organism producing chronic meningitis is _____
the most common organism producing chronic meningitis is mycobacterium tuberculosis and fungi
describe meningococcemia
describe what is seen in the image
describe what causes gonorrhea and the pathogenesis
caued by Neisseria gonorrhea (G-ve diplococci)
- pathogenesis: organism invades mucosa surface using its pili and membrane proteins and causes inflammation
describe the clinical features of gonorrhea in females
- dysuria, vaginal discharge, intermenstrual bleeding
- cervicitis, salpingitis (pelvic inflammatory disease) and peritonitis
- if chronic → scarring of the fallopian tubes leading to infertility
describe the clinical features of gonorrhea in males
- urethritis, epididymitis
- mucopurulent urethral discharge and dysuria
- oropharyngitis (oral sex)
- proctitis (anal sex)
describe gonorrhea in the newborn
- infection acquired during passage of the fetus through cervix during labor
- purulent conjunctivitis (ophthalmia neonatorum)
- use of erythromycin/silver nitrate eye drops after birth can prevent it
describe the diagnosis of gonorrhea in males vs. females
describe the etiology of typhoid fever
- salmonella typhi (G-ve rod)
- salmonella paratyphi (predominate in travelers & those living in developed countries)
- humans are the sole reservoir
describe the pathogenesis of typhoid fever
- acquired through ingestion (contaminated food and water)
- enter the ileal wall and taken up by M-cells and engulfed by mononuclear cells in the lymphoid tissue (no lesions at this time) → enter blood stream → bacteremia (1st week)
describe the spread of typhoid fever in the body
describe the clinical features of enteric fever
describe the complications of typhoid fever
describe the mechanism of septic shock
describe the etiology of urinary tract infections
- etiology: E. coli (most common cause)
describe the pathogenesis, clinical features and investigations of UTIs
-
pathogenesis:
- most common in females
- ascending infxns through the urethra
-
clinical features:
- fever, dysuria, frequency, suprapubic, tenderness and cloudy urine
-
investigations:
- CBC, urinalysis
describe G-ve septicemia and clinical features
- UTI is complicated by septicemia in this case
- E. coli is the most common cause of G-ve sepsis
- it is a natural commensal but pathogenic in some situations e.g.
- immune deficiency and mucous membrane breakage
- other causes of G-ve sepsis include:
- H. influenza, Pseudomonas aeruginosa, Klebsiella, Proteus and Serratia
- clinical features:
- high grade fever, DIC, hypotension → death
rickettsia are obligate ____ bacteria
rickettsia are obligate intracellular bacteria
based on rickettsial organisms, 3 different illnesses can occur:
- epidemic typhus caused by R. prowazecki
- Rocky Mountain Spotted Fever caused by R. rickettsii
- Q fever caused by Coxiella burnetti
describe the etiology and vector of epidemic typhus
- etiology: R. prowazeckii
- small G-ve bacillus
- spread by head and body lice
describe the pathogenesis of epidemic typhus
- skin penetration or nasal mucous membrane → blood stream → entered endothelial cells of small vessels in different organs, mainly the skin → endothelial proliferation and perivascular inflammation → vasculitis, thrombosis and hemorrhage
- fibrin thrombi formed in capillaries
- sparse lymph mononuclear cell response
describe clinical features, investigations and complications of epidemic typhus
-
clinical features:
- severe headaches, generalized aches and high fever
- then maculopapular rash on the torso → extremities (centrifugal spread)
- can cause pneumonia, hepatitis
- CNS involvement (typhus nodule)
- apaty, stupor, coma, death
- if severe: necrosis or earlobes, scrotum, nose and finger
-
investigations:
- immunofluorescence → demonstrate organism
- Weil Felix test: antibodies cross-react with Proteus spp. antigen
-
complications:
- interstitial pneumonia, myocarditis, encephalitis
describe what is seen in the image
describe the etiology and epidemiology of Rocky Moutain spotted fever
- etiology:
- Rickettsia rickettsii
- small G-ve intracellular coccobacillus
- spread by wood tick
- epidemiology:
- GOAT states: Georgia, Oklahoma, Arkansas, Tennessee
describe the pathogenesis of RMSF
- pathogenesis
- centrifugal spread of rash (extremities → center)
- incubation period ranges from 3-12 days
- necrosis, hemorrhage, vasculitis and thrombosis
describe the investigation and complications of RMSF
- investigation
- immunofluorescence on skin biopsy
- complications:
- interstitial pneumonia, interstitial myocarditis and DIC
describe what is seen in the image
describe the etiology of Q fever
- etiology:
- Coxiella burnetti
- spread via respiratory droplet (air borne) from infected sheep and cattle
describe the clinical features of Q fever
-
clinical features
- pneumonia, liver, spleen, bone marrow
- ring granuloma in liver biopsy = central fat, fibrinoid material, surrounded by epithelioid cells
- skin rash is not common
-
investigation:
- PCR, immunofluorescence, serology