Gram Negative Bacteria

Question 1

Neisseria meningitidis is transmitted by ____

Answer 1

Neisseria meningitidis is transmitted by respiratory droplets (nasopharynx)

Question 2

____ is the most common cause of acute pyogenic meningitis in adolescents and young adults

Answer 2

Neisseria meningitidis is the most common cause of acute pyogenic meningitis in adolescents and young adults

Question 3

describe clinical features of meningitis

Answer 3

• 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

Question 4

describe the lab investigations in meningitis and other causes of meningitis

Answer 4

Question 5

the most common organism producing meningitis in neonates is _____

Answer 5

the most common organism producing meningitis in neonates is group B streptococci and E. coli

Question 6

the most common organism producing meningitis in adolescence and younger adults is _____

Answer 6

the most common organism producing meningitis in adolescents and younger adults is Neisseria meningtidis

Question 7

the most common organism producing meningitis in older adults is _____

Answer 7

the most common organism producing meningitis in older adults is Strep. pneumoniae and Listeria monocytogenes

Question 8

the most common organism producing chronic meningitis is _____

Answer 8

the most common organism producing chronic meningitis is mycobacterium tuberculosis and fungi

Question 9

describe meningococcemia

Answer 9

Question 10

describe what is seen in the image

Answer 10

Question 11

describe what causes gonorrhea and the pathogenesis

Answer 11

caued by Neisseria gonorrhea (G-ve diplococci)

• pathogenesis: organism invades mucosa surface using its pili and membrane proteins and causes inflammation

Question 12

describe the clinical features of gonorrhea in females

Answer 12

• dysuria, vaginal discharge, intermenstrual bleeding
• cervicitis, salpingitis (pelvic inflammatory disease) and peritonitis
• if chronic → scarring of the fallopian tubes leading to infertility

Question 13

describe the clinical features of gonorrhea in males

Answer 13

• urethritis, epididymitis
• mucopurulent urethral discharge and dysuria
• oropharyngitis (oral sex)
• proctitis (anal sex)

Question 14

describe gonorrhea in the newborn

Answer 14

• 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

Question 15

describe the diagnosis of gonorrhea in males vs. females

Answer 15

Question 16

describe the etiology of typhoid fever

Answer 16

• salmonella typhi (G-ve rod)
• salmonella paratyphi (predominate in travelers & those living in developed countries)
• humans are the sole reservoir

Question 17

describe the pathogenesis of typhoid fever

Answer 17

• 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)

Question 18

describe the spread of typhoid fever in the body

Answer 18

Question 19

Answer 19

Question 20

describe the clinical features of enteric fever

Answer 20

Question 21

describe the complications of typhoid fever

Answer 21

Question 22

describe the mechanism of septic shock

Answer 22

Question 23

describe the etiology of urinary tract infections

Answer 23

• etiology: E. coli (most common cause)

Question 24

describe the pathogenesis, clinical features and investigations of UTIs

Answer 24

• pathogenesis:
  
  • most common in females
  • ascending infxns through the urethra
• clinical features:
  
  • fever, dysuria, frequency, suprapubic, tenderness and cloudy urine
• investigations:
  
  • CBC, urinalysis

Question 25

describe G-ve septicemia and clinical features

Answer 25

* 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

Question 26

rickettsia are obligate ____ bacteria

Answer 26

rickettsia are obligate **intracellular** bacteria

Question 27

based on rickettsial organisms, 3 different illnesses can occur:

Answer 27

* **epidemic typhus** caused by *R.* *prowazecki* * **Rocky Mountain Spotted Fever** caused by *R.* *rickettsii* * **Q fever** caused by *Coxiella* *burnetti*

Question 28

describe the etiology and vector of epidemic typhus

Answer 28

* etiology: R. prowazeckii * small G-ve bacillus * spread by head and body **lice**

Question 29

describe the pathogenesis of epidemic typhus

Answer 29

* 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

Question 30

describe clinical features, investigations and complications of epidemic typhus

Answer 30

* _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

Question 31

describe what is seen in the image

Answer 31

Question 32

describe the etiology and epidemiology of Rocky Moutain spotted fever

Answer 32

* etiology: * Rickettsia rickettsii * small G-ve intracellular coccobacillus * spread by wood **tick** * epidemiology: * GOAT states: Georgia, Oklahoma, Arkansas, Tennessee

Question 33

describe the pathogenesis of RMSF

Answer 33

* pathogenesis * centrifugal spread of rash (extremities → center) * incubation period ranges from 3-12 days * necrosis, hemorrhage, vasculitis and thrombosis

Question 34

describe the investigation and complications of RMSF

Answer 34

* investigation * immunofluorescence on skin biopsy * complications: * interstitial pneumonia, interstitial myocarditis and DIC

Question 35

describe what is seen in the image

Answer 35

Question 36

describe the etiology of Q fever

Answer 36

* etiology: * Coxiella burnetti * spread via respiratory droplet (air borne) from infected sheep and cattle

Question 37

describe the clinical features of Q fever

Answer 37

* _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