Gram Negative Bacterial Infection

What are cytolytic toxins

Destroy the cytoplasmic membrane

What do exotoxins do

Produce characteristic disease

What do endotoxins do

Fever, weakness, aching

What are enterobacteriaceae

Rods, facultative anaerobes, have flagella if motile; catalase positive and oxidase negative; ferment glucose; use MacConkey agar

What is the characteristic of E coli

Circular, convex, smooth colonies with distinct edges

What is the characteristic of klebsiella

Mucoid and thick polysaccharide capsule

What is tripe sugar iron used for

Differentiate salmonellae and shigellae from othergram negative rods

TSI result if lactose/sucrose is fermented

yellow slant

TSI result if lactose/sucrose is NOT fermented

Red slant

TSI result if glucose is fermented

Yellow deep

TSI result if glucose is NOT fermented

Red Deep

Black precipitate is what and what does it indicate

H2S; indicates salmonella

What are O antigens

LPS resistant to heat and alcohol

What are H antigens

On flagella and are denatured/removed by heat/alcohol

What are K antigens

Form large capsules make of K antigens covering O or H antigen

Enterobacteriaceae causes what disease

UTI, E.Coli associated diarrhea disease, sepsis, meningitis

What are the signs of UTI caused by enterobacteriaceae

Urinary frequency, dysuria, hematuria, pyuria. Upper tract has flank pain

What is enteroinvasive E. coli

Invades colonic epithelial cell and lyses phagosome

What is enteropathogenic E.coli

Adhere to small bowel enterocytes, type 3 secretion to destroy microvili, lead to inflammatory response and diarrhea

What is enterotoxigenic E.Coli

Adhere to small bowel enterocyte and induce watery diarrhea by heat labile enterotoxin

what is enterohaemorrhagic E.coli/shiga producing E.coli

Adhere to small bowel enterocytes, secrete Shiga toxin can lead to life threatening complications

What is enteroaggressive E.coli

Adheres to small and large bowel epithelia in biofilm and secretes endo/exotoxins

What is bacteremia

Bacteria in bloodstream (does not always RESULT in sepsis)

What is septicemia

Bacterial infection that spreads into blood

What is sepsis

Body response to infection that will trigger whole body inflammation

What is klebsiella pneumoniae

Non motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped; resistant to ampicillin; has O and K antigen; lead to necrosis and abcess formation, septicemia, UTI, meningitis

What is the diag for klebsiella pneumoniae

urine, blood, pus, spinal fluid, sputum; look for large capsules; plated on blood agar

What is shigella

Slender, facultative anaerobes but grow better with O2; convex circular transparent colonies with intact edges; ferment glucose; ferment mannitol test

How does shigella enter the body

M cell membrane ruffling and epithelial barrier destabilization

What is sign of shigella infection

Diarrhea (watery, bloody), shigellosis dysentery, diarrhea, fever, abdominal pain

How is shigella transmitted

Fecal-oral route

Shiga enterotoxin function

Bind to small intestine that block electrolyte absorption, glucose and amino acid in intestine; large intestine infection leads to blood and pus in stool

Shiga neurotoxin function

Dysenteriae infection and reaction from CNS

What are the clinical findings of shigella

1-2 day incubation, onset of abdominal pain, fever and watery diarrhea; infection involving ileum and colon present with bloody/pus stool

Symptoms for adult with shigella

Fever and diarrhea subside spontaneously in 2-5 days

Symptoms for children and elderly adults with shigella

Loss water and electrolytes that may lead to death

What is the diag for shigella

Fresh stool, mucus flecks, rectal swab samples (locate fecal leukocytes and RBC); culture with MacConkey and selective agar, NO H2S, alkaline slant in medium

Shigella treatment

Ciprofloxacin, ampicillin, doxycycline, trimethoprim, sulfamethoxazole

What is pseudomonas aeruginosa

Motile, aerobic rods, oxidase positive; found in medical devices; many colony types; produce bluish pyocyanin that gives a green color in agar; grow at 42 C

What are the antigenic structure and toxin in pseudomonas aeruginosa

LPS, protease, hemolysin, Exotoxin A (causes tissue necrosis); thick biofilm

What is the pathogenesis of pseudomonas aeruginosa

Colonizes mucous membrane or skin, invades LOCALLY and produces systemic disease; pathogenesis only in immunocompromised areas; antimicrobial resistant

What is the diag for pseudomonas aeruginosa

Does not ferment lactose; should not treat with single drug therapy (low success and high chance of resistance)

Treatment for pseudomonas aeruginosa

Penicillin extended spectrum with aminoglycoside (tobramycin)

What are the two types of burkholderia pseudomalleii

B. pseudomalleii (causes melioidosis) and B. cepacia complex (causing opportunistic infection); found in soil and fresh water

What is burkholderia pseudomalleii pathogenesis

Localized suppurative infection at skin breakage points

What are the signs and symptoms of burkholderia pseudomalleii

Depend on major sites of involvement

What is the diag for burkholderia pseudomalleii

Wright stain/methylene blue stain; blood, pus, sputum, urine sample

Treatment for burkholderia pseudomalleii

Ceftazidime or imipenem; if infection is localized surgical drainage

What is neisseriae

Diplococci, facultative intracellular organism, non-motile, oxidase and catalase positive; killed by heat, drying and disinfectants

What culture media does N. meningitidis grow on

sheep blood agar

What sugar does N. meningitidis ferment

Maltose and glucose

What does N gonorrhoeae ferment

Glucose only

What culture media does N. Gonorrhoeae grow on

Thayer Martin Agar

What does meningococci cause

Upper respiratory tract infection and meningitis

What does gonococci cause

Genital infections

What is N. gonorrhoeae

Smaller colonies; cause gonorrhea; urethritis and cervicitis

What is the antigenic structure of N. gonorrhoeae

Pili, Opa, Por proteins, LOS envelope protein, IgA protease

Clinical findings of N. gonnorhoeae

1-14 day incubation; urethritis/cervicitis; gonococcal bacteremia leads to skin lesion; gonococcal opthalmia neonatorum

What is used for diag of N. gonorrhoeae

Pus, secretions from urethra/cervix, rectum, conjunctiva, throat; smear has diplococci with pus cell; Thayer-Martin culture; positive oxidase and glucose oxidation

What is treatment for N. gonorrhoeae

Fluoroquinolone; uncomplicated genital/rectal infection use ceftriaxone; azithromycin for pregnant women

What is Neisseria meningitidis

Round bacteria (diplococcus); cause meningitis; transfer by droplets/oral secretions/close contact; 10% are asymptomatic in nasopharynx

What is the antigenic structure of N. meningitidis

Has serogroup A-C, X, Y, W; similar to N. gonorrhoeae (LOS and IgA protease)

What are clinical findings of N. meningitidis

enter through nasopharynx and attach to epithelial cells by pili; if bacteremia symptoms are similar to upper respiratory tract infection; fulminant meningococcemia is more severe with high fever and hemorrhagic rash

What is the diag for N. meningitidis

Blood, CSF and nasopharyngeal swab samples; gram stained smears show neisseriae in polymorphonuclear leukocytes; chocolate agar for CSF samples

What is the treatment for N. meningitidis

Penicillin G; if allergic chloramphenicol or third gen cephalosporin; vaccinate with two conjugate or polysaccharide vaccine