micro - bacteria 5: G- rods

gram negative cell wall

thin peptidoglycan wall surrounded by outermembrane containing LPS

most G- rods are in the family


G- rods are the most common cause of

diarrhea and UTIs

gram negative rods tend to be resistant to

penicillin and vancomycin

G- bacteria retain what part of the gram stain


klebsiella pneumoniae identifying features (6)

G-rodnon-motileencapsulatedrapid lactose fermenter

motility of klebsiella

non-motile, no flagellum

lactose fermenting status of klebsiella

RAPID lactose fermenter

klebsiella infects what kinds of hosts

immunocompromised- alcoholics- diabetics- nosocomial

infections associated with klebsiella pneumoniae

lobar pneumonialung abscessesUTIs (rare)liver abscesses

pneumonia in klebsiella infection

RED CURRANT JELLY sputumoften occurs after aspiration of GI contents

red currant jelly sputum

Klebsiella pneumoniae

pneumonia resulting from klebsiella infection often results from

aspiration of GI contents (alcoholics)

lung abscesses are usually caused by

mouth anaerobes

number one cause of UTIs

E. coli

number two cause of UTIs

s. saprophyticus

liver abscesses in klebsiella infection may result in patients with

underlying liver disease (alcoholics)

pt with long history of alcohol abuse, presenting with lobar pneumonia, liver abscesses, and a red currant jelly sputum

klebseilla pneumoniae

pathogenicity of E. coli

most non-pathogenic normal gut flora

selected virulence factors of pathogenic E coli species

fimbriae/pilicapsule with K antigen

K1 antigen

capsular antigen found on some strains of E. coli

capsulated status of E. coli

most are non-capsulatedsome strains have a capsule with K1 antigen

K1 antigen is found in 75% of

E. coli induced infant meningitis

role of K antigen

inhibit phagocytosis and complement activation

number one cause of pyelonephritis

E. coli

E. coli bacteremia/sepsis

rare, but would result from UTI typically if it occurs (secondary bacteremia)

infections associated with E. coli

UTI/pyelonephritisdysentery or water diarrheameningitis

lactose fermenting status of E. coli

RAPID lactose fermenter

major types of pathogenic E. coli


which strains of E. coli cause bloody diarrhea


which strains of E. coli cause watery diarrhea


enteroinvasive E. coli (EIEC)

Invades the intestinal mucosa cause necrosis, inflammation and bloody diarrhea

EIEC similarity to shigella

similar but NO TOXINS

which pathogenic strains of E. coli produce toxins


which pathogenic strains of E. coli do not produce toxins


which pathogenic strain of E. coli produces a shiga-like toxin


which infection of a pathogenic strain of E. coli occurs mostly in children

EPECthink: P for pediatric

enteropathogenic E. coli (EPEC)

blunt vill prevents absorptionno toxin, no inflammation

EPEC causes

diarrhea, usually in children

which strains of E. coli do not cause inflammation



T = Traveler's diarrhea (watery)T = Two Toxins - labile and heat stable

toxins of ETEC

labile and heat stable

which pathogenic strain of E. coli is associated with traveling


classic serotype of EHEC


EHEC grows on


EHEC toxin

Shiga-like toxin

which pathogenic strain of E. coli invades host cells


cause of bloody diarrhea in EIEC

invasion of ORGANISM

cause of bloody diarrhea in EHEC

shiga-like TOXIN (bacteria doesn't invade host cells)

EHEC infection may result from consumption of

undercooked beef

effects of EHEC shiga-like toxin

swelling of endothelium in GI vessels --> narrowing of lumen --> deposition of fibrin and platelets --> inflammation, necrosis, bleeding

hemolytic uremic syndrome caused by


HUS occurs in

10% of EHEC infections

HUS is most often observed in


HUS triad

hemolytic anemiathrombocytopenia (petechiae of lower legs, ecchymosis, etc)acute renal failure (uremia)

HUS usually occurs how many days after dysentery in EHEC

5 to 7 days

enterobacter is and occasional cause of nosocomial


lactose fermenting status of enterobacter

RAPID lactose fermenting

virulence factor of enterobacter

extended spectrum beta lactamase

extended spectrum beta lactamase

enterobacter resistance factor

enterobacter is resistant to most

beta lactams- penicillin- cephalosporins- aztreonam


normal gut floraoccasional sepsis

citrobacter gram stain

G- rod

citrobacter lactose fermenting status

SLOW lactose fermenter

serratia gram stain

G- rod

serratia colonies

red colonies

red colonies on growth media


catalase of serratia


serratia infections

nosocomialmay cause osteomyelitis in IV drug users

osteomyelitis in IV drug users


identifying characteristics of citrobacter (3)

G-rodslow lactose fermenter

identifying characteristics of serratia (4)

G-rodslow lactose fermentercatalase positive

lactose fermenters mnemonic (and what are they)

macConKEESCitrobacter (slow)Klebsiella (rapid)E. coli (rapid)Enterobacter (rapid)Serratia (slow)

types of salmonella (3)

typhoidal: s. typhinontyphoidal: s. enterica and enteriditis

non-typhoid strains of salmonella

S. entericaS. enteriditis

non-typhoidal strains of salmonella cause


major shared identifying features of salmonella (4)


capsule status of salmonella


motility of salmonella

motile (flagellated)

unique feature of immune response elicited by S. typhi

largely monocytic

H2S test

used to differentiate shigella from salmonellasalmonella turns media black

how to differentiate shigella from salmonella

TSI- salmonella produces H2S and turns media black

infection of S. enterica causes

INVASIVE gastroenteritis

symptoms of invasive gastroenteritis resulting from non-typhoidal (enterica) salmonella infection

N/V/C/bloody diarrhea

diarrhea in S. enterica infection


normal flora location for s. enterica

guts of reptiles, birds, mammals

s. enterica infection may occur following the ingestion of

contaminated eggs, poultry

if s. enterica disseminates through the blood, it may cause


symptoms of typhoid fever

fever, diarrhea, abdominal pain, headache+rose spots, pulse/temp dissociation

typhoid fever typically involves travel to

africa, asia, south america

classic presentation of salmonella typhi

rose spotspulse temperature dissociateosteomyelitis (if sickle cell)

number one cause of osteomyelitis in patients with sickle cell anemia

S. typhi

pt with sickle cell anemia and osteomyelitis

S. typhi

rose spots

s. typhisalmon color macules on trunk and abdomen

salmon colored macules on trunk and abdomen

S. typhi

pulse temperature dissociation

high fever with low pulse

shigella motility


shigella stain


identifying characteristics of shigella (3)


immune response illicited by shigella infection

largely PMNs

immune response in salmonella vs shigella

salmonella: monocytic shigella: PMN

what is invaded in salmonella enterica infection

GI mucosa

what is invaded in shigella infection

M cells of peyer's patches

invasion of peyer's patch M cells


H2S status salmonella


H2S status shigella


oxidase status of shigella


lactose fermenting status of shigella


major identifying characteristics of shigella (6)

G-rodnon-motilenon-lactose fermenteroxidase negativeH2S negative

how does shigella invade M cells


when shigella invades M cells, what is the result


how does shigella infection spread


difference in spread of infection: salmonella vs shigella

salmonella: bloodstreamshigella: cell to cell

shigella toxin

shiga toxin

bacteria needed to cause disease in shigella infection

VERY low (roughly 10)

major identifying features of proteus (6)

G-rodurease positiveswarming phenotypenon-lactose fermenteroxidase negative

lactose fermenting status of proteus


urease status of proteus


swarming phenotype


bulls-eye on blood agar


proteus infection is associated with

struvite kidney stone formation

struvite kidney stone formation


major identifying features of pseudomonas aeruginosa (7)

G-rodobligate aerobewater lovingoxidase positivenon-lactose fermentingcapsulated

which G- rod loves water

P. aeruginosa

environmental preference of P. aeruginosa

aerobic (obligate)water

lactose fermenting status of P. aeruginosa


oxidase status of P. aeruginosa


P. aeruginosa colonies on media

fluorescent green

fluorescent green colonies on culture media

P. aeruginosa

pigment produced by P. aeruginosa


odor of P. aeruginosa

grape like(think green grape colonies)

hot tub folliculitis

Pseudomonas aeruginosa

mnemonic for P. aeruginosa associated infections (and what are they)

BE PSEUDOBurnsEndocarditisPneumoniaSepsisExternal otitis (swimmer's ear)UTIDrug usersOsteomyelitis

which G- rod is known to cause swimmer's ear (otitis externa)

P. aeruginosa

pneumonia in P. aeruginosa infection especially prevalent in patients with


most common cause of peptic ulcers

H. pylori

major identifying characteristics of Helicobacter pylori

G-rodmotikemicroaerophilicurease positive

environmental preference of H. pylori


H. pylori causes

peptic ulcersgastritis

urease status of H. pylori


how does H. pylori survive in the acidic stomach

urease hydrolyzes urea to ammonia (alkaline)

test for H. pylori

urea breath test (labelled urea - detection of isotype)

method of legionella transmission

aerosol (NOT airborne)

legionella classically associated with

contaminated water in hotel a/c cooling tanks

gram staining of legionella

G- (doesn't stain well, use silver stain instead)

what stain is used for identification of legionella

silver stain

special culture requirement of legionella

buffered charcoal yeast extract- contains Fe and Cys for growth- contains antibiotics to inhibit growth of other species- silver dyes for contrast

classic infection of legionella

pneumonia in nursing homes resulting/contaminated AC tanks

what metabolic disturbance is associated with legionella infection


diarrhea in legionella


symptoms of legionella

severe pneumoniawatery diarrheaN/V/APhyonatremia

nursing home pt presenting with watery diarrhea, pneumonia, hyponatremia


mnemonic for bacteria that don't gram stain well (and what are they)

These Rascals May Microscopically Lack ColorTreponemaRickettsiaMycobacteria (mycolic acid)Mycoplasma (no cell wall)LegionellaChlamydia (no peptidoglycan, lacks muramic acid)

major identifying characteristics of Bacteroides (3)

G-Rodobligate anaerobe

bacteroides infections are usually


infections associated with bacteroides fragilis

polymicrobial- peritonitis- intra-abdominal abscesses- lung abscesses

B. fragilis infections tend occur in junction with

E. coli/GNR infections

fecal leukocytes indicate

INVASIVE INFECTION --> bloody diarrhea

mucous/epithelial cells in fecal matter indicate

TOXIN mediated disease