Ambler Gram Negative

Question 1

Lactose fermenters

Answer 1

Ecoli
Klebsiella
Enterobacter
Citrobacter (slow)
Serratia (slow)
Provedencia (slow)

Question 2

Non lactose fermenters

Answer 2

Pseudomonas
Proteus
Acinetobacter
Stenotrophomonas
Moraxella
Shigella
Salmonella
Bordatella
Burkholderia

Question 3

Enterobactericeae

Answer 3

Mainly enteric. Also ubiquitous in environment
Found in Colon, vaginal tract, urethra
Most common pathogens for UTI

Ecoli, Salmonella, Shigella, Proteus, Klebsiella, Citrobacter, Enterobacter, Serratia

Question 4

Escherichia coli

Answer 4

Found: colon, vaginal tract
facultative anaerobe
Causes diarrhea, uti*, abdominal sepsis

Question 5

E. coli diarrhea

Answer 5

Enterotoxigenic (ETEC)
Enterohemorrhagic (EHEC)
Enteroinvasive (EIEC)
Enteropathogenic (EPEC)

Question 6

ETEC

Answer 6

Montezuma’s revenge (travelers diarrhea)
106-108 organisms for infection
Can have heat stable toxin
Exotoxin similar to cholera heat labile toxin (LT)
Inh the reabsorption of Na+ and Cl- and stimulates the secreation of Cl- and HCO3- into the lumen. Also looks like rice water like cholera. Afebrile.
Can get significant electrolyte loss
Treatment is support unless severe then FQ +/- loperamide or even bismuth has been used

Question 7

EHEC

Answer 7

O157:H7 main player
can infect with less than with 10 organisms
Has a shiga-like toxin (verotoxin) that inh pro synthesis by inhibiting 60S ribosome causing intestinal epithelial cell death.
Bloody* diarrhea with some purulence

HUS [hemolytic uremic syndrome]: anemia, thrombocytopenia and renal failure as the feared (and thus on boards) question

Question 8

EIEC

Answer 8

Similar to shigella
Shares a plamid with shigella and causes the bacteria to invade the epithelium and cause inflammation with FEVER.
Local invasion only
Bloody, purulent diarrhea.

Question 9

EPEC

Answer 9

Do not produce shiga-like toxins
Person to person spread
Watery diarrhea – severe with vomiting and may persist and can be bloody
Leading cause of infantile diarrhea in developing countries.
Support or abx if severe or protracted.

Question 10

Kleb pneumoniae

Answer 10

UTI and Pneumonia
Second to E.coli for causes of infection with the gram negatives.
Principle virulence factor is the polysaccharide capsule which inhibits phagocytosis
All resistant to ampicillin due to chromosomal penicillin-specific β-lactamase
Other resistance have been commonly described : ESBl (extended spectrum beta lactamase inhibitor) and CRE (carbapenemase reseistant enterobacteriae) has been in the news a lot

Question 11

Enterobacter

Answer 11

Most common are

• Enterobacter cloacae
• Enterobacter aerogenes

Causes disease in pneumonia, uti, intraabdominal, wounds
Inducible enzyme (cloacae) that can turn on resistance to 3rd generation cephalosporins during treatment (est 20-25%).  

Treatment of choices sulfa/tmp or carbapenum

Question 12

Serratia

Answer 12

Tends to colonize respiratory and urinary tract

Treat with advanced cephalosporins/carbapenums or FQ as may include resistance like that of enterobacter.

Question 13

Proteus

Answer 13

Mirabilis most common, 2nd vulgaris
Non Lactose fermenter and VERY motile
“swarms” the plate.
Urease splitting.
Buzzwords :  high pH urine and stones including staghorn calculi.

Question 14

Morganella morganii

Answer 14

Non lactose fermenter
Like enterobacter in that has inducible resistance so high generations cephalopsporins or carbapenums. Also piperacillin, FQ can be used.
Seen in abdominal infections, urine and elsewhere as common hospital infection

Question 15

Shigella dysenteriae

Answer 15

NON-MOTILE (not bacteremic), no H2S gas production
One of the most infective bacteria on the planet. Innoculum less than 200 orgs, could be 10’s of orgs
Bloody mucopurulent after incubation of 1-4 days.
Shiga toxin
B subunit binds to intestinal membrane
A subunit inactivates 60S ribo which stops protein synth, kills the lining cells and prevents fluid resorption

Question 16

Salmonella

Answer 16

MOTILE therefore can disseminate. H2S producer.
typhi, non-typhi is usually how reported
cholera-suis and paratyphi most common
Incubation 10-24 hours
infection with >105 organisms but possibly 10’s of orgs
Capsule (antigen Vi) helps protect from intracellular killing
Buzz : poultry, eggs and reptiles

Enteric Fever
Typhoid Fever after incubation 6 days-30 days
Fever, abd pain, hepatosplenomegaly, Rose spots and bacteremia
Paratyphoid Fever
Similar to typhoid symptoms
Chronic carrier (Typhoid Mary)
Gastroenteritis
Sepsis
Osteomyelitis in a sickle cell patient

Question 17

If you see osteomyelitis in a sickle cell patient, think…

Answer 17

salmonella

Question 18

Yersinia enterocolitica

Answer 18

Motile, pleomorphic gram negative rods
Enterocolitis in 1-4 yr olds
Fever, diarrhea and abd pain.  
Mesenteric adenitis and terminal ileitis in teens (clinically looks like apendicitis).
Can grow in cold ie contaminated meats.
Heat Stable toxin (ST) like Ecoli’s

Also can cause besides enterocolitis;
Sepsis and metastatic disease
Reactive polyarthropathy/Ankylosing Spondylitis
10-30% and seems to be HLA-B27 for long standing symptoms.
Exudative pharyngitis
Erythema nodusum 30%

Question 19

Yersinia pestis

Answer 19

Buzzwords
Pandemic
Justinian plague 541 AD with 25million deaths
“Black Death” or Great Plague. Origin China 1334 and killed 60% of Europe
Modern Plague 1860 China to Hong Kong 1894 with 10million deaths. Org first identified here.
Buboes ie “The Bubonic Plague”
Transmitted by rats but now most efficient vector is the oriental rat flea, Xenopsylla cheopis
In the US, sylvatic foci is burrowing rodents in the SW USA.

Question 20

Bubonic plague

Answer 20

Most common form of yersinia pestis
Incubation 2-7 days after bite and proliferates in lymph nodes
Sudden fever, chills, weakness and headaches with simultaneous or shortly after appearance of the bubo

Question 21

Septicemic Plague

Answer 21

Sudden fever, chills, weakness, abdominal pain, shock and possible bleeding into skin/organs. Necrosis may be visible.
Sepsis can be first symptom of infection.
Blood cultures only positive in 27%
33% mortality, 3 x higher than bubonic

Question 22

Pneumonic Plague

Answer 22

Fever, headache, weakness and rapidly developing pneumonia sometimes bloody.
Can be spread by droplet person to person*
50% mortality still

Question 23

plague treatment

Answer 23

Treatment is AG (streptomycin if you can get it or gentamicin.)

Doxycycline, ciprofloxacin and chloramphenicol used as well (Not orally)

Question 24

Vibrionaceae examples

Answer 24

Vibrio
Campylobacter
Helicobacter

Question 25

Vibrio cholera

Answer 25

Single flagellum
Fimbrae attach to cells but despite being motile, are not invasive.
104-106 organisms for infection
“rice water stools”
Enterotoxin (choleragen) similar to heat labile LT of Ecoli. Also has a mucinase.
Treatment is supportive with fluid/electrolyte repletion; severe tetracycline/FQ

Question 26

Vibrio parahaemolyticus

Answer 26

Salt requiring so think oral contaminated shellfish esp around Gulf coast.
Toxin like choleragen

GI illness within 24hrs of ingestion

• Diarrhea (occ blood) with low grade fever, mild chills and headache in less than 50%
• Supportive treatment

Question 27

Vibrio vulnificans

Answer 27

Ubiquitous from gulf up east coast.
Almost all oysters in Chesapeake bay and 10% crabs
Case fatality rate of 25% esp with compromised host (ie cirrhotic on boards). Doxycycline is treatment +/- aminoglycoside.
Soft tissue infections rapid within 24 to 72 hrs to necrosis after ingestion.
* Sepsis usually fatal within 48 hrs.*

Question 28

Campylobacter jejuni

Answer 28

Up to 2 million cases in US/year
500 orgs for infection
Zoonotic - poultry and unpasteurized milk
Fever and headache after 12hrs of crampy abd pain with bloody loose diarrhea
Can disseminate
LT toxin
Like yersinia and salmonella enteritidis, may cause pseudo-appendicitis
Guillain-Barré Syndrome, not common with infection but high association (stocking glove)

Question 29

Neisseria meningitidis

Answer 29

Nasopharynx of humans only
Transmission : respiratory droplets
Capsule
Diplococci

meningitis in close quarters (dorms/military) or very young.
associated with MAC (membrane attack complex) deficiency, which is a C5-9 complement deficiency (or undiagnosed HIV)
not hard to see on Gram stain
can cause non-meningeal sepsis as well.
Treatment is ceftriaxone IV big doses but decreases mortality tremendously.
Boards like to test on Waterhouse-Friderichsen
adrenal hemorrhage with infection leading to system collapse

Question 30

N. gonorrhoeae DGI

Answer 30

Disseminated Gonococcal Infection

arthritis in adults. presents with triad of dermatitis, tenosynovitis and MIGRATORY polyarthalgia or polyarthritis. typically severe and asymmetrical.
25% aspirated joints positive….
up to 80% pcr of synovial joints positive.
can also do cervical(80-90%)/urethral swab(50-70%) if suspicious

ceftriaxone now DOC although FQ can be used except in Asia and resistance to FQ creeping around the world.

Question 31

Eikenella corrodens

Answer 31

‘human bite’

think of someone who punched another in the mouth (teeth contact) with nasty wound

Question 32

if you see oxidase positive, non-lactose fermenting gram negative rod =>

Answer 32

think P. aero first!

Question 33

Pseudomonas aeruginosa

Answer 33

‘blue green pigment’
oxidase POS NLFGNR
if you see oxidase positive, non-lactose fermenting gram negative rod => think P. aero first!
inherently resistant
FQ, carbapenums and some cephalosporins as well as various aminoglycosides.
Problematic in chronic lung patients and hospitalizied patients as well as CF (mucoid strains)
“hot tub folliculitis”
“Burn patient with lung and wounds”
“ecthyma gangrenosum”
“Puncture wound from nail through sneakers”
“malignant otitis externa/mastoiditis”
“perichondritis following cartilaginous ear piercing or acupuncture”
“green nail syndrome” – self explanatory

Question 34

Moraxellacea- aerobes

Answer 34

Moraxella catarrhalis – 3rd most common CAP
similar to H. influ but usually not as severe.
copd/chronic bronchitis patients. also otitis media and sinusitis.

Acinetobacter baumannii-haemolyticus complex
very resistant. Seen in severe respiratory patients, ie vent who have a lot of abx history.
Oxidase NEG, non-lactose fermenting GNR (unlike P. aero which is ox POS.

Question 35

Burkholderiaceae –aerobe

Answer 35

Burkholderia cepacia group
very hardy so infection control a problem
survives in betadine and lower percent chlorhexadine
very resistant.
Can see if really bad lung patients and CF.

Burkholderia pseudomallei
‘melioidosis’ in Asia with lung, bone or joint involvment, skin.
subclinical to death in 1-2 days: bioweapon agent

Burkholderia mallei
‘glanders’ zoonotic and highly communicable to humans
cutaneous glanders ‘farcy’ has nodular lymphatic skin abscesses with oily yellow pus.
also has acute and chronic systemic like melioidosis.

Question 36

Xanthomonadaceae

Answer 36

Stenotrophomonas maltophilia . Somewhat opportunistic.
seen as colonizer to pathogen mainly in lung
also seen in post cardiac surgical wounds including freshly cracked sternums
Sulfa/TMP (Bactrim®) really DOC.
Resistant to carbapenums is a unique feature