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  #1  
Old 09-04-2012
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q) a 32 yr old female comes to physician for evaluation of burning micturition...she complains of dysuria,decreased frequency of micturition associated with fever since 1 week.her previous history includes a similar history 7 yrs ago when she delivered a baby and treated with empirical antibiotics..on p/e---her pulse and b.p are normal...lab tests reveal mild leukocytosis predominantly neutrophils,no wbc or rbc casts,gram stain detects bacteria and lekocyte esterase +ve and nitrite test -ve..which of the following is the most likely causative organism the physician can suspect...?

a) staphylococci
b) bacillus
c)proteus
d) escherichia
e) pseudomonas
f) listeria
g) chlamydia
h) neisseria gonorrhea
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Old 09-04-2012
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Default my answer :)

d) escherichia
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Old 09-04-2012
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Quote:
Originally Posted by Casandra View Post
d) escherichia
E-coli is nitrite positive I guess. May be Neisseria gonorrhea is the answer
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Old 09-04-2012
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Quote:
Originally Posted by venky2600 View Post
q) a 32 yr old female comes to physician for evaluation of burning micturition...she complains of dysuria,decreased frequency of micturition associated with fever since 1 week.her previous history includes a similar history 7 yrs ago when she delivered a baby and treated with empirical antibiotics..on p/e---her pulse and b.p are normal...lab tests reveal mild leukocytosis predominantly neutrophils,no wbc or rbc casts,gram stain detects bacteria and lekocyte esterase +ve and nitrite test -ve..which of the following is the most likely causative organism the physician can suspect...?

a) staphylococci
b) bacillus
c)proteus
d) escherichia
e) pseudomonas
f) listeria
g) chlamydia
h) neisseria gonorrhea
It says gram stain detects, so its Gram positive . Would be A if its staph. Saprophyticus
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Old 09-05-2012
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C) Proteus?
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Old 09-05-2012
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Staph saprophyticus
A
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Old 09-05-2012
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I guess my answer's wrong. Can't be Proteus, cause I checked FA and it says: Leucocyte esterase (+) means it's Bacterial. And nitrite (+) means it's gram negative. Saprophyticus is unique in being a gram negative bug that also gives a positive nitrite test, so I doubt it's Saprophyticus either..

What does it leave us with, then? Listeria?
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Old 09-05-2012
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When it comes to UTI. E. Coli ;-)
But leukocyte estrase positive. So my final bet is for
Chlamydia trachomatis...

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Quote:
Originally Posted by Jondez View Post
E-coli is nitrite positive I guess. May be Neisseria gonorrhea is the answer
I think e Coli is nitrite positive. This is one of the test we do to detect e Coli. As I remember. As this test has less sensitivity but high specificity.


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I knew it was not ecoli but den got held in between proteus and Staph saphrophyticus. Went through a web site and found a good explanation


First: people with Proteus infections are more likely to get renal stones. Proteus has urease, which raises the pH of the urine, making stone formation more likely. Second, young women with uncomplicated UTIs have an increased incidence of Staph saprophyticus infection. E. coli is still the most common bug – but Staph saprophyticus is pretty common too. That’s important to remember because one of the parameters that you look at when evaluating for a UTI is nitrites. Most gram negative organisms (like E. coli) reduce nitrates to nitrites – so the little nitrite square on the urinary dipstick will be positive in most normal UTIs. Gram positive organisms (like Staph) generally don’t reduce nitrates – so the nitrites will not be increased in these infections. You wouldn’t want to only use that parameter to diagnose UTIs, obviously!
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Correct Answer A

well, the correct answer is A) staphylococcus...(staph. saprophyticus)

from the case above we can easily diagnose it as UTI case from symptoms of dysuria,burning micturition,previous similar history during parturition(mc period of entry)----most common cause of uti in females is via colonization with vaginal bacteria coz their urethra is shorter comparative to males....
...although staph saprophyticus is involved in UTI's of newly married female(hence, aka honeymoon cystitis),it can also be commonly seen in sexually active females b/w 25-35 yrs age.......

Exclusion method-----1) gram stain detects bacteria------chlamydia can be excluded since, it's rarely found in gram stain
2) leukocyte esterase +ve(implies bacterial cause) and nitrite -ve( implies for all gram negative bacteria)-----since nitrite test is negative---all gram negative bacteria can be excluded----C,D,E,H are excluded
.this leaves with A,B,F

Explanation
------staphylococcus saprophyticus is the 2nd most common cause of UTI in sexually active women(most common is E.coli)......
all gram negative bacteria's can reduce nitrates to nitrites.....so, nitrite test will be positive in all gram negative...
it is most commonly used for diagnosing any kind of UTI ,coz many causative organisms causing UTI are gram negative..except 2 pathogens----staph.saprophyticus and enterococcus.as enterococcus is not mentioned in the options....staph.saprophyticus is the most appropriate answer physician would suspect....

as for bacillus and listeria-----they are very rare in causing UTI----bacillus cause anthrax,food poisoning(bacillus cereus)
listeria cause-----meningitis,septicemia(in pregnants during labor) commonly(granulomatosis infantiseptica)


Quote:
Originally Posted by dockhi View Post
I guess my answer's wrong. Can't be Proteus, cause I checked FA and it says: Leucocyte esterase (+) means it's Bacterial. And nitrite (+) means it's gram negative. Saprophyticus is unique in being a gram negative bug that also gives a positive nitrite test, so I doubt it's Saprophyticus either..

What does it leave us with, then? Listeria?
yes, you are right but, first aid says that nitrite test-positive---gram negative( except staph.saprophyticus)-----implies it is nitrase negative...as, all the other bacteria given in 1st column of F.A are gram negative except staph.saprophyticus...(i think you've mistaken)..
i hope it understands well....

S. Saprophyticus subsp. saprophyticus is distinguished by its being nitrate reductase negative and pyrrolidonyl arylamidase(PYR) negative ------------------source wikipedia

Last edited by venky2600; 09-05-2012 at 08:00 AM.
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  #12  
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okay, i forgot about discussing other options

E.coli---most common cause of UTI in females, colonies on EMB agar--nitrite positive
---pathogenic factors-----> for UTI,pyelonephritis---fimbrial antigen ; for septic shock,bacteremia----lipopolysaccharide ; for diarrhea,pneumonia,meningitis-----K capsule

proteus vulgaris/mirabilis---urease +ve with swarming motility..increases urine pH,cause struvite/staghorn calculi

pseudomonas-----water source is the transmission..oxidase +ve with pigment production...causes nosocomial UTI,malignant otitis externa,hot tub folliculitis,infections in burn/splenectomised patients

chlamydia-----intracellular parasite(cn't produce their ATP)---weakly gram -ve..causes conjunctivits(trachoma),pneumonia(atypical),LGV(bu boes are seen ),PID in females(leading to infertility),fitz hugh curtis syndrome(perihepatitis)

neisseria ---causes gonorrhea,meningitis,otitismedia ....gm -ve diplococci.....grows on chocolate agar....also implicated in PID along with chlamydia.......polysaccharide capsular vaccine is preventive.
also cause water-house fredrichsen syndrome(bilateral adrenal hemorrhage).resistance aquired by transformation

listeria-----cause meningitis,septicemia in newborns....gm +ve bacilli....transmitted by cold foods

bacillus----cause anthrax(cutaneous,woolsorter's, GI) and food poisoning by bacillus cereus.......it's capsule is different from others(made of d-glutamate)not polysaccharide.....
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Old 09-05-2012
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[venky: yes, you are right but, first aid says that nitrite test-positive---gram negative( except staph.saprophyticus)-----implies it is nitrase negative...as, all the other bacteria given in 1st column of F.A are gram negative except staph.saprophyticus...(i think you've mistaken)..
i hope it understands well....

S. Saprophyticus subsp. saprophyticus is distinguished by its being nitrate reductase negative and pyrrolidonyl arylamidase(PYR) negative ------------------source wikipedia[/QUOTE]

Perfectly, YES. Btw, thanks for this question. You saved a major conceptual blunder I was gonna make!
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Quote:
Originally Posted by dockhi View Post
Perfectly, YES. Btw, thanks for this question. You saved a major conceptual blunder I was gonna make!
that's ok...actually i framed this question on the basis of F.A sentence itself....
actually i was unable to remember it like given...so i framed it so ican remember it.....now i can remember
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