Help reading C&S results

kaitlynelisabeth · Apr 11, 2013

The C determines what type of bacteria we are fighting antimicrobial, fungal, viral.. The S determines the bacterias dose response to drug therapy and what drug is the right drug needed to kill the bacteria or inhibit further growth. If the med has an R- it os resistant to that particular drug, the I- is the intermittent med and the S is susceptibility the infection has to drug treatment. The higher the lab value the more sensitive that bacteria is to the drug listed. You would choose based on your patients current meds, allergies, pre existing medical conditions renal or hepatic functions. The drug with the highest number (the drug that the bacteria is most sensative too) based on your patient

Look on the report example... where we have val*ues listed under UG/ML. This is the con*cen*tra*tion of an antibi*otic that inhibits the par*tic*u*lar organ*ism known as the Min*i*mum Inhibitory Con*cen*tra*tion (MIC). This tells you the level of antibi*otic that is asso*ci*ated with effec*tive treat*ment of the infec*tion and the low*est con*cen*tra*tion you need to treat that organ*ism. A lower MIC is an indi*ca*tion of a bet*ter antimi*cro*bial agent. In actu*al*ity you will need a higher con*cen*tra*tion than the MIC to fight the infection.

When reporting to the M.D make sure you exclude all meds that pt is allergic to remember those pt with allergies to penicillin are also at risk for reactions with cephalosporins. Omit drugs that have the "R" because the bacteria is resistant they won't work! Drugs that are unsuitable due to pts renal and hepatic function. Make sure you can pronounce the drug name and be sure to know what that drugs mechanism is... Ex. Amoxicillins will inhibit bacterial cell wall synthesis and any extra precautions and interventions needed monitor allergic reaction with 1st dose, pt teaching on taking med with food, increase fluid intake, avoid combo therapy with tetracyclines and aminoglycosides. Use upur clinical judgement and have a route of administration to tell the doctor. PO may not be the best option if it is a GI infection or the pt has dehydration, poor nutrition, or is simply vomiting. Pick your two best drugs, that way if the M.D shuts down your first pick you have a backup! Overkill of accurate info is always better. Hope this was helpful!

nurseprnRN, BSN, RN · Apr 11, 2013

Minimum = smallest amount

Inhibitory = hinders bacterial growth

Concentration = amount of dose to cause inhibitory effect, in micrograms per milliliter

So the MIC is telling you which antibiotics would be most effective against a given bacterium. You note that the antibiotic against which the bacterium is resistant would require really high doses, whereas the susceptible ones vary but are generally lower doses.

They are not strictly equivalent mcg per mcg, as the different drugs work in different ways*, so you can't say that a 2 is automatically better than a 4, but it gives you a good idea.

*for example, Demerol 25mg is a pretty ineffective pain medication (which is why it's not used anymore); morphine 25mg is a good whopping dose to an opioid-naive person; Dilaudid 25mg would probably kill ya.

nrsang97, BSN, RN · Apr 11, 2013

I am in microbiology right now. We did cultures with the Kirby bauer method. (This determines sensitivity or resistance to an antibiotic). We cultured E.Coli. It is resistant to vancomycin which means when the antibiotic disc was put on the plate with bacteria we didn't see a zone if inhibition( no place where there was no growth). The lab will grow up the cultures and use the antibiotic discs and measure the zone of inhibition. The larger the zone if inhibition the more sensitive the organism to the antibiotic. I can't remember what E.Coli was most sensitive to at this moment. From your lab results it is sensitive to tobramycin, rocephin, etc (anything with the S). The larger the number the greater the sensitivity.

tua42321 · Apr 14, 2013

thank you all for your help! I get it a bit better now!

nurseprnRN, BSN, RN · Apr 15, 2013

I am in microbiology right now. We did cultures with the Kirby bauer method. (This determines sensitivity or resistance to an antibiotic). We cultured E.Coli. It is resistant to vancomycin which means when the antibiotic disc was put on the plate with bacteria we didn't see a zone if inhibition( no place where there was no growth). The lab will grow up the cultures and use the antibiotic discs and measure the zone of inhibition. The larger the zone if inhibition the more sensitive the organism to the antibiotic. I can't remember what E.Coli was most sensitive to at this moment. From your lab results it is sensitive to tobramycin, rocephin, etc (anything with the S). The larger the number the greater the sensitivity.

The greater the size of the zone of inhibition, the greater the sensitivity, true. However, in the report the OP posted, the greater the number, the less the sensitivity.

classicdame, MSN, EdD · Apr 15, 2013

it does not hurt to call the lab and ask for help either. Different labs have different reporting systems.