types of antibiotic



i need help about the types of antibiotic. I'm confuse about antibiotic. There are a lot of antibiotic. each antibiotic have their own strength right? But how do i know and how to compare which one is the strongest antibiotic. or it is still depend on patient? but my patient pediatric pt who undergone cardiac surgery but they were on different types antibiotic but still have same symptom like fever or consider as to prevent infection following surgery. So why they have different types antibiotic to prevent infection following surgery?Can someone explain to me, please?

JustBeachyNurse, LPN

1 Article; 13,952 Posts

Specializes in Complex pedi to LTC/SA & now a manager. Has 13 years experience.

Antibiotic choice is (or should be) based upon microbiological culture results.

Fever is not always a bad thing as it shows that the immune system is functioning. Also, fever is not only caused by infectious processes. Post anesthesia reactions and certain types of brain injuries can also cause rises in core temperature.

As far as choice of prophylactic (preventative) antibiotic post surgery it depends on the type and site of surgery. Cardiac surgery would require a different antibiotic than gastric or oral surgery due to the different types of bacteria normally present. If you are an RN you should have taken microbiology and some sort of pathophysiology (LPNs also take the same but less in depth).

Antibiotic choice is determined by whether it is a gram negative or gram positive organism; whether it is a cocci, bacilli, or spirochete; and a few other bacterial characteristics such as whether it is a beta-lactamase producer, per oxidase producer, likely resistant organism. Examples: penicillin VK is often used for oral/dental infections or surgery.

While Wikipedia is not always the greatest source this is a decent explanation.



you can google, since Google often has scholarly links. There I s also Medline, Medscape, Centers for Disease Control and Prevention, and web md. http://www.medicalnewstoday.com/articles/10278.phphttp://www.nlm.nih.gov/medlineplus/antibiotics.html

Edited to add:

I saw from your other posts that you are originally from Malasyia. Where did you complete your education and what country are you working in now? Not all countries haven access to the same medications and laboratory testing. Thus that would change some of my responses.

psu_213, BSN, RN

3,878 Posts

Specializes in Emergency, Telemetry, Transplant. Has 14 years experience.

It is going to be impossible to write a totally thorough answer on here, but I agree with what was said above...antibiotic choice, over the long run, is going to be based on culture results. In the short term, choice of antibiotic is based on the the type of infection (e.g. pneumonia, UTI, cellulitis, etc.) and how bad the infection is. For example, a fairly minor cellulitis may be treated outpatient with oral keflex--which I look at as fairly middle of the road in terms of strength. A more severe cellulitis will be treated inpatient with IV Vancomycin--one of the strongest antibiotics, given IV for the vast majority of diseases (it is poorly absorbed by the GI tract, so I have only seen it given PO for C diff). The problem is that Vanc has several side effects--including renal- and oto-toxicity--and the development of resistance--VRA, VISA, etc.

Many surgical procedures will have prophylactic antibiotics given before and/or after the procedure..the choice of antibiotic there will depend on scientific evidence for which antibiotic works best for the given procedure.

There is a lot more that goes into choosing an antibiotic other that just "they have an infection, let's given an antibiotic."

Esme12, ASN, BSN, RN

4 Articles; 20,908 Posts

Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma. Has 43 years experience.

this link will be valuable to you. http://www.emedexpert.com/classes/antibiotics.shtml

although there are several classification schemes for antibiotics, based on bacterial spectrum (broad versus narrow) or route of administration (injectable versus oral versus topical), or type of activity (bactericidal vs. bacteriostatic), the most useful is based on chemical structure. antibiotics within a structural class will generally have similar patterns of effectiveness, toxicity, and allergic potential.

most commonly used types of antibiotics are: aminoglycosides, penicillins, fluoroquinolones, cephalosporins, macrolides, and tetracyclines. while each class is composed of multiple drugs, each drug is unique in some way.


the penicillins are the oldest class of antibiotics. penicillins have a common chemical structure which they share with the cephalosporins. penicillins are generally bactericidal, inhibiting formation of the cell wall. penicillins are used to treat skin infections, dental infections, ear infections, respiratory tract infections, urinary tract infections, gonorrhea.

there are four types of penicillins:

  • the natural penicillins are based on the original penicillin-g structure. penicillin-g types are effective against gram-positive strains of streptococci, staphylococci, and some gram-negative bacteria such as meningococcal.
  • penicillinase-resistant penicillins, notably methicillin and amoxicillin, are active even in the presence of the bacterial enzyme that inactivates most natural penicillins.
  • aminopenicillins such as ampicillin and amoxicillin have an extended spectrum of action compared with the natural penicillins. extended spectrum penicillins are effective against a wider range of bacteria.

penicillins side effects

penicillins are among the least toxic drugs known. the most common side effect of penicillin is diarrhea. nausea, vomiting, and upset stomach are also common. in rare cases penicillins can cause immediate and delayed allergic reactions - specifically, skin rashes, fever, and anaphylactic shock. penicillins are classed as category b during pregnancy.


cephalosporins have a mechanism of action identical to that of the penicillins. however, the basic chemical structure of the penicillins and cephalosporins differs in other respects, resulting in some difference in the spectrum of antibacterial activity. like the penicillins, cephalosporins have a beta-lactam ring structure that interferes with synthesis of the bacterial cell wall and so are bactericidal. cephalosporins are derived from cephalosporin c which is produced from cephalosporium acremonium.

cephalosporins are used to treat pneumonia, strep throat, staph infections, tonsillitis, bronchitis, otitis media, various types of skin infections, gonorrhea, urinary tract infections cephalosporin antibiotics are also commonly used for surgical prophylaxis. cephalexin can also be used to treat bone infections.

cephalosporins are among the most diverse classes of antibiotics, they are grouped into "generations" by their antimicrobial properties. each newer generation has a broader spectrum of activity than the one before.

  • the first generation cephalosporins include: their spectrums of activity are quite similar. they possess generally excellent coverage against most gram-positive pathogens and variable to poor coverage against most gram negative pathogens. the first generation cephalosporins include:
    • cephalothin
    • cefazolin
    • cephapirin
    • cephradine
    • cephalexin
    • cefadroxil

    [*]the second generation cephalosporins. in addition to the gram positive spectrum of the first generation cephalosporins, these agents have expanded gram negative spectrum. cefoxitin and cefotetan also have good activity against bacteroides fragilis. enough variation exists between the second generation cephalosporins in regard to their spectrums of activity against most species of gram negative bacteria, that susceptibility testing is generally required to determine sensitivity. the second generation cephalosporins include:

    • cefaclor
    • cefamandole
    • cefonicid
    • ceforanide
    • cefuroxime

    [*]the third generation cephalosporins have much expanded gram negative activity. however, some members of this group have decreased activity against gram-positive organisms. they have the advantage of convenient dosing schedules, but they are expensive. the third generation cephalosporins include:

    • cefcapene
    • cefpodoxime
    • cefditoren
    • cefetamet
    • cefixime
    • cefmenoxime
    • cefodizime
    • cefoperazone
    • cefotaxime
    • cefpimizole
    • cefpodoxime
    • ceftibuten
    • ceftriaxone

    [*]the fourth generation cephalosporins are extended-spectrum agents with similar activity against gram-positive organisms as first-generation cephalosporins. they also have a greater resistance to beta-lactamases than the third generation cephalosporins. many fourth generation cephalosporins can cross blood brain barrier and are effective in meningitis. the fourth generation cephalosporins include:

    • cefclidine
    • cefepime
    • cefluprenam
    • cefozopran
    • cefpirome
    • cefquinome

the article continues to explain the how and why antibiotics are choosen. it should help you.


139 Posts

i'd been completed my study in malaysia. in my ward, basically doctor will prescribe antibiotic for those who undergone cardiac surgery. I knew that there are antibiotic to prevent infection following surgery. Plus when pt getting fever and spike, doctor will prescribe antibiotic such as meropenem, imipenem, ceftazidine, ceftriaxone that are commonly prescribe for patient. doctor also will take blood culture to see whether it is gram -ve or +ve germ then doctor will prescibe the suitable antibiotic for pt. if to prevent infection following surgery, isn't it we use broad spectrum antibiotic?