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Antibiotics (Other Bacteria (Antibiotics active against non-bacterial…
Antibiotics
Other Bacteria
-
N. gonorrhoeae
Resistance widespread & increasing
- amoxycillin, penicillin
- 1st & 2nd gen cephalosporins
- tetracyclines (eg. doxycycline)
- quinolones (eg. ciprofloxacin)
Treatment
Consider infection acquired
- Locally / overseas
- metro / country
rural & remote areas
- amoxycillin & probenicid
- b/c multiresistance uncommon
Metro areas
- Until recently - ciprofoxacin single dose
- Now - ceftriaxone IMI
b/c quinolone resistance now prevalent
-
Macrolides
Types
-
-
azithromycin
Commonly use: single dose treatment (1 gm) of Chlamydia
trachomatis infection.
Other important uses:
- “atypical” pneumonia
- enteric infections
- typhoid fever
-
-
-
"atypical pneumoniae"
Causes
Likely
- Mycoplasma pneumoniae
- Chlamydophila pneumoniae
- Influenza, depending on season
Less Likely
- Legionella pneumophila
- Legionella longbeachae
- Chlamydophila psitacci
Empirical Treatment
- doxycycline po (a tetracycline)
- clarithromycin po (a macrolide)
- azithromycin po (a macrolide)
Clarithromycin/azithromycin have superseded erythromycin, an older macrolide
- Amoxycillin po used for S. pneumoniae & H. influenze, common pneumoniae causes.
- Amoxycillin doesn't cover atypical pneumoniae causes
-
Diabetic Foot Ulcer
Likely Pathogens = PolymicrobialGram -ve:
- Enterobacteriaceae
- Pseudomonas aeruginosa
Gram +ve:
- Staphylococcus aureus
- β-haemolytic streps
- α-haemolytic streps
Anaerobes:
- Bacteroides & others
- Peptococcus spp.
- Peptostreptococcus spp.
Treatment
Surgery
- Surgical debridement important.
- Amputation often necessary.
-
-
-
Basic cephalosporin structure
Basic penicillin strucure
-
Mechanisms of resistance to antibiotics:
- Inhibition of ingress of antibiotic.
- Enhanced egress of antibiotic
- Enzymatic destruction of antibiotic
- Alteration of antibiotic target
For a penicillin susceptible Streptococci, e.g. S. mitis, Gentamicin, used primarily in Gram negative infections, can be used w/- penicillin for its SYNERGISTIC activity. e.g. requires 2 weeks of treatment instead of 4 weeks for penicillin alone.
- Gram -ve activity Increase w/- successive gen.
- Gram +ve activity Decreases w/- successive gen.'s Until 5th Gen where it increases
Pseudomonas aeruginosa
- Antibiotic Resistance Mechanisms
a. Reduced ingress (imipenem, aminoglycosides)
b. Active efflux mechanisms for β-lactams
c. Enzymatic destruction - β-lactamases
d. PBPs & DNA gyrases with low affinity for β-lactams and quinolones
- Antibiotic Susceptibility
a. β-lactams (Penicillins [ticarcillin, piperacillin], Cephalosporins [ceftazidame, cefepim], Carbapenams [imipenem, meropenem], Monobactams [aztreonam])
b. Aminoglycosides (Gentamicin, Tobramicin)
c. Quinolones (Norfloxacin, Ciprofloxacin, Moxifloxacin)
(anti-pseudomonal antibiotics but active against many others)
(Particular strains may be resistant to antibiotics in this group)
Empirical antibiotics for Bacterial Meningitis
Need to cover potential pathogens
- Neisseria meningitidis (penicillin drug of choice)
- Streptococcus pneumoniae (relative/absolute resistant to penicillin
- Haemophilus influenzae (many β-lactamase producers)
Initial choice = ceftriaxone – covers all (although some S. pneumos have ↑ MIC to ceftriaxone)
- People exposed may have become carriers need “prophylaxis” to eradicate possible N. meningitidis carrier state.
- penicillin will not eradicate carrier state
- Adults / children > 12 ciprofloxacin po 1 dose
- Children rifampicin po bd for 2 days
- Pregnant women ceftriaxone single IM
Lab Acronyms
- MC&S = Microscopy, culture & susceptibility
- MSU = mid stream urine
- FVU for PCR testing = First-void urine for polymerase chain reaction testing (usu. Chlamydia trachomatis)