The principles involved in the choice of antibiotic selection for particular conditions have all been outlined and discussed in the previous parts of this chapter. It is critical that all factors are considered.
The causal bacterium: its nature and characteristics
The host: sex (and pregnancy status), age, general and particular health status, liver function, renal function, allergies.
Drug factors: antibacterial spectrum, resistant organisms, pharmacodynamics (blood concentrations, how high and for how long), pharmacokinetics (metabolism and excretion). As an example, two patients infected with the identical organism may require different antibiotics because of:
o Differences in the site of infection. o Drug allergies.
o Underlying illness. o Concomitant drug therapy. o Age.
o Pregnancy.
In the absence of allergies, pregnancy, other underlying illness and potential drug interactions, there are often
accepted antibiotics of choice for common bacterial infections. The appropriate antibiotic choices for selected common pathogens are presented in Table 6.19.
ADVERSE EFFECTS OF ANTIBIOTICS
Nearly all can cause Clostridium difficile enteritis
Aminoglycosides can cause irreversible aplastic anemia and the gray baby syndrome Sulfonamides can cause a skin rash, Stevens-Johnson syndrome, and toxic
epidermal necrolysis
Tetracycline can discolor the teeth if given to children under 8 years of age
Table 6-19. Drugs of choice and alternatives for selected common bacterial pathogens
Bacterium Drug(s) of choice Alternatives Comments
Streptococcus species Penicillin A first-generation
cephalosporin Some strains are penicillin-resistant, especially a growing proportion of S.
pneumoniae
Erythromycin Erythromycin is only for mild infections
Clindamycin Vancomycin is only for serious infections
Vancomycin Certain fluoroquinolones are active against S. pneumoniae
Enterococcus species Penicillin or ampicillin
plus gentamicin Vancomycin plus gentamicin There are some strains for which streptomycin is synergistic but gentamicin is not
Quinupristin-
dalfopristin Some strains are resistant to synergy with any aminoglycoside Linezolid Some strains are resistant to
vancomycin (VRE)
Staphylococcus
species An antistaphylococcal penicillin A first-generation cephalosporin Vancomycin is required for methicillin-resistant strains Vancomycin Rifampin is occasionally used to
eradicate the nasal carriage state
Neisseria meningitidis Penicillin A third-generation
cephalosporin Chloramphenicol
Rare strains are penicillin-resistant
Neisseria gonorrhoeae Cefixime Ciprofloxacin
A third-generation cephalosporin
Some strains are fluoroquinolone- resistant (especially in Asia)
Bordetella pertussis Erythromycin TMP-SMZ
(trimethoprim- sulfamethoxazole)
Other macrolides are also active in vitro
Pasteurella multocida Penicillin A first-generation cephalosporin Haemophilus influenzae Aminopenicillin Cefuroxime A third-generation cephalosporin Chloramphenicol Approximately 30% are aminopenicillin-resistant; therefore aminopenicillins should not be used empirically in serious infections until susceptibility results are available Rifampin is used to eradicate the nasal carriage state
Enterobacteriaceae in
urine TMP-SMZ Ciprofloxacin Gentamicin β Lactams are less effective than TMP-SMZ or fluoroquinolones for the treatment of urinary tract infection
Enterobacteriaceae in cerebrospinal fluid
A third-generation cephalosporin
Meropenem In neonates only, aminoglycosides are equivalent to third-generation cephalosporins
TMP-SMZ Experience with TMP-SMZ in
Enterobacteriaceae elsewhere (blood, lung, etc.) Gentamicin or a third- generation cephalosporin or ciprofloxacin
TMP-SMZ Two-drug therapy is sometimes used in serious infection
Carbapenems Monotherapy with a third-generation cephalosporin should be avoided if the pathogen is Enterobacter
cloacae, E. aerogenes, Serratia marcescens or Citrobacter freundii
Pseudomonas aeruginosa Antipseudomonal penicillin plus aminoglycoside Ceftazidime Ciprofloxacin A carbapenem
Two-drug therapy recommended except for urinary tract infection
Bacteroides fragilis Metronidazole or
clindamycin A carbapenem A penicillin β lactamase inhibitor
B. fragilis is usually involved in
polymicrobial infections; therefore another antibiotic active against Enterobacteriaceae is often required
Mycoplasma pneumoniae
A macrolide (e.g.
erythromycin) A tetracycline Although tetracyclines are as effective as macrolides, the latter are recommended because of better activity against Pneumococcus, which can mimic this infection
Ureaplasma urealyticum
A tetracycline Erythromycin A few strains are tetracycline- resistant
Mycoplasma hominis A tetracycline Clindamycin Erythromycin is not active against M. hominis
Chlamydia trachomatis
A tetracycline Azithromycin Azithromycin is the only therapy effective in a single dose
Erythromycin Erythromycin is used in pregnancy Rickettsial species A tetracycline Chloramphenicol
Listeria monocytogenes Ampicillin plus gentamicin Vancomycin plus gentamicin
Legionella species A macrolide A tetracycline
A fluoroquinolone Rifampin is occasionally used as a second agent in severe cases
Clostridium difficile Metronidazole Vancomycin (oral) Mycobacterium
tuberculosis
Isoniazid plus rifampin Streptomycin Directly observed therapy (DOT) is recommended
plus pyrazinamide A fluoroquinolone Isoniazid is used alone for treatment of latent tubercular infection
plus ethambutol Ethionamide
Cycloserine
Viomycin
Capreomycin
Mycobacterium avium
complex Clarithromycin plus ethambutol ± rifabutin Ciprofloxacin Amikacin
Mycobacterium leprae Dapsone plus rifampin
± clofazimine Clarithromycin Thalidomide is useful for erythema nodosum leprosum
FURTHER READING
Akins RL, Haase KK. Gram-positive resistance: pathogens, implications, and treatment options: insights from the Society of Infectious Diseases Pharmacists. Pharmacotherapy 2005; 25: 1001-1010.
Boffito M, Acosta E, Burger D et al. Therapeutic drug monitoring and drug-drug interactions involving antiretroviral drugs. Antivir Ther 2005; 10: 469- 477.
Bratzler DW, Houck PM. Antimicrobial prophylaxis for surgery: An advisory statement from the National Surgical Infection Prevention Project. Clin
Infect Dis 2004; 38: 1706-1715. [Guidelines for the use of antibiotics in surgery.] Dando TM, Perry CM. Related Enfuvirtide. Drugs 2003; 63: 2755-2766.
Fraaij PL, van Kampen JJ, Burger DM, de Groot R. Pharmacokinetics of antiretroviral therapy in HIV-1-infected children. Clin Pharmacokinet 2005;
44: 935-956.
MacDougall C, Polk RE. Antimicrobial stewardship programs in health care systems. Clin Microbiol Rev 2005; 18: 638-656. Medical Letter Choice of antibacterial drugs: Treatment guidelines. Med Let 2004; 2: 13-26.
Onyebujoh P, Zumla A, Ribeiro I et al. Treatment of tuberculosis: present status and future prospects. Bull World Health Organ 2005; 83: 857-865 [A world view of the problem of tuberculosis and its treatment with drugs.]
Rom WN, Gray SM eds. Tuberculosis: 2nd Edition. Lippincott, Williams [amp ] Wilkins, Philadelphia, 2004 [The definitive and current text on tuberculosis and its treatment with drugs with individual chapters on different antitubercular drugs.]
Shefet D, Robenshtok E, Paul M, Leibovici L. Empirical atypical coverage for inpatients with community-acquired pneumonia: systematic review of randomized controlled trials. Arch Intern Med 2005; 165: 1992-2000.
USEFUL WEBSITES
http://www.cdc.gov/drugresistance/healthcare. [This site is a useful one for obtaining current information regarding resistance to antibiotics.]
http://www.nlm.nih.gov/medlineplus/antibiotics.html [Provides general information regarding bacteria and antibiotic drugs.]