Table 4.

Intrinsic resistance of microorganisms to antimicrobial agents³¹

Intrinsic resistance in bacteria and yeast like fungi
Microorganisms	Antibiotics/antifungals intrinsically resistant to
Citrobacter freundii	Ampicillin, amoxicillin–clavulanate, first- and second-generation cephalosporins, cephamycins, and cefuroxime.
Citrobacter diversus	Ampicillin, piperacillin, ticarcillin.
Enterobacter species	Ampicillin, amoxicillin–clavulanate, first- and second-generation cephalosporins, cephamycins, and cefuroxime.
Klebsiella pneumoniae	Ampicillin, ticarcillin.
Morganella morganii	Ampicillin, amoxicillin–clavulanate, first- and second-generation cephalosporins, tigecycline, nitrofurantoin, polymyxin B, and colistin.
Proteus mirabilis	Tetracyclines, tigecycline, nitrofurantoin, polymyxin B, and colistin.
Proteus vulgaris	Ampicillin, first- and second-generation cephalosporins, tetracyclines, tigecycline, nitrofurantoin, polymyxin B, and colistin.
Providencia species	Ampicillin, amoxicillin-clavulanate, first-generation cephalosporins, tetracyclines, tigecycline, nitrofurantoin, polymyxin B, and colistin.
Serratia marcescens	Ampicillin, amoxicillin-clavulanate, first- and second-generation cephalosporins, cephamycins, nitrofurantoin, polymyxin B, and colistin.
Acinetobacter baumannii	Ampicillin, amoxicillin, amoxicillin–clavulanate, aztreonam, ertapenem, trimethoprim, chloramphenicol, fosfomycin.
Pseudomonas aeruginosa	Ampicillin, amoxicillin, amoxicillin–clavulanate, cefotaxime, ceftriaxone, ertapenem, tetracyclines/tigecycline, trimethoprim, trimethoprim sulfamethoxazole, chloramphenicol.
Burkholderia cepacia	Ampicillin, amoxicillin–clavulanate, cefotaxime, ceftriaxone, cefepime, aztreonam, imipenem, ertapenem, colistin, aminoglycosides, fosfomycin, piperacillin, ticarcillin, piperacillin–tazobactam, trimethoprim.
Stenotrophomonas maltophilia	Ampicillin, amoxicillin–clavulanate, cefotaxime, ceftriaxone, aztreonam, imipenem, meropenem, ertapenem, aminoglycosides, fosfomycin, piperacillin, ticarcillin, piperacillin–tazobactam, trimethoprim.
Salmonella and Shigella	Aminoglycosides, first- and second-generation cephalosporins, and cephamycins.
Enterococcus species	Cephalosporins, low-level aminoglycosides, clindamycin, trimethoprim, trimethoprim–sulfamethoxazole, fusidic acid.
Candida krusei and C. glabrata	Fluconazole, flucytosine.
C. lusitaniae	Amphotericin B.
C. guilliermondii	Amphotericin B, flucytosine.
C. albicans serotype B	Flucytosine.