Antibiotic – intrinsic resistance
drsuryabrata@gmail.comMicroorganisms are only listed as “intrinsically resistant” to an agent (or group of agents) when a vast majority of wild-type isolates exhibit MIC values that are so high that the agent should not be considered for either therapy or clinical susceptibility testing (EUCAST).
Enterobacterales & Aeromonas
Enterobacterales and Aeromonas are intrinsically resistant to benzylpenicillin, glycopeptides, lipoglycopeptides, fusidic acid, macrolides (Except Azithromycin, effective for typhoid/paratyphoid fever and erythromycin for travellers’ diarrhoea), lincosamides, streptogramins, rifampicin, and oxazolidinones.
| Bacteria | Beta-lactams | Non-beta-lactams |
| Klebsiella pneumonia complex, Klebsiella oxytoca Roultella sp. Citrobacter koseri, Citrobacter amalonaticus | Amoxicillin, Ticarcillin | |
| Klebsiella aerogenes, Enterobacter cloacae complex Citrobacter freundii Hafnia alvei | Amoxicillin, Coamoxiclav, 1st generation cephalosporins Cefoxitin | |
| Serratia marcescens | Amoxicillin, Coamoxiclav, 1st and 2nd generation cephalosporin | Tetracycline, doxycycline (not minocycline or tigecycline) Colistin, Nitrofurantoin |
| Bacteria | Beta-lactams | Non beta-lactams |
| Proteus mirabilis | Tetracycline, Tigecycline Colistin, Nitrofurantoin | |
| Proteus vulgaris | Amoxicillin 1st generation cephalosporins, cefuroxime | Tetracycline, Tigecycline Colistin, Nitrofurantoin |
| Providencia stuartii, P rettgeri | Amoxicillin, Coamoxiclav 1st generation cephalosporin | Tetracycline Colistin, Nitrofurantoin |
| Morganella morganii | Amoxicillin, Coamoxiclav 1st generation cephalosporin | Tetracycline Colistin, Nitrofurantoin |
| Bacteria | Beta-lactams | Non-beta-lactams |
| Yersinia enterocolitica | Amoxicillin, Coamoxiclav, 1st generation cephalosporins 2nd generation – cefoxitin (but not cefuroxime) | |
| Yersinia pseudotuberculosis | Colistin | |
| Aeromonas hydrophila Aeromonas caviae | Amoxicillin, coamoxiclav, Cefoxitin |
Non-fermentative gram-negative bacteria
Generally intrinsically resistant to benzylpenicillin, first- and second-generation cephalosporins, glycopeptides, lipoglycopeptides, fusidic acid, macrolides, lincosamides, streptogramins, rifampicin and oxazolidinones.
| Bacteria | Beta-lactam | Non-beta-lactam |
| Acinetobacter baumannii, Acinetobacter pittii, Acinetobacter nosocomialis | Amoxicillin, Coamoxiclav Ceftriaxone, Cefotaxime, Ertapenem, Aztreonam | Trimethoprim, Fosfomycin, Tetracycline, Doxycycline (Not Minocycline/Tigecycline) |
| Pseudomonas aeruginosa | Amoxicillin, Coamoxiclav Ceftriaxone, Cefotaxime, Ertapenem | Trimethoprim Chloramphenicol Tetracycline group, Tigecycline Kanamycin, Neomycin |
| Burkholderia cepacia complex | Amoxicillin, Coamoxiclav Ticar-clavulinic acid, Pip-tazobactam, Ceftriaxone, Cefotaxime, Ertapenem, Aztreonam | Trimethoprim, Chloramphenicol, Ciprofloxacin, Fosfomycin, Colistin Aminoglycoside |
| Stenotrophomonas maltophilia | Amoxicillin, Coamoxiclav Pip-tazobactam, Ceftriaxone, Cefotaxime, Ertapenem, Meropenem, Aztreonam | Aminoglycoside, Trimethoprim (cotrimoxazole), Fosfomycin, Tetracycline (Not doxycycline, minocycline, tigecycline) |
| Bacteria | Beta-lactams | Non-beta-lactams |
| Achromobacter xylosoxidans | Amoxicillin, Ceftriaxone, Cefotaxime, Ertapenem | |
| Ochrobactrum anthropi | Amoxicillin, Coamoxiclav Ticar-clavulinic acid, Pip-tazobactam, Ceftriaxone, Cefotaxime, Ceftazidime, Cefepime Ertapenem , Aztreonam | |
| Elizabethkingia meningoseptica | Amoxicillin, Coamoxiclav Ticar-clavulinic acid, Ceftriaxone, Cefotaxime, Ceftazidime, Cefepime Ertapenem , Aztreonam Meropenem | Colistin |
Other gram negatives
All of them are intrinsically resistant to glycopeptides, lipoglycopeptides, lincosamides, and oxazolidinones. Additionally…
| Bacteria | Antibiotic |
| Haemophilus influenzae | Fusidic acid, Streptogramins |
| Moraxella catarrhalis | Trimethoprim |
| Neisseria spp | Trimethoprim |
| Campylobacter jejuni, Campylobacter coli | Fusidic acid, Streptogramins, Trimethoprim |
| Campylobacter fetus | Fusidic acid, Streptogramins, Trimethoprim, nalidixic acid |
Gram-positive bacteria
Gram-positive bacteria are also intrinsically resistant to aztreonam, temocillin, polymyxin B/colistin and nalidixic acid.
| Bacteria | Beta-lactams | Aminoglycoside, MLSB | Others |
| Staphylococcus saprophyticus | Ceftazidime | Fosfomycin Novobiocin | |
| Staph cohnii, Staph xylosus | Ceftazidime | Novobiocin | |
| Staph capitis | Ceftazidime | Fosfomycin | |
| Staph aureus, other CoNs | Ceftazidime | ||
| Streptococcus | Ceftazidime | Aminoglycoside (low-level resistance*) | |
| Enterococcus faecalis | Cephalosporins | Aminoglycoside (low-level resistance*) Macrolides, clindamycin Quinupristin-dalfopristin | Fusidic acid, Sulfonamide |
| Enterococcus gallinarum, Enterococcus casseliflavus | Cephalosporins | Aminoglycoside (low-level resistance*) Macrolides, clindamycin Quinupristin-dalfopristin | Fusidic acid, Sulfonamide, Vancomycin |
| Enterococcus faecium | Cephalosporins | Aminoglycosides (low-level resistance+AAC(6’)-I**) Macrolide | Fusidic acid Sulfonamide |
| Corynebacterium spp. | Fosfomycin | ||
| Listeria | Cephalosporins | ||
| Leuconostoc spp., Pediococcus spp. Lactobacillus spp. (L. casei, L. casei var. rhamnosus) | Vancomycin Teicoplanin |
** Low-level resistance + AAC(6’)-I enzyme – the synergy is only seen in gent, amikacin and streptomycin.
Anaerobes
Anaerobes are intrinsically resistant to aztreonam, aminoglycosides, polymyxin B/colistin and nalidixic acid.
Additionally,
Clostridium ramosum & Clostridium innocuum are resistant to vancomycin.
Reference:
https://www.eucast.org/expert_rules_and_intrinsic_resistance/
