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Antibiotic Resistance in Gram-Negative Bacteria

Mechanisms, epidemiology, and treatment of multidrug-resistant Gram-negative bacterial infections including ESBL, AmpC, carbapenemase-producing, and pan-drug resistant organisms.

Written by: Saygı Hospital Health Guide Editorial Board
Last updated:

This content has been compiled by the Saygı Hospital Health Guide Editorial Board and is periodically reviewed by a specialist physician.

References (5)

This content is for informational purposes only and does not constitute medical advice. You can book an appointment at our Internal Medicine department. Book Appointment →

What is Antibiotic Resistance in Gram-Negative Bacteria?

Antibiotic resistance in Gram-negative bacteria has emerged as a leading global health threat. Major resistant phenotypes include extended-spectrum beta-lactamases (ESBLs — CTX-M, TEM, SHV), AmpC beta-lactamases, carbapenemase producers (Klebsiella pneumoniae carbapenemase KPC, New Delhi metallo-beta-lactamase NDM, OXA-48-like, VIM, IMP), polymyxin resistance (mcr-1 plasmids), fluoroquinolone resistance, and difficult-to-treat resistance in Pseudomonas aeruginosa and Acinetobacter baumannii.

Resistance arises by enzymatic hydrolysis of beta-lactams, porin loss, efflux pump upregulation, target modification (gyrA/parC for fluoroquinolones, lipid A for polymyxin), aminoglycoside-modifying enzymes, and 16S rRNA methyltransferases. Plasmid-mediated resistance allows rapid horizontal spread within and between species. Risk factors include prior antibiotic exposure, hospitalization, ICU stay, indwelling devices, immunosuppression, travel to endemic regions, and healthcare exposure.

Treatment requires rapid identification, susceptibility testing (broth microdilution, VITEK, MALDI-TOF), and rational selection of newer agents: ceftolozane-tazobactam and ceftazidime-avibactam for ESBL/KPC and Pseudomonas; meropenem-vaborbactam and imipenem-relebactam for KPC; cefiderocol (siderophore cephalosporin) for metallo-beta-lactamase organisms and difficult-to-treat resistance; eravacycline and plazomicin for selected indications; polymyxins B/E (colistin) as last-resort with toxicity caveats. Combination therapy with two active agents is sometimes used for severe infections, especially with metallo-beta-lactamase. Antimicrobial stewardship, infection prevention (hand hygiene, contact precautions), and surveillance are essential.

Symptoms

Urinary tract infection (cystitis, pyelonephritis) — often outpatient ESBL
Bloodstream infection, sepsis, septic shock
Hospital-acquired and ventilator-associated pneumonia
Intra-abdominal infection, biliary sepsis
Surgical site infection
Catheter-associated bloodstream infection
Skin and soft tissue infection (especially Acinetobacter)
Meningitis (post-neurosurgical)
Burn wound infection
Failure of empirical antibiotic with persistent fever
Recurrent infection with same organism
Septic shock requiring ICU
Multi-organ failure in severe MDR sepsis
Nosocomial outbreaks with resistant organism
Asymptomatic carriage in stool or rectum (colonization)

Risk Factors

Prior antibiotic exposure within 90 days
Recent hospitalization or ICU stay
Long-term care facility residence
Indwelling urinary or vascular catheter
Mechanical ventilation
Immunosuppression, transplant, hematologic malignancy
Chronic kidney or liver disease, dialysis
Recent surgery, especially abdominal
Travel to high-prevalence regions (South Asia, Middle East, Mediterranean, Latin America)
Healthcare exposure abroad
Long hospital stay
Outbreak in healthcare facility
Carbapenem use, broad-spectrum antibiotics
Burn injury
Older age, comorbidities

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • Persistent fever despite empirical antibiotics
  • Hospital-acquired infection or ventilator-associated pneumonia
  • Recurrent UTI failing standard therapy
  • Sepsis in immunocompromised host
  • Travel-related complicated UTI or bacteremia after travel to endemic region
  • Catheter-related bloodstream infection
  • ICU-acquired infection
  • Suspicion of carbapenem-resistant organism (any prior MDR culture, healthcare contact abroad)
  • Outbreak investigation needed
  • Allergy to standard antibiotics with MDR infection

Treatment Methods

01
Rapid identification by MALDI-TOF and antimicrobial susceptibility testing
02
Source control: catheter removal, abscess drainage, foreign body removal, surgical source control
03
Empirical therapy guided by local antibiogram, prior cultures, severity, and risk factors for MDR
04
ESBL infections: carbapenem (ertapenem, meropenem) is reference standard; piperacillin-tazobactam suboptimal in severe; ceftolozane-tazobactam, ceftazidime-avibactam for selected; oral options for cystitis (fosfomycin, nitrofurantoin)
05
AmpC: cefepime or carbapenem; avoid ceftriaxone if AmpC inducible enterobacter
06
KPC carbapenem-resistant Enterobacterales: ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam
07
Metallo-beta-lactamase (NDM, VIM, IMP): cefiderocol, ceftazidime-avibactam + aztreonam combination, polymyxin combinations
08
OXA-48-like: ceftazidime-avibactam first-line; cefiderocol alternative
09
Difficult-to-treat Pseudomonas aeruginosa: ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam, cefiderocol
10
Acinetobacter baumannii MDR: sulbactam-containing regimen, polymyxin combinations, cefiderocol; durlobactam-sulbactam where available
11
Stenotrophomonas maltophilia: trimethoprim-sulfamethoxazole first-line; minocycline, levofloxacin, cefiderocol alternatives
12
Polymyxin (colistin, polymyxin B): reserve for last-line; nephrotoxicity, neurotoxicity
13
Aminoglycoside (amikacin, plazomicin) adjunct in selected
14
Combination therapy for severe metallo-beta-lactamase or critically ill
15
Therapeutic drug monitoring for polymyxin, vancomycin, aminoglycosides, beta-lactams in critically ill
16
Duration: standard for the infection type; longer in deep-seated, immunocompromised, or persistent bacteremia
17
Stewardship: timely de-escalation, oral switch, dose optimization, duration limit
18
Infection prevention: hand hygiene, contact precautions, decontamination of equipment, environmental cleaning, screening on admission in high-prevalence
19
Surveillance: notify infection control, public-health reporting in outbreaks
20
Multidisciplinary management: infectious disease, microbiology, pharmacy, infection control
21
Patient and family education on adherence, transmission prevention, signs of recurrence
22
Consider phage therapy in compassionate use for unresponsive infections (research)
23
Vaccination of contacts (pneumococcal, influenza) per general guidelines

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Health Disclaimer: The information on this page is prepared for general informational purposes only. It does not replace medical diagnosis and treatment. Please consult your physician for your complaints. Saygı Hospital does not accept responsibility for actions taken based on the information on this page.