Enterobacter Infections

Excerpt

Enterobacter are gram-negative, facultatively anaerobic bacilli within Enterobacteriaceae that inhabit soil and water and comprise part of the normal human gastrointestinal microbiota. Although they are frequently commensal, these organisms can act as opportunistic pathogens in hospitalized or immunocompromised hosts. Clinically important species include the Enterobacter cloacae complex and Klebsiella aerogenes (formerly Enterobacter aerogenes). These organisms are significant causes of healthcare-associated infections, including bloodstream infections, ventilator-associated pneumonia, urinary tract infections, surgical-site infections, and device-associated infections. Less commonly, they can cause meningitis and intra-abdominal infection.

Indwelling devices, recent invasive procedures, prior exposure to broad-spectrum antibiotics, and admission to intensive care or neonatal intensive care units increase risk. Transmission typically occurs through contaminated equipment or the hands of healthcare personnel when infection prevention practices are not followed. Outbreaks in high-acuity units, particularly among premature infants and critically ill adults, are associated with substantial morbidity and mortality.

A major challenge in managing Enterobacter infections is the development of multidrug resistance. Enterobacter species possess inducible chromosomal AmpC β-lactamases and frequently acquire extended-spectrum β-lactamases or carbapenemases, narrowing therapeutic options.[6][7]] Current guidance emphasizes that organisms at moderate risk for clinically significant AmpC β-lactamase production (eg, Enterobacter cloacae complex and K aerogenes) often fail third-generation cephalosporins and piperacillin–tazobactam in invasive disease, and treatment strategies increasingly depend on carbapenems or newer β-lactam/β-lactamase inhibitor combinations when indicated.

As of 2024, carbapenem-resistant Enterobacterales remain designated by global and national health authorities as critical-priority and urgent threats, reflecting high mortality, rapid spread, and limited treatment options. Surveillance indicates an increasing global prevalence of carbapenem-resistant Enterobacterales, with the E cloacae complex prevalent in North America and Europe and frequent carriage of transferable carbapenemases, eg, KPC (Klebsiella pneumoniae carbapenamase), NDM (New Delhi metallo-β-lactamase), and OXA-48 (Oxacillinase-48). Recent reports from the United States and Europe highlight shifts, including the rising detection of NDM and the continued transmission of high-risk clones.