What is Enterobacter Aerogenes?

Enterobacter species are important nosocomial pathogens responsible for various infections, including bacteremia, lower respiratory tract infections, skin and soft tissue infections, urinary tract infections (UTIs), endocarditis, intra-abdominal infections, septic arthritis, osteomyelitis, and ophthalmic infections.

Risk factors for nosocomial (Hospital Acquired) Enterobacter species infections include hospitalization of greater than 2 weeks, invasive procedures in the past 72 hours, treatment with antibiotics in the past 30 days, and the presence of a central venous catheter. Specific risk factors for infection with nosocomial multidrug-resistant strains of Enterobacter species include the recent use of broad-spectrum cephalosporins or aminoglycosides and ICU care.

These ICU bugs cause significant morbidity and mortality, and infection management is complicated by multiple antibiotic resistance. Enterobacter species possess inducible beta-lactamases, which are undetectable in vitro but are also responsible for resistance during treatment. Physicians treating patients infected with these bacteria are advised to avoid certain antibiotics, particularly third-generation cephalosporins, because resistant mutants can quickly appear.

The crucial first step is appropriate identification of the bacteria. Antibiograms must be interpreted with respect to the different resistance mechanisms and their respective frequency, as is reported for bacteria belonging to this genus, even if the resistance mechanisms have not been detected by routine in vitro antibiotic susceptibility testing.

Enterobacter species rarely cause disease in a healthy individual. This opportunistic pathogen, similar to other members of the Enterobacteriaceae family, possesses an endotoxin known to play a major role in the pathophysiology of sepsis and its complications.

Although community-acquired infections are occasionally observed, nosocomial infections are, by far, the most frequent. Patients most susceptible to acquiring Enterobacter infections are those who stay in the hospital, especially the ICU, for prolonged periods. Other major risk factors include the prior use of antimicrobial agents, concomitant malignancy (especially hemopoietic and solid organ malignancies) hepatobiliary disease, ulcers of the upper gastrointestinal tract, use of foreign devices such as intravenous catheters, and serious underlying conditions such as burns, mechanical ventilation, and immunosuppression.

The source of infection may be endogenous via colonization of the skin, gastrointestinal tract, or urinary tract or exogenous resulting from the ubiquitous nature of these bacteria. Multiple reports have incriminated the hands of personnel, endoscopes, blood products, devices for monitoring intra-arterial pressure, and stethoscopes as sources of infection. Outbreaks have been traced to various common sources: total parenteral nutrition solutions, isotonic saline solutions, albumin, digital thermometers, and dialysis equipment.