What is the significance of a Gram stain positive for Enterobacter cloacae (Gram-negative rod) in a wound culture?

From the Guidelines

Enterobacter cloacae wound infections should be treated with carbapenems, such as meropenem 1g IV every 8 hours or imipenem 500mg IV every 6 hours, or a combination of piperacillin-tazobactam 4.5g IV every 6 hours, for 7-14 days, depending on infection severity and clinical response, as recommended by the most recent guidelines 1. When identified in a wound culture, Enterobacter cloacae indicates a potential infection that requires appropriate antibiotic therapy.

• The recommended treatment for E. cloacae wound infections typically includes carbapenems or a combination of piperacillin-tazobactam.
• Treatment duration is generally 7-14 days depending on infection severity and clinical response.
• E. cloacae often demonstrates resistance to multiple antibiotics, including many cephalosporins, due to its inducible AmpC beta-lactamase production.
• Therefore, susceptibility testing is crucial to guide definitive therapy, as suggested by the Infectious Diseases Society of America guidelines 1. In addition to antibiotic treatment, proper wound care including:
• Regular cleaning
• Debridement of necrotic tissue if present
• Appropriate dressing changes are essential components of management. Monitoring the wound for signs of healing or worsening infection is important, and treatment should be adjusted based on clinical response and culture results, as recommended by the IWGDF guidance on the diagnosis and management of foot infections in persons with diabetes 1. It is also important to consider the patient's medical history, including any recent antibiotic use, and the local prevalence of antibiotic-resistant organisms, such as MRSA and ESBL-producing gram-negative bacilli, when selecting an antibiotic regimen, as suggested by the 2014 practice guidelines for the diagnosis and management of skin and soft tissue infections 1.

From the FDA Drug Label

Gram-negative bacteria Citrobacter freundii Enterobacter cloacae Escherichia coli Haemophilus influenzae Klebsiella oxytoca Klebsiella pneumoniae Legionella pneumophila

The tigecycline drug label indicates that Enterobacter cloacae is susceptible to tigecycline. Key points:

• Tigecycline has been shown to be active against Enterobacter cloacae.
• The drug label does not provide information on the minimum inhibitory concentration (MIC) for Enterobacter cloacae.
• Tigecycline is considered bacteriostatic against most bacteria, but has demonstrated bactericidal activity against some isolates. 2

From the Research

GRAMS STAIN and MICRO ORGANISM: Enterobacter cloacae in wound culture

• Enterobacter cloacae is a Gram-negative rod with multidrug-resistant potential due to chromosomally-induced AmpC β-lactamase 3
• The recovery of Enterobacter cloacae from a leg wound has been reported, and it can be simultaneously colonized with other pathogens such as Trichosporon asahii 4

Treatment and Outcomes

• Cefepime is one of the therapeutic alternatives for cefepime-susceptible E. cloacae bacteremia, but it is inefficient for cases of cefepime-SDD E. cloacae bacteremia compared with carbapenem therapy 5
• Piperacillin/tazobactam has been shown to be comparable to cefepime or ertapenem for the treatment of Enterobacter pneumonia, but a prospective trial with a larger population is needed to determine if definitive treatment with piperacillin/tazobactam is non-inferior to definitive treatment with cefepime or ertapenem 6
• The inoculum effect, which is an increase in MIC with a higher inoculum, is most consistently detected with cefepime, and this may have implications for the treatment of infections caused by ESBL-producing strains 7

Clinical Characteristics and Outcomes

• Patients with E. cloacae infections had greater shock indices, required more initial blood products, and had longer duration of antibiotic therapy and hospitalizations compared to patients with non-E. cloacae infections 3
• The presence of critical illness, rapidly fatal underlying disease, ESBL producers, and cefepime-SDD isolates was independently associated with 30-day mortality in patients with monomicrobial Enterobacter cloacae bacteremia 5