Enterobacter cloacae complex: Introduction, Morphology, Pathogen

Introduction

Table of Contents

The Enterobacter cloacae complex (ECC) is a group of closely related bacterial species, including Enterobacter cloacae, Enterobacter hormaechei, and others, that can cause a variety of infections, particularly in healthcare settings. ECC is a significant cause of nosocomial (hospital-acquired) infections, including bloodstream infections, pneumonia, and urinary tract infections.

Morphology of Enterobacter cloacae complex

Here’s a more detailed breakdown:

Fig. Enterobacter cloacae complex (ECC) colony morphology on CLED agar

Gram Stain: Gram-negative.
Shape: Rod-shaped, also described as bacilli.
Flagella: Peritrichous, meaning they have multiple flagella distributed all over the cell.
Motility: Generally motile due to the flagella.
Aerobic/Anaerobic: Facultatively anaerobic, meaning it can grow with or without oxygen.
Size: Typically, 0.3-0.6 µm x 0.8-2.0 µm.
Colonies: Non-pigmented or yellow-pigmented.
Other characteristics: It may have encapsulate and it can ferment mannitol, produce gas from some sugars, but not starch.

Pathogenicity

Lab Diagnosis of Enterobacter cloacae complex

Culturing:

Blood cultures: Two sets of blood cultures (aerobic and anaerobic) are recommended to isolate ECC.
MacConkey agar: Used to determine lactose fermentation, a characteristic of some Enterobacter species.

Gram Staining:

Direct Gram staining helps in the rapid identification of Gram-negative bacilli.

Phenotypic Methods:

IMViC tests: These tests assess indole production, methyl red reaction, Voges-Proskauer test, and citrate utilization.
VITEK 2 Compact System: A commercially available system that uses automated methods for bacterial identification and antimicrobial susceptibility testing.

Molecular Methods:

MALDI-TOF MS: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry is a rapid and accurate method for species identification.
PCR: Polymerase chain reaction (PCR) assays, including multiplex PCR, can be useful for differential identification of ECC species.

Treatment

Carbapenems: The carbapenems, such as imipenem and meropenem, are generally effective against ECC due to their resistance to ESBLs.
Aminoglycosides: Aminoglycosides like amikacin and gentamicin can be used, especially when carbapenems are not suitable.
Fluoroquinolones: Fluoroquinolones, such as levofloxacin, are also used in some cases.
Temocillin: Temocillin, a carboxypenicillin, is stable against β-lactamases and can be used for multidrug-resistant ECC infections.
Other Options: Piperacillin/tazobactam can also be considered.
Supportive Care: In addition to antibiotics, supportive care, such as wound debridement and daily dressing changes, may be necessary for severe infections.

Prevention

Here’s a more detailed preventive strategy:

1. Hand Hygiene:

Frequent and proper hand washing:
Gloves and gowns:

2. Contact Precautions:

Isolation:
Environmental cleaning and disinfection:

3. Minimizing Risk Factors:

Avoidance of unnecessary medical devices: Invasive medical devices, such as catheters, can increase the risk of ECC colonization or infection.
Appropriate antibiotic use: Overuse or inappropriate use of antibiotics can contribute to the development of antibiotic-resistant ECC strains. Healthcare providers should adhere to guidelines for antibiotic prescribing.

4. Surveillance and Monitoring:

Surveillance for ECC
Monitoring of antimicrobial resistance:

5. Other Considerations:

Public health measures:
Water quality monitoring:
One Health approach: A “One Health” approach, which considers the interconnectedness of human, animal, and environmental health, is important in addressing the spread of ECC, especially regarding food safety.

Keynotes

Opportunistic Pathogen: ECCs are opportunistic pathogens, meaning they primarily cause infections in individuals with weakened immune systems or those who have undergone medical procedures.
Common Hospital Pathogen: ECCs are frequently isolated in hospital settings and are associated with a range of hospital-acquired infections, including pneumonia, urinary tract infections, and sepsis.
Antibiotic Resistance: ECCs are known for their ability to develop resistance to a wide array of antibiotics. They can generate carbapenemases, enzymes that break down carbapenem antibiotics, rendering them ineffective.
Resistance Mechanisms: ECC utilizes various mechanisms to achieve antibiotic resistance. These include: Carbapenemase production, AmpC or ESBL production, and decreased expression of outer membrane proteins
Clinical Significance: ECC infections can be serious and pose challenges for treatment due to the increasing prevalence of antibiotic resistance.
Impact on Healthcare: The emergence of antibiotic-resistant ECC strains highlights the need for careful antibiotic stewardship and infection control measures in healthcare settings.

Enterobacter cloacae complex: Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, Prevention, and Keynotes