ENTEROBACTER AEROGENES: CHARACTERISTICS, SYMPTOMS AND TREATMENT - BIOLOGY - 2025

The Enterobacter aerogenes is a gram - negative bacterium of the genus Enterobacter, facultative anaerobic (can grow or develop in the presence or absence of oxygen), rod-shaped. with rounded ends and non-spore-producing.

Currently, more than 14 species of the genus Enterobacter are known that can be identified according to their biochemical or genomic characteristics. This group of microbes has representatives that inhabit humans as part of the usual microbial biota.

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Species that decompose dead organic matter have also been detected and others have been isolated as intra-hospital (or nosocomial) pathogens, that is, they produce diseases that are acquired in hospitals or health care centers.

Main features

Edge and discovery

Enterobacter aerogenes is part of the human and other animal gastrointestinal microflora. It is also found in soil, bodies of water, and even in dairy products.

It was described by Kruse in 1896, it belongs to the Enterobacteriaceae family and its taxonomic classification has been the subject of discussion since the 70's of the last century until today.

Medical interest

This species is of particular interest in medicine, since it has been isolated in human clinical samples from the respiratory, urinary, blood and gastrointestinal tracts.

It is known that epidemiological outbreaks have been reported in Europe since 1993 and until 2003 it was considered a multi-resistant pathogen, especially in intensive care units.

In Belgium, this species is associated with a high mortality of infected patients.

Transmission

Due to the different habitats where E. aerogenes is found, infections can be acquired in different ways.

Generally, infections arise in:

• The patient's own flora.
• Through the hands of healthcare workers, during the insertion of medical devices (catheters or injectors) in patients.
• In surgical procedures where contaminated equipment is introduced into the patient and organ transplants, in which case the transmitter of the bacteria is the donor.

It should be noted that most nosocomial infections appear to arise endogenously from a previously colonized site in the patient involved. And immunosuppressed people, children and the elderly tend to be more susceptible to these infections.

Pathology and symptoms

The species E. aerogenes is considered an opportunistic pathogen and rarely causes disease in healthy individuals. As an opportunist, it has become important due to nosocomial infections.

Very little is known about the factors that can affect its pathogenicity or virulence (ability to cause disease). However, resistance to disinfectants and antimicrobial agents play a role in the increasing prevalence as nosocomial pathogens.

This bacterium can cause multiple pathologies such as:

• Infections in the urinary and gastrointestinal tract.
• Thrombocytopenia (reduction of platelets in the bloodstream).
• Respiratory system infections: Infections of this type include asymptomatic colonization, tracheobronchitis, pneumonia, lung abscess, and empyema.
• Soft Tissue and Skin Infections: Conditions caused by E. aerogenes in these tissues include cellulitis, fasciitis, myositis, abscesses, and wound infections.
• Urinary Tract Infections: Pyelonephritis (infection of the kidney and renal pelvis), prostatitis, and cystitis can be caused by E. aerogenes and other Enterobacter bacteria.
• Central nervous system infections: very little is known about Enterobacter aerogenes infections in the nervous system, however, since the 1940s meningitis caused by Enterobacter spp.

Symptoms

There is no clinical presentation specific enough to differentiate them from other acute bacterial infections. Even so, these are some of the symptoms that present specific conditions:

Bacteremia: physical examination consistent with systemic inflammatory response syndrome, temperature greater than 38 ° C or less than 36 ° C, fever, hypotension and shock, septic shock, purpura fulminans and hemorrhagic bullae, ecthyma gangrenosum, cyanosis and spots.

Lower Respiratory Tract Infections - These conditions manifest identically to those caused by Streptococcus pneumoniae and other organisms. The physical examination may include the following: high fever or hypothermia, tachycardia, hypoxemia, tachypnea, and cyanosis.

Resistance

Enterobacter infections are usually caused by bacteria common in the human digestive tract. In the United States, infections caused by this genus rank it as the eighth most common pathogen in nosocomial infections.

These organisms are multi-resistant, which indicates that they are not sensitive to the treatments that are considered useful to fight the infections they cause.

E. aerogenes is known to employ at least three resistance mechanisms; inactivating enzymes, alteration of drug targets and alteration of the ability of drugs to enter and / or accumulate in your cells.

Additionally, being a gram-negative bacterium, it is highly antibiotic and a producer of β-lactamases, which implies that it is highly resistant to different antibiotics such as β-lactams, ampicillin, amoxicillin, clavulanic acid, cephalothin and cefoxitin, thanks to the fact that they produce the enzyme β-lactamases.

Prevention

The control options for E. aerogenes are considered to be very complex and limited, as most infections come from an endogenous source and many strains are highly resistant to antibiotics.

With regard to prevention, hand hygiene, decontamination of the environment, constant hospital monitoring of antibiotic resistance, controlled use of antibiotics, and the asepsis of catheters and devices that will be implanted in patients are very necessary.

These tasks reduce the transmission of the organism and therefore of the possible disease. The use of targeted prophylactic antibiotic treatments such as Colistin has also been suggested to prevent E. aerogenes infections.

Treatment

There have been many treatments used for the control and cure of infections caused by Enterobacter aerogenes. The resistance of these gram-negative bacteria has been very well documented by the scientific community, yet antimicrobial therapy is indicated in practically all Enterobacter infections.

With a few exceptions, the main classes of antibiotics used to treat bacterial E. aerogenes infections are: Beta-lactams, Aminoglycosides, Fluoroquinolones, and Trimethoprim-sulfamethoxazole.

References

1. Anne Davin-Regli & Jean-Marie Pagès. Enterobacter aerogenes and Enterobacter cloacae; versatile bacterial pathogens confronting antibiotic treatment. Frontiers in Microbiology. 2015; 6: 392.
2. Bertona E., Radice M., Rodríguez CH, Barberis C., Vay C., Famiglietti A., Gutkind G. Phenotypic and genotypic characterization of the enzymatic resistance to third-generation cephalosporins in Enterobacter spp. Argentine Journal of Microbiology. 2005; 37: 203-208.
3. Giamarellou H. Multidrug resistance in Gram-negative bacteria that produces extended-spectrum beta-lactamases (ESBLs). Clinical Microbiology and Infection. 2005 11 (Suppl 4): 1-16.
4. Kruse, Walther. "Systematik der Streptothricheen und Bakterien". Flü'e, C. (ed.) Die Mikroorganismen. 1896; 3 Aufl. 2: 48–66, 67–96, 185–526.
5. Sanders WE Jr. & Sanders CC Enterobacter spp: pathogens poised to flourish at the turn of the century. Clinical Microbiology Reviews. 1997; 10 (2): 220-241.
6. Susan L. Fraser. Enterobacter Infections. Medscape. Updated: Sep. 05, 2017 Retrieved from emedicine.medscape.com.