ENTEROBACTER CLOACAE: CHARACTERISTICS, MORPHOLOGY, DISEASES - BIOLOGY - 2025

Enterobacter cloacae is a rod-shaped Gram-negative bacterium belonging to the Enterobacteriaceae family. It is facultative and mobile anerobic thanks to the presence of peritrichous flagella. This bacterium does not have a capsule or spores. It does not ferment lactose and produces gas as a result of the fermentation of glucose.

It is a ubiquitous bacterium in nature and can be found anywhere, including pure water and waste, the soil, as well as in the intestinal flora of various species of animals (including humans). It is part of a complex of species, which bears her name and to which, to date, six species have been assigned.

Growth of rough and smooth colonies of Enterobacter cloacae, grown on tryptic soy broth agar. Taken and edited from: See page for author.

Additionally, it belongs to a species complex that contains five other species, including Enterobacter hormaechei, which in turn has three subspecies.

Complex species

Enterobacter asburiae

Taxon erected in 1986 in homage to the North American bacteriologist Mary Alyce Fife-Asbury, who described new serotypes of Klebsiella and Salmonella, as well as new genera and new species of bacteria. Researchers have isolated this species from soil and human hosts.

Enterobacter

This species is a common part of the intestinal microflora of humans and many animal species, it is also an opportunistic pathogen responsible for various nosocomial diseases.

Enterobacter

Taxon erected in homage to Estenio Hormaeche, a Uruguayan microbiologist who, together with PR Edwards, described the genus Enterobacter. This species has three different subspecies that can only be differentiated between them based on their particular properties, together with biochemical tests. It is an important nosocomial pathogen.

Enterobacter

Species baptized in homage to the city of Kobe in Japan, where it was isolated for the first time. It differs from the rest of the species in the complex by giving a negative result in the Voges – Proskauer test.

Enterobacter ludwigii

Species that receives its name from Wolfgang Ludwig, famous bacteriologist responsible for the so-called ARB project, which allows to process genetic information of different organisms and to elaborate phylogenetic trees from it. This species differs from E. cloacae in that it tests negative for sucrose and raffinose.

Enterobacter nimipressuralis

Species very similar to E. cloacae, but which, unlike this one, gives negative tests for sucrose and raffinose.

Enterobacter cloacae on MacConkey agar. Taken and edited from: A doubt.

Lifecycle

Enterobacter cloacae is an opportunistic parasite, that is, it does not require a host to complete its life cycle. Outside the host it can live on the ground or in water.

In any of these environments, it reproduces by binary fission, which is a type of asexual reproduction that consists of the duplication of genetic material, the elongation of the cell and the formation of a septum that separates two daughter cells from the cell. parent.

Diseases

Enterobacter cloacae is part of the normal intestinal flora of the human being, where it lives without causing apparent damage. However, it is an opportunistic pathogen that can cause numerous diseases mainly in people with depressed immune systems.

This species has become in recent years one of the main causes of diseases acquired in health centers (nosocomial diseases), due to its resistance, natural or acquired, to numerous antibiotics that are useful to act against other bacteria.

Another factor that has favored E. cloacae to become an emerging pathogen is its ability to form biofilms that allows it to colonize different devices for intrahospital use, such as catheters, stethoscopes, digital thermometers, blood products, among others.

Diseases caused by E. cloacae are not specific to this bacterium, but can be produced by different pathogens, for which it is necessary to carry out different laboratory tests to confirm their responsibility in each case.

Among these diseases are the presence of the bacteria in the blood (bacteremia), infections of the eyes, lower respiratory tract, skin, soft tissues as well as intra-abdominal infections. It is also responsible for endocarditis, septic arthritis, and inflammation of the bones (osteomyelitis).

These diseases have high levels of morbidity and mortality and are also complicated due to the resistance of the bacteria to multiple antibiotics.

Researchers have also determined that there is a relationship between obesity and the presence of Enterobacter cloacae, at least in laboratory tests with mice.

Symptoms

As we have already pointed out, Enterobacter cloacae is responsible for different diseases, which can have different levels of danger and which will present different symptoms.

Bladder and urinary tract infections can cause severe pain or a burning sensation during urination, reduced urinary flow, pressure and an urge to urinate very frequently, as well as a feeling of not having completely urinated.

Lower respiratory tract infections manifest as yellow phlegm, feeling short of breath, fever, and severe cough. The bacteria can cause pneumonia, which has less severe symptoms than other types of pneumonia, but higher death rates.

Infections of the skin and soft tissues are, after diseases of the soft respiratory tract, the most common forms of bacterial infections in humans. Depending on the severity of the case, symptoms can include inflammation, fever, hypothermia, hypotension, hyperglycemia, and even mental confusion.

Endocarditis causes heart murmurs, severe cough, fever, tired feeling, hematuria, and circulatory failure. For its part, Enterobacter cloacae arthritis causes intense pain in the affected area, sweating, cold, among others.

Treatments

The treatment of infections caused by Enterobacter cloacae is complicated by the resistance of the bacteria to multiple antibiotics. The main cause of resistance of E. cloacae to antibiotics is due to the presence of β-lactamases of the AmpC type. You can also acquire resistance genes from plasmids.

Β-lactamases confer natural resistance to E. cloacae to aminopenicillins, first generation cephalosporins, and cefoxitin, in addition to variable susceptibility to third and fourth generation cephalosporins.

Carbapenems generally constituted the first therapeutic option in infections caused by this bacterium, because the presence of carbapenems was rare. However, in recent decades they have become more frequent, increasing its resistance to these drugs and making its treatment more difficult.

An alternative treatment when resistance to carbapenems appears is the use of amikacin, which is effective in most cases. However, recently researchers have found resistant strains also to this drug in a hospital in Bogotá, Colombia.

In addition to amikacin (to which 95% of the strains showed resistance), they also showed resistance to a greater or lesser degree to cefotaxime, ceftazidime, ceftriaxone, aztreonam, ciprofloxacin, gentamicin, chloramphenicol, trimethoprim / sulfamethoxazole and cefepime. Review that all were sensitive to imipenem.

References

1. ML Mezzatesta, F. Gona & S. Stefani (2012). Enterobacter cloacae complex: clinical impact and emerging antibiotic resistance. Future Microbiology.
2. F. Silva, TMP Martínez (2018). Enterobacter cloacae complex. Chilean journal of infectology.
3. Enterobacter cloacae. On Wikipedia. Recovered from: en.wikipedia.org.
4. Techne. Enterobacter cloacae. Quantification of Enterobacter cloacae genomes. 1 Advanced kit handbook.
5. Enterobacter cloacae bacteria. Recovered from: scribb.com.
6. Biochemical Test and Identification of Enterobacter cloacae. Recovered from: microbiologyinfo.com.
7. S, Octavia & R. Lan (2014). The Family Enterobacteriaceae. In E. Rosenberg et al. (eds.), The Prokaryotes - Gammaproteobacteria, Springer-Verlag Berlin Heidelberg.