Citrobacter braakii

Citrobacter braakii is a species of Gram-negative bacteria belonging to the genus Citrobacter. It is a member of the family Enterobacteriaceae, which includes several other clinically significant genera such as Escherichia, Klebsiella, and Salmonella.

Morphology and Physiology

Citrobacter braakii is a rod-shaped, non-spore-forming bacterium. It is motile due to the presence of peritrichous flagella. Like other members of the Enterobacteriaceae family, it is a facultative anaerobe, capable of growing in both aerobic and anaerobic conditions. C. braakii ferments glucose and other carbohydrates, producing gas as a byproduct.

Biochemical Characteristics

Citrobacter braakii is oxidase-negative and catalase-positive. It can utilize citrate as a sole carbon source, which is a distinguishing feature of the genus Citrobacter. The bacterium is capable of reducing nitrate to nitrite and can hydrolyze urea. It is also capable of producing hydrogen sulfide on triple sugar iron agar.

Habitat and Ecology

Citrobacter braakii is commonly found in the environment, particularly in soil, water, and sewage. It is also part of the normal intestinal flora of humans and animals. However, under certain conditions, it can become an opportunistic pathogen.

Pathogenicity

While Citrobacter braakii is generally considered to be of low virulence, it can cause infections in immunocompromised individuals or those with underlying health conditions. It has been associated with urinary tract infections, bacteremia, and wound infections. In rare cases, it can cause meningitis and brain abscesses, particularly in neonates and infants.

Clinical Significance

In clinical settings, Citrobacter braakii is often isolated from urine, blood, and wound cultures. It is important to accurately identify this organism to differentiate it from other more virulent members of the Enterobacteriaceae family. Treatment of infections caused by C. braakii typically involves the use of antibiotics, although the bacterium can exhibit resistance to multiple drugs.

Antibiotic Resistance

Citrobacter braakii has been reported to exhibit resistance to several classes of antibiotics, including beta-lactams, aminoglycosides, and fluoroquinolones. The presence of extended-spectrum beta-lactamases (ESBLs) in some strains can complicate treatment options. Therefore, susceptibility testing is crucial for guiding appropriate antibiotic therapy.

Laboratory Identification

In the laboratory, Citrobacter braakii can be identified using a combination of biochemical tests and molecular methods. Traditional biochemical tests include the use of MacConkey agar, where C. braakii forms lactose-fermenting colonies. Molecular techniques such as polymerase chain reaction (PCR) and 16S rRNA sequencing can provide definitive identification.

Prevention and Control

Preventing infections caused by Citrobacter braakii involves standard infection control practices, particularly in healthcare settings. This includes proper hand hygiene, sterilization of medical equipment, and isolation of infected patients when necessary.

Research and Future Directions

Ongoing research is focused on understanding the mechanisms of antibiotic resistance in Citrobacter braakii and developing new strategies for treatment. Studies are also exploring the role of this bacterium in the human microbiome and its potential impact on health and disease.

See Also

• Enterobacteriaceae
• Opportunistic infection
• Antibiotic resistance

External Links

• [CDC - Citrobacter Infections](https://www.cdc.gov/)
• [NCBI Taxonomy Browser - Citrobacter braakii](https://www.ncbi.nlm.nih.gov/Taxonomy/)