Citrobacter koseri is a type of bacterium found in various environments and within the human body. This microorganism is a Gram-negative bacterium, meaning it does not retain a specific stain used in laboratory identification. While often present without causing harm, Citrobacter koseri can become an opportunistic pathogen, leading to infections, particularly in individuals with compromised health.
Characteristics and Habitat
Citrobacter koseri, previously known as Citrobacter diversus, is a rod-shaped bacterium that belongs to the Enterobacteriaceae family. This family includes many bacteria commonly found in the digestive tracts of humans and animals. The bacterium is facultative anaerobic, which means it can grow and thrive both in the presence and absence of oxygen.
This microorganism is widely distributed in nature, frequently found in soil, water, and sewage. It also exists as part of the normal flora within the gastrointestinal systems of humans and animals.
Infections It Causes
Citrobacter koseri is particularly known for causing severe central nervous system (CNS) infections in neonates, such as meningitis and brain abscesses. Brain abscesses are a complication of neonatal meningitis caused by this bacterium, associated with high mortality and long-term neurological damage. Neonates infected with C. koseri may present with symptoms like sepsis, seizures, apnea, and a bulging fontanelle.
Beyond neonatal CNS infections, Citrobacter koseri can cause a range of other infections in broader populations, especially in hospital settings or in immunocompromised individuals. Urinary tract infections (UTIs) are among the most common, manifesting with symptoms such as frequent urination, lower abdominal discomfort, painful urination, and cloudy or strong-smelling urine. Other potential infections include bloodstream infections (sepsis), wound infections (at surgical sites or around medical devices), respiratory tract infections (pneumonia), and rarer conditions like osteomyelitis and endocarditis.
Diagnosis and Treatment
Diagnosing Citrobacter koseri infections typically involves laboratory analysis of samples taken from the affected areas of the body. Healthcare professionals collect specimens such as blood, cerebrospinal fluid, urine, or sputum to culture and identify the presence of the bacteria. For suspected brain abscesses, medical imaging like CT scans is often utilized to visualize the extent of the infection.
Once Citrobacter koseri is identified, antibiotic susceptibility testing guides treatment. This testing determines which antibiotics will be most effective against the specific strain of bacteria causing the infection. Treatment generally involves the use of appropriate antibiotics, chosen based on these susceptibility results.
A notable challenge in treating Citrobacter koseri infections is the bacterium’s ability to develop antibiotic resistance. C. koseri can be inherently resistant to certain antibiotics like ampicillin and has shown emerging resistance to beta-lactams and aminoglycosides. This often necessitates the use of broad-spectrum antibiotics, such as carbapenems, or a combination of different drugs. The duration of antibiotic treatment varies depending on the type and severity of the infection, with complicated cases like meningitis or abscesses requiring several weeks of therapy.
Prevention and Risk Factors
Several factors can increase an individual’s susceptibility to Citrobacter koseri infections. Prematurity is a risk factor for neonates, as their immune systems are still developing. Hospitalization, especially in intensive care units and for prolonged periods, elevates the risk of acquiring these infections. The presence of invasive medical devices, such as catheters and ventilators, provides additional entry points for bacteria, further increasing infection risk. Recent antibiotic use can also alter the body’s normal bacterial flora, potentially allowing opportunistic pathogens like C. koseri to proliferate.
Preventing these infections involves general hygiene practices, with consistent handwashing being a highly effective method to reduce transmission. In healthcare settings, careful management of medical devices and adherence to strict infection control protocols are important. Appropriate antibiotic stewardship, which promotes the responsible use of antibiotics, helps minimize the development and spread of resistant strains.