Introduction
Citrobacter species is an opportunistic nosocomial infection (acquired during a hospital stay). Citrobacter species are the third most common organism causing urinary tract infections in hospitalized patients. It consists of eleven different species, and the most common ones affecting humans are C. koseri, C. feundii, C. amalonaticus, C. youngae, and C. braakii. The majority of infection is due to C. koseri and C. freundii. Because of mutational changes, they have high resistance to many antibiotics. These organisms first settle in the oral cavity, respiratory tract, or gastrointestinal tract and later spread to various sites and cause central nervous system (CNS) infection and bacteremia (blood-containing live bacteria). Outbreaks of this diseases are mostly due to gastrointestinal and healthcare workers hand carriage.
What Is Citrobacter Infection?
Citrobacter species are from the family of Enterobacteriaceae, which are facultatively anaerobic (organisms that can survive with or without oxygen), gram-negative bacilli, and motile by utilizing peritrichous flagella. They are commonly found in water, food, soil, and the gastrointestinal tract of animals and humans. When these organisms increase in number in the body, they cause Citrobacter infections, including urinary tract infections, bacteremia, Intra-abdominal sepsis, joint infection, wound infection, bloodstream infections, brain abscesses, pneumonia, and other neonatal infections such as meningitis, and neonatal sepsis.
How Does Citrobacter Infection Spread?
It spreads through direct contact with hospital members, mother-to-child, or environmental sources. Most of the patients who acquired Citrobacter infection were elderly hospitalized males who were subjected to urethral catheterization (a procedure to drain the urine), genitourinary instrumentation, or had obstructive uropathy (a condition where urine cannot drain from the urinary tract) due to loss of bactericidal activity of prostatic secretions, and prostate enlargement.
What Are the Clinical Manifestations of Citrobacter Infection?
The clinical manifestations of citrobacter infection are:
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In neonates, it can cause brain sepsis and meningitis (inflammation of coverings of the brain); it can be severe and associated with necrotizing encephalitis. Fever, lethargy, poor feeding, vomiting, irritability, bulging fontanelle, seizures, and jaundice are common presenting features.
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Intra-abdominal infection through the urinary tract, hepatobiliary tract, or gastrointestinal tract.
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Bacteremia (presence of viable bacteria in the bloodstream).
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Urinary tract infection (infection of any part of the urinary system, which is kidneys, bladder, ureters, and urethra), which can cause a frequent need to urinate, dysuria (painful urination), pyuria (pus in urine), hematuria (blood in urine) and flank (side) pain in patients with urinary tract infection.
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Surgical site infection.
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Wound infection with purulent healing.
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Respiratory infections like lung abscess bronchitis, and pneumonia (infection of the lungs that causes inflammation of lung tissues and have symptoms such as fever, cough, and sputum).
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Asymptomatic bacteriuria (presence of bacteria in urine but no signs of infection) in pregnant women, neonates, and elderly diabetic patients.
What Are the Methods to Diagnose Citrobacter Infection?
The methods include the following:
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Blood Cultures Evaluation: The white blood cell count may show leukocytosis or leukopenia.
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CSF Fluid Evaluation: It usually shows elevated protein levels, polymorphonuclear cell elevation, and depressed glucose levels; gram-negative rods may be seen on the smear. It is done in most types of neonatal bacterial meningitis.
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Urine culture in case of urinary tract infection.
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Cytology, which involves examining cells infected by Citrobacter.
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Gram staining to check the type of bacteria.
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A computed tomography (CT) scan in case of brain abscess.
How Is Citrobacter Infection Treated?
After obtaining specific strains from patients, therapeutic agents should be given based on in-vitro susceptibility results. Different species of Citrobacter have different antimicrobial susceptibility. For example, C. freundii is more resistant to antimicrobials than C. koseri, including Ampicillin and Carbenicillin, and newer agents, such as Piperacillin, Monobactam, and third-generation Cephalosporins.
Therapeutic agents for C. freundii infections include:
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Carbapenems such as Ertapenem, Imipenem, and Meropenem.
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Fluoroquinolones such as Levofloxacin, Ciprofloxacin.
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Aminoglycosides such as Gentamicin, Netilmicin, and Amikacin.
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Fourth-generation Cephems, such as Cefepime and Cefpirome.
Therapeutic agents for C. koseri infections, along with the agents mentioned above, include:
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Third-generation Cephalosporins and Monobactams like Aztreonam, Piperacillin, and Piperacillin plus Tazobactam are considered first-line drugs for treating C. koseri infections.
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New oral cephems (Ceftibuten, Cefpodoxime proxetil, Cefixime cefprozil, and Cefetamet pivoxil).
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In the case of C. koseri meningitis or brain abscess, surgical aspiration and drainage of the abscess should be done, and Trimethoprim and Sulfamethoxazole is used for the treatment. After the treatment, cerebrospinal fluid is monitored until it is sterile using the lumbar puncture technique. In addition, a computed tomography (CT) scan should be performed to monitor any brain abscesses during therapy.
Treatment should be continued until the symptoms resolve, such as negative blood and urine culture, resolving of cough, fever, and sputum in case of pneumonia, no purulent discharge in the wound, and positive wound healing.
How Is Citrobacter Infection Treated for Specific Diseases?
Treatment for specific diseases includes:
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Citrobacter Bacteremia: Citobacter bacteremia is commonly seen in elderly patients associated with comorbidities like intra-abdominal diseases and malignancies, and the leading primary focus is hepatobiliary tract (gallbladder, liver, and bile ducts). A beta-lactam agent and an aminoglycoside are used. The antimicrobial agents should be given until signs and symptoms of infection disappear, such as a negative blood culture and the resolution of fever.
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Citrobacter Meningitis: Third-generation cephalosporin, along with an aminoglycoside, is the treatment of choice. The dosage should be high enough, for example, Cefotaxime 300 milligrams per 2.2 pounds per day, to enter the central nervous system. Antibiotic therapy for a minimum of 21 days should be given to avoid recurrence, and therapy for more than six weeks should be given in case a brain abscess develops after the sterilization of cerebrospinal fluid.
Conclusion
Citrobacter infection is a rare and third most common organism causing urinary tract infection and is highly resistant to many antibiotics. These organisms spread through the hands of hospital staff members, environmental sources, or carriers of family members. Infection control measures should be taken to prevent Citrobacter infection, such as washing hands after every procedure, maintaining good hygiene, and maintaining a sterile environment. Treatment should be given until the symptoms resolve, and constant monitoring should be done.
