Citrobacter werkmanii-Introduction, Morphology, Pathogenicity, Lab

Introduction

Table of Contents

Citrobacter werkmanii is a gram-negative bacterium belonging to the genus Citrobacter. It is commonly found in the environment, including soil, water, and sewage. This bacterium is part of the normal flora of the human intestinal tract but can act as an opportunistic pathogen. C. werkmanii has been associated with various infections, including urinary tract infections (UTIs) and wound infections.

It can also cause bacteremia, particularly in immunocompromised individuals. Like other Citrobacter species, C. werkmanii exhibits resistance to certain antibiotics, making treatment more challenging. Therefore, identification of this pathogen is crucial for appropriate therapeutic management.

Morphology

Citrobacter werkmanii, a gram-negative bacterium, appears as rod-shaped (bacilli) cells.

Lactose fermenting colony of Citrobacter werkmanii — Fig. Lactose fermenting colony of *Citrobacter werkmanii*

It typically ranges from 0.5 to 0.8 micrometers in diameter and 1.0 to 3.0 micrometers in length. The bacterium is motile, possessing peritrichous flagella, which allows it to move. C. werkmanii often appears as a pale, off-white colony on agar plates. It grows well in aerobic and facultatively anaerobic conditions. Additionally, it ferments glucose, producing acid, a common feature of many Citrobacter species. It does not typically produce gas during fermentation and is usually non-spore-forming.

Citrobacter werkmanii unstained footage — Fig. *Citrobacter werkmanii* unstained footage

The bacterium can be distinguished from other Citrobacter species through biochemical tests and growth patterns.

Pathogenicity

Citrobacter werkmanii is an opportunistic pathogen, that primarily affects immunocompromised individuals. It has been associated with urinary tract infections (UTIs), particularly in patients with catheters or urinary abnormalities. Additionally, C. werkmanii can cause wound infections and bacteremia, especially in hospitalized patients. The bacterium’s ability to produce biofilms enhances its persistence in medical devices, contributing to chronic infections. Furthermore, antibiotic resistance is a concern, as it may resist common beta-lactam antibiotics, complicating treatment. The pathogenicity of C. werkmanii is linked to its ability to evade host defenses and cause infections in vulnerable individuals. Therefore, early identification and appropriate antimicrobial therapy are critical in managing infections caused by this bacterium.

Lab Diagnosis

The laboratory diagnosis of Citrobacter werkmanii involves several steps. First, a clinical specimen (such as urine, blood, or wound swab) is collected from the patient. Gram staining is performed, revealing gram-negative rod-shaped bacteria.

Citrobacter werkmanii on CLED agar — Fig. *Citrobacter werkmanii* on CLED agar

Subsequently, the bacterium is cultured on selective media such as MacConkey agar or nutrient agar, where it forms pale colonies. Biochemical tests are used to identify C. werkmanii, including glucose fermentation and oxidase-negative results.

Citrobacter werkmanii in saline wet mount of culture microscopy — Fig. *Citrobacter werkmanii* in a saline wet mount of culture microscopy

The bacterium also exhibits urease production and indole-negative reactions. API 20E or Vitek 2 systems may also be used for more accurate identification. Finally, antimicrobial susceptibility testing helps assess the appropriate treatment options for C. werkmanii infections.

Treatment

The treatment of Citrobacter werkmanii infections typically involves the use of antibiotics. However, the bacterium is known to exhibit antibiotic resistance, particularly to beta-lactams. Therefore, susceptibility testing is essential to guide therapy. Carbapenems, such as imipenem or meropenem, are often effective against resistant strains. Additionally, fluoroquinolones, aminoglycosides, and trimethoprim-sulfamethoxazole may also be used, depending on susceptibility results. For urinary tract infections (UTIs), cephalosporins or nitrofurantoin may be effective. In severe cases, such as bacteremia or wound infections, combination therapy might be required. Furthermore, treating underlying conditions, such as catheter-associated infections, is important for successful outcomes. Lastly, infection control measures in healthcare settings are crucial to prevent transmission.

Prevention

Prevention of Citrobacter werkmanii infections primarily focuses on infection control measures in healthcare settings. First, strict hand hygiene and the use of personal protective equipment (PPE) can minimize transmission. Additionally, careful handling and sterilization of medical devices, such as catheters, are essential to prevent device-related infections. Moreover, antibiotic stewardship is crucial to reduce the development of antibiotic resistance. Regular screening of high-risk patients, especially those in intensive care units (ICUs), helps identify C. werkmanii colonization early. Lastly, ensuring prompt diagnosis and appropriate treatment of infections can prevent complications and improve patient outcomes.

Keynotes

Citrobacter werkmanii is a gram-negative bacterium often found in the intestinal flora of humans.
It is an opportunistic pathogen, primarily affecting immunocompromised individuals.
C. werkmanii can cause urinary tract infections (UTIs), wound infections, and bacteremia.
The bacterium is motile and produces biofilms, contributing to chronic infections.
Antibiotic resistance is common, complicating treatment, especially with beta-lactams.
Early diagnosis involves gram staining, culture, and biochemical tests.
Susceptibility testing is necessary to determine the appropriate antibiotic therapy.
Preventive measures include proper hand hygiene, infection control, and sterilization of medical devices.
C. werkmanii is most concerning in hospitalized patients or those with underlying health conditions.
Treatment often involves carbapenems, fluoroquinolones, or aminoglycosides, based on susceptibility.

Citrobacter werkmanii-Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, Prevention, and Keynote