Infectious Disease and Microbiology – Ochrobactrum anthropi

Overview

Ochrobactrum anthropi is an aerobic, Gram-negative bacillus that is widely distributed in the environment and is an uncommon opportunistic human pathogen. It is particularly associated with healthcare-associated bloodstream infections involving indwelling intravascular devices, especially central venous catheters.

Although bacteremia is the most characteristic infection, O. anthropi has also been reported to cause peritonitis, septic arthritis, and other invasive infections, particularly in patients with underlying illness or implanted medical devices.

Classification

Genus: Ochrobactrum

Species: Ochrobactrum anthropi

Organism type: Gram-negative bacillus

Clinical role: Opportunistic environmental pathogen

Microbiologic Characteristics

O. anthropi is:

• Gram-negative

• Bacillary in morphology

• Aerobic

• Environmental

• Opportunistic

It is a nonfermenting Gram-negative organism and can survive in environmental and healthcare-associated settings.

High-Yield Microbiology Pattern

Aerobic Gram-negative bacillus

• ●

Environmental organism

• ●

Opportunistic infection

• ●

Indwelling vascular catheter

→ Consider Ochrobactrum anthropi

Incubation Period

The incubation period for O. anthropi infection is:

Unknown

The timing of infection depends largely on the type of exposure, presence of an invasive device, and host factors.

Epidemiology

O. anthropi is a:

Rare cause of human infection

The organism has been recovered from numerous:

• Environmental sources

• Healthcare environments

• Human clinical specimens

Its environmental distribution provides opportunities for contamination of medical equipment or devices.

Risk Factors

Clinically significant infection is most strongly associated with:

• Central venous catheters

• Other indwelling medical devices

• Prolonged hospitalization

• Immunocompromised states

• Serious underlying disease

• Repeated invasive procedures

Central Venous Catheter-Related Bacteremia

The major infection associated with O. anthropi is:

Central venous catheter-related bloodstream infection

The organism can adhere to artificial surfaces and persist in association with intravascular devices.

Clinical Manifestations

Catheter-associated bacteremia may present with:

• Fever

• Chills

• Malaise

• Positive blood cultures

• Sepsis in more severe cases

Persistent or recurrent bacteremia should raise concern for an infected catheter or another colonized device.

High-Yield Clinical Pattern

Hospitalized or medically complex patient

• ●

Central venous catheter

• ●

Unexplained bacteremia

• ●

Environmental Gram-negative bacillus isolated from blood

→ Consider Ochrobactrum anthropi

Device-Associated Infection

A major principle in O. anthropi infection is its association with:

Foreign material

Therefore, treatment may require not only appropriate antimicrobial therapy but also:

Removal or replacement of the infected device

when clinically indicated.

Peritonitis

The source reports:

Peritonitis

as another manifestation of O. anthropi infection.

Device-associated peritonitis may occur particularly in patients undergoing:

Peritoneal dialysis

although this remains an uncommon infection.

Septic Arthritis

O. anthropi has also been reported as a rare cause of:

Septic arthritis

Patients may present with:

• Joint pain

• Swelling

• Restricted movement

• Fever

• Inflammatory synovial fluid

Diagnosis depends on recovery of the organism from appropriate clinical specimens.

Other Invasive Infections

Although uncommon, O. anthropi can occasionally produce other opportunistic infections.

The significance of an isolate should therefore be interpreted according to:

• Site of isolation

• Repeated positive cultures

• Presence of compatible symptoms

• Presence of invasive devices

• Host immune status

Diagnosis

The primary diagnostic method is:

Culture

Depending on the clinical syndrome, specimens may include:

• Blood

• Catheter-associated specimens

• Peritoneal fluid

• Synovial fluid

• Other normally sterile-site specimens

Blood Cultures

For suspected catheter-related infection:

Blood cultures

are particularly important.

Recovery of O. anthropi from multiple blood cultures in a patient with an intravascular catheter supports the diagnosis of clinically significant bacteremia rather than incidental contamination.

Identification

Laboratory identification is important because uncommon nonfermenting Gram-negative bacilli may sometimes be difficult to differentiate using traditional biochemical methods.

Modern laboratory methods can improve species-level identification.

Treatment

The source lists:

Trimethoprim–sulfamethoxazole (TMP-SMX)

as the primary treatment option.

Additional Treatment Options

The source also lists:

• Imipenem

• Aminoglycosides

• Fluoroquinolones

However, antimicrobial susceptibility can vary, so therapy should ideally be:

Guided by susceptibility testing

Antimicrobial Resistance

An important characteristic of O. anthropi is that it may demonstrate resistance to multiple antimicrobial agents.

In particular, resistance to several:

β-lactam antibiotics

can occur.

Therefore, treatment should not be selected solely on the basis of the organism being a Gram-negative bacillus.

Treatment Principle

Culture-confirmed O. anthropi infection

↓

Perform antimicrobial susceptibility testing

↓

Select an active antimicrobial

• ●

Evaluate for an infected:

Catheter or other foreign body

↓

Remove or replace infected device when indicated

Source Control

For catheter-associated bacteremia, an important management principle is:

Source control

Persistent bacteremia may be difficult to eradicate if the colonized catheter remains in place.

Therefore:

Antimicrobial therapy

• ●

Appropriate catheter management

may be necessary for successful treatment.

Prevention

Because O. anthropi infections are frequently healthcare- and device-associated, prevention focuses on:

• Strict aseptic technique during catheter insertion

• Proper catheter maintenance

• Hand hygiene

• Appropriate disinfection procedures

• Avoiding unnecessary prolonged catheterization

• Prompt removal of intravascular devices when no longer required

Ochrobactrum anthropi vs. Other Nonfermenting Gram-Negative Bacilli

Ochrobactrum anthropi

→ Environmental organism

→ Rare opportunistic pathogen

→ Central venous catheter bacteremia is characteristic

→ May show multidrug resistance

→ Susceptibility-guided treatment is important

Pseudomonas aeruginosa

→ Much more common opportunistic pathogen

→ Pneumonia, bacteremia, burns, wounds, UTIs, device infections

→ Characteristic pigment and other microbiologic features

Stenotrophomonas maltophilia

→ Healthcare-associated opportunist

→ Often associated with devices and immunocompromised patients

→ Notable intrinsic antimicrobial resistance

→ TMP-SMX is a classic therapeutic association

High-Yield Clinical Pattern

Rare environmental Gram-negative bacillus

• ●

Hospitalized or immunocompromised patient

• ●

Central venous catheter

• ●

Catheter-related bacteremia

→ Think Ochrobactrum anthropi

Exam Essentials

Organism: Ochrobactrum anthropi

Type: Aerobic Gram-negative bacillus

Clinical behavior: Opportunistic environmental pathogen

Incubation period: Unknown

Frequency: Rare human pathogen

Reservoir: Various environmental sources

Major infection: Central venous catheter-related bacteremia

Other infections: Peritonitis and septic arthritis

Major risk factor: Indwelling medical device

Diagnosis: Culture

Source treatment: Trimethoprim–sulfamethoxazole

Additional source options: Imipenem, aminoglycosides, fluoroquinolones

Resistance: Variable; resistance to multiple β-lactams may occur

Treatment principle: Susceptibility-guided antimicrobial therapy

Device-associated disease: Consider catheter/device removal when indicated

Prevention: Aseptic catheter care and minimizing unnecessary indwelling devices

Key clinical pearl: Ochrobactrum anthropi is a rare environmental Gram-negative bacillus with a strong association with central venous catheter-related bacteremia. When it is repeatedly isolated from blood in a patient with an indwelling catheter, consider it a true opportunistic pathogen, obtain susceptibility testing, and address the infected device as part of source control.