Infectious Disease and Microbiology – Pantoea agglomerans

Overview

Pantoea agglomerans is an aerobic Gram-negative bacillus that is widely distributed in the environment and is a rare cause of human infection. It was formerly known as Enterobacter agglomerans.

Human disease is most often opportunistic and may be healthcare-associated, particularly in patients with invasive devices. Reported infections include bacteremia, urinary tract infection, pneumonia, neonatal meningitis, and liver abscess.

Classification

Genus: Pantoea

Species: Pantoea agglomerans

Former name: Enterobacter agglomerans

Organism type: Gram-negative bacillus

Microbiologic Characteristics

P. agglomerans is:

• Gram-negative

• Bacillary in morphology

• Aerobic

• An environmental organism

• An uncommon opportunistic human pathogen

It belongs to the order Enterobacterales and is closely associated with environmental sources, particularly plants and plant material.

High-Yield Microbiology Pattern

Gram-negative bacillus

• ●

Formerly Enterobacter agglomerans

• ●

Environmental/plant-associated organism

• ●

Opportunistic infection

→ Think Pantoea agglomerans

Incubation Period

The incubation period is:

Unknown

The timing of disease varies according to the route of exposure and type of infection.

Epidemiology

Human infection with P. agglomerans is:

Rare

and has been reported:

Worldwide

Although environmental exposure can be relevant, the source particularly emphasizes its role as a cause of:

Nosocomial infection

Environmental Reservoir

P. agglomerans is widely associated with:

• Plants

• Soil

• Plant material

• Other environmental sources

This environmental association is important because infection may occasionally follow penetrating trauma involving plant material, such as a thorn or wooden splinter.

Healthcare-Associated Infection

An important clinical setting for P. agglomerans infection is:

Healthcare-associated disease

The organism has been associated with:

• Intravascular devices

• Central venous catheters

• Hospitalized patients

• Contaminated medical materials or fluids in reported outbreaks

Bacteremia

One of the most important invasive manifestations is:

Bacteremia

Bloodstream infection may be:

Central venous catheter-related

or

Unrelated to a central venous catheter

Catheter-Associated Bacteremia

Patients with indwelling vascular devices may develop:

• Fever

• Chills

• Malaise

• Positive blood cultures

• Sepsis in severe infection

When a central venous catheter is implicated, appropriate:

Source control

should be considered in addition to antimicrobial treatment.

High-Yield Clinical Pattern

Hospitalized patient

• ●

Central venous catheter

• ●

Gram-negative bacteremia

• ●

Pantoea agglomerans isolated on culture

→ Consider catheter-associated bloodstream infection

Urinary Tract Infection

P. agglomerans can rarely cause:

Urinary tract infection

Clinical manifestations may include:

• Dysuria

• Frequency

• Urgency

• Suprapubic discomfort

• Fever in more complicated disease

Diagnosis depends on compatible symptoms together with an appropriate urine culture.

Pneumonia

The organism has also been associated with:

Pneumonia

This remains an uncommon manifestation.

Patients may present with:

• Fever

• Cough

• Dyspnea

• Pulmonary infiltrates

Clinical correlation is important because environmental Gram-negative organisms recovered from respiratory specimens do not always indicate invasive disease.

Neonatal Meningitis

An important but rare manifestation is:

Neonatal meningitis

Although P. agglomerans is not among the most common causes of neonatal meningitis, it should be recognized as a possible opportunistic Gram-negative pathogen.

Liver Abscess

The source also reports:

Liver abscess

as a possible invasive manifestation.

Diagnosis may involve:

• Blood cultures

• Imaging

• Culture of aspirated abscess material when obtained

Management of an abscess may require both antimicrobial therapy and appropriate drainage/source control.

Plant-Associated Traumatic Infection

An additional clinically useful association is infection following:

Penetrating trauma with plant material

For example:

Thorn injury

↓

Environmental inoculation of P. agglomerans

↓

Localized inflammation

↓

Possible septic arthritis or other deep infection

This plant-associated exposure is a useful clue when P. agglomerans is recovered from a normally sterile site after penetrating trauma.

Diagnosis

The primary diagnostic method is:

Culture

Depending on the clinical syndrome, specimens may include:

• Blood

• Urine

• Cerebrospinal fluid

• Respiratory specimens

• Abscess material

• Other normally sterile fluids or tissues

Interpretation of Culture

Because P. agglomerans is an environmental organism, the significance of an isolate should be interpreted according to:

• Clinical symptoms

• Site of isolation

• Repeated positive cultures

• Presence of an invasive device

• Evidence of systemic infection

• Relevant environmental or healthcare exposure

Recovery from a normally sterile site in a symptomatic patient provides stronger evidence of true infection.

Treatment

The source lists a:

Third-generation cephalosporin

as the principal treatment option.

Because susceptibility may vary, definitive therapy should ideally be based on:

Antimicrobial susceptibility testing

Additional Treatment Options

The source lists:

• Ciprofloxacin

• Carbapenems, such as imipenem or meropenem

• Aminoglycosides

• Aztreonam

Selection should depend on susceptibility results, infection severity, site of infection, and patient-specific factors.

Source Control

When infection involves a:

Central venous catheter

or a:

Drainable abscess

successful management may require:

Active antimicrobial therapy

• ●

Appropriate source control

For example, catheter removal or abscess drainage may be considered when clinically indicated.

Pantoea agglomerans vs. Enterobacter

A useful historical distinction is:

Pantoea agglomerans

→ Formerly Enterobacter agglomerans

→ Environmental and plant-associated

→ Rare opportunistic pathogen

→ Healthcare-associated bacteremia possible

→ Infection may follow thorn/plant trauma

Enterobacter species

→ Enterobacterales

→ Important healthcare-associated pathogens

→ UTIs, pneumonia, bacteremia, and other invasive infections

→ Antimicrobial resistance is an important clinical consideration

Important Exposure Clue

A particularly memorable association is:

THORN / PLANT INJURY

• ●

Localized deep infection or septic arthritis

→ Consider Pantoea agglomerans

This reflects the organism’s strong environmental and plant association.

High-Yield Clinical Pattern

Rare environmental Gram-negative bacillus

• ●

Formerly Enterobacter agglomerans

• ●

Nosocomial infection or central venous catheter

• ●

Bacteremia

→ Think Pantoea agglomerans

Alternative High-Yield Pattern

Penetrating thorn injury

• ●

Subsequent joint or soft-tissue infection

• ●

Gram-negative bacillus

→ Think Pantoea agglomerans

Exam Essentials

Organism: Pantoea agglomerans

Former name: Enterobacter agglomerans

Type: Gram-negative bacillus

Incubation period: Unknown

Distribution: Worldwide

Frequency: Rare human pathogen

Reservoir: Environment, especially plants and plant material

Major clinical setting: Healthcare-associated infection

Major infection: Bacteremia, including central venous catheter-related bacteremia

Other source-listed infections: UTI, pneumonia, neonatal meningitis, and liver abscess

Additional classic association: Infection following penetrating plant/thorn trauma

Diagnosis: Culture

Source treatment: Third-generation cephalosporin

Additional source options: Ciprofloxacin, imipenem, meropenem, aminoglycosides, and aztreonam

Treatment principle: Susceptibility-guided antimicrobial therapy

Source control: Important for infected catheters and drainable abscesses

Key clinical pearl: Pantoea agglomerans is a rare environmental Gram-negative bacillus formerly called Enterobacter agglomerans. Remember two particularly useful associations: healthcare-associated bacteremia involving central venous catheters and infection following penetrating trauma with plant material, especially thorn injuries.