Ampicillin Treatment of Intracellular Listeria monocytogenes Triggers Formation of Persistent, Drug-Resistant L-Form...

Area of Science:

• Microbiology
• Infectious Diseases
• Cell Biology

Background:

• Listeria monocytogenes is a dangerous foodborne pathogen causing listeriosis.
• High mortality rates in at-risk individuals highlight the severity of L. monocytogenes infections.
• Reported infection relapses after antibiotic treatment suggest bacterial persistence mechanisms.

Purpose of the Study:

• To investigate the intracellular generation of antibiotic-resistant L-forms of L. monocytogenes.
• To determine if L. monocytogenes can evade antibiotic treatment by forming dormant subpopulations.
• To characterize the viability and proliferative capacity of intracellular L-forms.

Main Methods:

• Infection of host cells with L. monocytogenes followed by Ampicillin treatment.
• Detection and identification of intracellular L. monocytogenes L-forms using fluorescence in situ hybridization and confocal laser scanning microscopy.
• Isolation of single intracellular L-form cells via micromanipulation for subsequent culture.

Main Results:

• Intracellular generation of antibiotic-resistant L-forms of L. monocytogenes was observed after Ampicillin treatment.
• Fluorescence in situ hybridization and confocal microscopy confirmed the presence of these L-forms within host cells.
• Micromanipulation enabled the isolation of viable intracellular L-forms capable of regrowth in fresh medium.

Conclusions:

• Antibiotic treatment of infected host cells can induce the formation of L-forms from intracellular L. monocytogenes.
• Intracellular L-forms persist within host cells, representing viable bacteria.
• These findings suggest that intracellular L-forms contribute to persistent L. monocytogenes infections and potential treatment failure.