Ultrastructural alterations of bacteria during the postantibiotic effect

Area of Science:

• Microbiology
• Cell Biology
• Pharmacology

Background:

• The postantibiotic effect (PAE) is a crucial parameter in antibacterial therapy, representing the period of growth inhibition after antibiotic exposure.
• Understanding the morphological changes bacteria undergo during PAE can provide insights into mechanisms of action and resistance.

Purpose of the Study:

• To investigate the ultrastructural alterations in Staphylococcus aureus and Pseudomonas aeruginosa during the postantibiotic effect (PAE) following exposure to various antibiotics.
• To correlate observed morphological changes with the duration of the PAE.

Main Methods:

• Transmission electron microscopy (TEM) was employed to visualize ultrastructural changes in bacterial cells.
• Bacterial viability was assessed using viable counts to determine the duration of the PAE.

Main Results:

• Staphylococcus aureus exposed to dicloxacillin showed increased crosswall formation, while rifampin induced cell wall thickening. Gentamicin caused minimal changes.
• Pseudomonas aeruginosa exhibited intracellular electrondense aggregates after exposure to imipenem, tobramycin, and ciprofloxacin. Imipenem also induced globoid cell formations.
• Observed ultrastructural alterations varied among individual organisms but consistently correlated with the determined PAE duration.

Conclusions:

• Antibiotic exposure induces specific and observable ultrastructural changes in bacteria during the PAE.
• These morphological changes are linked to the duration of the PAE, providing a visual correlate to bacterial growth inhibition.