Antimicrobial Effect of Natural Polyphenols With or Without Antibiotics on Chlamydia pneumoniae Infection In Vitro

Address correspondence to: Caterina Romano Carratelli, PhD, Section of Microbiology and Clinical Microbiology, Department of Experimental Medicine, Faculty of Medicine and Surgery, Second University of Naples, Via Santa Maria di Costantinopoli, 16, Napoli 80138, Italy, E-mail: [email protected]

Introduction

Chlamydia pneumoniae is a Gram-negative human respiratory pathogen that causes acute respiratory infection.²³ It is a common infectious agent and has a tendency to cause chronic infections that have been associated with atherosclerotic diseases, including coronary heart disease.^26,12

Chlamydiae show a unique developmental life cycle that includes the metabolically inactive but infective elementary bodies (EBs) and the metabolically active but noninfective reticulate bodies, which multiply inside the host cell cytoplasm.²

C. pneumoniae is able to enter a nonreplicative persistent state within the host cells, forming morphologically aberrant inclusions.^18,36 Persistent C. pneumoniae is refractory to antibiotic treatment and is associated with chronic infection, as demonstrated in an infected vasculature.¹⁸

This intracellular bacterium has been shown to survive 30 days of antibiotic treatment in a cell culture mimicking chronic infection,²⁴ and similar persistence has been shown in animal models.⁴³ Hammerschlag et al.¹⁷ described five patients with culture-positive C. pneumoniae respiratory infections who had multiple positive cultures over several months despite specific antibiotic therapy. The most commonly used antibiotics against C. pneumoniae are ofloxacin and clarithromycin. Clarithromycin (macrolide) is highly effective against Chlamydia in vitro, but resistance to this compound, can develop.³⁰

It has been demonstrated that in the Mycobacterium avium complex, the activity of the efflux pumps has been identified as an important contributor to bacterial resistance and is recognised as an important cause of intrinsic antibiotic resistance.⁴⁵ Ofloxacin (fluoroquinolone) is widely used...