Chlamydia pneumoniae Infection in Circulating Human Monocytes Is Refractory to Antibiotic Treatment

Abstract

Background-Recovery of the intracellular bacterium Chlamydia pneumoniae from atherosclerotic plaques has initiated large studies on antimicrobial therapy in coronary artery disease. The basic concept that antibiotic therapy may eliminate and prevent vascular infection was evaluated in vitro and in vivo by examining the antibiotic susceptibility of C pneumoniae in circulating human monocytes, which are thought to transport chlamydiae from the respiratory tract to the vascular wall. Methods and Results-Blood monocytes (CD14ϩ) from 2 healthy volunteers were obtained before and after oral treatment with azithromycin or rifampin and then inoculated with a vascular C pneumoniae strain and continuously cultured in the presence of the respective antibiotic. Progress of infection and chlamydial viability was assessed by immunogoldlabeling and detection of C pneumoniae-specific mRNA transcripts. Circulating monocytes from patients undergoing treatment with experimental azithromycin for coronary artery disease were examined for C pneumoniae infection by cell culture. Antibiotics did not inhibit chlamydial growth within monocytes. Electron microscopy showed development of chlamydial inclusion bodies. Reverse transcription-polymerase chain reaction demonstrated continuous synthesis of chlamydial mRNA for 10 days without lysis of the monocytes. The in vivo presence of viable pathogen not eliminated by azithromycin was shown by cultural recovery of C pneumoniae from the circulating monocytes of 2 patients with coronary artery disease. Key Words: Chlamydia pneumoniae Ⅲ atherosclerosis Ⅲ infection Ⅲ azithromycin Ⅲ rifampin T he obligate intracellular pathogen Chlamydia pneumoniae has been related to atherosclerosis by seroepidemiology, detection of chlamydial structures and, most recently, recovery of viable chlamydiae from atherosclerotic plaques. 1,2 Chlamydiae may thus have a role in the multifactorial pathogenesis of atherosclerosis, a chronic inflammatory condition of the vascular wall. 3,4 On the basis of these findings, antimicrobial treatment studies are currently underway, with the intention to improve the clinical condition of patients with coronary artery disease (CAD) by chlamydial eradication from atheromatous plaques. 5 Endothelial and smooth muscle cells can acquire a productive chlamydial infection that can be inhibited in vitro by common antichlamydial antibiotics. 6 However, chlamydiae are notorious for causing chronic infections, 7 and treatment failure is common. These infections and failures may be due to the establishment of a nonreplicating but viable state of chlamydiae in the host cells. 8 Systemic dissemination of C pneumoniae from the respiratory tract to the cells of the vascular wall requires a cellular transport system, because chlamydiae replicate exclusively within their host cells. The elementary body, the metabolically inactive extracellular life stage of chlamydiae, has never been found circulating free within the bloodstream. Circulating monocytes, which are pivotal to the development of ather...

Infection-induced inflammatory response of adipocytes in vitro

“…33 The absence of an effect of antibiotic treatment on vascular events may be due to ineffective treatment strategies not affecting Cp in circulating monocytes. 34 Also, it can still be argued that viral infections, not affected by macrolide treatment, are involved in atherogenesis, arterial thrombosis and plaque rupture. 35,36 Recently, Ad infections were considered to play a role in the development of obesity and are associated with plasma lipid abnormalities.…”

CD14 promoter polymorphism −159C>T is associated with susceptibility to chronic Chlamydia pneumoniae infection in peripheral blood monocytes

“…PBMC from the 610 study patients were separated in a Ficoll-Histopaque density gradient (Sigma, St Louis, MO, USA). 2 For C. pneumoniae detection, purified DNA was resuspended in 100 ml water and subjected to PCR using the HL-1/HR-1 primers that amplify a genomic 438-bp C. pneumoniae target sequence. For enhanced specificity, a nested PCR protocol was used with the nested oligonucleotide primer pair In-1 (5 0 -AGT TGA GCA TAT TCG TGA GG-3 0 ) and In-2 (5 0 -TTT ATT TCC GTG TCG TCC AG-3 0 ), which yield a 128-bp product.…”

“…For confirmation, nonradioactive DNA hybridization was performed using oligonucleotide HM-1 3 0 -tailed with digoxigenin-11-dUTP/dATP (Roche Diagnostics) as the probe. 2 Sera were tested for C. pneumoniae-specific antibodies with a microimmunofluorescence (MIF) assay (IgG, IgA, IgM; Labsystems, Helsinki/Finland). MIF-anti-C. pneumoniae IgG titer X1 : 16 indicated previous C. pneumoniae infection.…”

“…The obligate intracellular bacterium Chlamydia (Chlamydophila) pneumoniae is frequently found in atherosclerotic lesions and appears to use blood monocytes (PBMC) as a vector for its dissemination within the circulation. 2 Chlamydial interaction with pattern recognition receptors of the innate immune system results in uptake of the pathogen and MAPkinase-dependent inflammatory signalling. 3 Chlamydial heat-shock protein 60 (cHSP60) mediates inflammation in endothelial cells and macrophages via the TLR4-MD2 complex and the MyD88-dependent pathway.…”

Effects of coadministration of natural polyphenols with doxycycline or calcium modulators on acute Chlamydia pneumoniae infection in vitro

“…10 It has been suggested that C. pneumoniae infection of macrophages is often in a persistent form, which explains the observed refractory behavior of C. pneumoniae infection to antibiotic treatment in cells of monocyte-macrophage line. 11,12 Thus, new treatments are needed to fight the chlamydial infections and avoid the treatment failures.…”