Antimicrobial susceptibility and therapy of infections caused by Chlamydia pneumoniae

From coughs to complications: the story of Chlamydia pneumoniae

Chlamydia pneumoniae is an obligate intracellular bacterium and a significant cause of respiratory infections. It is associated with upper and lower respiratory tract diseases, including bronchitis and pneumonia. The pathogen employs specific virulence factors, such as the Type III Secretion System (T3SS) and Inc proteins, to invade and subvert host cell machinery during its peculiar developmental life cycle. Chronic infections have been linked to asthma and, more controversially, to atherosclerosis and neurodegenerative diseases. Diagnosis primarily relies on PCR-based molecular assays, while treatment includes macrolides, tetracyclines or fluoroquinolones. Despite its clinical relevance, research on C. pneumoniae has declined in recent years, highlighting the need for renewed scientific focus.

Chlamydia Serine Protease Inhibitor, targeting HtrA, as a New Treatment for Koala Chlamydia infection

The koala, an iconic marsupial native to Australia, is a threatened species in many parts of the country. One major factor in the decline is disease caused by infection with Chlamydia. Current therapeutic strategies to treat chlamydiosis in the koala are limited. This study examines the effectiveness of an inhibitor, JO146, which targets the HtrA serine protease for treatment of C. pecorum and C. pneumoniae in vitro and ex vivo with the aim of developing a novel therapeutic for koala Chlamydia infections. Clinical isolates from koalas were examined for their susceptibility to JO146. In vitro studies demonstrated that treatment with JO146 during the mid-replicative phase of C. pecorum or C. pneumoniae infections resulted in a significant loss of infectious progeny. Ex vivo primary koala tissue cultures were used to demonstrate the efficacy of JO146 and the non-toxic nature of this compound on peripheral blood mononuclear cells and primary cell lines established from koala tissues collected at necropsy. Our results suggest that inhibition of the serine protease HtrA could be a novel treatment strategy for chlamydiosis in koalas.

N-acylated derivatives of sulfamethoxazole and sulfafurazole inhibit intracellular growth of Chlamydia trachomatis

Antibacterial compounds with novel modes of action are needed for management of bacterial infections. Here we describe a high-content screen of 9,800 compounds identifying acylated sulfonamides as novel growth inhibitors of the sexually transmitted pathogen Chlamydia trachomatis. The effect was bactericidal and distinct from that of sulfonamide antibiotics, as para-aminobenzoic acid did not reduce efficacy. Chemical inhibitors play an important role in Chlamydia research as probes of potential targets and as drug development starting points.

Chlamydia pneumoniae infection and Alzheimer's disease: a connection to remember?

Alzheimer's disease (AD) is the most common cause of dementia in the elderly, whereby it is customary to distinguish between early familial FAD and late-onset AD (LOAD). The development of LOAD, the most prevalent form of AD, is believed to be a multifactorial process that may also involve infections with bacterial or viral pathogens. After the first report on the presence of Chlamydia pneumoniae (Cpn) in brains of patients with AD appeared in 1998, this bacterium has most often been implicated in AD pathogenesis. However, while some studies demonstrate a clear association between Cpn infection and AD, others have failed to confirm these findings. This might be due to heterogeneity of the specimens analyzed and lack of standardized detection methods. Additionally, non-availability of suitable chlamydial infection models severely hampers research in the field. In this review, we will critically discuss the possible role of Cpn in the pathogenesis of LOAD in light of the available data. We will also present three mutually non-exclusive hypotheses how Cpn might contribute to the pathogenesis of AD.

Pharmacokinetics of pradofloxacin and doxycycline in serum, saliva, and tear fluid of cats after oral administration

The pharmacokinetic properties of pradofloxacin and doxycycline were investigated in serum, saliva, and tear fluid of cats. In a crossover study design, six cats were treated orally with a single dose of pradofloxacin (Veraflox Oral Suspension 2.5%) and doxycycline (Ronaxan 100 mg) at 5 mg/kg body weight. Following administration, samples of serum, saliva, and tear fluid were taken in regular intervals over a period of 24 h and analysed by turbulent flow chromatography/tandem mass spectrometry. All values are given as mean +/- SD. Pradofloxacin reached a mean maximum serum concentration (C(max)) of 1.1 +/- 0.5 microg/mL after 1.8 +/- 1.3 h (t(max)). In saliva and tear fluid, mean C(max) was 6.3 +/- 7.0 and 13.4 +/- 20.9 microg/mL, respectively, and mean t(max) was 0.5 +/- 0 and 0.8 +/- 0.3 h, respectively. Doxycycline reached a mean C(max) in serum of 4.0 +/- 0.8 microg/mL after 4.3 +/- 3.2 h. Whilst only at two time-points doxycycline concentrations close to the limit of quantification were determined in tear fluid, no detectable levels were found in saliva. The high concentrations of pradofloxacin in saliva and tear fluid are promising to apply pradofloxacin for the treatment of conjunctivitis and upper respiratory tract infections in cats. As doxycycline is barely secreted into these fluids after oral application the mechanisms of its clinical efficacy remain unclear.

Isolation and antimicrobial susceptibilities of Chlamydial isolates from Western barred bandicoots

A range of species of Chlamydiales have previously been detected in a variety of Australian marsupials, including koalas and western barred bandicoots. Thirty-seven ocular, urogenital, or nasal swabs were obtained from 21 wild western barred bandicoots. Chlamydia culture and antibiotic susceptibility testing were performed for cycloheximide-treated HEp-2 cells in 96-well microtiter plates. Chlamydia spp. were isolated from 11 specimens from 9 (42.8%) bandicoots. All isolates were identified as Chlamydiales by conventional PCR with 16S and 23S rRNA gene primers specific to Chlamydiales and were confirmed to be Chlamydia pneumoniae by a C. pneumoniae-specific ompA-based real-time PCR assay and 16S rRNA and 23S rRNA gene signature sequence analyses. The MICs of azithromycin, doxycycline, ciprofloxacin, and enrofloxacin for 10 C. pneumoniae isolates from these bandicoots ranged from 0.015 to 1 microg/ml, 0.25 to 1 microg/ml, 0.25 to 2 microg/ml, and 0.25 to 0.5 microg/ml, respectively. The MICs at which 90% of isolates were inhibited and the minimal bactericidal concentrations were within the ranges reported previously for human isolates of C. pneumoniae.

Isolation of Chlamydophila pneumoniae from atheromas of the carotid artery and their antibiotics susceptibility profile

BACKGROUND

Atherosclerosis is pathogenically similar to a chronic inflammatory response. Peripheral arterial disease (PAD) is a common manifestation of atherosclerosis. Chlamydophila pneumoniae has been suggested to play a role in the origin of PAD.

OBJECTIVE

To determine whether C. pneumoniae is present in atherosclerosis lesions of the carotid artery wall in patients with PAD through several diagnostic methods and to characterize C. pneumoniae susceptibility profiles.

METHODS

The presence of C. pneumoniae in 9 tissue samples from atherosclerotic lesions obtained by carotid endarterectomy was investigated by 3 methods. Karnofsky-fixed specimens were examined by transmission electron microscopy (TEM), isolation of C. pneumoniae was attempted in LLCMK2 cell structure (ICC), and the presence of chlamydial DNA was investigated by polymerase chain reaction (PCR). The in vitro activities of azithromycin, roxithromycin and penicillin were tested in 4 isolations and the reference strain of C. pneumoniae (AR39).

RESULTS

C. pneumoniae was detected in atherosclerotic plaques from 4 patients with PAD. The pathogen was identified by TEM, PCR and ICC. We report data of the in vitro susceptibility of 4 strains. These strains did not differ from respiratory AR39 strain in their susceptibility patterns to azithromycin, roxithromycin and penicillin.

CONCLUSIONS

C. pneumoniae is frequently found in the advanced carotid atherosclerotic lesions of patients undergoing endarterectomy. Although these findings do not establish causality in carotid artery atherosclerosis, they should stimulate investigation of the possible causal or pathogenic role of C. pneumoniae. Notably, the profiles of antibiotic susceptibility of C. pneumoniae isolated from 4 of the patients did not differ from those of the reference strain.

Protective effect of doxycycline use on coronary artery disease?

OBJECTIVES

The potential role of Chlamydia pneumoniae infection in the pathogenesis of atherosclerosis has received increasing attention. The present study was conducted to test the hypothesis that use of doxycycline in doses prescribed in routine clinical practice for brucellosis, decreases the risk of coronary artery disease (CAD).

METHODS

A general practice (GP) database in Western Greece was used. One hundred and twenty-nine newly diagnosed patients with coronary artery disease from 2001 to 2003 were contrasted to 196 controls randomly selected from the same practice. General practice records were reviewed to confirm a diagnosis of incident CAD event and obtain information on other cardiovascular risk factors. CAD events were defined as: Stable/unstable angina, acute myocardial infarction or ischemic death.

RESULTS

The results indicate a significant association between doxycycline use and occurrence of CAD (OR: 0.37, 95% CI: 0.17-0.78).

CONCLUSIONS

These results persisted when adjustment for potential confounding factors was made. The findings should be interpreted cautiously because of lack of information about C. pneumoniae infection. However, the results suggest directions for future epidemiologic studies in this relatively uncharted field.

Frequency of spontaneous mutations that confer antibiotic resistance in Chlamydia spp

Mutations in rRNA genes (rrn) that confer resistance to ribosomal inhibitors are typically recessive or weakly codominant and have been mostly reported for clinical strains of pathogens possessing only one or two rrn operons, such as Helicobacter pylori and Mycobacterium spp. An analysis of the genome sequences of several members of the Chlamydiaceae revealed that these obligate intracellular bacteria harbor only one or two sets of rRNA genes. To study the contribution of rRNA mutations to the emergence of drug resistance in the Chlamydiaceae, we used the sensitivities of Chlamydia trachomatis L2 (two rrn operons) and Chlamydophila psittaci 6BC (one rrn operon) to the aminoglycoside spectinomycin as a model. Confluent cell monolayers were infected in a plaque assay with about 10(8) wild-type infectious particles and then treated with the antibiotic. After a 2-week incubation time, plaques formed by spontaneous spectinomycin-resistant (Spc(r)) mutants appeared with a frequency of 5 x 10(-5) for C. psittaci 6BC. No Spc(r) mutants were isolated for C. trachomatis L2, although the frequencies of rifampin resistance were in the same range for both strains (i.e., 10(-7)). The risk of emergence of Chlamydia strains resistant to tetracyclines and macrolides, the ribosomal drugs currently used to treat chlamydial infections, is discussed.

Advances in the management of Chlamydia pneumoniae infections

One of the major characteristics of Chlamydia spp. is its ability to cause prolonged, often subclinical infections. Chronic, persistent infection with Chlamydia pneumoniae has been implicated in the pathogenesis of several chronic diseases initially not thought to be infectious, including asthma, arthritis and atherosclerosis. C. pneumoniae is susceptible in vitro to a wide range of antimicrobial agents that target either protein or DNA synthesis, including macrolides, ketolides, tetracyclines, quinolones and rifamycins. Practically all treatment studies evaluating presented or published to date have used serology alone for diagnosis of C. pneumoniae infection, which only provides a clinical end point. The results of several treatment studies that did perform culture found that erythromycin, azithromycin (Zithromax, clarithromycin (Biaxin, levofloxacin (Levaquin and moxifloxacin (Avelox had a 70 to 90% efficacy in eradicating C. pneumoniae from the respiratory tract of children and adults with pneumonia. Persistence of the organism does not appear to be due to the development of antibiotic resistance. However, one cannot extrapolate from this experience to the treatment of chronic C. pneumoniae infection, especially cardiovascular disease. As there are no reliable serologic markers for chronic or persistent C. pneumoniae infection, it cannot be determined who is infected and who is not, which means that it cannot be assumed that any effect seen is due to successful treatment or eradication of C. pneumoniae.

Effect of levofloxacin on the viability of intracellular Chlamydia pneumoniae and modulation of proinflammatory cytokine production by human monocytes

Although antibiotics are known to affect the intracellular growth of Chlamydia pneumoniae in acute infections, their efficacy in therapy for chronic infections, including atherosclerosis, remains debatable. Human monocyte-derived macrophages (MDM) obtained from monocytes of healthy donors were infected with C. pneumoniae AR-39 and treated with levofloxacin (8 microg/mL) immediately after infection (0 hours) or 24 hours after infection. Levofloxacin treatment at 24 hours, but not at 0 hours, resulted in a significant decrease in the number of C. pneumoniae inclusions within the MDM (p < 0.05). Also decreased were concentrations of proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, and IL-8 in the extracellular medium (p < 0.01). Viable counts in titrations remained similar to those in untreated controls. In summary, levofloxacin administered to MDM at serum-attainable levels 24 hours after C. pneumoniae infection significantly decreased inclusion counts and proinflammatory cytokine production, but did not eliminate the C. pneumoniae infection.

Development and validation of a time-resolved fluorometric immunoassay for screening of antichlamydial activity using a genus-specific europium-conjugated antibody

The lack of high-throughput assays has limited the screening of new antimicrobials against obligate intracellular bacteria, including chlamydia, which cause a variety of diseases. In this study, a novel technological approach was developed to detect intracellular bacteria using time-resolved fluorometric immunoassay (TR-FIA), and the method was validated for susceptibility testing of Chlamydia pneumoniae. In this cell-based, 96-well plate assay, chlamydial inclusions are labeled with europium-conjugated antibody and quantified as time-resolved fluorometric signals by means of a multilabel counter. To confirm the reliability of the TR-FIA, susceptibilities of C. pneumoniae reference strain Kajaani 7 to a set of antimicrobial agents were determined by the TR-FIA, conventional immunofluorescence staining, and real-time polymerase chain reaction. Minimum inhibitory concentrations measured using the different methods demonstrated good to excellent correlation. Data relating to reproducibility (day-to-day variation 9.0%), as well as to the signal-to-background, signal-to-noise, and Z' values (6.5, 6.9, and 0.4, respectively), showed the suitability of the TR-FIA for screening. By means of dual labeling with sulfornodamine B the cytotoxicity of test compounds could be detected simultaneously with the susceptibility testing. In summary, the TR-FIA is a convenient, reliable, and objective alternative for detecting chlamydia in vitro. By being considerably less labor intensive and offering significantly higher throughput, the TR-FIA is especially suitable for screening of new antichlamydial compounds.

In vitro activities of garenoxacin and levofloxacin against Chlamydia pneumoniae are not affected by presence of Mycoplasma DNA

We studied 20 Chlamydia pneumoniae isolates obtained from respiratory sites and atheroma tissue of patients from various geographic areas to determine the susceptibilities of these isolates to a new des-fluoroquinolone, garenoxacin, and to levofloxacin. In addition, we assessed the cultures with these isolates by PCR for the presence or absence of Mycoplasma sp. DNA. Both the MIC at which 90% of isolates are inhibited (MIC(90)) and the minimal bactericidal concentration at which 90% of isolates are killed (MBC(90)) for garenoxacin were 0.06 microg/ml, and both the MIC(90) and the MBC(90) for levofloxacin were 2.0 microg/ml. The activity of garenoxacin against C. pneumoniae was 32-fold greater than that of levofloxacin. Mycoplasma sp. DNA was detected by PCR in 17 of 20 cultures. Mycoplasma amplicons from five Mycoplasma DNA-positive C. pneumoniae cultures were sequenced and found to represent four Mycoplasma species. Our data demonstrate that C. pneumoniae cultures frequently contain Mycoplasma DNA and that its presence in C. pneumoniae cultures does not appear to affect the susceptibility results for the two fluoroquinolones that we tested.

Antibiotics in primary prevention of myocardial infarction among elderly patients with hypertension

BACKGROUND

Given the premise that certain bacteria (such as Chlamydia pneumoniae) may play a role in the etiology of atherosclerosis, subjects treated with antibiotics that have antibacterial activity against C pneumoniae may be at lower risk for the development of an acute myocardial infarction (MI) than untreated subjects.

METHODS

A case-control design, nested within a cohort of 29,937 elderly subjects in whom antihypertensive therapy was initiated (1982-1995) was used, in which each subject who was hospitalized with a primary discharge diagnosis of MI between 1987 and 1995 (n = 1047) was matched on calendar time to 5 randomly selected control subjects for exposure contrasts. Conditional logistic regression analyses were conducted to adjust for predisposing factors for MI.

RESULTS

Although no clear consistent effect of antibiotics use was found in relation to MI, a trend was observed for a decreased risk of acute MI in patients receiving a prescription for antichlamydial antibiotics in the preceding 3 months (odds ratio 0.68, 95% CI 0.46-1.00). Antibiotics without antichlamydial activity showed no benefit in MI risk.

CONCLUSION

The beneficial effect of certain antichlamydial antibiotics in reducing the risk of MI cannot be excluded on the basis of this representative cohort of elderly patients in a routine clinical care setting. Larger prospective studies are required to confirm the usefulness of antibiotics in the primary prevention of MI.

The intracellular life of chlamydiae

The ability to cause persistent infection is one of the major characteristics of all chlamydial species in their appropriate hosts. Persistent infection with Chlamydia trachomatis and Chlamydia pneumoniae has been implicated in the pathogenesis of many chronic diseases, some initially not thought to be infectious, including pelvic inflammatory disease, arthritis, asthma, and atherosclerosis. Chlamydiae have a unique developmental cycle with morphologically distinct infectious and reproductive forms: elementary (EB) and reticulate bodies (RB). Chlamydiae appear to circumvent the host endocytic pathway and inhabit a nonacidic vacuole that is dissociated from late endosomes and lysosomes. Chlamydiae also have been demonstrated to enter a persistent state after treatment with cytokines such as interferon-gamma (IFN-gamma), treatment with antibiotics, or restriction of certain nutrients, or to enter this state spontaneously under certain culture conditions. While the organism is in the persistent state, metabolic activity is reduced, and the organism is often refractory to antibiotic treatment. Ultrastructural analysis of IFN-gamma-treated C pneumoniae demonstrates atypical inclusions containing large reticulate-like aberrant bodies with no evidence of redifferentiation into EBs. Persistent C pneumoniae infection appears to be associated with continued expression of genes associated with DNA replication but not with those genes involved with bacterial cell division. The latter observation may explain the appearance of the large abnormal RBs seen in ultrastructural studies. Studies of the association of chlamydiae with chronic disease have been hampered by difficulties in diagnosing chronic, persistent infection with the organism, which, in turn, render determining the efficacy of antibiotic therapy very difficult.

The evolution and role of macrolides in infectious diseases

Two of the most significant changes in the field of infectious disease management during the last few decades are the emergence of atypical and/or new pathogens that may have devastating consequences and the re-emergence of well-recognised organisms that have acquired antimicrobial resistance through a variety of mechanisms. Erythromycin, the prototype macrolide, was originally marketed approximately five decades ago as a useful alternative agent in the treatment of patients allergic to beta-lactam antibiotics. While clinically useful, its pharmacokinetic and adverse-event profile limited the use of erythromycin to these individuals. Enhancements of the macrolide structure circumvented many of the limitations of erythromycin and resulted in the development of azithromycin and clarithromycin. The clinical uses of clarithromycin and azithromycin are substantially wider than erythromycin due to the wide spectra of activity against the atypical and newer pathogens. In addition, these agents are well-tolerated and have a pharmacokinetic profile that allows once- or twice-daily administration. Studies also indicate that the more common of the two mechanisms of macrolide resistance in the US and Canada imparts only low-level resistance. The multitude of studies substantiating clinical as well as bacteriological success with these two agents indicates that, when used appropriately, they will stand the test of time and continue to be useful antimicrobial agents.

The macrolides

Erythromycin, which was introduced over 50 years ago, was the first macrolide to be used clinically. "New" macrolides, for the treatment of patients with various infectious diseases, were not clinically introduced until 40 years later. The pharmacokinetic and adverse events profile of erythromycin initially limited its use to an alternative agent for patients with allergy to beta-lactam agents. However, the emergence of atypical and/or new pathogens and the ongoing escalation of acquired antimicrobial resistance has impacted on the empirical and organism directed therapy of infectious diseases. Azithromycin and clarithromycin were developed by enhancing the basic macrolide structure. Some of the basic features associated with these new agents include a pharmacokinetic profiles that allow once or twice daily dosing with a much lower incidence of side effects and a substantially broader spectrum of activity which includes some Gram-negative bacilli, atypical pathogens and new, unconventional or uncommon pathogens. Clinical trial data has supported the use of "new" macrolides in a wide range of clinical indications, however, some specific indications are currently restricted to treatment with either azithromycin or clarithromycin. Macrolide resistance is a class effect and depending on the mechanism will confer either low or high level resistance. While resistance is problematic, it does not always result in clinical failure. The macrolides are a valuable class of antimicrobial agent and play an important role in the management of infectious diseases.

In vitro activities of BMS-284756 against Chlamydia trachomatis and recent clinical isolates of Chlamydia pneumoniae

The in vitro activities of BMS-284756 (a novel des-fluoroquinolone), levofloxacin, moxifloxacin, and clarithromycin were tested against 5 strains of Chlamydia trachomatis and 20 isolates of Chlamydia pneumoniae. The MIC at which 90% of the isolates were inhibited and the minimal bactericidal concentration at which 90% of the isolates were killed by BMS-284756 for all isolates of C. pneumoniae and C. trachomatis was 0.015 microg/ml (range, 0.015 to 0.03 microg/ml). BMS-284756 was the most active quinolone tested.

Relation of antibiotic use to risk of myocardial infarction in the general population

There are conflicting reports of an association between Chlamydia pneumoniae (C. pneumoniae) infection and coronary artery disease (CAD); randomized trials of antibiotics for the secondary prevention of CAD are currently underway. Physicians may be tempted to believe that their choice of antibiotic class in treating any infection may alter the risk of CAD. Our objective was to determine if the use of antibiotics with antichlamydial activity in the general population reduces the risk of myocardial infarction. A healthcare claims database with 354,258 patients with continuous health and pharmacy coverage for at least 2 years between January 1, 1991 and December 31, 1997 was used for the analyses. Hazard ratios were derived from proportional hazards models with time-dependent covariates, relating antibiotic prescription to first claim related to incident first myocardial infarction during the observation period, adjusting for previous CAD, age, sex, diabetes, hypertension, hyperlipidemia, and chronic obstructive pulmonary disease. There were a total of 1,684,091 person-years of observation and 16,139 incident myocardial infarctions. The adjusted hazard ratios were 1.10 (95% confidence intervals [CI] 1.04 to 1.16) for macrolides, 1.20 (95% CI 1.13 to 1.26) for quinolones, 1.10 (95% CI 0.96 to 1.21) for cephalosporins, 1.00 (95% CI 0.96 to 1.06) for tetracyclines, 1.01 (95% CI 0.96 to 1.06) for penicillins, and 1.13 (95% CI 0.98 to 1.30) for trimetroprim-sulfamethoxazole. The hazard ratios for individual antibiotics with activity against C. pneumoniae within each group were similar. Use of antibiotics with activity against C. pneumoniae does not reduce the risk of myocardial infarction in the general population.

Antibiotic use and risk of ischemic stroke in the elderly

PURPOSE

To determine whether treating infections with antibiotics that have antichlamydial activity decreases the risk of ischemic stroke in the elderly.

SUBJECTS

We analyzed data from 199 553 subjects 65 years and older in a health care claims database who had continuous health and pharmacy coverage for at least 2 years between January 1, 1991, and September 30, 1997. Using proportional hazards models with time-dependent covariates for prior antibiotic prescription and adjusting for cardiovascular risk factors, we determined the associations between antibiotic use and first claim for ischemic stroke (n = 7,335) during the observation period.

RESULTS

Rates of stroke (per 1,000 person-years) were 6.64 for macrolides, 9.27 for quinolones, 7.49 for tetracyclines, 6.88 for penicillins, 7.97 for cephalosporins, 8.58 for trimethoprim-sulfamethoxazole, and 7.29 for subjects with no antibiotic claims. The adjusted hazard ratios (HR) were 0.94 (95% confidence interval [CI]: 0.87 to 1.01) for macrolides, 1.04 (95% CI: 0.91 to 1.18) for tetracyclines, 1.02 (95% CI: 0.95 to 1.08) for penicillins, and 1.00 (95% CI: 0.82 to 1.22) for trimethoprim-sulfamethoxazole. Subjects with claims for quinolone antibiotics (HR = 1.17; 95% CI: 1.09 to 1.26) and cephalosporins (HR = 1.09; 95% CI: 1.02 to 1.16) had a slightly higher risk of stroke.

CONCLUSION

Exposures to short courses of antibiotics are not associated with lower risk of ischemic stroke in patients aged 65 years and older.

Effect of azithromycin plus rifampin versus amoxicillin alone on eradication and inflammation in the chronic course of Chlamydia pneumoniae pneumonitis in mice

The effects of treatment with azithromycin plus rifampin (A+R), amoxicillin (A), or placebo (P) on the chronic course of experimental Chlamydia pneumoniae pneumonitis in mice were assessed by culture, PCR, and immunocytochemistry as well as by degree of inflammation in lung tissue. Eradication of the pathogen was significantly more frequent and inflammation in tissue was significantly reduced after treatment with A+R compared to after treatment with A or P. Combination therapy with azithromycin plus rifampin showed favorable effects in the chronic course of C. pneumoniae pneumonitis.

Potential for antimicrobial resistance in Chlamydia pneumoniae

Antimicrobial resistance has not yet been described in wild type Chlamydia pneumoniae isolates, nor has selective emergence of resistance in the laboratory after exposure to subinhibitory concentrations of antibiotic. However, few clinical isolates have been tested for resistance, especially strains with resistance phenotypes (i.e., those associated with clinical failure or persistence). More widespread testing of such strains is needed. Further understanding of antimicrobial resistance in chlamydiae would benefit from the development of standardized methods. Further, more physiologic testing methodologies that more closely mimic the chronic intracellular infection usually being treated in vivo would be of value. Animal models demonstrate persistence of C. pneumoniae after antimicrobial therapy and could be used to better define the clinical correlates of in vitro testing.

Antibiotics in the prevention and treatment of coronary heart disease

Seroepidemiology, pathology, and animal studies provide evidence for a possible association between Chlamydia pneumoniae infections and atherosclerosis, coronary heart disease, and myocardial infarction. If this association exists, then exposure to certain antibiotics may positively affect the clinical course after an acute ischemic cardiac event (secondary prevention) and affect the risk of developing a first-time myocardial infarction (primary prevention). Preliminary evidence from clinical trials suggests that treatment with new macrolide antibiotics may improve outcome after ischemic events, and evidence from a large case-control analysis indicates that exposure to tetracyclines or quinolones may reduce the risk of developing a first-time myocardial infarction. However, antibiotics for the treatment or prevention of ischemic heart disease must not be recommended yet. This review of published studies briefly summarizes the currently available literature on the effects of antibiotics on the risk of developing coronary heart disease and myocardial infarction.

The Role of Chlamydia in Upper Respiratory Tract Infections

Although Chlamydia pneumoniae and Chlamydia psittaci are well-established causes of community-acquired pneumonia, little is known about the role of Chlamydia species in upper respiratory tract infections. C. pneumoniae may play a role in the pathogenesis of acute otitis media. Although C. pneumoniae has been isolated from the middle-ear fluid of children with otitis, children in whom the organism was isolated from middle-ear fluid improved despite being treated with antibiotics that are not active against C. pneumoniae. Although many patients with community-acquired pneumonia caused by C. pneumoniae have symptoms suggestive of sinusitis, there is only one report of isolation of the organism from the maxillary sinus of a patient with sinusitis. Studies of the association with pharyngitis are all based on serology, which often has a poor correlation with isolation of the organism by culture.

Activity of quinolones against Chlamydia pneumoniae

Quinolones are currently being used as empirical therapy for the treatment of community-acquired pneumonia and other respiratory infections as they cover a broad range of conventional bacterial and 'atypical' pathogens, including Chlamydia pneumoniae. C. pneumoniae has been associated with 10 to 20% of community-acquired pneumonia in adults and recently has been implicated as being associated with several nonrespiratory conditions, including atherosclerosis. However, data on the treatment of even respiratory infection due to C. pneumoniae are limited. Although currently available quinolones have good activity against C. pneumoniae in vitro, all published treatment studies have relied on serological diagnosis, thus microbiological efficacy has not been assessed. Anecdotal experience suggests that in vitro activity may not always correlate with efficacy in vivo.

Levofloxacin

Levofloxacin (DR-3355, Daiichi) is a new fluoroquinolone antibiotic which is the active isomer of ofloxacin (DL-8280, Daiichi). By removing the inactive isomer, the in vitro activity of levofloxacin is 8-128 times higher than that of ofloxacin. This means that bacterial species, which have borderline susceptibility to ofloxacin and other first generation fluoroquinolones (e.g., pneumococci and organisms causing atypical pneumonia), are considerably more sensitive to levofloxacin. The pharmacokinetics of levofloxacin, which is available for both oral and i.v. administration, are characterised by a very high bioavailability, low (30-40%) protein binding, high tissue concentrations and elimination via the kidneys with minimal liver metabolism. As a consequence of the low degree of metabolism, levofloxacin does not interact with other drugs to any major extent. The safety and efficacy of levofloxacin are well documented in lower respiratory tract infections, skin and soft tissue infections, and urinary tract infections. The safety profile seems advantageous and the risks of phototoxicity, CNS toxicity and cardiac reactions (prolongation of QT-time) are low. Serious liver toxicity, leading to the recent withdrawal of trovafloxacin, has not been a problem in levofloxacin studies. Levofloxacin is a valuable addition to the group of fluoroquinolone antibiotics.

In-vitro activity of gatifloxacin against Chlamydia trachomatis and Chlamydia pneumoniae

We compared the activity of gatifloxacin, a new quinolone, ofloxacin and erythromycin against five isolates of Chlamydia trachomatis and 20 isolates of Chlamydia pneumoniae, including TW183 and clinical isolates from the USA and Japan. Testing was done in cycloheximide-treated HEp-2 cells. Gatifloxacin was slightly less active against C. trachomatis and slightly more active against C. pneumoniae than ofloxacin, with MICs at which 90% of the isolates had no inclusions and minimal chlamydicidal concentrations at which 90% of the isolates had no inclusions after passage of 0.25 mg/L. Gatifloxacin was less active than erythromycin for both species.

The possible role of infections in acute myocardial infarction

Cardiovascular diseases, particularly coronary heart disease (CHD) and myocardial infarction (MI), are among the leading causes for morbidity and mortality in industrialized countries [2, 77]. During the past decades, various clinical or lifestyle risk factors for myocardial infarction such as hyperlipidemia, hypertension, obesity, lack of physical exercise and smoking have been identified. However, it is also recognized that these well-documented risk factors do not sufficiently account for all new cases of myocardial infarction [77]. Many patients with myocardial infarction have only a borderline risk profile or even lack known risk factors. The question arises: What additional risk factors may play a role in the etiology of atherosclerosis and ischemic heart disease?

In vitro susceptibilities of Chlamydia pneumoniae isolates from German patients and synergistic activity of antibiotic combinations

The susceptibilities of six Chlamydia pneumoniae type strains and of six German patient isolates to erythromycin, azithromycin, roxithromycin, clarithromycin, doxycycline, ofloxacin, and rifampin were investigated. MICs and minimal chlamydicidal concentrations were all within the ranges reported previously. Combinations of azithromycin with either ofloxacin, doxycycline, or rifampin, as well as combinations of three antibiotics (rifampin, azithromycin, and ofloxacin or doxycycline), showed synergistic activity against C. pneumoniae.

Effect of azithromycin plus rifampin versus that of azithromycin alone on the eradication of Chlamydia pneumoniae from lung tissue in experimental pneumonitis

Azithromycin, doxycycline, and rifampin, alone or in combination, were tested in vitro against Chlamydia pneumoniae AR-39. The combination of azithromycin plus rifampin showed the strongest activity and produced higher rates of eradication of C. pneumoniae from lung tissues than azithromycin alone in experimental mouse pneumonitis.

Azithromycin: single 1.5 g dose in the treatment of patients with atypical pneumonia syndrome--a randomized study

An open comparative study was undertaken in order to assess the efficacy and safety of a single dose of azithromycin in the treatment of community-acquired atypical pneumonia. A total of 100 adult patients with atypical pneumonia syndrome were randomized to receive 1.5 g of azithromycin as a single dose, or 500 mg once daily for 3 days. The presence of Mycoplasma pneumoniae, Chlamydia pneumoniae, Chlamydia psittaci, Coxiella burnetii, and Legionella pneumophila infection was diagnosed by serological tests. Control clinical examinations were performed 72 h, 10-12 days and 4 weeks after treatment initiation. Among 96 patients (48 in each group) who were evaluable for clinical efficacy M. pneumoniae infection was confirmed in 24, C. pneumoniae in nine, C. psittaci in five, C. burnetii in six, and L. pneumophila in five. Forty-seven patients (97.9%) in each group were cured. Side effects were observed in two patients in the single-dose group, and one patient in the 3-day group. In conclusion, a single 1.5 g dose of azithromycin may be an alternative to the standard 3-day azithromycin regimen in the treatment of outpatients with atypical pneumonia syndrome.

An epidemic of a pertussis-like illness caused by Chlamydia pneumoniae

BACKGROUND

Between June and July, 1994, we encountered an epidemic of a pertussis-like illness in adolescents in a junior high school located in a rural area of Japan. The purposes of this study were to record the clinical manifestations and to identify an etiology.

PATIENTS AND METHODS

We interviewed patients and parents and we performed physical examinations on patients with cough during the epidemic. The chest radiographs were also reviewed by us. To identify an etiology we performed culture and serologic studies for a variety of bacteria, Mycoplasma, chlamydiae and viruses. Polymerase chain reaction (PCR) for Chlamydia pneumoniae was carried out on throat swab specimens.

RESULTS

Of a total of 230 students 136 (59%) had severe cough illnesses. One developed pneumonia, 9 had bronchitis and the remaining 126 (93%) presented upper respiratory tract infections (URI). The mean duration of cough in cases with URI was 17.4 days and that in cases with bronchitis and pneumonia was 30.4 days. Serology and/or cultures for Bordetella pertussis, Bordetella parapertussis, Mycoplasma pneumoniae, Chlamydia trachomatis, Chlamydia psittaci or viruses were negative. Detection of C. pneumoniae infection was carried out in 46 patients with pneumonia, bronchitis or URI by serology and PCR. The patient with pneumonia, 7 of 7 patients with bronchitis and 32 (84%) of 38 patients with URI were documented to be infected by C. pneumoniae either by serology, PCR or both tests.

CONCLUSION

An epidemic of a pertussis-like illness in a junior high school population was caused by C. pneumoniae.

In vitro susceptibilities of Chlamydia pneumoniae strains recovered from atherosclerotic coronary arteries

Chlamydia pneumoniae strains have been recovered from arteriosclerotic coronary arteries, but their antibiotic susceptibility profiles have not yet been examined. We report in vitro susceptibility data for five cardiovascular C. pneumoniae isolates. These strains did not differ significantly from respiratory strains in their patterns of susceptibility to azithromycin, erythromycin, roxithromycin, ofloxacin, doxycycline, rifampin, and penicillin G. Roxithromycin was the most active macrolide, and rifampin was the most effective drug overall.

The role of atypical pathogens: Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila in respiratory infection

Infections caused by M. pneumoniae, C. pneumoniae, and Legionella spp. are important causes of community-acquired pneumonia (CAP). In the past decade, considerable new information has come to light concerning these organisms. Despite this, debate continues concerning the syndromic approach to CAP and the scientific merit of lumping these pathogens together. Because the etiologic diagnosis of these pathogens is established only in a minority of cases, the true prevalence tends to be underestimated. In clinical practice, these pathogens are often empirically treated. More rapid and cost-effective diagnostic techniques are needed so that the clinical course of patients with these infections can be better characterized.

Implications for macrolide treatment in community-acquired pneumonia. Hopkins CAP Team

STUDY OBJECTIVES

To identify associated clinical parameters, concurrent respiratory tract infections, and the association between macrolide-based therapy and mortality in patients with community-acquired pneumonia ascribed to atypical.

DESIGN

Secondary analysis of prospective, cross-sectional study.

SETTING

Tertiary care hospital.

PATIENTS

Three hundred eighty-five consecutive patients who were admitted to the Johns Hopkins Hospital from November 11, 1990, through November 10, 1991, and treated for community-acquired pneumonia.

RESULTS

An atypical pathogen was identified in 29 of 385 adults (7.5%). A second pathogen was detected in 16 of 29 patients (55.2%) in whom an atypical pathogen was detected, compared with 13 of 137 patients (9.5%) in whom conventional bacterial pathogens were detected (odds ratio, 10.22; 95% confidence interval, 3.7 to 28.8; p<0.0001). During hospitalization, only four patients (13.8%) with detection of an atypical pathogen received at least 7 days of either a macrolide or tetracycline. No patient identified to have an atypical pathogen died. For patients who either provided paired sera or who died, 24 of 197 (12.2%) had atypical pathogens detected.

CONCLUSIONS

Despite vigorous study methods, atypical pathogens were uncommon in our hospitalized population. A second concurrent respiratory pathogen was identified for most patients with atypical pneumonia. Although macrolide use was rare in this patient population, mortality was zero for patients in whom an atypical pathogen was detected, affirming that macrolide-based therapy need not be routine in the therapeutic management of community-acquired pneumonia.

In vitro activities of doxycycline and enrofloxacin against European Chlamydia psittaci strains from turkeys

The in vitro susceptibility of 14 European Chlamydia psittaci strains from turkeys to the antibiotics doxycycline and enrofloxacin was tested. For doxycycline the MIC ranged from 0.05 to 0.2 microg/ml, with an average of 0.1 microg/ml. For enrofloxacin the MIC was 0.25 microg/ml. Acquired resistance was not detected against doxycycline and enrofloxacin.

Chlamydia pneumoniae in acute otitis media

BACKGROUND

Aerobic bacterial pathogens are recovered from 65 to 85% of patients with acute otitis media (AOM). Although Chlamydia pneumoniae is a common pathogen of pediatric pneumonia, it has rarely been cultured from children with chronic otitis media and its role in AOM is unknown.

METHODS

We cultured for C. pneumoniae in tympanocentesis aspirates and nasopharyngeal swabs from 101 consecutive, otherwise healthy children with AOM or refractory AOM. A control group of 50 similarly aged, healthy children was evaluated for nasopharyngeal carriage of C. pneumoniae. Specimens were also evaluated by PCR for C. pneumoniae.

RESULTS

C. pneumoniae was recovered by tympanocentesis in 8 (8%) of 101 children with AOM. Among the 8 children with C. pneumoniae-positive-AOM, 5 had C. pneumoniae detected by PCR in middle ear fluid, none had C. pneumoniae recovered by nasopharyngeal culture or PCR and 5 were younger than 16 months. C. pneumoniae was the sole pathogen isolated in 2 patients. Copathogens included beta-lactamase-positive positive Haemophilus influenzae (2), beta-lactamase positive Moraxella catarrhalis (1), penicillin-resistant Streptococcus pneumoniae (2) and penicillin-susceptible S. pneumoniae (1). C. pneumoniae was recovered from nasopharyngeal culture in 2 additional patients with C. pneumoniae-negative AOM and in none of 50 healthy control children, although 2 controls were positive by PCR from the nasopharynx.

CONCLUSIONS

This is the first study to report the isolation of C. pneumoniae in middle ear fluid of children with AOM.

Future indications for macrolides

The antimicrobial spectrum of azithromycin and clarithromycin suggests a number of further uses for these newer macrolides. Favorable clinical and bacteriologic responses have been reported with both antibiotics in children with community-acquired pneumonia. Response rates were high for overall patient populations and for subgroups with infection caused by Mycoplasma pneumoniae and Chlamydia pneumoniae. Treatment with azithromycin or clarithromycin has resulted in a reduction in mycobacteremia and an improvement in clinical symptoms in adult AIDS patients with disseminated Mycobacterium avium-intracellulare complex. Prophylactic treatment with azithromycin may prevent M. avium-intracellulare complex, especially when combined with rifabutin. Preliminary evidence suggests that both azithromycin and clarithromycin in multidrug combinations may effectively eradicate Helicobacter pylori and that azithromycin may be useful in treating bacterial gastritis caused by Campylobacter species. Trachoma and infections caused by Bordetella pertussis and Ureaplasma urealyticum are other possible future indications for the newer macrolides. Limited clinical evidence also suggests that azithromycin may be effective in the prevention and treatment of malaria.

In vitro activities of azithromycin and doxycycline against 15 isolates of Chlamydia pneumoniae

Fourteen isolates of Chlamydia pneumoniae, 12 from clinically ill patients and 2 from subjectively healthy individuals from an area within a 400-km proximity of Gävle, Sweden, and strain IOL-207, originally from the eye of an Iranian child, were tested for susceptibilities to the antibiotics doxycycline and azithromycin. MICs and minimum chlamydiacidal concentrations were found to correlate well with values reported earlier by other investigators. In addition to MIC and minimum chlamydiacidal concentration testing, testing for the viability of C. pneumoniae after exposure to antibiotic concentrations as high as 50 mg/liter was carried out by passaging antibiotic-treated, infected cell cultures four times in the absence of antibiotics. It was found that all Chlamydia strains were viable after four passages, regardless of antibiotic concentration in the cell culture.

Prospective study of epidemiology and prognostic factors in community-acquired pneumonia

Of 342 patients with community-acquired pneumonia, 100 were diagnosed etiologically. In these patients, disease epidemiology, prognostic factors, and influence of antibiotic treatment were analyzed prospectively. Fifty-two patients were treated with a broad-spectrum antibiotic (ceftriaxone), and 48 received a medium-spectrum antibiotic (cefuroxime); some patients in each group also received erythromycin. Streptococcus pneumoniae was the most frequently isolated microorganism (43%), followed by Chlamydia pneumoniae (21%), Haemophilus influenzae (19%), and Mycoplasma pneumoniae (11%). Factors significantly associated with increased mortality were initially critical or poor clinical condition, involvement of two or more lobules, and complications. Prior administration of antibiotics was predictive of penicillin and erythromycin resistance in Streptococcus pneumoniae, but had no effect on the course of the disease. Eight patients died, 89 were cured, and three had recurrences; there was no significant difference in outcome between treatment groups, regardless of whether patients also received erythromycin. Increased knowledge of epidemiological, predictive, and prognostic factors can significantly improve early diagnosis of community-acquired pneumonia and facilitate the choice of appropriate antibiotic treatment, thereby helping to reduce morbidity and mortality.

In vitro activities of azithromycin, clarithromycin, erythromycin, and tetracycline against 13 strains of Chlamydia pneumoniae

Thirteen strains of Chlamydia pneumoniae were evaluated for their in vitro susceptibilities to azithromycin, clarithromycin, erythromycin, and tetracycline. The MIC ranges were 0.125 to 0.5 micrograms/ml for azithromycin, 0.031 to 1.0 micrograms/ml for clarithromycin, 0.125 to 1.0 micrograms/ml for erythromycin, and 0.25 to 1.0 micrograms/ml for tetracycline. The ranges for the minimal lethal concentrations were 0.125 to 0.5 micrograms/ml for azithromycin, 0.031 to 1.0 micrograms/ml for clarithromycin, 0.125 to 1.0 micrograms/ml for erythromycin, and 0.25 to 1.0 micrograms/ml for tetracycline. Clarithromycin and azithromycin were the most active antibiotics against C. pneumoniae in vitro.

Persistent Chlamydia pneumoniae infection in a Swedish family

Chlamydia pneumoniae, an etiological agent for respiratory tract infection, was found as a cause of persistent infection in a family group. During the observation period of 2 1/2 years, serology and polymerase chain reaction for C. pneumoniae demonstrated a failure to eradicate the organism, despite several prolonged courses of antibiotics known to be effective against chlamydia species.