Treatment of Chlamydia trachomatis with a small molecule inhibitor of the Yersinia type III secretion system disrupts progression of the chlamydial developmental cycle

The obligate intracellular bacterium Chlamydia trachomatis possesses a biphasic developmental cycle that is manifested by differentiation of infectious, metabolically inert elementary bodies (EBs) to larger, metabolically active reticulate bodies (RBs). The cycle is completed by asynchronous differentiation of dividing RBs back to a population of dormant EBs that can initiate further rounds of infection upon lysis of the host cell. Chlamydiae express a type III secretion system (T3SS) that is presumably employed to establish and maintain the permissive intracellular niche by secretion of anti-host proteins. We hypothesize that T3SS activity is essential for chlamydial development and pathogenesis. However, the lack of a genetic system has confounded efforts to establish any role of the T3SS. We therefore employed the small molecule Yersinia T3SS inhibitor N'-(3,5-dibromo-2-hydroxybenzylidene)-4-nitrobenzohydrazide, designated compound 1 (C1), to examine the interdependence of the chlamydial T3SS and development. C1 treatment inhibited C. trachomatis but not T4SS-expressing Coxiella burnetii development in a dose-dependent manner. Although chlamydiae remained viable and metabolically active, they failed to divide significantly and RB to EB differentiation was inhibited. These effects occurred in the absence of host cell cytotoxicity and were reversible by washing out C1. We further demonstrate that secretion of T3S substrates is perturbed in C1-treated chlamydial cultures. We have therefore provided evidence that C1 can inhibit C. trachomatis development and T3SS activity and present a model in which progression of the C. trachomatis developmental cycle requires a fully functional T3SS.

Lateral gene transfer in vitro in the intracellular pathogen Chlamydia trachomatis

Genetic recombinants that resulted from lateral gene transfer (LGT) have been detected in sexually transmitted disease isolates of Chlamydia trachomatis, but a mechanism for LGT in C. trachomatis has not been described. We describe here a system that readily detects C. trachomatis LGT in vitro and that may facilitate discovery of its mechanisms. Host cells were simultaneously infected in the absence of antibiotics with an ofloxacin-resistant mutant and a second mutant that was resistant to lincomycin, trimethoprim, or rifampin. Selection for doubly resistant C. trachomatis isolates in the progeny detected apparent recombinant frequencies of 10(-4) to 10(-3), approximately 10(4) times more frequent than doubly resistant spontaneous mutants in progeny from uniparental control infections. Polyclonal doubly resistant populations and clones isolated from them in the absence of antibiotics had the specific resistance-conferring mutations present in the parental mutants; absence of the corresponding normal nucleotides indicated that they had been replaced by homologous recombination. These results eliminate spontaneous mutation, between-strain complementation, and heterotypic resistance as general explanations of multiply resistant C. trachomatis that originated in mixed infections in our experiments and demonstrate genetic stability of the recombinants. The kind of LGT we observed might be useful for creating new strains for functional studies by creating new alleles or combinations of alleles of polymorphic loci and might also disseminate antibiotic resistance genes in vivo. The apparent absence of phages and conjugative plasmids in C. trachomatis suggests that the LGT may have occurred by means of natural DNA transformation. Therefore, the experimental system may have implications for genetically altering C. trachomatis by means of DNA transfer.

Efficacy of an immune modulator in experimental Chlamydia trachomatis infection of the female genital tract

Objective. The aim of this study was to determine if vaginal application of the immune response modifier imiquimod (Aldara cream, 3M Pharmaceuticals, St Paul, Minn) would alter the course and/or outcome of female genital tract infection with a human isolate of Chlamydia trachomatis in a murine model. Methods. Groups of CF-1 mice were treated with Aldara on three different schedules: (1) ongoing beginning 5 days prior to and continuing through day 5 of infection; (2) a single prophylactic dose 2 hours prior to infection; and (3) therapeutic from day 4 to day 14 of infection. Mice were infected vaginally with a serovar D strain of C trachomatis, and monitored by culture to determine the level of shedding and duration of infection. Results. We observed a significant reduction in both duration of infection and the level of shedding during the acute phase in mice treated on an ongoing basis commencing 5 days prior to infection. There was no effect with respect to the other regimens. Conclusion. These results demonstrate that ongoing Aldara treatment has efficacy and may enhance local innate immunity which reduces the duration of subsequent infection with human isolates of C trachomatis in a murine model of female genital tract infection.

The effect of penicillin on Chlamydia trachomatis DNA replication

Chlamydia trachomatis L2 was used to infect BGMK cells at an m.o.i. of 1.0, and the developmental cycle was followed by transmission electron microscopy and quantitative PCR (QPCR) for both chromosomal and plasmid DNA. Samples were taken at sequential 6 h time points. Subsequent analysis by QPCR showed that there was an initial slow replication period (0-18 h), followed by a rapid phase (18-36 h) coinciding with exponential division when the DNA doubling time was 4.6 h. Chromosomal DNA was amplified 100-200-fold corresponding to 7-8 generations for the complete developmental cycle. Penicillin (10 and 100 units ml(-1)) was added to cultures at 20 h post-infection (p.i.). This blocked binary fission and also prevented reticulate body (RB) to elementary body transition. However, exposure to penicillin did not prevent chromosomal or plasmid DNA replication. After a short lag period, following the addition of penicillin, chlamydial chromosomal DNA replication resumed at the same rate as in control C. trachomatis-infected cells. C. trachomatis-infected host cells exposed to penicillin did not lyse, but instead harboured large, aberrant RBs in massive inclusions that completely filled the cell cytoplasm. In these RBs, the DNA continued to replicate well beyond the end of the normal developmental cycle. At 60 h p.i. each aberrant RB contained a minimum of 16 chromosomal copies.

A small-molecule inhibitor of type III secretion inhibits different stages of the infectious cycle of Chlamydia trachomatis

The intracellular pathogen Chlamydia trachomatis possesses a type III secretion (TTS) system believed to deliver a series of effector proteins into the inclusion membrane (Inc-proteins) as well as into the host cytosol with perceived consequences for the pathogenicity of this common venereal pathogen. Recently, small molecules were shown to block the TTS system of Yersinia pseudotuberculosis. Here, we show that one of these compounds, INP0400, inhibits intracellular replication and infectivity of C. trachomatis at micromolar concentrations resulting in small inclusion bodies frequently containing only one or a few reticulate bodies (RBs). INP0400, at high concentration, given at the time of infection, partially blocked entry of elementary bodies into host cells. Early treatment inhibited the localization of the mammalian protein 14-3-3beta to the inclusions, indicative of absence of the early induced TTS effector IncG from the inclusion membrane. Treatment with INP0400 during chlamydial mid-cycle prevented secretion of the TTS effector IncA and homotypic vesicular fusions mediated by this protein. INP0400 given during the late phase resulted in the detachment of RBs from the inclusion membrane concomitant with an inhibition of RB to elementary body conversion causing a marked decrease in infectivity.

Different growth rates of Chlamydia trachomatis biovars reflect pathotype

BACKGROUND

Despite small genomic differences, Chlamydia trachomatis biovars exhibit diverse disease manifestations and different growth rates in vivo and in cell culture models.

METHODS

Chlamydial inclusion-forming units were enumerated over time in HeLa cells, to evaluate the length of the developmental cycle for C. trachomatis strains A, B, C, and E/Bour (ocular strains) as well as D, E/UW5/Cx, F, and L2 (genital strains). Prototype strains A, D, and L2 were selected for detailed analysis of reticulate body growth, division, and genomic replication. The impact that changing host cells and that coinfection with different strains has on growth was also assessed.

RESULTS

The genital strains completed the developmental cycle in 36-44 h, whereas the ocular strains lagged behind considerably. Differences were the result of a longer lag phase (entry plus differentiation) and generation time for the ocular strains. A prototype ocular strain grew faster in conjunctival cells than in cervical cells. Coinfection with genital (D or L2) and ocular strains expedited recovery of the ocular strain.

CONCLUSIONS

Precise temporal evaluation of the chlamydial developmental cycle for selected genital and ocular C. trachomatis biovars provides a means for investigating genomic differences that define chlamydial pathotype.

Preclinical safety and efficacy assessments of dendrimer-based (SPL7013) microbicide gel formulations in a nonhuman primate model

Three gel formulations (1%, 3%, and 5% [wt/wt]) of SPL7013, a dendrimer known to have antiviral (anti-human immunodeficiency virus and anti-herpes simplex virus) activities, completed a range of preclinical tests in the pigtailed macaque models for vaginally and rectally applied topical microbicide safety assessments. The vaginal safety profile of the 3% SPL7013 gel formulation was equal to that of the 1% formulation but was superior to that of the 5% formulation. The 3% SPL7013 gel was further evaluated for rectal safety and for antichlamydial efficacy with cervical challenge with Chlamydia trachomatis. This first-generation dendrimer-based product was shown to be safe to the vaginal and rectal microenvironments with repeated daily use. However, a single intravaginal application of the 3% (wt/wt) SPL7013 gel did not provide protection from the acquisition of cervical chlamydial infection.

Development potential of rifalazil and other benzoxazinorifamycins

Rifalazil and other benzoxazinorifamycins (new chemical entities [NCEs]) are rifamycins that contain a distinct planar benzoxazine ring. Rifalazil has excellent antibacterial activity, high intracellular levels and high tissue penetration, which are attributes that favour its use in treating diseases caused by the obligate intracellular pathogens of the genus Chlamydia. Recent studies have shown that rifalazil has efficacy in the treatment of human sexually transmitted disease caused by Chlamydia trachomatis. The extraordinary potency of rifalazil and other NCEs, such as ABI-0043, extends to the related microorganism, C. pneumoniae, a respiratory pathogen that can disseminate and persist chronically in the vasculature, resulting in increased plaque formation in animal studies. A pivotal clinical trial with rifalazil has been initiated for the treatment of peripheral arterial disease. Other opportunities include gastric ulcer disease caused by Helicobacter pylori and antibiotic-associated colitis caused by infection with Clostridium difficile in the colon. The NCEs could prove to be valuable as follow-on compounds in these indications, as rifampin replacements in antibacterial combination therapy or as stand-alone topical antibacterials (e.g., to treat acne). Neither rifalazil nor NCEs appear to induce the cytochrome P450 3A4, an attribute of rifampin that can result in adverse events due to drug-drug interactions.

In vivo and in vitro studies of Chlamydia trachomatis TrpR:DNA interactions

We previously reported that Chlamydia trachomatis expresses the genes encoding tryptophan synthase (trpBA) and the tryptophan repressor (trpR). Here we employ primer extension analysis to identify the transcriptional origins of both trpR and trpBA, allowing for the identification of the putative operator sequences for both trpR and trpBA. Moreover we demonstrate that native recombinant chlamydial TrpR binds to the predicted operator sequence upstream of trpR. A restriction endonuclease protection assay was designed and used to demonstrate that 5-fluorotryptophan was the only tryptophan analogue capable of activating binding of native recombinant chlamydial TrpR to its operator. Additionally, 5-fluorotryptophan was the only analogue that repressed expression of trpBA at a level analogous to L-tryptophan itself. Based on these findings, a mutant selection protocol was designed and a C. trachomatis isolate containing a frameshift mutation in trpR was isolated. This chlamydial mutant synthesizes a truncated TrpR protein that cannot regulate expression of trpBA and trpR in response to changes in tryptophan levels. These findings provide the first genetic proof that TrpR acts as a negative regulator of transcription in C. trachomatis.

Effects of sustained antibiotic bactericidal treatment on Chlamydia trachomatis-infected epithelial-like cells (HeLa) and monocyte-like cells (THP-1 and U-937)

Chlamydia trachomatis is a human pathogen that causes multiple diseases worldwide. Despite appropriate therapy with existing antichlamydial antibiotics, chronic exacerbated diseases often occur and lead to serious sequelae. Since C. trachomatis has been found to enter a persistent state after exposure to deleterious conditions, the role of persistence in the failure of chlamydial antibiotherapy is questioned. HeLa, THP-1 and U-937 cells were infected with 10(4)C. trachomatis serovar L2 infectious particles. Three days later the infected cells were treated with minimal bactericidal concentrations of doxycycline (DOX), erythromycin (ERY) or tetracycline (TET) for 24 days or 30 days. Antibiotic efficacy was assessed by measuring chlamydial inclusions and infectious particles, by investigating the resumption of chlamydial growth after antibiotic removal and by testing Chlamydia viability using reverse transcriptase polymerase chain reaction targeting unprocessed 16S rRNA, processed 16S rRNA and Omp-1 mRNA. Treatment of infected HeLa cells with the usual antichlamydial antibiotics suppressed chlamydial active growth. The infection remained unapparent. However, 24 days post treatment the bacterium was found to be viable, as proved by continued expression of unprocessed and processed 16S rRNA and Omp-1 mRNA. This inactive unapparent chlamydial state is not infectious, suggesting Chlamydia persistence. Chlamydia trachomatis also developed persistence both in permissive THP-1 and non-permissive U-937 cells. Unlike in HeLa cells, persistent chlamydial infection in THP-1 and U-937 cells was resolved after 30 days of DOX treatment. Of interest, we noticed that only THP-1 and U-937 cells that were persistently infected following their interaction with infected HeLa cells remained capable of transmitting active infection to HeLa cells. These findings suggest that DOX, TET and ERY, usually administered to combat chlamydial diseases, fail to resolve persistent infection occurring during treatment in non-immune HeLa cells. However, in immune THP-1 and U-937 cells, the persistent infection is resolved by therapy with DOX. Epithelial cells could be the reservoir of persistent chlamydial particles.

Inhibition of chlamydiae by primary alcohols correlates with the strain-specific complement of plasticity zone phospholipase D genes

Members of the genus Chlamydia are obligate intracellular pathogens that have a unique biphasic developmental cycle and interactions with host cells. Many genes that dictate host infection tropism and, putatively, pathogenic manifestations of disease are clustered in a hypervariable region of the genome termed the plasticity zone (PZ). Comparative genomics studies have determined that an uncharacterized family of PZ genes encoding orthologs of eukaryotic and prokaryotic members of the phospholipase D (PLD) enzyme family varies among chlamydiae. Here, we show that the PZ PLD (pzPLD) of Chlamydia trachomatis are transcribed during both normal and persistent infection and that the corresponding PLD proteins are predominantly localized in reticulate bodies on the inner leaflet of the inclusion membrane. Further, we show that strains of chlamydiae encoding the pzPLD, but not a strain lacking these genes, are inhibited by primary alcohols, potent PLD inhibitors, during growth in HeLa 229 cells. This inhibitory effect is amplified approximately 5,000-fold during recovery from persistent infection. These findings suggest that the chlamydial pzPLD may be important, strain-specific, pathogenesis factors in vivo.

An Observational Cohort Study of Chlamydia trachomatis Treatment in Pregnancy

BACKGROUND AND OBJECTIVES

Currently, azithromycin is not considered a first-line treatment for Chlamydia trachomatis in pregnant women. We evaluated the use, efficacy, and safety of azithromycin compared with erythromycin and amoxicillin in the treatment of genital chlamydial infection during pregnancy.

METHODS

This was a retrospective cohort study of pregnant women with genital chlamydial infection. Data on antibiotics prescribed, test-of-cure (TOC) results, and maternal and infant complications were collected from medical records.

RESULTS

Of the 277 women in the study sample, 69% were initially prescribed azithromycin, 9% amoxicillin, and 19% erythromycin. Eight-one percent of subjects had a TOC 7 or more days after diagnosis and before delivery. Treatment efficacy, as defined by a negative TOC, was 97% (95% confidence interval [CI], 92.9-99.2) for azithromycin, 95% (95% CI, 76.2-99.9) for amoxicillin, and 64% (95% CI, 44.1-81.4) for erythromycin. The efficacy of azithromycin was significantly higher than erythromycin (P < 0.0001). There were no significant differences in efficacy by age, race/ethnicity, concurrent sexually transmitted disease diagnosis, partner treatment, or substance use. Furthermore, there was no difference in complications for women or infants exposed to azithromycin compared with those treated with other regimens.

CONCLUSION

Clinical outcome data from this study population of women and infants support both efficacy and safety of azithromycin for treatment of C. trachomatis in pregnancy.

Impact of mass distribution of azithromycin on the antibiotic susceptibilities of ocular Chlamydia trachomatis

In a community of Tanzania where trachoma is endemic, we cultured conjunctival swabs from all residents who had active trachoma and were PCR positive for ocular Chlamydia trachomatis, both before (43 isolates) and 2 months after (9 isolates) mass antibiotic treatment. No clinically or programmatically significant increase in azithromycin or tetracycline resistance was observed.

Activities of rifamycin derivatives against wild-type and rpoB mutants of Chlamydia trachomatis

Rifalazil, a semisynthetic rifamycin, was shown previously to have exceptional potency against Chlamydia trachomatis (MIC of 0.00025 microg/ml). We therefore tested 250 additional rifamycin derivatives and identified 12 with activities that are eightfold more potent than that of rifalazil. These compounds also showed exceptional activities against rifampin-resistant strains that carry missense mutations in the rpoB gene. The antimicrobial potency and intracellular penetration of these agents suggest their potential in treatment of chlamydial infections.

[Inhibitory impacts of Niaoluqing on urogenital Chlamydia trachomatis in vitro]

OBJECTIVE

To explore the inhibitory effects of Niaoluqing, an oral liquid of traditional Chinese medicine, on the growth of urogenital chlamydia trachomatis (Ct).

METHODS

Niaoluqing's applying concentration was 1 g/ml and 10 serologically untyped strains of Ct from the STD clinic were used. And the inhibitory effects of Niaoluqing on Ct was evaluated by McCoy cell microculture technique in vitro.

RESULTS

Niaoluqing had inhibitory activity for urogenital Ct, and was capable of reducing inclusion numbers notably in the concentrations of 50 to 200 mg/ml. The number and volume of Ct inclusions reduced gradually and disappeared finally with the rising of the medicinal concentration.

CONCLUSION

The traditional Chinese medicine Niaoluqing has inhibitory effects on the growth of urogenital Ct.

Therapeutic approaches toChlamydiainfections

Chlamydia trachomatis ocular and urogenital infections represent major public health problems, whereas Chlamydophila pneumoniae is a common aetiological agent of community-acquired pneumonia. The obligate intracellular lifestyle of these established pathogens poses challenges to both their diagnosis and treatment. Tetracyclines, macrolides and quinolones remain the antimicrobials of choice for the treatment of infections due to Chlamydiaceae.

Biological activity assessment of a novel contraceptive antimicrobial agent

Microbicides are a new category of compounds being developed as a prophylactic approach for the prevention of transmission of sexually transmitted diseases (STDs), including the human immunodeficiency virus (HIV). These are primarily being developed as women-controlled methods, with the target of designing new compounds or formulations that can be used without the knowledge of a male partner. Microbicide screening can be initially based on their hyaluronidase-inhibiting (HI) activity, as this enzyme plays a major role in the sperm and microbe penetration into the substrate. Derivatives of hesperidin, a citrus flavonoid glycoside, have been reported in the literature for their HI effects. Hesperidin was thereby sulphonated under strictly controlled conditions and the active fraction isolated and characterized, based on its HI activity. This derivative was screened for antimicrobial and enzyme-inhibitory activities, specifically for the reproductive tract. Sulphonated hesperidin (SH) was found to completely inhibit the sperm enzymes hyaluronidase, giving an indication toward its contraceptive effects. It was also been found to inhibit various sexually transmitted pathogens, including Chlamydia trachomatis, Neisseria gonorrhoea, HIV, and Herpes Simplex virus type 2 (HSV-2). Its safety assessment was based on its noninterference in sperm motility and its penetration through the cervical mucus, and no effect on the growth of lactobacilli, the normal vaginal flora. It was also found to be nontoxic to the HIV substrate cells (MT2 cells). The study concludes that sulphonated hesperidin can be developed as a potential microbicide for a dual prophylaxis of contraception and transmission of STDs and AIDS.

Serotonin and melatonin, neurohormones for homeostasis, as novel inhibitors of infections by the intracellular parasite chlamydia

OBJECTIVES

Chlamydiae are obligate intracellular bacteria, causing a variety of diseases, i.e. pneumonia, sexually transmitted disease, conjunctivitis and zoonosis. Tryptophan depletion by interferon-gamma (IFN-gamma) is the most important host defence system against chlamydial infection. Thus chlamydial tryptophan metabolism is thought to play key roles for IFN-gamma resistance, persistent infection and host/tissue tropisms. We tested tryptophan derivatives for activity against chlamydia-infected cells.

METHODS

Rates of chlamydial infection and sizes of the inclusions were evaluated by in vitro infection using three Chlamydiaceae species, Chlamydia trachomatis, Chlamydophila pneumoniae and Chlamydophila felis, which show significant divergence of tryptophan synthesis genes and different susceptibilities to IFN-gamma.

RESULTS

Melatonin and serotonin, which are recognized as neural hormones for maintenance of organism homeostasis, reduced chlamydial infection but not other bacterial growth tested here. Unlike IFN-gamma, melatonin limited infection of all three chlamydiae and the effects were not recovered by tryptophan supplementation. Melatonin treatment only of host cells could diminish infection and the infection reduction was neutralized by a pertussis toxin, an inhibitor of G proteins. Ligands of melatonin and serotonin receptors also hampered infection.

CONCLUSIONS

Inhibition mechanisms of chlamydial infection by melatonin and serotonin appear to be different from those of IFN-gamma and involve specific G-protein-coupled receptors. Melatonin is deemed to inhibit early progression of the chlamydial development cycle, such as establishment of intracellular infection and/or conversion from elementary body to reticulate body. Utilization of melatonin, serotonin or their derivatives may be advantageous for harmless prevention of chlamydial infection.

Characterization of Chlamydia MurC-Ddl, a fusion protein exhibiting D-alanyl-D-alanine ligase activity involved in peptidoglycan synthesis and D-cycloserine sensitivity

Recent characterization of chlamydial genes encoding functional peptidoglycan (PG)-synthesis proteins suggests that the Chlamydiaceae possess the ability to synthesize PG yet biochemical evidence for the synthesis of PG has yet to be demonstrated. The presence of D-amino acids in PG is a hallmark of bacteria. Chlamydiaceae do not appear to encode amino acid racemases however, a D-alanyl-D-alanine (D-Ala-D-Ala) ligase homologue (Ddl) is encoded in the genome. Thus, we undertook a genetics-based approach to demonstrate and characterize the D-Ala-D-Ala ligase activity of chlamydial Ddl, a protein encoded as a fusion with MurC. The full-length murC-ddl fusion gene from Chlamydia trachomatis serovar L2 was cloned and placed under the control of the arabinose-inducible ara promoter and transformed into a D-Ala-D-Ala ligase auxotroph of Escherichia coli possessing deletions of both the ddlA and ddlB genes. Viability of the E. coliDeltaddlADeltaddlB mutant in the absence of exogenous D-Ala-D-Ala dipeptide became dependent on the expression of the chlamydial murC-ddl thus demonstrating functional ligase activity. Domain mapping of the full-length fusion protein and site-directed mutagenesis of the MurC domain revealed that the structure of the full fusion protein but not MurC enzymatic activity was required for ligase activity in vivo. Recombinant MurC-Ddl exhibited substrate specificity for D-Ala. Chlamydia growth is inhibited by D-cycloserine (DCS) and in vitro analysis provided evidence for the chlamydial MurC-Ddl as the target for DCS sensitivity. In vivo sensitivity to DCS could be reversed by addition of exogenous D-Ala and D-Ala-D-Ala. Together, these findings further support our hypothesis that PG is synthesized by members of the Chlamydiaceae family and suggest that D-amino acids, specifically D-Ala, are present in chlamydial PG.

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.

In vitro inhibitory effects of hinokitiol on proliferation of Chlamydia trachomatis

The inhibitory effects of hinokitiol (beta-thujaplicin) on Chlamydia trachomatis D/UW-3/Cx were shown by MIC, minimum lethal concentration (MLC), and preinoculation minimal microbicidal concentration assays using HeLa 229 cells. The MIC and the MLC were both 32 microg/ml. Further evaluation of hinokitiol as a topical agent against C. trachomatis is warranted.

Biosynthesized tea polyphenols inactivate Chlamydia trachomatis in vitro

Biosynthesized tea polyphenols showed antichlamydial activity against Chlamydia trachomatis D/UW-3/Cx and L2/434/Bu using cell culture. The most active compounds were (-)-epigallocatechin gallate and (-)-epicatechin gallate, followed by (-)-epicatechin (EC). (+)-Epicatechin and (-)-epigallocatechin were intermediate. EC was the least toxic. These results warrant evaluation of tea polyphenols as topical antichlamydial agents.

A cumulative experience examining the effect of natural and synthetic antimicrobial peptides vs. Chlamydia trachomatis

We tested the activity of 48 structurally diverse antimicrobial peptides against Chlamydia trachomatis, serovar L2. The peptides' activity against C. trachomatis, serovar L2 was measured in 48-h McCoy cell shell vial assays. Peptides of 16-20 amino acids were more active than larger peptides, such as defensins. Beta-sheet protegrins, as well as alpha-helical peptides such as novispirin (G-10) were equally active. Enantiomers were as active as native structures. Moderate-sized circular mini-defensins were less effective against C. trachomatis. Moderate-sized cationic peptides may be useful in microbicide preparations designed to prevent chlamydial infection.

Chlamydia trachomatis survival in the presence of two fluoroquinolones (lomefloxacin versus levofloxacin) in patients with chronic prostatitis syndrome

Fluoroquinolones are recommended in the therapy of chronic prostatitis. Chlamydia trachomatis is one of the possible aetiological agents of chronic prostatitis. However, little is known about chlamydia survival in the presence of fluoroquinolones in patients with chronic prostatitis syndrome. For the first time, chlamydia survival in vitro in the presence of lomefloxacin (LOMX) (mostly recommended in the treatment of chronic prostatitis) versus levofloxacin (LVFX) (recommended in the therapy against chlamydia infection) is examined and analysed in the 33 chlamydia-infected patients with chronic prostatitis syndrome in this study. Antichlamydial activity in vitro of LOMX in patients with C. trachomatis and prostatitis was found to be more effective than LVFX. However, further clinical trials for these agents are recommended.

Growth cycle-dependent pharmacodynamics of antichlamydial drugs

Chlamydiae are obligate intracellular pathogens that exhibit an extensive intracellular developmental cycle in vivo. Clinical treatment of chlamydial infection is typically initiated upon occurrence of symptomatology and is directed against an asynchronous population of different chlamydial developmental forms. Pharmacodynamics of antichlamydial drugs are predominantly characterized by MICs; however, in vitro determinations of MIC may not reflect differential susceptibilities of the developmental cycle. In this study, we correlated the antichlamydial effect of erythromycin, rifampin, doxycycline, and ciprofloxacin with the developmental stage of a fast-replicating and a slow-replicating chlamydial species. In addition, we describe the influence of concentration on killing. Extracellular elementary bodies and very-early-phase and late-phase chlamydiae were refractory to all tested antibiotics except rifampin, which was very effective against early-cycle chlamydiae. Rifampin was the most effective antibiotic overall, killed in a dose dependent matter, and exhibited moderate synergism with erythromycin. These considerations provide important information on chlamydial biology and antimicrobial susceptibility. A combinational therapy of rifampin and a macrolide should be considered in therapy-refractory infections.