In vitro susceptibility of urogenital Chlamydia trachomatis strains in a country with high azithromycin consumption rate

Therapeutic Options for Chlamydia trachomatis Infection: Present and Future

Sexually transmitted infections (STIs), such as Chlamydia trachomatis (Ct) infection, have serious consequences for sexual and reproductive health worldwide. Ct is one of the most common sexually transmitted bacterial infections in the world, with approximately 129 million new cases per year. C. trachomatis is an obligate intracellular Gram-negative bacterium. The infection is usually asymptomatic, notwithstanding, it could also be associated with severe sequels and complications, such as chronic pain, infertility, and gynecologic cancers, and thus there is an urgent need to adequately treat these cases in a timely manner. Consequently, beyond its individual effects, the infection also impacts the economy of the countries where it is prevalent, generating a need to consider the hypothesis of implementing Chlamydia Screening Programs, a decision that, although it is expensive to execute, is a necessary investment that unequivocally will bring financial and social long-term advantages worldwide. To detect Ct infection, there are different methodologies available. Nucleic acid amplification tests, with their high sensitivity and specificity, are currently the first-line tests for the detection of Ct. When replaced by other detection methods, there are more false negative tests, leading to underreported cases and a subsequent underestimation of Ct infection's prevalence. Ct treatment is based on antibiotic prescription, which is highly associated with drug resistance. Therefore, currently, there have been efforts in line with the development of alternative strategies to effectively treat this infection, using a drug repurposing method, as well as a natural treatment approach. In addition, researchers have also made some progress in the Ct vaccine development over the years, despite the fact that it also necessitates more studies in order to finally establish a vaccination plan. In this review, we have focused on the therapeutic options for treating Ct infection, expert recommendations, and major difficulties, while also exploring the possible avenues through which to face this issue, with novel approaches beyond those proposed by the guidelines of Health Organizations.

Nationwide surveillance of the antimicrobial susceptibility of Chlamydia trachomatis from male urethritis in Japan: Comparison with the first surveillance report

The Urogenital Sub-committee and the Surveillance Committee of the Japanese Society of Chemotherapy, The Japanese Association for Infectious Diseases, and the Japanese Society for Clinical Microbiology conducted the second nationwide surveillance of the antimicrobial susceptibility of Chlamydia trachomatis. In this second surveillance study, clinical urethral discharge specimens were collected from patients with urethritis in 26 hospitals and clinics from May 2016 to July 2017. Based on serial cultures, the minimum inhibitory concentration (MIC) could be determined for 41 isolates; the MICs (MIC₉₀) of ciprofloxacin, levofloxacin, tosufloxacin, sitafloxacin, doxycycline, minocycline, erythromycin, clarithromycin, azithromycin and solithromycin were 2 μg/ml (2 μg/ml), 1 μg/ml (0.5 μg/ml), 0.25 μg/ml (0.25 μg/ml), 0.125 μg/ml (0.063 μg/ml), 0.125 μg/ml (0.125 μg/ml), 0.25 μg/ml (0.25 μg/ml), 0.031 μg/ml (0.031 μg/ml), 0.25 μg/ml (0.125 μg/ml), and 0.016 μg/ml (0.008 μg/ml), respectively. In summary, this surveillance project did not identify any strains resistant to fluoroquinolone, tetracycline, or macrolide agents in Japan. In addition, the MIC of solithromycin was favorable and lower than that of other antimicrobial agents. However, the MIC of azithromycin had a slightly higher value than that reported in the first surveillance report, though this might be within the acceptable margin of error. Therefore, the susceptibility of azithromycin, especially, should be monitored henceforth.

Chlamydial clinical isolates show subtle differences in persistence phenotypes and growth in vitro

Urogenital Chlamydia trachomatis infection is the most common sexually transmitted bacterial infection throughout the world. While progress has been made to better understand how type strains develop and respond to environmental stress in vitro, very few studies have examined how clinical isolates behave under similar conditions. Here, we examined the development and persistence phenotypes of several clinical isolates, to determine how similar they are to each other, and the type strain C. trachomatis D/UW-3/Cx. The type strain was shown to produce infectious progeny at a higher magnitude than each of the clinical isolates, in each of the six tested cell lines. All chlamydial strains produced the highest number of infectious progeny at 44 h post-infection in the McCoy B murine fibroblast cell line, yet showed higher levels of infectivity in the MCF-7 human epithelial cell line. The clinical isolates were shown to be more susceptible than the type strain to the effects of penicillin and iron deprivation persistence models in the MCF-7 cell line. While subtle differences between clinical isolates were observed throughout the experiments conducted, no significant differences were identified. This study reinforces the importance of examining clinical isolates when trying to relate in vitro data to clinical outcomes, as well as the importance of considering the adaptations many type strains have to being cultured in vitro.

Azithromycin in the treatment of rectogenital Chlamydia trachomatis infections: end of an era?

INTRODUCTION

Azithromycin was recommended as the first-line therapeutic regimen for treatment of genital infections in men and women by the Centers for Disease Control in 1998. A series of studies of azithromycin for treatment of rectal chlamydial infection in men who have sex with men (MSM) found that azithromycin was significantly less effective than doxycycline.

AREAS COVERED

Literature on treatment of rectal C. trachomatis from 2000 through May 2020 was searched using PubMed. Retrospective and observational studies were identified documenting the frequency and treatment of rectal chlamydial infection in MSM, heterosexual men and women that reported lower efficacy of single-dose azithromycin compared to doxycycline. Literature on possible reasons for the lower efficacy were also reviewed including studies of antibiotic resistance, impact of organism load, and persistent infection in rectal specimens and pharmacokinetics and pharmacodynamics of azithromycin in rectal tissue.

EXPERT OPINION

The available data suggests that single-dose azithromycin is not as effective as azithromycin for the treatment of rectal infection in MSM and women. Most of these data have been retrospective or from observational studies. Final recommendations will depend on the outcome of prospective, randomized, treatment studies. We may also need to examine other dosage regimens for azithromycin.

Urogenital chlamydia trachomatis treatment failure with azithromycin: A meta-analysis

Background

Chlamydia Trachomatis is one of the most common pathogens transmitted through the genital tract in humans that leads to urogenital infection.

Objective

Given the high prevalence of chlamydia infection and its adverse effects on the health of women and men, the present meta-analysis was conducted to determine the rate of treatment failure with azithromycin.

Materials and Methods

Databases including MEDLINE, ISI - Web of Science, PubMed, EMBASE, Scopus, ProQuest, and Science Direct were searched for articles published between 1991 and 2018. The quality of the selected articles was assessed using the Cochrane risk of bias assessment tool. Heterogeneity was determined using the I2 and Cochrane Q-Test. Subgroup analysis and meta-regression were used to compare the prevalence rates on different levels of the variables.

Results

A total of 21 articles that met the inclusion criteria were ultimately assessed. The pooled estimate of azithromycin failure rate was 11.23% (CI 95%: 8.23%-14.24%). Also, the azithromycin failure rate was 15.87% (CI 95%: 10.20%-21.54%) for the treatment of urethritis, 7.41% (CI 95%: 0.60%-14.22%) for cervicitis, and 7.14% (CI 95%: 10.90%-3.39%) for genital chlamydia. The pooled estimate of failure rate difference was 2.37% (CI 95%: 0.68%-4.06%), which shows that azithromycin has a higher failure rate in the treatment of chlamydia compared to doxycycline and other examined medications. The meta-regression results showed that the patient's age contributes significantly to the heterogeneity for azithromycin treatment failure rate (β░=░0.826; p░=░0.017).

Conclusion

Azithromycin has a higher failure rate than doxycycline and other studied medications in treating urogenital chlamydia infections.

Phenotypic antimicrobial susceptibility testing of Chlamydia trachomatis isolates from patients with persistent or successfully treated infections

Objectives

Antimicrobial susceptibility data for Chlamydia trachomatis are lacking. Methodologies for susceptibility testing in C. trachomatis are not well-defined, standardized or performed routinely owing to its intracellular growth requirements. We sought to develop an assay for the in vitro susceptibility testing of C. trachomatis isolates from two patient cohorts with different clinical outcomes.

Methods

Twenty-four clinical isolates (11 from persistently infected and 13 from successfully treated patients) were overlaid with media containing two-fold serial dilutions of azithromycin or doxycycline. After incubation, aliquots were removed from the stock inoculum (SI) and each antimicrobial concentration for total RNA extraction, complementary DNA generation and real-time PCR. The MIC was defined as the lowest antimicrobial concentration where a 95% reduction in transcription was evident in comparison with the SI for each isolate.

Results

MICs of azithromycin were comparable for isolates from the two patient groups (82% ≤ 0.25 mg/L for persistently infected and 100% ≤ 0.25 mg/L for successfully treated patients). Doxycycline MICs were at least two-fold lower for isolates from the successfully treated patients (53.9% ≤ 0.064 mg/L) than for the persistently infected patients (100% ≥ 0.125 mg/L) (P = 0.006, Fisher's exact test). Overall, 96% of isolates gave reproducible MICs when re-tested.

Conclusions

A reproducible assay was developed for antimicrobial susceptibility testing of C. trachomatis. MICs of azithromycin were generally comparable for the two different patient groups. MICs of doxycycline were significantly higher in the persistently infected patients. However, interpretation of elevated MICs in C. trachomatis is extremely challenging in the absence of breakpoints, or wild-type and treatment failure MIC distribution data.

Antimicrobial Resistance Screening in Chlamydia trachomatis by Optimized McCoy Cell Culture System and Direct qPCR-Based Monitoring of Chlamydial Growth

Obligate intracellular localization of Chlamydia trachomatis (C. trachomatis) complicates antimicrobial sensitivity testing efforts that we are so accustomed to in routine bacteriology. Cell culture systems with immunofluorescence staining, to identify cellular inclusions in the presence of various concentrations of antimicrobial drugs, are still the most pervasive techniques, but more specific and sensitive nucleic acid concentration measuring methods are increasingly being used. Here we describe how to approach antimicrobial susceptibility/resistance screening in C. trachomatis by using a McCoy cell culture system, optimized by a research group from Croatia, and direct qPCR-based monitoring of chlamydial growth, optimized by a research group from Hungary.

Macrolide and fluoroquinolone resistance is uncommon in clinical strains of Chlamydia trachomatis

We analyzed the 23S rRNA, gyrA and parC genes of Chlamydia trachomatis DNAs from men with urethritis and determined microbiological outcomes of an extended-release azithromycin (azithromycin-SR) regimen (2 g once daily for 1 day) and a sitafloxacin regimen (100 mg twice daily for 7 days) for chlamydial urethritis to clarify the macrolide and fluoroquinolone resistance status of clinical strains of C. trachomatis. We amplified the portions of 2 alleles of the 23S rRNA gene and the gyrA and parC genes from C. trachomatis DNAs in 284 first-voided urine specimens from men with chlamydial urethritis by PCR and sequenced their PCR products. We enrolled 369 men with chlamydial urethritis, comprising 314 and 55 treated with the azithromycin-SR regimen and the sitafloxacin regimen, respectively. Alleles 1 and/or 2 of the 23S rRNA gene were analyzed in 162 specimens. No mutations were found in the sequenced regions, including the central portion of domain V. The gyrA and parC genes were analyzed in 118 and 113 specimens, respectively. No amino acid changes were found within the quinolone resistance-determining region of the gyrA gene and in the sequenced region of the parC gene. The microbiological outcomes of the azithromycin-SR and sitafloxacin regimens were assessed in 176 and 30 men, respectively. The eradication rates were 96.0% (95% CI 93.1%-98.9%) for the azithromycin-SR regimen and 100% for the sitafloxacin regimen. Clinical strains of C. trachomatis with macrolide and/or fluoroquinolone resistance would be uncommon, and azithromycin or fluoroquinolone regimens could be recommended as treatments for chlamydial infections.

Azithromycin Treatment Failure for Chlamydia trachomatis Among Heterosexual Men With Nongonococcal Urethritis

BACKGROUND

Three recent prospective studies have suggested that the 1-g dose of azithromycin for Chlamydia trachomatis (Ct) was less effective than expected, reporting a wide range of treatment failure rates (5.8%-22.6%). Reasons for the disparate results could be attributed to geographic or methodological differences. The purpose of this study was to reexamine the studies and attempt to harmonize methodologies to reduce misclassification as a result of false positives from early test-of-cure (TOC) or reinfection as a result of sexual exposure rather than treatment failure.

METHODS

Men who had sex with women, who received 1-g azithromycin under directly observed therapy for presumptive treatment of nongonococcal urethritis with confirmed Ct were included. Baseline screening was performed on urethral swabs or urine, and TOC screening was performed on urine using nucleic acid amplification tests. Posttreatment vaginal sexual exposure was elicited at TOC. Data from the 3 studies were obtained and reanalyzed. Rates of Ct retest positive were examined for all cases, and a sensitivity analysis was conducted to either reclassify potential false positives/reinfections as negative or remove them from the analysis.

RESULTS

The crude treatment failure rate was 12.8% (31/242). The rate when potential false positives/reinfections were reclassified as negative was 6.2% (15/242) or when these were excluded from analysis was 10.9% (15/138).

CONCLUSIONS

In these samples of men who have sex with women with Ct-related nongonococcal urethritis, azithromycin treatment failure was between 6.2% and 12.8%. This range of failure is lower than previously published but higher than the desired World Health Organization's target chlamydia treatment failure rate of < 5%.

Assessing the Need for Routine Screening for Mycoplasma genitalium in the Low-risk Female Population: A Prevalence and Co-infection Study on Women from Croatia

BACKGROUND

There is an ongoing debate regarding possible cost and benefits, but also harm of universal screening for the emerging sexually transmitted pathogen Mycoplasma genitalium.

METHODS

From the initial pool of 8665 samples that were tested, a subset of Chlamydia trachomatis-positive and randomly selected C. trachomatis-negative cervical swabs were further interrogated for M. genitalium by real-time polymerase chain reaction, using a 224 bp long fragment of the glyceraldehyde-3-phosphate dehydrogenase gene.

RESULTS

M. genitalium was detected in 4.8% of C. trachomatis-positive samples and none of C. trachomatis-negative samples. Accordingly, a significant association was shown between M. genitalium and C. trachomatis (P < 0.01), but also between M. genitalium and Mycoplasma hominis infection (P < 0.01).

CONCLUSIONS

Based on the results, routine screening is recommended only for women with one or more identified risk factors. Moreover, younger age does not represent an appropriate inclusion/exclusion criterion for M. genitalium testing in the low-risk female population.

Nationwide surveillance of the antimicrobial susceptibility of Chlamydia trachomatis from male urethritis in Japan

Genital chlamydial infection is a principal sexually transmitted infection worldwide. Chlamydia trachomatis can cause male urethritis, acute epididymitis, cervicitis, and pelvic inflammatory disease as sexually transmitted infections. Fortunately, homotypic resistant C. trachomatis strains have not been isolated to date; however, several studies have reported the isolation of heterotypic resistant strains from patients. In this surveillance study, clinical urethral discharge specimens were collected from patients with urethritis in 51 hospitals and clinics in 2009 and 38 in 2012. Based on serial cultures, the minimum inhibitory concentration (MIC) could be determined for 19 isolates in 2009 and 39 in 2012. In 2009 and 2012, the MICs (MIC90) of ciprofloxacin, levofloxacin, tosufloxacin, sitafloxacin, doxycycline, minocycline, erythromycin, clarithromycin, and azithromycin were 2 μg/ml and 1 μg/ml, 0.5 μg/ml and 0.5 μg/ml, 0.125 μg/ml and 0.125 μg/ml, 0.063 μg/ml and 0.063 μg/ml, 0.125 μg/ml and 0.125 μg/ml, 0.125 μg/ml and 0.125 μg/ml, 0.016 μg/ml and 0.016 μg/ml, and 0.063 μg/ml and 0.063 μg/ml, respectively. In summary, this surveillance project did not identify any resistant strain against fluoroquinolone, tetracycline, or macrolide agents in Japan.

Chlamydial Antibiotic Resistance and Treatment Failure in Veterinary and Human Medicine

The Chlamydiaceae are widespread pathogens of both humans and animals. Chlamydia trachomatis infection causes blinding trachoma and reproductive complications in humans. Chlamydia pneumoniae causes human respiratory tract infections and atypical pneumonia. Chlamydia suis infection is associated with conjunctivitis, diarrhea, and failure to gain weight in domestic swine. Chlamydial infections in humans and domesticated animals are generally controlled by antibiotic treatment—particularly macrolides (usually azithromycin) and tetracyclines (tetracycline and doxycycline). Tetracycline-containing feed has also been used to limit infections and promote growth in livestock populations, although its use has decreased because of growing concerns about antimicrobial resistance development. Because Sandoz and Rockey published an elegant review of chlamydial anti-microbial resistance in 2010, we will review the following: (i) antibiotic resistance in C. suis, (ii) recent evidence for acquired resistance in human chlamydial infections, and (iii) recent non-genetic mechanisms of antibiotic resistance that may contribute to treatment failure.

Association of the in vitro susceptibility of clinical isolates of chlamydia trachomatis with serovar and duration of antibiotic exposure

BACKGROUND

The presence of persistent Chlamydia trachomatis infection after treatment does not always correlate with in vitro susceptibility testing.

METHODS

The in vitro minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of azithromycin, clarithromycin, roxithromycin, doxycycline, tetracycline, ofloxacin, and penicillin were tested against 61 clinical isolates of C. trachomatis on 6 serovars, and the MIC/MBC of azithromycin and ofloxacin at different points in time after antibiotic administration to infected cultures.

RESULTS

Of the 7 antibiotics tested, clarithromycin showed the greatest activity against C. trachomatis isolates with MIC90 of 0.032 μg/mL and MBC90 of 0.064 μg/mL, followed by doxycycline with MIC90 0.064 μg/mL and MBC90 0.064 μg/mL, and azithromycin with MIC90 0.160 μg/mL and MBC90 0.320 μg/mL. Azithromycin had roughly the same MIC50 values (0.08 μg/mL) as the other serovars isolates tested, and other antibiotics showed a 2- to 4-fold difference in MICs50 between serovars. In addition, an increase in the azithromyin MIC was observed by 8 hours and the ofloxacin MIC by 16 hours. At 24 hours, the azithromycin MICs were greater than 40 μg/mL and ofloxacin MICs were greater than 64 μg/mL.

CONCLUSIONS

The current data demonstrated that the antimicrobial susceptibility of C. trachomatis was influenced by both the serovar type and the duration of exposure to antibiotics in infected cultures.

Treatment of Chlamydial infections: 2014 update

INTRODUCTION

Chlamydiae are obligate intracellular bacterial pathogens whose entry into mucosal epithelial cells is required for intracellular survival and subsequent growth. The life cycle of Chlamydia spp. and the ability to cause persistent, often subclinical infection, has major ramifications for diagnosis and treatment of Chlamydia trachomatis and C. pneumoniae infections in humans.

AREAS COVERED

This paper reviews the current literature on the antimicrobial susceptibilities and treatment of genital infections due to C. trachomatis and respiratory infections due to C. pneumoniae published since 2011.

EXPERT OPINION

Chlamydiae are susceptible to antibiotics that interfere with DNA and protein synthesis, including tetracyclines, macrolides and quinolones, which are the compounds that have been most extensively studied and used for treatment of human infection. Since our original review was published in 2011, there have been some major advances in diagnostic tests for C. trachomatis and the introduction of the first FDA-approved test for the detection of C. pneumoniae in respiratory samples. However, the options for treating chlamydial infections have largely remained the same. There are a small number of new drugs currently in preclinical development and early clinical trials that may have a role in the treatment of chlamydial infections.

Chlamydia trachomatis and Genital Mycoplasmas: Pathogens with an Impact on Human Reproductive Health

The most prevalent, curable sexually important diseases are those caused by Chlamydia trachomatis (C. trachomatis) and genital mycoplasmas. An important characteristic of these infections is their ability to cause long-term sequels in upper genital tract, thus potentially affecting the reproductive health in both sexes. Pelvic inflammatory disease (PID), tubal factor infertility (TFI), and ectopic pregnancy (EP) are well documented complications of C. trachomatis infection in women. The role of genital mycoplasmas in development of PID, TFI, and EP requires further evaluation, but growing evidence supports a significant role for these in the pathogenesis of chorioamnionitis, premature membrane rupture, and preterm labor in pregnant woman. Both C. trachomatis and genital mycoplasmas can affect the quality of sperm and possibly influence the fertility of men. For the purpose of this paper, basic, epidemiologic, clinical, therapeutic, and public health issue of these infections were reviewed and discussed, focusing on their impact on human reproductive health.

On the pathway to better birth outcomes? A systematic review of azithromycin and curable sexually transmitted infections

The WHO recommends the administration of sulfadoxine-pyrimethamine (SP) to all pregnant women living in areas of moderate (stable) to high malaria transmission during scheduled antenatal visits, beginning in the second trimester and continuing to delivery. Malaria parasites have lost sensitivity to SP in many endemic areas, prompting the investigation of alternatives that include azithromycin-based combination (ABC) therapies. Use of ABC therapies may also confer protection against curable sexually transmitted infections and reproductive tract infections (STIs/RTIs). The magnitude of protection at the population level would depend on the efficacy of the azithromycin-based regimen used and the underlying prevalence of curable STIs/RTIs among pregnant women who receive preventive treatment. This systematic review summarizes the efficacy data of azithromycin against curable STIs/RTIs.