Effects of S-adenosylmethionine on AfsKRS regulation in pristinamycin biosynthesis in Streptomyces pristinaespiralis

In Streptomyces pristinaespiralis, AfsKRS system has differential regulation for PI and PII component biosynthesis of pristinamycin, but it is unknown whether S-adenosylmethionine (SAM) plays an important role in the AfsK-AfsR-AfsS signal transduction cascade during pristinamycin production. The possible target of exogenous SAM in the AfsKRS system and the biological role of SAM during the production of PI and PII were investigated using three mutantsΔafsK,ΔafsR andΔafsS defective in signal cascade pathway of AfsKRS. It was found that external SAM had a significant activation of PI production (1.85-fold increase) but had no obvious effect on PII production in the original strain F618 with the normal response of AfsKRS regulation. Addition of SAM resulted in a similar increase in pristinamycin yield in the mutant with defective afsK or afsR, but induced more crucial activation of PI biosynthesis than PII biosynthesis both in ΔafsK (1.65-fold and 1.15-fold increase respectively) and ΔafsR (1.27-fold and 1.09-fold increase respectively). Exogenous SAM only significantly enhanced PII production in ΔafsS (1.1-fold increase). These results could provide valuable insights into the regulatory function of the AfsKRS system in S. pristinaespiralis.

Treatment of Mycoplasma genitalium infection in pregnancy: A systematic review of international guidelines

BACKGROUND

Mycoplasma genitalium is an emerging pathogen, which has been linked to cervicitis, urethritis and pelvic inflammatory disease (PID). With the advent of multiplex polymerase chain reaction (PCR) panels for sexually transmitted infections, it is increasingly being identified in pregnant women.

OBJECTIVES

The aim was to review international guidelines, which had explicit recommendations for treatment of M. genitalium infection in pregnancy and breastfeeding.

SEARCH STRATEGY

PubMed, EMBASE and Cochrane databases were reviewed with no age, species, language or date restrictions.

SELECTION CRITERIA

Studies were included if they had an explicit recommendation for treatment of M. genitalium in pregnancy. Studies were excluded if there was no recommendation in pregnancy, if they referred to other international guideline recommendations or were historical versions of guidelines.

DATA COLLECTION AND ANALYSIS

References were manually reviewed and 50 papers were selected for review. Only four guidelines were included in the final analysis and they were from Europe, UK, Australia and Aotearoa New Zealand.

MAIN RESULTS

All studies recommended azithromycin as first-line treatment, and advised against moxifloxacin use. The dosing schedule of azithromycin, varied between guidelines, as did the utility/safety of pristinamycin for macrolide resistant infections. Safety data was generally reassuring for azithromycin but inconsistent for pristinamycin.

CONCLUSIONS

Azithromycin is the first-line treatment for macrolide susceptible or unknown resistance infections, but there is a lack of consistency regarding dosing of azithromycin or the utility/safety of pristinamycin for macrolide resistant infections in pregnancy/lactation.

Pristinamycin-induced toxic epidermal necrolysis: A case report

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are acute, life-threatening and rare severe cutaneous adverse reactions induced by drugs in most cases. The drugs most often reported to be implicated in inducing TEN/SJS are allopurinol, antibacterial sulfonamides, antiepileptic drugs and oxicam. Pristinamycin is an oral streptogramin antibiotic with bactericidal activity against Gram-positive bacteria that is rarely linked to TEN. Typically, this condition develops 4-28 days after drug exposure, Herein, we report a case of a 71-year-old female who developed TEN within 3 days of administration of pristinamycin and was managed successfully with supportive care, including intravenous fluids, pain control, prophylactic antibiotics and intravenous methylprednisolone. This case of rapidly developing SJS/TEN after administration of pristinamycin highlights the possibility that these complications can develop within only a few days following ingestion of drugs thought to be probably safe.

Results of patch testing in Acute generalized exanthematous pustulosis (AGEP): a literature review

The literature on positive patch test results in acute generalized exanthematous pustulosis (AGEP) is reviewed. 93 drugs were identified that have together caused 259 positive patch tests in 248 patients suffering from AGEP. The drug classes causing the highest number of reactions are beta-lactam antibiotics (25.9%), other antibiotics (20.8%), iodinated contrast media (7.3%) and corticosteroids (5.4%), together accounting for nearly 60% of all reactions. The highest number of reactions to individual drugs was to amoxicillin (n=36), followed by pristinamycin (n=25), diltiazem (n=14), amoxicillin-clavulanic acid (n=13), clindamycin (n=11) and iomeprol (n=8); 59 of the 93 drugs each caused a single case only. The "Top-10" drugs together caused over 50% of all reactions. The sensitivity of patch testing (percentage of positive reactions) in patients with AGEP is largely unknown, but may generally be around 50%, which also applies to pristinamycin. Patch testing in AGEP appears to be safe, although mild recurrence of AGEP skin symptoms or other rashes may occur occasionally. Clinical aspects of AGEP, including epidemiology, etiology and pathophysiology, clinical features, histology, treatment, and prognosis are briefly presented, as are diagnosing the disease and identifying the culprit drugs with patch tests, intradermal tests, in vitro tests, and challenge tests. This article is protected by copyright. All rights reserved.

Pristinamycin production using Streptomyces pristinaespiralis and date sirup as substrate-process modeling, optimization, and scale-up

Pristinamycin biosynthesis using Streptomyces pristinaespiralis and date sirup (DS) as substrates was optimized before scale-up. DS was filter sterilized as heat sterilization primes Maillard reactions having negative effects on antibiotic production. Multilinear regression modeling (MLR) predicted optimum medium composition, specifying components with positive and negative effects on production. The MLR showed that to maximize bacterial growth, DS, arginine, CaCl₂, and KH₂PO₄ must be fixed at the highest concentration, but to maximize antibiotic production, these factors have to be fixed at a low level. A noticeable difference in productivity was observed in a shake flask experiments with 50.4 and 43.1 mg/L pristinamycin final concentration for the DS and the glucose substrates, respectively. In the 2 L bioreactor, the DS medium resulted in a 66.6 mg/L antibiotic, while the scale-up in the 100 L resulted in 39.0 mg/L. The low yield in the 100 L bioreactor could be attributed to the relatively high stirring rate applied which was the minimum possible in the bioreactor used. This high stirring rate prevented pellet formation by the cells, which is described as necessary for antibiotic formation by the bacterium. Hence, a successful scale-up to pilot-scale should consider the effect of stirring rate.

Production, separation, and antimicrobial activity assessment of pristinamycin produced using date fruit extract as substrate

Date fruits extract was assessed as substrate for pristinamycin production in shake flasks using Streptomyces pristinaespiralis DSMZ 40338 as production organism. A process of microfiltration, concentration, and solvent extraction was used to recover the antibiotic from the fermentation broth and its antimicrobial activity was tested using a well assay method. During a fermentation period of 120 h, the bacterium consumed approximately 28.4 g/l sugars, grew from 0.4 g/l to 4.0 g/l dry weight, and produced 51.0 mg/L pristinamycin. The microfiltration, concentration, and ethyl acetate solvent extraction applied resulted in 71% pristinamycin recovery. The antibiotic showed inhibition capacity comparable to that of the pristinamycins IA and IIA standards. The inhibited bacteria were Staphylococcus aureus, Escherichia coli, and Enterococcus faecium. Clear inhibition zones of 13.3-19.6 mm diameter were formed.

Streptogramins for the treatment of infections caused by Gram-positive pathogens

INTRODUCTION

Streptogramins (pristinamycin and quinupristin-dalfopristin) can be interesting options for the treatment of infections due to Gram-positive cocci, especially multidrug-resistant isolates.

AREAS COVERED

This review provides an updated overview of structural and activity characteristics, mechanisms of action and resistance, pharmacokinetic/pharmacodynamic, and clinical use of streptogramins.

EXPERT OPINION

The streptogramin antibiotics act by inhibition of the bacterial protein synthesis. They are composed of two chemically distinct compounds, namely type A and type B streptogramins, which exert a rapid bactericidal activity against a wide range of Gram-positive bacteria (including methicillin-resistant staphylococci and vancomycin-resistant enterococci). Several mechanisms of resistance have been identified in staphylococci and enterococci but the prevalence of streptogramin resistance among clinical isolates remains very low. Even if only a few randomized clinical trials have been conducted, the efficacy of pristinamycin has been largely demonstrated with an extensive use for 50 years in France and some African countries. Despite its effectiveness in the treatment of severe Gram-positive bacterial infections demonstrated in several studies and the low rate of reported resistance, the clinical use of quinupristin-dalfopristin has remained limited, mainly due to its poor tolerance. Altogether, streptogramins (especially pristinamycin) can be considered as potential alternatives for the treatment of Gram-positive infections.

Modular synthesis of streptogramin antibiotics

Streptogramins are antibiotics produced by several species of Streptomyces bacteria that are used in both human and veterinary medicine. Group A streptogramins comprise 23-membered macrocyclic polyketide/nonribosomal peptide hybrids for which several innovative, fully synthetic routes have been developed. Herein we describe in detail our scalable routes to natural group A streptogramins and compare these routes to other reported syntheses.

Prevalence and Antimicrobial Susceptibility of Mycoplasma hominis and Ureaplasma Species in Nonpregnant Female Patients in South Korea Indicate an Increasing Trend of Pristinamycin-Resistant Isolates

Mycoplasma hominis and Ureaplasma species, commonly found in the lower urogenital tract, have been associated with various urogenital infections. This study aimed to estimate the prevalence and antimicrobial susceptibility trend of M. hominis and Ureaplasma sp. in female patients and to evaluate the risk factors for the acquisition of pristinamycin-resistant mycoplasma. Endocervical swab specimens obtained between March 2016 and December 2018 were analyzed using a Mycoplasma IST2 kit.

Mycoplasma hominis and Ureaplasma species, commonly found in the lower urogenital tract, have been associated with various urogenital infections. This study aimed to estimate the prevalence and antimicrobial susceptibility trend of M. hominis and Ureaplasma sp. in female patients and to evaluate the risk factors for the acquisition of pristinamycin-resistant mycoplasma. Endocervical swab specimens obtained between March 2016 and December 2018 were analyzed using a Mycoplasma IST2 kit. Because pristinamycin and josamycin are not available in South Korea, we conducted an age- and date-matched case-control study to evaluate the risk factors for the acquisition of pristinamycin-resistant isolates. Among 4,035 specimens, 1,589 (39.4%) cases were positive for genital mycoplasma, which included 49 (3.1%) cases of M. hominis, 1,243 (78.2%) cases of Ureaplasma sp., and 297 (18.7%) cases of both M. hominis and Ureaplasma species. Based on antimicrobial susceptibility tests, the antibiotic susceptible rate of both M. hominis and Ureaplasma species to pristinamycin decreased annually during the study period (100%, 97.1%, and 87.3% for 2016, 2017, and 2018, respectively, P < 0.001). According to a multivariate analysis, josamycin resistance (odds ratio, 7.18; 95% confidence interval, 1.20 to 43.00; P = 0.027) and coinfection (odds ratio, 145.38; 95% confidence interval, 21.80 to 3,017.23; P < 0.001) with Candida species were independent risk factors for the acquisition of pristinamycin-resistant isolates. Antibiotic-resistant genital mycoplasmas have been gradually increasing annually. Nationwide surveillance, proper antibiotic stewardship, and appropriate culture-based treatment strategies are required to control this upcoming threat.

Use of Pristinamycin for Macrolide-Resistant Mycoplasma genitalium Infection

High levels of macrolide resistance and increasing fluoroquinolone resistance are found in Mycoplasma genitalium in many countries. We evaluated pristinamycin for macrolide-resistant M. genitalium in a sexual health center in Australia. Microbiologic cure was determined by M. genitalium–specific 16S PCR 14–90 days after treatment began. Of 114 persons treated with pristinamycin, infection was cured in 85 (75%). This percentage did not change when pristinamycin was given at daily doses of 2 g or 4 g or at 3 g combined with 200 mg doxycycline. In infections with higher pretreatment bacterial load, treatment was twice as likely to fail for each 1 log₁₀ increase in bacterial load. Gastrointestinal side effects occurred in 7% of patients. Pristinamycin at maximum oral dose, or combined with doxycycline, cured 75% of macrolide-resistant M. genitalium infections. Pristinamycin is well-tolerated and remains an option where fluoroquinolones have failed or cannot be used.

Identification and Validation of Aspartic Acid Semialdehyde Dehydrogenase as a New Anti-Mycobacterium Tuberculosis Target

Aspartic acid semialdehyde dehydrogenase (ASADH) lies at the first branch point in the essential aspartic acid biosynthetic pathway that is found in bacteria and plants but is absent from animals. Mutations in the asadh gene encoding ASADH produce an inactive enzyme, which is lethal. Therefore, in this study, we investigated the hypothesis that ASADH represents a new anti-Mycobacterium tuberculosis (MTB) target. An asadh promoter-replacement mutant MTB, designated MTB::asadh, in which asadh gene expression is regulated by pristinamycin, was constructed to investigate the physiological functions of ASADH in the host bacteria. Bacterial growth was evaluated by monitoring OD₆₀₀ and ASADH expression was analyzed by Western blotting. The results showed that the growth and survival of MTB::asadh was completely inhibited in the absence of the inducer pristinamycin. Furthermore, the growth of the mutant was rigorously dependent on the presence of the inducer in the medium. The starved mutant exhibited a marked reduction (approximately 80%) in the cell wall materials compared to the wild-type, in addition to obvious morphological differences that were apparent in scanning electron microscopy studies; however, with the addition of pristinamycin, the cell wall contents and morphology similar to those of the wild-type strain were recovered. The starved mutant also exhibited almost no pathogenicity in an in vitro model of infection using mouse macrophage J774A.1 cells. The mutant showed a concentration-dependent recovery of pathogenicity with the addition of the inducer. These findings implicate ASADH as a promising target for the development of novel anti-MTB drugs.

Macrolide resistance and azithromycin failure in a Mycoplasma genitalium-infected cohort and response of azithromycin failures to alternative antibiotic regimens

BACKGROUND

Our aim was to determine the efficacy of 1 g azithromycin and alternative antibiotic regimens in a prospective cohort of Mycoplasma genitalium-infected participants, and factors associated with azithromycin failure.

METHODS

Consecutive eligible M. genitalium-infected men and women attending the Melbourne Sexual Health Centre between July 2012 and June 2013 were treated with 1 g of azithromycin and retested by polymerase chain reaction (PCR) on days 14 and 28. Cure was defined as PCR negative on day 28. Cases failing azithromycin were treated with moxifloxacin, and those failing moxifloxacin were treated with pristinamycin. Pre- and posttreatment samples were assessed for macrolide resistance mutations (MRMs) by high-resolution melt analysis. Mycoplasma genitalium samples from cases failing moxifloxacin were sequenced for fluoroquinolone resistance mutations. Multivariable analysis was used to examine associations with azithromycin failure.

RESULTS

Of 155 participants treated with 1 g azithromycin, 95 (61% [95% confidence interval {CI}, 53%-69%]) were cured. Pretreatment MRM was detected in 56 (36% [95% CI, 28%-43%]) participants, and strongly associated with treatment failure (87% [95% CI, 76%-94%]; adjusted odds ratio, 47.0 [95% CI, 17.1-129.0]). All 11 participants who had MRM detected in posttreatment samples failed azithromycin. Moxifloxacin was effective in 53(88% [95% CI, 78%-94%]) of 60 cases failing azithromycin; all failures had gyrA and parC mutations detected in pretreatment samples. Six of 7 patients failing moxifloxacin treatment received pristinamycin, and all were PCR negative 28 days after pristinamycin treatment.

CONCLUSIONS

We report a high azithromycin failure rate (39%) in an M. genitalium-infected cohort in association with high levels of pretreatment macrolide resistance. Moxifloxacin failure occurred in 12% of patients who received moxifloxacin; all had pretreatment fluoroquinolone mutations detected. Pristinamycin was highly effective in treating macrolide- and quinolone-resistant strains.