Comparative effect of tetracycline and doxycycline on the occurrence of resistant Escherichia coli in the fecal flora

Tetracyclines uptake from irrigation water by vegetables: Accumulation and antimicrobial resistance risks

Wastewater irrigation may introduce antibiotic residues in the soil-plant systems. This study aimed to investigate the uptake of tetracyclines by spinach and collard greens and assess associated ecological and human health risks. Synthetic wastewater spiked with 1 ppm and 10 ppm of oxytetracycline, doxycycline, and tetracycline was used to grow vegetables in a greenhouse pot experiment. The uptake and accumulation of the tetracyclines were low and residual concentrations in the soil were negligible. All the tetracyclines were detected at concentrations ranging from 1.68 to 51.41 μg/g (spinach) and 1.94-30.95 μg/g (collard greens). The accumulation rate was in a dose-response scenario with a bioconcentration factor of 6.34 mL/kg (spinach) and 2.64 mL/kg (collard greens). Oxytetracycline had the highest accumulation in leaves, followed by doxycycline and tetracycline, and the residual concentrations followed the same order. The highest residual concentration was in soils receiving 10 ppm oxytetracycline. Residual concentrations in the soil were lower than accumulated levels and exerted negligible ecological risks. Tetracyclines accumulation in spinach significantly differed between the vegetables demonstrating a subspecies difference in uptake and accumulation. Ecological risk quotient (RQ) and human health risk quotient (HQ) were below thresholds that would exert toxicity and resistance selection impacts. Although RQs and HQs are low (<0.1), this study shows that the vegetables accumulate tetracyclines from irrigation water, posing plausible human health risks to allergic individuals. Similarly, the ecological risks cannot be ignored because the synergistic and antagonistic effects of sublethal concentrations can perturb ecosystem processes.

Facile One-Pot Strategy for Radiosynthesis of 99mTc-Doxycycline to Diagnose Staphylococcus aureus in Infectious Animal Models

The accurate and early diagnosis of infection is an important feature in the biomedical sciences for better treatment and to decrease the rate of morbidity associated with diseases. Doxycycline (DC) is a semisynthetic antibiotic that belongs to tetracycline family and usually prescribed to treat a variety of infections. The objective of the present research work was to develop a new radiopharmaceutical ^99mTc-Doxycycline (^99mTc-DC), by using SnCl₂·2H₂O as a reducing agent for diagnostic applications. It was confirmed through this study that ^99mTc-DC possessed high radiolabeling yield (95%). In vitro studies were performed by incubating ^99mTc-DC in human serum at 37 °C. The in vitro binding interaction of the labeled antibiotic was analyzed with bacterial strain (live Staphylococcus aureus cells), and its stability was further determined. Moreover, for in vivo infection imaging study, the infection was induced with S. aureus (gram positive) cells intramuscularly injected in mice models followed by biodistribution studies for ^99mTc-DC that were performed. Biodistribution studies of ^99mTc-DC showed that the radiotracer was significantly accumulated at the site of infection and indicated the renal route of excretion. Scintigraphic images obtained as a result of in vivo study showed good uptake of prepared radiotracer (^99mTc-DC) in the infectious lesions at 1-, 4-, and 24-h post-injection. Target-to-non-target ratios for ^99mTc-DC were significantly different for the infectious lesions and non-infected tissues and remained 2.13 ± 0.3 up to 24-h post-injection of ^99mTc-DC. ^99mTc-DC showed preferential binding to living bacterial infected sites as compared to other parts of the body, and thus it can be inferred that ^99mTc-DC might be a potential candidate to diagnose the infection.

Antibacterial Mechanisms and Efficacy of Sarecycline in Animal Models of Infection and Inflammation

Prolonged broad-spectrum antibiotic use is more likely to induce bacterial resistance and dysbiosis of skin and gut microflora. First and second-generation tetracycline-class antibiotics have similar broad-spectrum antibacterial activity. Targeted tetracycline-class antibiotics are needed to limit antimicrobial resistance and improve patient outcomes. Sarecycline is a narrow-spectrum, third-generation tetracycline-class antibiotic Food and Drug Administration (FDA)-approved for treating moderate-to-severe acne. In vitro studies demonstrated activity against clinically relevant Gram-positive bacteria but reduced activity against Gram-negative bacteria. Recent studies have provided insight into how the structure of sarecycline, with a unique C7 moiety, interacts with bacterial ribosomes to block translation and prevent antibiotic resistance. Sarecycline reduces Staphylococcus aureus DNA and protein synthesis with limited effects on RNA, lipid, and bacterial wall synthesis. In agreement with in vitro data, sarecycline demonstrated narrower-spectrum in vivo activity in murine models of infection, exhibiting activity against S. aureus, but reduced efficacy against Escherichia coli compared to doxycycline and minocycline. In a murine neutropenic thigh wound infection model, sarecycline was as effective as doxycycline against S. aureus. The anti-inflammatory activity of sarecycline was comparable to doxycycline and minocycline in a rat paw edema model. Here, we review the antibacterial mechanisms of sarecycline and report results of in vivo studies of infection and inflammation.

An overview of sarecycline for the treatment of moderate-to-severe acne vulgaris

INTRODUCTION

Sarecycline is a novel, tetracycline-class antibiotic specifically designed to treat inflammatory acne. It offers a narrow spectrum of activity (mainly against Cutinebacterium acnes), and it shows less in vitro activity than other tetracyclines against enteric Gram-negative bacteria, offering advantages over older tetracyclines by decreasing the disruption of the gastrointestinal microbiome and the likelihood of developing bacterial resistance.

AREAS COVERED

The drug's pharmacology, safety profile, and clinical efficacy are discussed. Results of phase I, II and III clinical trials have shown that 1.5 mg/kg/day sarecycline is safe, well tolerated and more effective than placebo in treating inflammatory acne in patients 9 years old and older. Furthermore, sarecycline's narrow spectrum of activity leads to a lower incidence of undesirable off-target antibacterial effects and consequently less adverse events such as diarrhea, fungal overgrowth and vaginal candidiasis.

EXPERT OPINION

Sarecycline could become the first-line antibiotic therapy used in acne in the near future as it is an effective option for treating inflammatory acne lesions. Due to its narrow spectrum of activity, it could have a more adequate safety profile than older tetracyclines; however, head-to-head trials comparing the efficacy and safety profile of sarecycline with other tetracyclines are still needed to prove sarecycline's superiority.

Sarecycline: a narrow spectrum tetracycline for the treatment of moderate-to-severe acne vulgaris

Sarecycline is a novel, narrow-spectrum, once-daily tetracycline-derived oral antibiotic that is FDA-approved in the US to be taken with or without food for moderate-to-severe acne vulgaris for ages 9 years of age and older. Sarecycline possesses anti-inflammatory properties and potent activity against Gram-positive bacteria, including activity against multiple strains of Cutibacterium acnes, while exhibiting minimal activity against enteric aerobic Gram-negative bacteria. Unlike many acne studies, sarecycline was investigated for chest and back acne. Significant reduction in inflammatory lesions was seen at week 12 at 1.5 mg/kg/day of sarecycline, with statistically significant improvement seen as early as week 3. No reports of phototoxicity, dizziness, pseudotumor cerebri or lupus but 1.2% nausea and 1.2% vaginal candidiasis was reported in the pivotal Phase III studies.

Microbiological Profile of Sarecycline, a Novel Targeted Spectrum Tetracycline for the Treatment of Acne Vulgaris

Sarecycline is the first narrow-spectrum tetracycline-class antibiotic being developed for acne treatment. In addition to exhibiting activity against important skin/soft tissue pathogens, sarecycline exhibits targeted antibacterial activity against clinical isolates of Cutibacterium acnes.

Sarecycline is the first narrow-spectrum tetracycline-class antibiotic being developed for acne treatment. In addition to exhibiting activity against important skin/soft tissue pathogens, sarecycline exhibits targeted antibacterial activity against clinical isolates of Cutibacterium acnes. In the current study, sarecycline was 16- to 32-fold less active than broad-spectrum tetracyclines—such as minocycline and doxycycline—against aerobic Gram-negative bacilli associated with the normal human intestinal microbiome. Also, reduced activity against Escherichia coli was observed in vivo in a murine septicemia model, with the 50% protective doses, or the doses required to achieve 50% survival, being >40 mg/kg of body weight and 5.72 mg/kg for sarecycline and doxycycline, respectively. Sarecycline was also 4- to 8-fold less active than doxycycline against representative anaerobic bacteria that also comprise the normal human intestinal microbiome. Additionally, C. acnes strains displayed a low propensity for the development of resistance to sarecycline, with spontaneous mutation frequencies being 10⁻¹⁰ at 4 to 8 times the MIC, similar to those for minocycline and vancomycin. When tested against Gram-positive pathogens with defined tetracycline resistance mechanisms, sarecycline was more active than tetracycline against tet(K) and tet(M) strains, with MICs ranging from 0.125 to 1.0 μl/ml and 8 μl/ml, respectively, compared with MICs of 16 to 64 μl/ml and 64 μl/ml for tetracycline, respectively. However, sarecycline activity against the tet(K) and tet(M) strains was decreased compared to that against the wild type, which demonstrated MICs ranging from 0.06 to 0.25 μl/ml, though the decrease in the activity of sarecycline against the tet(K) and tet(M) strains was not as pronounced as that of tetracycline. These findings support sarecycline as a narrow-spectrum tetracycline-class antibiotic that is effective for the treatment of acne, and further investigation into the potential reduced effects on the gut microbiome compared with those of other agents is warranted.

Mitochondria as oncotarget: a comparison between the tetracycline analogs doxycycline and COL-3

Tetracyclines have anticancer properties in addition to their well-known antibacterial properties. It has been proposed that tetracyclines slow metastasis and angiogenesis through inhibition of matrix metalloproteinases. However, we believe that the anticancer effect of tetracyclines is due to their inhibition of mitochondrial protein synthesis, resulting in a decrease of the mitochondrial energy generating capacity. Several groups have developed analogs that are void of antibacterial action. An example is COL-3, which is currently tested for its anticancer effects in clinical trials. We have undertaken a comparative study of the tetracycline analogs COL-3 and doxycycline, which has an antibacterial function, to further investigate the role of the mitochondrial energy generating capacity in the anticancer mechanism and, thereby, evaluate the usefulness of mitochondria as an oncotarget. Our experiments with cultures of the human A549, COLO357 and HT29 cancer cells and fibroblasts indicated that COL-3 is significantly more cytotoxic than doxycycline. Mitochondrial translation assays demonstrated that COL-3 has retained its inhibitory effect on mitochondrial protein synthesis. Both drugs caused a severe decrease in the levels of mitochondrially encoded cytochrome-c oxidase subunits and cytochrome-c oxidase activity. In addition, COL-3 produced a marked drop in the level of nuclear-encoded succinate dehydrogenase subunit A and citrate synthase activity, indicating that COL-3 has multiple inhibitory effects. Contrary to COL-3, the anticancer action of doxycycline appears to be based specifically on inhibition of mitochondrial protein synthesis, which is thought to affect rapidly proliferating cancer cells more than healthy tissue. Doxycycline is likely to cause less side effects that COL-3.

Serogrouping and antibiotic resistance of Escherichia coli isolated from broiler chicken with colibacillosis in center of Algeria

AIM

Colibacillosis is considered as one of the major bacterial infections in avian pathology. The excessive use of antibiotics reduced their effectiveness, which eventually led to the risk of emergence of antibiotic resistance. The aim of this study was to isolate, identify and serotype the pathogenic Escherichia coli strains and to determine their antibiotic susceptibility.

MATERIALS AND METHODS

A total of 180 samples from different organs of broilers with colibacillosis lesions were collected (liver, spleen, lung, and heart) in center of Algeria. The isolation and identification of E. coli were carried out using conventional techniques. Then, these strains were serotyped and tested over 13 antibiotics.

RESULTS

A total of 156 strains of E. coli were isolated. Serotyping results showed that 50 strains belong to 3 serotypes (23 for O1, 11 for O2, 16 for O78) which represent 32% of isolates. The antimicrobial susceptibility test, presented high level of resistance to tetracyclines (94.12%), flumequine (91.5%), sulfamethoxazole-trimethoprim (88.89%), enrofloxacin (86.27%), nalidixic acid (85.62%), ampicillin (83.01%) and doxycycline (75.81%), medium level resistance to chloramphenicol (39.22%), and amoxicillin-clavulanic acid (43.13%). All the strains were susceptible to cefotaxime, excepting three, which presented an extended spectrum β-lactamase (ESBL). In addition, the results of multi-resistance showed that all the strains were resistant at the minimum to two antibiotics and 66.66% of strains were resistant to at least seven antibiotics.

CONCLUSION

The antibiotic resistance continues to rise at an alarming rate, and the emergence of ESBL is considered as a threat for public health.

Multidrug-resistant gram-negative bacteria colonization of healthy US military personnel in the US and Afghanistan

Background

The US military has seen steady increases in multidrug-resistant (MDR) gram-negative bacteria (GNB) infections in casualties from Iraq and Afghanistan. This study evaluates the prevalence of MDR GNB colonization in US military personnel.

Methods

GNB colonization surveillance of healthy, asymptomatic military personnel (101 in the US and 100 in Afghanistan) was performed by swabbing 7 anatomical sites. US-based personnel had received no antibiotics within 30 days of specimen collection, and Afghanistan-based personnel were receiving doxycycline for malaria chemoprophylaxis at time of specimen collection. Isolates underwent genotypic and phenotypic characterization.

Results

The only colonizing MDR GNB recovered in both populations was Escherichia coli (p=0.01), which was seen in 2% of US-based personnel (all perirectal) and 11% of Afghanistan-based personnel (10 perirectal, 1 foot+groin). Individuals with higher off-base exposures in Afghanistan did not show a difference in overall GNB colonization or MDR E. coli colonization, compared with those with limited off-base exposures.

Conclusion

Healthy US- and Afghanistan-based military personnel have community onset-MDR E. coli colonization, with Afghanistan-based personnel showing a 5.5-fold higher prevalence. The association of doxycycline prophylaxis or other exposures with antimicrobial resistance and increased rates of MDR E. coli colonization needs further evaluation.

The effects of systemic isotretinoin and antibiotic therapy on the microbial floras in patients with acne vulgaris

BACKGROUND

Although there are several studies about the alteration in skin flora, limited number of reports about changes in the microbial contents and their resistance profile of other body sites in patients treated with isotretinoin for acne vulgaris.

OBJECTIVES

The aim of this study was to investigate the effects of systemic isotretinoin and antibiotic therapy on the microbial floras of oropharynx, nose and feces in acne patients.

METHODS

Treatment groups of isotretinoin and antibiotics consisting of 20 and 15 patients, respectively were included. Microbiological culture samples were taken at baseline and once a month during 4-6 months of treatment period.

RESULTS

Difference in microbial flora throughout the treatment period was detected at least among one of all culture samples of 15 (75%) and 5 (33%) patients in isotretinoin and antibiotic groups. There was statistically significant difference between two groups in means of alteration of the microbial flora (P = 0.013). The difference was definitely observed among nasal cultures (65%) in isotretinoin group and fecal cultures (20%) in the other. Staphylococcus aureus colonization was prominent in the microbial floras of nose and oropharynx and 2 of 14 nasal isolates were detected to be methicilline resistant while Escherichia coli with extended spectrum beta lactamase activity was detected in fecal floras of patients in isotretinoin group.

CONCLUSIONS

Systemic isotretinoin and antibiotic treatments in acne patients precisely caused variations in the microbial floras of several sites of the body, while isotretinoin was commonly more responsible than antibiotics. Knowing that alterations in the microbial colonization of the flora regions may preceede infectious disease and bacterial resistance, treatment options and follow-up procedures in acne vulgaris should be carefully determined to reduce the risk of destruction of the microbial flora.

Suspected side effects of doxycycline use in dogs - a retrospective study of 386 cases

This study investigated doxycycline-related side effects in a large population of dogs. Data from 386 dogs that had received doxycycline for the treatment of various infectious diseases were analysed retrospectively. Potential side effects that developed during treatment were documented, and correlations with signalment, dose, duration of treatment, frequency of application, doxycycline preparation and use of additional drugs were investigated. Vomiting was reported in 18.3 per cent of dogs, 7.0 per cent developed diarrhoea and 2.5 per cent developed anorexia. While being treated with doxycycline, 39.4 per cent of dogs showed an increase in alanine aminotransferase (ALT) activity and 36.4 per cent showed an increase in alkaline phosphatase (ALP) activity. There was a dose-related risk of an increase in ALP activity (P=0.011, odds ratio [OR]=1.27, 95 per cent confidence interval [CI] 1.06 to 1.53), and older dogs treated with doxycycline were more likely to develop an increase in ALT activity (P=0.038, OR=1.23, 95 per cent CI 1.01 to 1.50) and vomiting (P=0.017, OR=1.11, 95 per cent CI 1.02 to 1.21).

Antibiotics in the human food chain: establishing no effect levels of tetracycline, neomycin, and erythromycin using a chemostat model of the human colonic microflora

A chemostat model of the healthy human large bowel ecosystem was used to establish no effect levels for tetracycline, neomycin, and erythromycin. For each compound, the equivalent to four oral doses (0, 1.5, 15, and 150 mg/60 kg person/d) was studied. Concentrations of the test compounds in the chemostat medium were intended to simulate fecal levels that might be expected following consumption of food containing antibiotic residue and were based on published oral doses and fecal levels. We monitored the following parameters: short chain fatty acids, bile acids, sulfate reduction, azoreductase and nitroreductase activities, beta-glucosidase and beta-glucuronidase activities, a range of bacterial counts and, lastly, the susceptibility among sentinel bacteria to each test compound. Neomycin and erythromycin reduced bile acid metabolism. Neomycin elevated propionate levels and caused a marginal diminution in azoreductase activity. Based on our results, the no observed effect level (NOEL) of both tetracycline and erythromycin was 15 mg/60 kg person/d. The NOEL for neomycin was 1.5 mg/60 kg person/d.

Cardiovascular effects and fatalities associated with intravenous administration of doxycycline to horses and ponies

Intravenous use of doxycycline in horses is associated with deleterious side effects on the cardiovascular system which may result in fatalities. At dosages and infusion rates used in these studies, supraventricular tachycardia, systemic arterial hypertension, clinical signs of discomfort, collapse and death were observed. Results of the present study suggest that the intravenous use of doxycycline should be avoided in horses.

Impact of antimicrobial agents on human intestinal microflora

The most common and significant cause of disturbances in the normal intestinal microflora is the administration of antimicrobial agents. The microflora can be influenced by antimicrobial agents because of incomplete absorption of any orally administered antimicrobial agent, secretion of an antimicrobial agent in the bile, or secretion from the intestinal mucosa. In most cases, the influence is not beneficial to the patient because suppression of the indigenous microorganisms often permits potential pathogens to overgrow and cause septic conditions, stomatitis, diarrhea, or colitis. Antimicrobial agents that influence the normal microflora also promote the emergence of antimicrobial-resistant strains. During the last fifteen years, the impact of different antimicrobial agents on the human microflora has been studied by several investigators. In this article published data on the impact of beta-lactam antibiotics, macrolides, tetracyclines, nitroimidazoles, clindamycin and quinolones on the human intestinal microflora are reviewed.

Impact of antimicrobial agents on the gastrointestinal microflora and the risk of infections

The most common and significant cause of disturbances in the normal gastrointestinal microflora is the administration of antimicrobial agents. The microflora can be influenced by antimicrobial agents because of incomplete absorption of any orally administered antimicrobial agent, secretion of an antimicrobial agent by the salivary glands and in the bile, or secretion from the intestinal mucosa. In most cases the influence is not beneficial to the patient because suppression of the indigenous microorganisms often permits potential pathogens to overgrow and cause septic conditions, diarrhea, or colitis. Antimicrobial agents that influence the normal microflora also promote the emergence of antimicrobial-resistant strains. The authors' experience on the impact of different beta-lactams, erythromycin, clindamycin, tetracycline, and nitroimidazoles on the gastrointestinal microflora and the risk of infections when these agents are used is reviewed.

Influence of doxycycline on the normal human flora and colonization of the oral cavity and colon

Doxycycline was given orally in doses of 100 mg every 24 h for 7 days to 10 subjects. Salivary and faecal specimens were taken up to 16 days for cultivation of aerobic and anaerobic microorganisms and for assay of doxycycline. Doxycycline was detected in both saliva and faeces. Only minor changes were observed regarding the number of aerobic and anaerobic microorganisms in the oral cavity. In the faecal flora a decrease in the number of aerobic microorganisms was observed in most subjects, while only minor changes in the number of anaerobic bacteria were noticed. A marked increase in doxycycline-resistant aerobic and anaerobic bacterial strains was noticed both in the oral cavity and the colon. Only a few patients were colonized with potentially pathogenic microorganisms.

Prophylactic doxycycline for travelers' diarrhea. Results of a prospective double-blind study of Peace Corps volunteers in Kenya

We performed a randomized double-blind study to determine the efficacy of doxycycline (100 mg daily) in preventing travelers' diarrhea among 39 Peace Corps volunteers during their first five weeks in Kenya. The volunteers took either doxycycline or placebo for three weeks and were observed for an additional two weeks. Nine of 21 taking placebo and one of 18 taking doxycycline had travelers' diarrhea during the treatment period (P = 0.012). The protection seemed to persist for at least one week after the drug was stopped. Enterotoxigenic Escherichia coli was the only pathogen isolated from the placebo group, but was not detected in persons taking doxycycline. None of these organisms were resistant to doxycycline or tetracycline, whereas resistance to tetracyclines and other antibiotics was common among the nonenterotoxigenic Esch. coli. We conclude that doxycycline effectively prevented most episodes of travelers' dirrhea.

Sulphonamides in the treatment of acute Escherichia coli infection of the urinary tract in women. Clinical and ecological effects of sulphasomidine and sulphalene

28 non-pregnant women were treated with conventional doses of sulphasomidine or sulphalene for acute urinary tract infections caused by Escherichia coli. Both preparations were found to be effective in simple cystitis infection with sulphonamide-sensitive organisms. Also, both were found to exert a selective pressure favouring sulphonamide-resistant E. coli in the faecal flora.