Steroid Drugs Inhibit Bacterial Respiratory Oxidases and Are Lethal Toward Methicillin-Resistant Staphylococcus aureus

BACKGROUND

Cytochrome bd complexes are respiratory oxidases found exclusively in prokaryotes that are important during infection for numerous bacterial pathogens.

METHODS

In silico docking was employed to screen approved drugs for their ability to bind to the quinol site of Escherichia coli cytochrome bd-I. Respiratory inhibition was assessed with oxygen electrodes using membranes isolated from E. coli and methicillin-resistant Staphylococcus aureus strains expressing single respiratory oxidases (ie, cytochromes bd, bo', or aa3). Growth/viability assays were used to measure bacteriostatic and bactericidal effects.

RESULTS

The steroid drugs ethinylestradiol and quinestrol inhibited E. coli bd-I activity with median inhibitory concentration (IC50) values of 47 ± 28.9 µg/mL (158 ± 97.2 µM) and 0.2 ± 0.04 µg/mL (0.5 ± 0.1 µM), respectively. Quinestrol inhibited growth of an E. coli "bd-I only" strain with an IC50 of 0.06 ± 0.02 µg/mL (0.2 ± 0.07 µM). Growth of an S. aureus "bd only" strain was inhibited by quinestrol with an IC50 of 2.2 ± 0.43 µg/mL (6.0 ± 1.2 µM). Quinestrol exhibited potent bactericidal effects against S. aureus but not E. coli.

CONCLUSIONS

Quinestrol inhibits cytochrome bd in E. coli and S. aureus membranes and inhibits the growth of both species, yet is only bactericidal toward S. aureus.

Antifertility effects of quinestrol in male lesser bandicoot rat, Bandicota bengalensis, and potential in managing rodent population under field conditions

Integrating fertility control techniques using steroid hormones after lethal control can help reduce post control rebuildup of rodent populations. The current study is the first to assess the antifertility effects of quinestrol in male lesser bandicoot rat, Bandicota bengalensis which is the predominant rodent pest species in Southeast Asia. Rats in different groups were fed bait containing 0.00%, 0.01%, 0.02%, and 0.03% quinestrol for 10 days in laboratory and evaluated immediately, and 15, 30, and 60 days after treatment discontinuation for effect on reproduction and other antifertility parameters. Effect of 0.03% quinestrol treatment for 15 days was also observed in managing rodent populations in groundnut crop fields. Treatment resulted in average consumption of 19.53 ± 1.80, 67.63 ± 5.50, and 246.67 ± 1.78 mg/kg bwt active ingredient by three treated groups of rats, respectively. No reproduction was observed in female rats mated with male rats treated with 0.03% quinestrol, even 30 days after cessation of treatment. Post-mortem examination showed a significant (P < 0.0001) effect of treatment on organ weights (testis, cauda epididymis, seminal vesicles, and prostate gland) and different sperm parameters (sperm motility, sperm viability, sperm count, and sperm abnormality) in the cauda epididymal fluid with partial reversibility after 60 days. A significant (P < 0.0001) effect of quinestrol on the histomorphology of testis and cauda epididymis was observed, suggesting its effect on spermatogenesis. Affected cell association and cell count in seminiferous tubules did not fully recover within 60 days of stopping treatment. Evaluation of the effects of quinestrol treatment in groundnut fields showed greater reductions in rodent activity in fields treated with 2% zinc phosphide followed by 0.03% quinestrol treatment as compared to fields treated with 2% zinc phosphide alone. Research concludes that quinestrol has the potential to reduce fecundity and post control rebuildup of B. bengalensis populations, but long-term studies of the effectiveness of quinestrol under large-scale field conditions are needed to use it as part of an integrated pest control program for rodents.

Antifertility effects of EP-1 (quinestrol and levonorgestrel) on Pacific rats (Rattus exulans)

Pest rodents pose a serious threat to island biodiversity. Fertility control could be an alternative approach to control the impact of rodents on these islands. In this study, we examined the antifertility effects of EP-1 baits containing quinestrol (E) and levonorgestrel (P) using a dose of 50 ppm E and P at three different ratios (E:P ratio = 1:2, 1:1, and 2:1) on Pacific rats (Rattus exulans) in the Xisha Islands, Hainan, China. Compared to the control group, all animals in EP-1 treatment groups showed significantly decreased food intake and body weight. In treated males, there were obvious abnormalities in testis structure and a significant decrease of relative seminal vesicle weight, but no significant effect on relative uterine and ovarian weights (g kg-1 body weight), or ovarian structure in females. Adding 8% sucrose to the original 50-ppm baits (E:P ratio = 1:1) significantly increased bait palatability for males and females. This dose induced uterine edema and abnormalities of ovarian structure in females but had no significant negative effect on the relative testis, epididymis, and seminal vesicle weights (g kg-1 body weight) or sperm density in males. In summary, 50-ppm EP-1 (1:1) baits have the potential to disrupt the fertility of females, and 8% sucrose addition to the EP-1 baits (E:P ratio = 1:1) could improve bait palatability. This dose disrupted the testis structure in males. Future studies are needed to improve bait acceptance and assess the antifertility effects of EP-1 (1:1) on Pacific rats in captive breeding trials and under field conditions.

Impact of fertility versus mortality control on the demographics of Mastomys natalensis in maize fields

The multimammate mouse, Mastomys natalensis, is the most common rodent pest species in sub-Saharan Africa. Currently, rodenticides are the preferred method used to reduce the population of rodent pests, but this method poses direct and indirect risks to humans and other non-target species. Fertility control is a promising alternative that has been argued to be a more sustainable and humane method for controlling rodent pests. In this study, we compared the effectiveness of fertility control bait EP-1 (quinestrol (E) and levonorgestrel (P), 10 ppm) and an anticoagulant rodenticide bait (bromadiolone, 50 ppm) on the population dynamics of M. natalensis in maize fields in Zambia during 2 cropping seasons. M. natalensis was the most abundant species in maize fields (77% of total captures). Fertility control reduced the number of juveniles and suppressed population growth of M. natalensis at the end of the 2019-2020 cropping season. The population density initially decreased after rodenticide treatment, but the population rapidly recovered through immigration. None of the treatments influenced maize damage by rodents at germination (F_2,67 = 1.626, P = 0.204). Applying the treatments during the maize seeding time was effective at suppressing population growth at the end of the cropping season than application the month before maize seeding. This research indicates that a single-dose delivery of EP-1 and rodenticide have comparable effects on the population dynamics of M. natalensis. These findings are important in developing fertility control protocols for rodent pest populations to reduce maize crop damage and improve yields.

Antifertility effects of levonorgestrel, quinestrol and their mixture (EP-1) on plateau zokor in the Qinghai-Tibetan Plateau

The plateau zokor (Eospalax baileyi Thomas, 1911) is a key species in the Qinghai-Tibetan Plateau ecosystem, and fertility control could be an ideal approach to manage populations of this subterranean species. In this laboratory study, we explored the effects of the mixture of levonorgestrel and quinestrol (EP-1, 1:2), quinestrol (E), and levonorgestrel (P) on the reproductive status of plateau zokors. Groups of five animals of each sex were treated with different concentrations of EP-1 (1, 5, and 10 mg/kg), E (0.33, 3.3, and 6.6 mg/kg), and P (0.67, 3.35, and 6.7 mg/kg) by oral gavage over 7 successive days and killed on day 15. Body mass reduction was observed in the EP-1 and E groups. EP-1 and E significantly reduced the weight of testis and epididymis at 10 and 3.3 mg/kg, respectively. Sperm count and motility were significantly reduced by 5 mg/kg EP-1 and 0.33 mg/kg E. The levels of serum testosterone, estradiol, luteinizing hormone, and follicle stimulating hormone were significantly reduced by 5 mg/kg EP-1 and 3.3 mg/kg E. EP-1 and E significantly reduced the uterine and ovarian weights at 10 and 3.3 mg/kg, respectively. In the plateau zokors, treatment with P had no influence on the reproductive status. These data demonstrate that EP-1 and E have an inhibitory effect on a range of reproductive parameters in the plateau zokors. Further assessment is required to determine the effects on breeding and recruitment in enclosure or field experiments. This article is protected by copyright. All rights reserved.

Pseudo-pheochromocytoma due to obstructive sleep apnea: a case report

SUMMARY

Obstructive sleep apnea (OSA) is a condition of intermittent nocturnal upper airway obstruction. OSA increases sympathetic drive which may result in clinical and biochemical features suggestive of pheochromocytoma. We present the case of a 65-year-old male with a 2.9-cm left adrenal incidentaloma on CT, hypertension, symptoms of headache, anxiety and diaphoresis, and persistently elevated 24-h urine norepinephrine (initially 818 nmol/day (89-470)) and normetanephrine (initially 11.2 µmol/day (0.6-2.7)). He was started on prazosin and underwent left adrenalectomy. Pathology revealed an adrenal corticoadenoma with no evidence of pheochromocytoma. Over the next 2 years, urine norepinephrine and normetanephrine remained significantly elevated with no MIBG avid disease. Years later, he was diagnosed with severe OSA and treated with continuous positive airway pressure. Urine testing done once OSA was well controlled revealed complete normalization of urine norepinephrine and normetanephrine with substantial symptom improvement. It was concluded that the patient never had a pheochromocytoma but rather an adrenal adenoma with biochemistry and symptoms suggestive of pheochromocytoma due to untreated severe OSA. Pseudo-pheochromocytoma is a rare presentation of OSA and should be considered on the differential of elevated urine catecholamines and metanephrines in the right clinical setting.

LEARNING POINTS

Obstructive sleep apnea (OSA) is a common condition among adults. OSA may rarely present as pseudo-pheochromocytoma with symptoms of pallor, palpitations, perspiration, headache, or anxiety. OSA should be considered on the differential of elevated urine catecholamines and metanephrines, especially in patients with negative metaiodobenzylguanidine (MIBG) scan results.

Assessment of non-target toxicity effects of synthetic estradiol, quinestrol, in chickens

Fertility control agents for the management of rodent populations are developing and maturing. Investigating the impacts on non-target species of consumption of these agents is essential. The present study assessed the non-target toxicity effects of quinestrol, a synthetic estrogen-based antifertility agent for managing rodent populations. Various quinestrol doses administered to male and female (n = 60 each) chickens through single oral gavage were 0 (A), 10 (B), 50 (C), and 150 (D) mg/kg body weight. Chickens were assessed for effect on body weight, weight of vital and reproductive organs, reproductive hormones, histology of reproductive organs and egg laying rates after 15, 30, and 135 days of treatment. Quinestrol did not induce mortality in chickens and its effects were time and dose dependent. The 90% egg-laying rates were delayed by 30, 60 for groups B and C compared with the control group, and group D did not reach the 90% egg-laying rate by 135 days. Reproductive organs in males and females returned to normal levels within 30 and 135 days, respectively. With the exception of the FSH concentration in group D, reproductive hormones of both sexes were similar to controls by 30 days. No other significant effects were found. The present research demonstrated the safety of quinestrol on non-target species and facilitates recommendations for the general administration of quinestrol for rodent pest management.

The status of fertility control for rodents-recent achievements and future directions

Management of overabundant rodents at a landscape scale is complex but often required to sustainably reduce rodent abundance below damage thresholds. Current conventional techniques such as poisoning are not species specific, with some approaches becoming increasingly unacceptable to the general public. Fertility control, first proposed for vertebrate pest management over 5 decades ago, has gained public acceptance because it is perceived as a potentially more species-specific and humane approach compared with many lethal methods. An ideal fertility control agent needs to induce infertility across one or more breeding seasons, be easily delivered to an appropriate proportion of the population, be species specific with minimal side-effects (behavioral or social structure changes), and be environmentally benign and cost effective. To date, effective fertility control of rodents has not been demonstrated at landscape scales and very few products have achieved registration. Reproductive targets for fertility control include disrupting the hormonal feedback associated with the hypothalamic-pituitary-gonadal axis, gonad function, fertilization, and/or early implantation. We review progress on the oral delivery of various agents for which laboratory studies have demonstrated efficacy in females and/or males and synthesize progress with the development and/or use of synthetic steroids, plant extracts, ovarian specific peptides, and immunocontraceptive vaccines. There are promising results for field application of synthetic steroids (levonorgestrel, quinestrol), chemosterilants (4-vinylcyclohexene diepoxide), and some plant extracts (triptolide). For most fertility control agents, more research is essential to enable their efficient and cost-effective delivery such that rodent impacts at a population level are mitigated and food security is improved.

Anti-fertility effect of levonorgestrel and/or quinestrol on striped field mouse (Apodemus agrarius): evidence from both laboratory and field experiments

The effect of combined levonorgestrel (P) and quinestrol (E) on the fertility of striped field mouse (Apodemus agrarius) has not been evaluated. We performed a series of experiments in both the laboratory and field to assess the effect of P and/or E on the fertility of A. agrarius. In the laboratory, to test the time-dependent anti-fertility effects of P and E, as well as their mixtures, 90 male striped field mice were randomly assigned to 6 treatment groups (n = 60), and a control group (n = 30). Mice in 3 treatment groups were administered 1 of the 3 compounds (1 mg⋅kg^{- 1} [body weight] EP-1, 0.34 mg⋅kg^-1 E, 0.66 mg⋅kg^-1 P) for 3 successive days (another half for 7 successive days) via oral gavage; mice were then sacrificed 15 and 45 days after initiating the gavage treatment. Our findings indicated that E and EP-1 treatment, but not P or control treatment, significantly decreased the sperm count in the caudal epididymis, as well as the weight of the testes, epididymides, and seminal vesicles. Additionally, fertile female mice mated with E- and EP-1-treated males produced smaller pups. These data indicate that E and EP-1 can induce infertility in male A. agrarius. In the field, the population density of A. agrarius was significantly influenced by EP-1, and the rodent density in the treatment group was lower than that in the control group. Overall, our results indicate that EP-1 is an effective contraceptive in A. agrarius, a dominant rodent species in the farmland.

Impact of contraceptive hormones on the reproductive potential of male and female commensal black rats (Rattus rattus)

The black rat is considered one of the world's top pests. With increased restrictions on rodenticides, new alternatives to manage rats are urgently needed. Research on the use of contraceptive hormones, levonorgestrel (LE), and quinestrol (QU), have been evaluated against some rodent species, and this research is the first study to assess these on black rats. Hormones were incorporated into rodent bait at 10 and 50 ppm concentrations singly and in combination (EP-1). Groups of 10 animals of each sex were fed the baits over 7 days. Lower bait consumption was observed with slight body mass reductions. On dissection, it was observed that the uterus was in a state of edema and male reproductive organs weighed less with reduced sperm counts/motility. The 2 most promising baits, 50 ppm QU and EP-1, were used to assess impact on pregnancy and litter size. Pregnancy was reduced from 70% success when both males and females consumed untreated bait, down to 30% when males had consumed contraceptive bait but females had not, and down to 0% when females had consumed contraceptive bait, regardless of whether they had paired with a treated or untreated male. Litter size in the untreated pairs was 8 pups, but only 4 pups in those cases where the male only had consumed the contraceptive. Further studies should investigate how long the effect lasts and its reversibility. Field studies at the population level may also shed light on the practicality of using contraceptive baits for black rats in different habitats.

Degradation Kinetics and Transformation Products of Levonorgestrel and Quinestrol in Soils

Levonorgestrel (LNG) and quinestrol (QUN) are typical endocrine disruptors that enter the soil via sewage irrigation and sludge return. However, the fates of both compounds in soil are not well-understood. Laboratory microcosm studies were conducted to fill the gap of understanding of LNG and QUN behavior in soils. High values of goodness-of-fit indices (GFIs) were obtained using the double-first-order in parallel (DFOP) model and the single-first-order (SFO) model to fit the degradation kinetics of LNG and QUN in soils, respectively. The end-points (DT₅₀ and DT₉₀) of LNG and QUN were positively correlated with soil total organic carbon (TOC). Soil water content and temperature were observed to be critical factors in degradation of LNG and QUN. The degradation rates of LNG and QUN were very slow under sterile and flooded conditions, indicating that the aerobic microbial degradation was dominant in the degradation of LNG and QUN. Moreover, major transformation products were identified, and biodegradation pathways of LNG and QUN were proposed. The present study is expected to provide basic information for ecological risk assessment of LNG and QUN in the soil compartment.

Recovery of fertility in quinestrol-treated or diethylstilbestrol-treated mice: Implications for rodent management

Fertility control is an alternative strategy to traditional culling for the management of rodent pests. Previous studies have demonstrated that quinestrol is a potential contraceptive for male rodents, but the recovery of fertility in quinestrol-treated rodents has not been evaluated. This study used C57BL/6J mice to evaluate the recovery rate of male fertility after the administration of quinestrol. Diethylstilbestrol (DES), a non-steroid estrogenic compound, was used for comparison. Different groups of mice were treated with 1 mg/kg quinestrol, 1 mg/kg DES, or castor oil separately for 7 days. These mice were then killed on days 8, 22 and 50 respectively. Our results indicated that the weight of epididymides and seminal vesicles decreased significantly on days 8 and 22 in quinestrol/DES-treated mice, with extensive histological changes in the seminiferous tubules. Sperm concentrations in the cauda epididymal fluid were significantly reduced on days 8 and 22 in both quinestrol and DES treatment groups and on day 50 for the DES, but not the quinestrol group. Further analysis revealed that DES-treated mice exhibited a higher proportion of abnormal sperm accumulation in the epididymis, indicating that the normal sperm transportation to the cauda epididymis was blocked. Our results indicate that the anti-fertility effects on male mice given quinestrol were of shorter duration than for those receiving DES at the dose of 1 mg/kg body weight.