Chlamydia trachomatis Variants Escaping Detection in the Aptima Combo 2 Assay in the United States.

BACKGROUND: The Aptima Combo 2 (AC2) assay manufactured by Hologic, Inc., detects Neisseria gonorrhoeae and/or Chlamydia trachomatis (CT) in urogenital and extragenital specimens by targeting either a 16S rRNA (N. gonorrhoeae) or 23S rRNA (CT) region. In 2019, a mutation (C1515T) in the 23S rRNA region was reported to cause false-negative/equivocal results in specimens collected in Finland. Specimens containing this variant (Fl-nvCT) were also discovered internationally. Working with specimens submitted to a large commercial laboratory, we sought to determine if this variant was also present in the United States. METHODS: A subset (n = 401) of specimens tested with the AC2 assay collected during a 5-week period in late 2019/early 2020 were evaluated using an updated AC2 assay. RESULTS: Although the FI-nvCT variant was not detected within this specimen panel, 2 CT variants containing 23S rRNA mutations (A1518G, G1526A) were identified. The updated AC2 assay targeting an additional region of the 23S rRNA detected both of these variants. A retrospective study of >18 million AC2 results tested between 2018 and 2019 did not display a decrease in CT positivity. CONCLUSIONS: Although we did not detect the Fl-nvCT variant among US specimens, we show evidence that the low occurrence of similar diagnostic-escape mutants can be detected with an updated AC2 assay using multiple 23S rRNA targets.

Detection of Lymphogranuloma Venereum-Associated Chlamydia trachomatis L2 Serovars in Remnant Rectal Specimens Collected from 7 US Public Health Laboratories.

ABSTRACT: The frequency of lymphogranuloma venereum or invasive Chlamydia trachomatis infection with serovar L1, L2, or L3 is unknown in the United States. While no diagnostic test is commercially available, we used a laboratory-developed test and detected lymphogranuloma venereum-associated serovar L2 in 14% of 132 remnant C. trachomatis-positive rectal swabs.

Role of Synonymous Mutations in the Evolution of TEM ß-Lactamase Genes.

Nonsynonymous mutations are well documented in TEM ß-lactamases. The resulting amino acid changes often alter the conferred phenotype from broad spectrum (2b) conferred by TEM-1 to extended spectrum (2be), inhibitor resistant (2br), or both extended spectrum and inhibitor resistant (2ber). The encoding blaTEM genes also deviate in numerous synonymous mutations, which are not well understood. blaTEM-3 (2be), blaTEM-33 (2br), and blaTEM-109 (2ber) were studied in comparison to blaTEM-1blaTEM-33 was chosen for more detailed studies because it deviates from blaTEM-1 by a single nonsynonymous mutation and three additional synonymous mutations. Genes encoding the enzymes with only nonsynonymous or all (including synonymous) mutations plus all permutations between blaTEM-1 and blaTEM-33 were expressed in Escherichia coli cells. In disc diffusion assays, genes encoding TEM-3, TEM-33, and TEM-109 with all synonymous mutations resulted in higher resistance levels than genes without synonymous mutations. Disc diffusion assays with the 16 genes carrying all possible nucleotide change combinations between blaTEM-1 and blaTEM-33 indicated different susceptibilities for different variants. Nucleotide BLAST searches did not identify genes without synonymous mutations but did identify some without nonsynonymous mutations. Energies of possible secondary mRNA structures calculated with mfold are generally higher with synonymous mutations, suggesting that their role could be to destabilize the mRNA and facilitate its unfolding for efficient translation. In summary, our data indicate that transition from blaTEM-1 to other variant genes by simply acquiring the nonsynonymous mutations is not favored. Instead, synonymous mutations seem to support the transition to other variant genes with nonsynonymous mutations leading to different phenotypes.

Prevalence of Urogenital Mycoplasma genitalium Infection, United States, 2017 to 2018.

ABSTRACT: During the 2017-2018 National Health and Nutrition Examination Survey, urine samples from participants aged 14 to 59 years were tested for Mycoplasma genitalium infection. Overall prevalence was 1.7% (95% confidence interval [CI], 1.1%-2.7%). Prevalence was similar between males (1.8% [95% CI, 0.9%-3.1%]) and females (1.7% [95% CI, 0.8%-3.0%]).

Personal respiratory protection and resiliency in a pandemic, the evolving disposable versus reusable debate and its effect on waste generation.

The COVID-19 pandemic sweeping much of the globe is not anticipated to be short in duration, with contingency plans suggesting that it may last at least eighteen months. In the United States, one of the critical issues in coping with the pandemic has been a lack of essential personal protective equipment (PPE), at the local, state, and national level. As COVID-19 is primarily transferred through respiratory routes, adequate respiratory protection is a dire necessity. The shift from durable and reusable medical supplies in recent years to their single use counterparts has reduced the resiliency of the medical system with respect to PPE and other critical supplies in the current pandemic. This work explores the role of reusable compared to single use respiratory protection in the current pandemic, including reprocessing of single use options, from the perspective of number of equivalent protection devices needed. The current state of literature is also reviewed to provide context to this work, with respect to resource procurement. The economic cost of PPE throughout a pandemic is explored, and it is found that utilizing reusable PPE options depending on filter cycling may be less costly. Increased waste production is another issue with the current pandemic, and this is explored utilizing a mass basis, finding that reusable respiratory PPE would generate less waste than using single use PPE in a business as usual scenario. As future outbreaks of COVID-19 are likely along with other future pandemics, this work provides insights at how to prepare from the standpoint of PPE, and in particular respiratory protection.

Guidelines for screening and management of late and long-term consequences of myeloma and its treatment.

A growing population of long-term survivors of myeloma is now accumulating the 'late effects' not only of myeloma itself, but also of several lines of treatment given throughout the course of the disease. It is thus important to recognise the cumulative burden of the disease and treatment-related toxicity in both the stable and active phases of myeloma, some of which is unlikely to be detected by routine monitoring. We summarise here the evidence for the key late effects in long-term survivors of myeloma, including physical and psychosocial consequences (in Parts 1 and 2 respectively), and recommend the use of late-effects screening protocols in detection and intervention. The early recognition of late effects and effective management strategies should lead to an improvement in the management of myeloma patients, although evidence in this area is currently limited and further research is warranted.

A Macaque Model for Rectal Lymphogranuloma Venereum and Non-Lymphogranuloma Venereum Chlamydia trachomatis: Impact on Rectal Simian/Human Immunodeficiency Virus Acquisition.

BACKGROUND: Sustained genital tract inflammation caused by sexually transmitted infections (STIs) is known to increase risk of vaginal human immunodeficiency virus (HIV) infections but, to our knowledge, there are no nonhuman primate studies that have evaluated its link to rectal HIV acquisition. METHODS: Rhesus macaques inoculated with Chlamydia trachomatis (CT) (serovars LGV-L2 and CT-E; n = 7) or saline (n = 7) received up to 20 rectal challenges twice a week of simian/HIV immunodeficiency virus (SHIVSF162p3). SHIV viremia was determined by real-time PCR and Chlamydia infection by APTIMA Combo 2 testing. The rectal cytokine-chemokine levels were evaluated by multiplex bead assays. RESULTS: Rectal Chlamydia infection was maintained throughout the study. We did not observe significant differences (P = 1.0) in frequency of SHIV acquisition between the STI and control arms. It took fewer SHIV challenges to infect the STI animals although the difference was not significant (P = 0.59). There were no significant differences in peak plasma viremia between STI and control arms (P = 0.63). The association of plasma viremia with rectal shedding was significantly different by arm (P = 0.038). CONCLUSIONS: In the first such study in a macaque model, we did not observe an increased risk of SHIV acquisition due to rectal Chlamydia coinfection. This macaque model can be further developed and expanded to better investigate the impact of different rectal STIs on HIV acquisition.

Development of a rectal sexually transmitted infection (STI) Model in Rhesus macaques using Chlamydia trachomatis serovars E and L2.

BACKGROUND: Rectal STI coinfection models enhance the understanding of rectal HIV transmission risk factors. MATERIALS AND METHODS: Rhesus macaques (n=9) were exposed to one of three rectal Chlamydia trachomatis (CT) challenges: C. trachomatis L2 (CT-L2 ); C. trachomatis serovar E (CT-E), followed by CT-L2 ; or CT-E, treatment/clearance, then CT-L2 . Infections were monitored by PCR. Weekly blood and rectal secretion/lavage samples were collected for cytokine analyzes and/or epithelial sloughing, occult, and overt blood determinations. RESULTS: Chlamydial infections were successfully established in each animal, with varying degrees of persistence. Mucosal IL-1beta was upregulated in animals consecutively infected with CT-E then CT-L2 (P=.05). Epithelial sloughing was also significantly increased post-infection in this group (P=.0003). CONCLUSIONS: This study demonstrates successful rectal infection of rhesus macaques with CT-E and CT-L2 and describes measures of assessing rectal inflammation and pathology. Different infection strategies yield varying inflammatory and pathologic outcomes, providing well-described models for future SIV/SHIV susceptibility studies.

Relationship of menstrual cycle and vaginal infection in female rhesus macaques challenged with repeated, low doses of SIVmac251.

Varying susceptibility during menstrual cycling could be a factor for S(H)IV infection risk in female rhesus macaques. We retrospectively determined vaginal SIV infection time points relative to the menstrual cycle in a group of rhesus macaques (n=11) enrolled in an HIV transmission trial. Eight of nine rhesus macaques became infected around menstruation time.

Techniques for intraoperative radiation therapy for early-stage breast carcinoma.

Intraoperative radiation therapy (IORT) is a method of accelerated partial breast irradiation developed to replace other longer courses of radiotherapy with a single radiation session administered at the time of breast-conserving surgery. The purpose of this review is to summarize the advantages and disadvantages of breast IORT techniques that are currently available, as well to consider potential alternative techniques for breast IORT or ultra-short course breast radiotherapy. Furthermore, we highlight the published outcomes for the IORT treatment approaches including: electron therapy, superficial photon therapy and other techniques. Potential future directions of IORT are explored including novel IORT techniques utilizing intraoperative brachytherapy with in-room imaging and rapid treatment planning.

Preclinical evaluation of the immunomodulatory lymphocyte trafficking drug FTY720 for HIV prevention in the female genital mucosa of macaques.

FTY720 has been shown to reduce inflammatory cytokines and immune cells in the genital mucosa of macaques. This pilot study examined the ability of FTY720 to inhibit HIV acquisition. Systemic treatment with FTY720 failed to prevent or delay vaginal SHIV transmission.

Evaluation of pigtail macaques as a model for the effects of copper intrauterine devices on HIV infection.

BACKGROUND: Long-acting, hormonal contraception may increase HIV risk. Copper intrauterine devices (IUDs) could serve as non-hormonal alternatives. We pilot a pigtail macaque model for evaluating HIV susceptibility factors during copper IUD use. METHODS: Frameless and flexible GyneFix(®) copper IUDs were surgically implanted into three SHIVSF 162p3 -positive macaques via hysterotomy and monitored for up to 4 months. Four macaques served as non-IUD controls. RESULTS: All animals retained the devices without complications. No consistent change in vaginal viral RNA or inflammatory cytokines was seen. Two animals had altered menstrual cycles and experienced marked thinning of vaginal epithelium after IUD insertion. Histological examination of uterine tissue at necropsy revealed endometrial ulceration and lymphocytic inflammation with glandular loss at sites of direct IUD contact. CONCLUSIONS: Although the need for insertion surgery could limit its usefulness, this model will allow studies on copper IUDs and SHIV shedding, disease progression, and HIV susceptibility factors.

SHIV susceptibility changes during the menstrual cycle of pigtail macaques.

BACKGROUND: Hormonal changes during menstrual cycling may affect susceptibility to HIV. METHODS: We determined the simian human immunodeficiency virus (SHIV) acquisition time point in 43 cycling pigtail macaques infected by repeated vaginal virus exposures initiated randomly in the cycle. RESULTS: SHIV infection was first detected in the follicular phase in 38 macaques (88%), and in the luteal phase in five macaques (12%), indicating a statistically significant timing difference. Assuming a 7-day eclipse phase, most infections occurred during or following a high-progesterone period associated with menstruation, vaginal epithelium thinning, and suppressed mucosal immunity. CONCLUSIONS: This raises questions whether other high-progesterone conditions (pregnancy, hormonal contraception) similarly affect HIV risk.

Use, reuse, and waste management of single-use products associated with the COVID-19 pandemic in the United States.

Single-use product usage is not a new concern. However, during the early stages of the COVID-19 pandemic, the use and disposal of single-use products, especially those related to managing the pandemic, rose to prominence. Reports of shortages-and at the same time litter formation arising from improper disposal of various pandemic-related materials such as gloves, masks, wipes, and food takeout containers-were frequently relayed. To address shortages, it was recommended that single-use products be reused in some instances. As these recommendations were widely adopted, it became essential to assess consumer preferences regarding single-use product usage. Aiming to fill that void, a survey was distributed to learn about single-use product usage, possible reuse of single-use products, and waste-management practices during the COVID-19 pandemic in the US. Respondents preferred reusable fabric masks followed by disposable surgical masks. A significant percentage of respondents answered that they would reuse a disposable mask and mostly selected rotating masks as the preferred "disinfection" method in between the reuse of single-use masks. Gloves were not used by most respondents whereas wipes and/or paper towels were used by more than half of respondents. Free-response answers were analyzed for common themes. Concerns related to pandemic-related product use and disposal, and food packaging or food preparation were observed in the free-response answers. This survey reveals that respondents perceived changes in their consumption and waste generation or perceived a change in the type of products consumed and discarded due to the pandemic. Overall, respondents expressed a preference for reuse and a concern over the increase in single-use products. Results of this study can be used to make projections on the consumption and reuse of single-use products in crisis scenarios. In addition, the data can be used to model the use and disposal phase in single-use product life-cycle assessments. Integr Environ Assess Manag 2024;00:1-11. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Estimation of Gait Parameters in Huntington's Disease Using Wearable Sensors in the Clinic and Free-living Conditions.

In Huntington's disease (HD), wearable inertial sensors could capture subtle changes in motor function. However, disease-specific validation of methods is necessary. This study presents an algorithm for walking bout and gait event detection in HD using a leg-worn accelerometer, validated only in the clinic and deployed in free-living conditions. Seventeen HD participants wore shank- and thigh-worn tri-axial accelerometers, and a wrist-worn device during two-minute walk tests in the clinic, with video reference data for validation. Thirteen participants wore one of the thigh-worn tri-axial accelerometers (AP: ActivPAL4) and the wrist-worn device for 7 days under free-living conditions, with proprietary AP data used as reference. Gait events were detected from shank and thigh acceleration using the Teager-Kaiser energy operator combined with unsupervised clustering. Estimated step count (SC) and temporal gait parameters were compared with reference data. In the clinic, low mean absolute percentage errors were observed for stride (shank/thigh: 0.6/0.9%) and stance (shank/thigh: 3.3/7.1%) times, and SC (shank/thigh: 3.1%). Similar errors were observed for proprietary AP SC (3.2%), with higher errors observed for the wrist-worn device (10.9%). At home, excellent agreement was observed between the proposed algorithm and AP software for SC and time spent walking (ICC [Formula: see text]). The wrist-worn device overestimated SC by 34.2%. The presented algorithm additionally allowed stride and stance time estimation, whose variability correlated significantly with clinical motor scores. The results demonstrate a new method for accurate estimation of HD gait parameters in the clinic and free-living conditions, using a single accelerometer worn on either the thigh or shank.

Sexually transmitted infections and depot medroxyprogesterone acetate do not impact protection from simian HIV acquisition by long-acting cabotegravir in macaques.

OBJECTIVE: We had previously shown that long-acting cabotegravir (CAB-LA) injections fully protected macaques from vaginal simian HIV (SHIV) infection. Here, we reassessed CAB-LA efficacy in the presence of depot medroxyprogesterone acetate and multiple sexually transmitted infections (STIs) that are known to increase HIV susceptibility in women. DESIGN: Two macaque models of increasing vaginal STI severity were used for efficacy assessment. METHODS: The first study (n = 11) used a double STI model that had repeated exposures to two vaginal STI, Chlamydia trachomatis and Trichomonas vaginalis. Six animals were CAB-LA treated and five were controls. The second study (n = 9) included a triple STI model with repeated exposures to C. trachomatis, T. vaginalis and syphilis, and the contraceptive, depot medroxyprogesterone acetate (DMPA). Six animals were CAB-LA treated and three were controls. All animals received up to 14 vaginal SHIV challenges. A survival analysis was performed to compare the number of SHIV challenges to infection in the drug-treated group compared with untreated controls over time. RESULTS: All six CAB-LA treated animals in both models, the double STI or the triple STI-DMPA model, remained protected after 14 SHIV vaginal challenges, while the untreated animals became SHIV-infected after a median of two challenges (log-rank P < 0.001) or one challenge (log-rank P = 0.002), respectively. Both models recapitulated human STI disease, with vaginal discharge, ulcers, and seroconversion. CONCLUSION: In these high and sustained susceptibility models spanning more than 3 months, CAB-LA maintained complete efficacy, demonstrating robustness of the CAB-LA dose used in clinical trials, and suggesting its insensitivity to multiple STIs and DMPA.

Sensory integration therapy for children with autism and sensory processing difficulties: the SenITA RCT.

BACKGROUND: Carers report unmet need for occupational therapy services addressing sensory difficulties in autism, yet insufficient evidence exists to recommend a therapeutic approach. OBJECTIVES: Our aim was to determine the clinical effectiveness and cost-effectiveness of sensory integration therapy for children with autism and sensory difficulties across behavioural, functional and quality-of-life outcomes. DESIGN: We carried out a parallel-group randomised controlled trial, incorporating an internal pilot and a process evaluation. Randomisation utilised random permuted blocks. SETTING AND PARTICIPANTS: Children were recruited via services and self-referral in Wales and England. Inclusion criteria were having an autism diagnosis, being in mainstream primary education and having definite/probable sensory processing difficulties. Exclusion criteria were having current/previous sensory integration therapy and current applied behaviour analysis therapy. INTERVENTION: The intervention was manualised sensory integration therapy delivered over 26 weeks and the comparator was usual care. OUTCOMES: The primary outcome was problem behaviours (determined using the Aberrant Behavior Checklist), including irritability/agitation, at 6 months. Secondary outcomes were adaptive behaviour, functioning and socialisation (using the Vineland Adaptive Behavior Scales); carer stress (measured using the Autism Parenting Stress Index); quality of life (measured using the EuroQol-5 Dimensions and Carer Quality of Life); functional change (according to the Canadian Occupational Performance Measure); sensory processing (determined using the Sensory Processing Measure™ at screening and at 6 months to examine mediation effects); and cost-effectiveness (assessed using the Client Service Receipt Inventory). Every effort was made to ensure that outcome assessors were blind to allocation. RESULTS: A total of 138 participants were randomised (n = 69 per group). Usual care was significantly different from the intervention, which was delivered with good fidelity and adherence and minimal contamination, and was associated with no adverse effects. Trial procedures and outcome measures were acceptable. Carers and therapists reported improvement in daily functioning. The primary analysis included 106 participants. There were no significant main effects of the intervention at 6 or 12 months. The adjusted mean difference between groups on the Aberrant Behavior Checklist - irritability at 6 months post randomisation was 0.40 (95% confidence interval -2.33 to 3.14; p = 0.77). Subgroup differences in irritability/agitation at 6 months were observed for sex of child (intervention × female = 6.42, 95% confidence interval 0.00 to 12.85; p = 0.050) and attention deficit hyperactivity disorder (intervention × attention deficit hyperactivity disorder = -6.77, 95% confidence interval -13.55 to -0.01; p = 0.050). There was an effect on carer stress at 6 months by region (intervention × South England = 7.01, 95% confidence interval 0.45 to 13.56; p = 0.04) and other neurodevelopmental/genetic conditions (intervention × neurodevelopmental/genetic condition = -9.53, 95% confidence interval -18.08 to -0.98; p = 0.030). Carer-rated goal performance and satisfaction increased across sessions (p < 0.001), with a mean change of 2.75 (95% confidence interval 2.14 to 3.37) for performance and a mean change of 3.34 (95% confidence interval 2.63 to 4.40) for satisfaction. Health economic evaluation suggests that sensory integration therapy is not cost-effective compared with usual care alone. LIMITATIONS: Limitations included variability of the intervention setting (i.e. NHS vs. private), delay for some receiving therapy, an error in administration of Vineland Adaptive Behavior Scales and no measurement of comparator arm goal performance. CONCLUSIONS: The intervention did not demonstrate clinical benefit above standard care. Subgroup effects are hypothesis-generating only. The intervention is likely to be effective for individualised performance goals, although it is unclear whether effects were in addition to standard care or were maintained. FUTURE WORK: Further investigation of subgroup effects is needed. TRIAL REGISTRATION: This trial is registered as ISRCTN14716440. FUNDING: This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 29. See the NIHR Journals Library website for further project information.

Children with autism often experience problems with processing sensory information (e.g. noise, touch, movement, taste and sight), and this can lead to problems in daily life. This study was designed to see if sensory integration therapy can help children with these difficulties. Sensory integration therapy is a type of face-to-face play-based treatment that is delivered by occupational therapists. We compared sensory integration therapy with the type of treatment normally offered to children with autism (i.e. 'usual care'). We recruited children and their carers from Wales and England. Children could take part in the study if they had an autism diagnosis, had sensory processing difficulties and were in mainstream primary education. The children taking part in the study were randomly split into two groups. Sixty-nine children were given sensory integration therapy and 69 children carried on with their usual care. The sensory integration therapy involved 24 face-to-face sessions in an occupational therapy clinic, followed by two telephone calls with the carer. The sensory integration therapy lasted for 26 weeks. We collected information on the type of care being given to children in the usual-care group. Carers of each child were asked questions about their child's behaviour 6 and 12 months after starting the study. Some carers also completed an interview to talk about what it was like taking part in the study. Therapists delivered the sensory integration therapy well. Carers and therapists said that they saw some improvements. However, sensory integration therapy was not significantly better than the usual care and is a more expensive option. We cannot say that sensory integration therapy is helpful for all children with autism and different sensory processing difficulties; however, it might be helpful for some children to focus on specific problems. Future work could focus on which children and problems it would help the most.

A pilot phase II trial of magnesium supplements to reduce menopausal hot flashes in breast cancer patients.

BACKGROUND: We tested if magnesium would diminish bothersome hot flashes in breast cancer patients. METHODS: Breast cancer patients with at least 14 hot flashes a week received magnesium oxide 400 mg for 4 weeks, escalating to 800 mg if needed. Hot flash score (frequency × severity) at baseline was compared to the end of treatment. RESULTS: Of 29 who enrolled, 25 women completed treatment. The average age was 53.5 years; six African American, the rest Caucasian; eight were on tamoxifen, nine were on aromatase inhibitors, and 14 were on anti-depressants. Seventeen patients escalated the magnesium dose. Hot flash frequency/week was reduced from 52.2 (standard error (SE), 13.7) to 27.7 (SE, 5.7), a 41.4% reduction, p = 0.02, two-sided paired t test. Hot flash score was reduced from 109.8 (SE, 40.9) to 47.8 (SE, 13.8), a 50.4% reduction, p = 0.04. Of 25 patients, 14 (56%) had a >50% reduction in hot flash score, and 19 (76%) had a >25% reduction. Fatigue, sweating, and distress were all significantly reduced. Side effects were minor: two women stopped the drug including one each with headache and nausea, and two women had grade 1 diarrhea. Compliance was excellent, and many patients continued treatment after the trial. CONCLUSIONS: Oral magnesium appears to have helped more than half of the patients and was well tolerated. Side effects and cost ($0.02/tablet) were minimal. A randomized placebo-controlled trial is planned.

An exploration of economic valuation of phosphorus in the environment and its implications in decision making for resource recovery.

In decision making processes today it is typically economic considerations that are the focus and that dictate what decisions are made; however, this approach neglects significant potential impacts these decisions can have, namely environmental impacts. One way to incorporate environmental considerations into current decision making processes is through monetary valuation. This work surveys environmental economics literature that quantifies the monetary valuation of nutrients and nutrient pollution, and applies monetary valuation of phosphorus to a case study of nutrient recovery in wastewater treatment. The literature review catalogues three different monetary valuation methods, economic consequences, mitigation and restoration, and willingness to pay, and highlights the different perspectives each of these methods addresses. Additionally, the case study demonstrates how monetary valuation can be applied in a realistic decision making scenario and highlights how variability in monetary valuation methods and results can affect decision making. From this literature and case study assessment a call can be made to establish more standardized methods for determining the monetary valuation of nutrients in an effort to promote and encourage the consideration of nutrient pollution issues in future decision making.

Mutation S115T in IMP-Type Metallo-ß-Lactamases Compensates for Decreased Expression Levels Caused by Mutation S119G.

(1) Background: Metallo-ß-lactamases (MBLs) have raised concerns due to their ability to inactivate carbapenems and newer generation cephalosporins and the absence of clinically available MBL inhibitors. Their genes are often transferred horizontally, and the number of MBL variants has grown exponentially, with many newer variants showing enhanced enzyme activity or stability. In this study, we investigated a closely related group of variants from the IMP family that all contain the combination of mutations S115T and S119G relative to IMP-1. (2) Methods: The effects of each individual mutation and their combination in the IMP-1 sequence background in comparison to IMP-1 were investigated. Their ability to confer resistance and their in-cell expression levels were determined. All enzymes were purified, and their secondary structure and thermal stability were determined with circular dichroism. Their Zn(II) content and kinetic constants with a panel of ß-lactam antibiotics were determined. (3) Results: All four enzymes were viable and conferred resistance to all antibiotics tested except aztreonam. However, the single-mutant enzymes were slightly deficient, IMP-1S115T due to decreased enzyme activity and IMP-1-S119G due to decreased thermal stability and expression, while the double mutant did not show these defects. (4) Conclusions: These observations suggest that S119G was acquired due to its increased enzyme activity and S115T to suppress the thermal stability and expression defect introduced by S119G.