Changes In Bacterial Load Research Articles

Exposure of Escherichia coli to antibiotic-efflux pump inhibitor combinations in a pharmacokinetic model: impact on bacterial clearance and drug resistance.

Efflux pump inhibitors (EPIs) offer an attractive therapeutic option when combined with existing classes. However, their optimal dosing strategies are unknown. MICs of ciprofloxacin (CIP)+/-chlorpromazine, phenylalanine-arginine β naphthylamide (PAβN) and a developmental molecule MBX-4191 were determined and the pharmacodynamics (PD) was studied in an in vitro model employing Escherichia coli MG1655 and its isogenic MarR mutant (I1147). Exposure ranging experiments were performed initially then fractionation. Changes in bacterial load and population profiles were assessed. Strains recovered after EPI simulations were studied by WGS. The CIPMICs for E. coli MG1655 and I1147 were 0.08 and 0.03 mg/L. Chlorpromazine at a concentration of 60 mg/L, PAβN concentrations of 30 mg/L and MBX-4191 concentrations of 0.5-1.0 mg/L reduced CIP MICs for I1147 and enhanced bacterial killing. Using CIP at an AUC of 1.2 mg·h/L, chlorpromazine AUC was best related to reduction in bacterial load at 24 h, however, when the time drug concentration was greater than 25 mg/L (T > 25 mg/L) chlorpromazine was also strongly related to the effect. For PaβN with CIP AUC, 0.6 mg·h/L PaβN AUC was best related to a reduction in bacterial load. MBX-4191T > 0.5-0.75 mg·h/L was best related to reduction in bacterial load. Changes in population profiles were not seen in experiments of ciprofloxacin + EPIs. WGS of recovered strains from simulations with all three EPIs showed mutations in gyrA, gyrB or marR. AUC was the pharmacodynamic driver for chlorpromazine and PAβN while T > threshold was the driver for MBX-4191 and important in the activity of chlorpromazine and PAβN. Changes in population profiles did not occur with combinations of ciprofloxacin + EPIs, however, mutations in gyrA, gyrB and marR were detected.

Assessing Changes in Bacterial Load and Antibiotic Resistance in the Legon Sewage Treatment Plant between 2018 and 2023 in Accra, Ghana.

Wastewater treatment plants are efficient in reducing bacterial loads but are also considered potential drivers of environmental antimicrobial resistance (AMR). In this study, we determined the effect of increased influent wastewater volume (from 40% to 66%) in the Legon sewage treatment plant (STP) on the removal of E. coli from sewage, along with changes in AMR profiles. This before and after study compared E. coli loads and AMR patterns in influent and effluent samples from a published baseline study (January-June 2018) with a follow-up study (March-May 2023). Extended-spectrum beta-lactamase (ESBL) E. coli were measured pre- and post-sewage treatment during the follow-up study. The follow-up study showed 7.4% and 24% ESBL E. coli proportions in influent and effluent, respectively. In both studies, the STP was 99% efficient in reducing E. coli loads in effluents, with no significant difference (p = 0.42) between the two periods. More E. coli resistance to antimicrobials was seen in effluents in the follow-up study versus the baseline study. The increased influent capacity did not reduce the efficiency of the STP in removing E. coli from influent wastewater but was associated with increased AMR patterns in effluent water. Further studies are required to determine whether these changes have significant effects on human health.

Antibacterial effect of seven days exposure to ceftolozane-tazobactam as monotherapy and in combination with fosfomycin or tobramycin against Pseudomonas aeruginosa with ceftolozane-tazobactam MICs at or above 4 mg/l in an in vitro pharmacokinetic model.

To use a pre-clinical pharmacokinetic infection model to assess the antibacterial effect of ceftolozane/tazobactam alone or in combination with fosfomycin or tobramycin against Pseudomonas aeruginosa strains with MICs at or higher than the clinical breakpoint (MIC ≥ 4 mg/L). An in vitro model was used to assess changes in bacterial load and population profiles after exposure to mean human serum concentrations of ceftolozane/tazobactam associated with doses of 2 g/1 g q8h, fosfomycin concentrations associated with doses of 8 g q8h or tobramycin at doses of 7 mg/kg q24 h over 168 h. Simulations of ceftolozane/tazobactam at 2 g/1 g q8h alone produced 3.5-4.5 log reductions in count by 6 h post drug exposure for strains with MIC ≤32 mg/L. The antibacterial effect over the first 24 h was related to ceftolozane/tazobactam MIC. There was subsequent regrowth with most strains to bacterial densities of >106 CFU/mL. Addition of either fosfomycin or tobramycin resulted in suppression of regrowth and in the case of tobramycin more rapid initial bacterial killing up to 6 h. These effects could not be related to either fosfomycin or tobramycin MICs. Changes in population profiles were noted with ceftolozane/tazobactam alone often after 96 h exposure but such changes were suppressed by fosfomycin and almost abolished by the addition of tobramycin. The addition of either fosfomycin or tobramycin to ceftolozane/tazobactam at simulated human clinically observed concentrations reduced P. aeruginosa bacterial loads and the risk of resistance to ceftolozane/tazobactam when strains had ceftolozane/tazobactam MIC values at or above the clinical breakpoint.

A phase IIb, open-label, randomized controlled dose ranging multi-centre trial to evaluate the safety, tolerability, pharmacokinetics and exposure-response relationship of different doses of delpazolid in combination with bedaquiline delamanid moxifloxacin in adult subjects with newly diagnosed, uncomplicated, smear-positive, drug-sensitive pulmonary tuberculosis

BackgroundLinezolid is an effective, but toxic anti-tuberculosis drug that is currently recommended for the treatment of drug-resistant tuberculosis. Improved oxazolidinones should have a better safety profile, while preserving efficacy. Delpazolid is a novel oxazolidinone developed by LegoChem Biosciences Inc. that has been evaluated up to phase 2a clinical trials. Since oxazolidinone toxicity can occur late in treatment, LegoChem Biosciences Inc. and the PanACEA Consortium designed DECODE to be an innovative dose-ranging study with long-term follow-up for determining the exposure–response and exposure–toxicity relationship of delpazolid to support dose selection for later studies. Delpazolid is administered in combination with bedaquiline, delamanid and moxifloxacin.MethodsSeventy-five participants with drug-sensitive, pulmonary tuberculosis will receive bedaquiline, delamanid and moxifloxacin, and will be randomized to delpazolid dosages of 0 mg, 400 mg, 800 mg, 1200 mg once daily, or 800 mg twice daily, for 16 weeks. The primary efficacy endpoint will be the rate of decline of bacterial load on treatment, measured by MGIT liquid culture time to detection from weekly sputum cultures. The primary safety endpoint will be the proportion of oxazolidinone class toxicities; neuropathy, myelosuppression, or tyramine pressor response.Participants who convert to negative liquid media culture by week 8 will stop treatment after the end of their 16-week course and will be observed for relapse until week 52. Participants who do not convert to negative culture will receive continuation phase treatment with rifampicin and isoniazid to complete a six-month treatment course.DiscussionDECODE is an innovative dose-finding trial, designed to support exposure-response modelling for safe and effective dose selection. The trial design allows assessment of occurrence of late toxicities as observed with linezolid, which is necessary in clinical evaluation of novel oxazolidinones. The primary efficacy endpoint is the change in bacterial load, an endpoint conventionally used in shorter dose-finding trials. Long-term follow-up after shortened treatment is possible through a safety rule excluding slow-and non-responders from potentially poorly performing dosages.Trial registrationDECODE was registered in ClinicalTrials.gov before recruitment start on 22 October 2021 (NCT04550832).

Evaluation of red-complex bacteria loads in complete denture patients: a pilot study

ObjectiveThis pilot study aimed to evaluate red-complex bacteria (RCB) loads in edentulous patients, before and after dentures’ insertion.Materials and methodsThirty patients were included in the study. Deoxyribonucleic acid (DNA) isolated from bacterial samples were obtained from the dorsum of the tongue before and 3 months after complete dentures (CDs) insertion in order to identify the presence of RCB (Tannerella forsythia, Porphyromonas gingivalis, and Treponema denticola) and quantify their loads, using real-time polymerase chain reaction (RT-PCR). Bacterial loads were represented as “Lg (genome equivalents/sample)” and the data classified according to the “ParodontoScreen” test.ResultsSignificant changes in bacterial loads were observed before and 3 months after the CDs insertion for: P. gingivalis (0.40 ± 0.90 vs 1.29 ± 1.64, p = 0.0007), T. forsythia (0.36 ±0.94 vs 0.87 ± 1.45, p = 0.005), and T. denticola (0.11 ± 0.41 vs 0.33 ± 0.75, p = 0.03). Before the CDs insertion, all patients had a normal bacterial prevalence range (100%) for all analyzed bacteria. Three months after the insertion, 2 (6.7%) of them had a moderate bacterial prevalence range for P. gingivalis, while 28 (93.3%) had a normal bacterial prevalence range.ConclusionThe use of CDs has a significant impact on increasing RCB loads in edentulous patients.

Detection and quantification of Klebsiella pneumoniae in American bullfrog (Rana catesbeiana) by Taqman MGB probe real-time fluorescence quantitative PCR

Klebsiella pneumoniae is an important pathogen in American bullfrog farming. It causes serious diseases, resulting in significant losses. However, the spread and replication of K. pneumoniae in infected bullfrog tissues are poorly understood. This study aimed to investigate the variation in K. pneumoniae loads in the organs of infected bullfrogs to clarify the effect of K. pneumoniae replication. In this work, a TaqMan minor groove binder probe fluorescence real-time quantitative polymerase chain reaction (qPCR) assay was developed to rapidly detect and quantify K. pneumoniae.The detection limit of the qPCR method was as low as 2.9 copies/μL, which was 100 times more sensitive than that of the conventional PCR. In addition, comparison of K. pneumoniae in tissue mixing and mucus showed similar positive rates, K. pneumoniae in bullfrogs could be preliminarily detected and monitored by anal mucus detection under noninvasive conditions. The changes in bacterial load detected by qPCR in different tissues of bullfrogs infected with K. pneumoniae showed that the bacterial concentrations increased tremendously 3 days after infection, and the spleen was the major site for K. pneumoniae replication. The determination of the changes in tissue bacterial load provided useful data for elucidating the pathogenesis of K. pneumoniae in bullfrogs, while the mucus assay could be an effective tool for the early surveillance and prevention of K. pneumoniae in bullfrogs.

Differentially culturable tubercle bacteria as a measure of tuberculosis treatment response.

Routine efficacy assessments of new tuberculosis (TB) treatments include quantitative solid culture or routine liquid culture, which likely miss quantification of drug tolerant bacteria. To improve these assessments, comparative analyses using additional measures such as quantification of differentially culturable tubercle bacteria (DCTB) are required. Essential for enabling this is a comparative measure of TB treatment responses using routine solid and liquid culture with liquid limiting dilutions (LLDs) that detect DCTB in sputum. We recruited treatment-naïve TB patients, with and without HIV-infection, and serially quantified their sputum for DCTB over the course of treatment. Serial sputum sampling in 73 individuals during their first 14 days of treatment demonstrated that clearance of DCTB was slower compared to routine solid culture. Treatment response appeared to be characterized by four patterns: (1) Classic bi-phasic bacterial clearance; (2) early non-responders with slower clearance; (3) paradoxical worsening with an increase in bacterial count upon treatment initiation; and (4) non-responders with no change in bacterial load. During treatment, LLDs displayed greater bacterial yield when compared with quantitative solid culture. Upon treatment completion, 74% [46/62] of specimens displayed residual DCTB and within this group, two recurrences were diagnosed. Residual DCTB upon treatment completion was associated with a higher proportion of MGIT culture, GeneXpert, and smear positivity at two months post treatment. No recurrences occurred in the group without residual DCTB. These data indicate that DCTB assays detect distinct subpopulations of organisms in sputum that are missed by routine solid and liquid culture, and offer important alternatives for efficacy assessments of new TB treatments. The residual DCTB observed upon treatment completion suggests that TB treatment does not always eliminate all bacterial populations, a finding that should be investigated in larger cohorts.

617. Pharmacodynamics of Ceftolozane-Tazobactam (C/T) as Monotherapy and in Combination with Tobramycin or Fosfomycin Against P.aeruginosa with C/T MICs at or Above 4mg/L

Abstract Background Ceftolozane (C/T) is widely used in clinical practice to treat difficult and/or multidrug resistant Pseudomonas aeruginosa (Pa). However, clinical data is absent on the use of C/T therapy to treat Pa strains with C/T MICs ≥ 4mg/L, that is outside the wild type population. To address this, we simulated 7-day courses of C/T against 8 strains of Pa C/T MICs 4-64mg/L as monotherapy and in combination with tobramycin (T) or fosfomycin (F) using an in vitro pharmacokinetic model. Methods A single compartment dilutional in vitro model was used, volume central chamber 360mL, inoculum 106 CFU/mL. Differing drugs t½ were simulated using add back. Pa strain C/T MICs were 4-64mg/L, T 0.25-8mg/L and F 4-1024mg/L. C/T doses of 2-1g, 8h (Cmax 112-32mg/L, t½ 2.5-1h), T doses 7mg/Kg 24h (Cmax 22mg/L, t½ 2.5h) and F doses 4g 8h (Cmax 250mg/L, t½ 2.5h) were simulated for 7 days. Endpoints were changes in bacterial load (log CFU/ml) and population profiles (growth on C/T containing media at MICx4 and MICx8 concentrations). Results C/T alone resulted in rapid clearance of all strains after 4-12h exposure, with the antibacterial effect being poorest with strains with the highest C/T MICs. Regrowth occurred with 7/8 strains after 24-48h, counts reaching 6-8 logs by 7 days. Combination of C/T plus T increased the rate of initial clearance and suppressed regrowth with all strains. Combination of C/T plus F did not increase the rate of initial clearance except in the strains with the highest C/T MICs but resulted in suppression of regrowth with final bacterial counts of 3-4 logs at day 7. Changes in C/T population profiles occurred after 7 days exposure with growth on C/T MICx8 containing media in 6/8 strains exposed to C/T alone, but 0/8 strains exposed to C/T plus T and 1/8 strains exposed to C/T plus F. Conclusion Combinations of C/T plus T or F resulted in long term suppression of Pa bacterial load and minimised emergence of resistance in Pa strains with C/T MICs on or just above the epidemiological cut off value (MIC 4mg/L-64mg/L). Disclosures Alasdair P. MacGowan, MD, GSK: Grant/Research Support|InfectoPharm: Grant/Research Support|Merck: Advisor/Consultant|Shionogi: Advisor/Consultant|Venatorx: Advisor/Consultant.

Assessment of poultry process hygiene and bacterial dynamics along two broiler slaughter lines in Norway

Good process hygiene in broiler slaughter is paramount to achieve safe products with long shelf-lives. Here we investigated changes in bacterial load and diversity on chicken carcasses at selected stages on slaughtering lines in two abattoirs in Norway. Carcasses included in the study, came from flocks that had been classified as either positive or negative for Campylobacter. In total, 120 neck-skins were collected at four sampling points: before scalding, after plucking, after evisceration, and after chilling. The bacterial load was analyzed at each sampling point using quantitative and qualitative cultivation while the bacterial composition was determined using amplicon sequencing of the 16S rRNA gene. Bacterial loads on carcasses decreased along the slaughter line by 2.1, 1.1, 1.1, and 1.0 log cfu per g for Total Plate Counts (TPC), Enterobacteriaceae, Escherichia coli, and Campylobacter, respectively. The largest reduction was observed after washing and chilling. For TPC, a large reduction was also observed after scalding and plucking. Scalding water samples had low amounts of E. coli and were negative for Campylobacter. Only a weak statistical association was found between indicator counts and Campylobacter. The 16S rRNA amplicon sequencing results showed a more diverse bacterial community at the start of the slaughter line, dominated by Staphylococcus, Escherichia-Shigella, and Streptococcus, which altered to a less-diverse community, dominated by Asinibacterium spp., Afipia spp., Pseudomonas, Polaromonas, and Psychrobacter after chilling. Both abattoirs were assessed as low risk by a new categorization method. This study contributes to identify factors that increases and decreases levels of Campylobacter and other bacteria during slaughter and should enable the implementation of control measures and thus improve meat safety.

Total Nitrogen and Bacterial Analysis in Oil-Based Drill Cuttings Contaminated Soils Planted with Grass Species

The possibility of grass species phytoremediating oil-based drill cuttings contaminated soils was examined by assessing changes in bacterial load, bacterial species, and soil nitrogen. The experiment was modelled in a randomized complete block design by factorial of 6 x 3 x 2 x 2 for grass species, drill cuttings, time, and growth stage. The parameters assessed were total nitrogen, nitrogen reduction, bacterial load, and bacterial load reduction in soils. There was significant decrease in nitrogen from day of planting to harvesting. The highest reduction was observed in 0% and 25% treatments in mature P. maximum and young C. virgata. The lowest reduction was seen in A. compressus at 50% treatment. Significant difference in bacterial load was noticed in time in each treatment. Highest reduction of bacterial load was seen in 0% treatment level planted with A. compressus, A. gayanus, young C. virgata, H. contortus, P. maximum, and unplanted soils, which were not significantly different from 25% and 50% oil-based drill cuttings treatment except in young H. contortus and P. maximum. The lowest reduction was observed in 25% treatment level of young H. contortus and P. maximum. Micrococcus sp, Bacillus sp., and Staphyloccocus aureus were found in soils of the three treatment levels at planting. In addition, Protus sp was seen in soils of 0% and 50% treatment levels. Erwinnia sp and Escherichia coli was identified in 25% and 50% oil-based drill cuttings treated soils. Klebsiella sp was isolated from 25% oil-based drill cuttings treated soils. Therefore, Erwinia sp, E. coli, and Klebsiella sp were associated with oil-based drill cuttings contamination.

Profiling Branchial Bacteria of Atlantic Salmon (Salmo salar L.) Following Exposure to Antimicrobial Agents

Microbial gill diseases caused by either opportunistic or specific pathogens are an emerging area of concern for aquaculture producers in part due to their sometimes complex and/or cryptic nature. Many antimicrobial treatments used in aquacultural settings are broad spectrum in nature. The effect of such therapeutics upon reduction and recolonization of commensal or pathogenic microbiota post-treatment has received little attention to date. Commensal bacteria are an integral component of the barrier function of mucosal surfaces in animals. This study evaluated the effect of several commercially relevant antimicrobial treatments upon the diversity and composition of branchial bacteria of Atlantic salmon. Here we exposed Atlantic salmon smolt to a number of commercially relevant antimicrobial treatments including chemotherapeutants (chloramine-t and hydrogen peroxide) and antibiotics (oxytetracycline and florfenicol) in vivo. Subsequently we examined the change in bacterial load, 16S rRNA gene expression, and taxonomic diversity post-treatment upon the gills. Results revealed a decrease in cultivable bacterial colonies after antimicrobial treatment, and a downstream decrease in bacterial richness and abundance post-treatment, with colonization of several prominent pathogenic taxa including Vibrio and Tenacibaculum. Temporal tracing over a 14-day period demonstrated that the bacteriome of gill mucus is sensitive to change, and altered by antimicrobial treatment and handling. This study identified candidate antimicrobial treatments which could be implemented in future studies to illustrate the effect of dysbiosis on microbial gill diseases.

Rapid Detection of Extensively Drug-Resistant Tuberculosis in Clinical Samples Using a Novel Tabletop Platform: Protocol for a Prospective Clinical Study.

BackgroundThe lack of accurate and efficient diagnostic devices for extensively drug-resistant tuberculosis (XDR-TB) makes it a severe threat to global public health. A prospective clinical study in an intended-use cohort was designed to evaluate the Akonni Biosystems XDR-TB TruArray and lateral flow cell (XDR-LFC) to address this gap in tuberculosis diagnostics.ObjectiveThis paper presents the protocol for a study that aims to document the conceptualization and design of this evaluation method for early dissemination while data collection and analysis are ongoing.MethodsThe clinical study was conducted in three phases. The first phase was to observe changes in bacterial load and culture positivity in patient sputa over time and better understand the diversity of prospective clinical samples. The second phase was to prospectively collect clinical samples for sensitivity and specificity testing of the Akonni Biosystems XDR-LFC device. Lastly, the third phase was to explore the anti-TB drug concentrations in serum throughout the drug-resistant tuberculosis treatment.ResultsThe methodology described includes the study design, laboratory sample handling, data collection, and the protection elements of human subjects of this clinical study to evaluate a potential new XDR-TB diagnostic device. A total of 664 participants were enrolled across the three phases. The implemented complex systems facilitated a thorough clinical data collection for an objective evaluation of the device. The study is closed to recruitment. The follow-up data collection and analysis are in progress.ConclusionsThis paper outlined a prospective cohort study protocol to evaluate a rapid XDR-TB detection device, which may be informative for other researchers with similar goals.International Registered Report Identifier (IRRID)DERR1-10.2196/26748

Metabolomic and Metataxonomic Fingerprinting of Human Milk Suggests Compositional Stability over a Natural Term of Breastfeeding to 24 Months.

Sparse data exist regarding the normal range of composition of maternal milk beyond the first postnatal weeks. This single timepoint, observational study in collaboration with the ‘Parenting Science Gang’ citizen science group evaluated the metabolite and bacterial composition of human milk from 62 participants (infants aged 3–48 months), nearly 3 years longer than previous studies. We utilised rapid evaporative ionisation mass spectrometry (REIMS) for metabolic fingerprinting and 16S rRNA gene metataxonomics for microbiome composition analysis. Milk expression volumes were significantly lower beyond 24 months of lactation, but there were no corresponding changes in bacterial load, composition, or whole-scale metabolomic fingerprint. Some individual metabolite features (~14%) showed altered abundances in nursling age groups above 24 months. Neither milk expression method nor nursling sex affected metabolite and metataxonomic fingerprints. Self-reported lifestyle factors, including diet and physical traits, had minimal impact on metabolite and metataxonomic fingerprints. Our findings suggest remarkable consistency in human milk composition over natural-term lactation. The results add to previous studies suggesting that milk donation can continue up to 24 months postnatally. Future longitudinal studies will confirm the inter-individual and temporal nature of compositional variations and the use of donor milk as a personalised therapeutic.

Changes in respiratory symptoms during 48-week treatment with ARD-3150 (inhaled liposomal ciprofloxacin) in bronchiectasis: results from the ORBIT-3 and -4 studies.

It is not known if inhaled antibiotics improve respiratory symptoms in patients with bronchiectasis. In the recent phase-3 ORBIT trials, 48 weeks' treatment with ARD-3150 (inhaled liposomal ciprofloxacin) did not significantly improve symptoms using the prespecified method of analysis comparing baseline symptoms to those after 48 weeks, when patients had been off treatment for 28 days. This method of analysis does not take account of possible improvements in symptoms while on active treatment.A post hoc analysis of two identical randomised trials of ARD-3150 (ORBIT-3 and -4) administered 28 days on and 28 days off in patients with bronchiectasis and chronic Pseudomonas aeruginosa infection. The quality-of-life bronchiectasis respiratory symptom scale (QOL-B-RSS), which has a one-week recall period, was administered every 28 days. We examined whether respiratory symptoms improved during on-treatment periods and the relationship of changes in QOL-B-RSS to changes in bacterial load using a mixed-model repeated measures approach.ARD-3150 treatment resulted in a significant improvement in respiratory symptoms during the on-treatment periods with concordant results between ORBIT-3 (estimate 1.4 points, se 0.49; p=0.004) and ORBIT-4 (estimate 1.1 point, se 0.41; p=0.006). The proportion of patients achieving a symptom improvement above the minimum clinically important difference was higher with ARD-3150 compared with placebo during on-treatment cycles (p=0.024). Changes in respiratory symptoms were correlated with changes in bacterial load in the treatment group (r=-0.89, p<0.0001). Individual estimates for decrements in the QOL-B RSS during exacerbation were -9.4 points (se 0.91) in ORBIT-3 and -10.8 points (0.74) in ORBIT-4 (both p<0.0001).Inhaled ARD-3150 resulted in significant improvements in respiratory symptoms during the on-treatment periods which were lost during off-treatment periods. These results supports the concept that reducing bacterial load can improve respiratory symptoms in patients with bronchiectasis.

The pharmacodynamics of fosfomycin against Staphylococcus aureus studied in an in vitro model of infection

ObjectivesThe pharmacodynamics of intravenous fosfomycin have not been described for Gram-positive pathogens such as Staphylococcus aureus (S. aureus). This paper described the dominant pharmacodynamic index for fosfomycin against S. aureus and its size for antibacterial effect. MethodsA single-compartment dilutional in vitro pharmacokinetic model was used to provide fosfomycin exposures against S. aureus, three methicillin-susceptible S. aureus (MSSA), two methicillin-resistant S. aureus (MRSA); fosfomycin MICs were 2 mg/L (one strain), 4 mg/L (one strain), 8 mg/L (two strains) and 16 mg/L (one strain). For all simulations, a fosfomycin half-life of 2.5 hours was modelled. Cmax/MICs from 0–74.8, AUC/MICs from 0–750 and T>MIC 0–100% were simulated. The primary end-points were changes in bacterial load after 24 hours and changes in population profiles after 48 hours. ResultsLog AUC/MIC R2 = 0.55 and log Cmax/MIC R2 = 0.66 were related to S. aureus log reduction in viable count at 24 hours; T>MIC was poorly related. Cmax/MIC for a 24 hour static, –1 log drop and –2 log drop were 3.0 ± 1.7, 4.6 ± 2.4 and 6.6 ± 3.8, respectively. AUC/MIC for a 24 hour static, –1 log drop and –2 log drop were 26.4 ± 11.8, 42.8 ± 21.8 and 66.6 ± 39.1. Emergence of resistance as indicated by > 2 log growth on MICx8 recovery media was maximal at AUC/MIC ratios of 10–40 and was suppressed at AUC/MIC ratios of ≥ 250. ConclusionsThe dominant pharmacodynamic index for fosfomycin against S. aureus was Cmax/MIC in terms of reduction of bacterial load and AUC/MIC in terms of suppressing emergence of resistance. AUC/MIC ratios of 20–75 were associated with a –1 log reduction in bacterial load and AUC/MIC of 10–40 maximally increased emergence of resistance.

The Effect of Antiretroviral Therapy Initiation on the Vaginal Microbiome in HIV-Infected Women.

The impact of antiretroviral therapy (ART) initiation on the vaginal microbiome is unknown. This is of particular importance among women living in sub-Saharan Africa. Understanding this relationship could help elucidate if and how the host immune system interacts with the vaginal microbiome. The vaginal microbiome of HIV-1/HSV-2-coinfected women (n = 92) in Uganda was evaluated from self-collected vaginal swabs 1 month pre-ART and at 4 and 6 months post-ART initiation. The vaginal microbiome was characterized by 16S rRNA gene-based sequencing and quantitative polymerase chain reaction. Vaginal community state types (CSTs) were identified using proportional abundance data. Changes in microbiome composition were assessed with permutational analyses of variance (PerMANOVA). Five vaginal CSTs were identified, which varied significantly by bacterial load (P < .01): CST-1 was characterized by Lactobacillus iners, CST-2 by Gardnerella, CST-3 by Gardnerella and Prevotella, CST-4 by Lactobacillus crispatus, and CST-5 was highly diverse. Vaginal microbiome composition also did not change significantly after ART initiation (P = .985). Immune reconstitution after ART initiation did not affect vaginal microbiome CST assignment (P = .722) or individual-level changes in bacterial load (log response ratio [interquartile range], -0.50 [-2.75 to 0.38] vs -0.29 [-2.03 to 1.42]; P = .40). The vaginal microbiome of HIV-infected women was not affected by the initiation of ART or immune reconstitution in this observational study. Further research is needed to explore the long-term effects of ART treatment on the vaginal microbiome.

Pharmacodynamics of plazomicin and a comparator aminoglycoside, amikacin, studied in an in vitro pharmacokinetic model of infection

The new aminoglycoside plazomicin shows in vitro potency against multidrug-resistant Enterobacteriales. The exposure-response relationship of plazomicin and the comparator aminoglycoside amikacin was determined for Escherichia coli, while for Klebsiella pneumoniae only plazomicin was tested. An in vitro pharmacokinetic model was used. Five E. coli strains (two meropenem-resistant) and five K. pneumoniae strains (two meropenem-resistant) with plazomicin MICs of 0.5-4 mg/L were used. Antibacterial effect was assessed by changes in bacterial load and bacterial population profile. The correlation between change in initial inoculum after 24 h of drug exposure and the AUC/MIC ratio was good (plazomicin R2 ≥ 0.8302; amikacin R2 ≥ 0.9520). Escherichia coli plazomicin AUC/MIC ratios for 24-h static, -1, -2 and -3 log drop were 36.1 ± 18.4, 39.3 ± 20.9, 41.2 ± 21.9 and 44.8 ± 24.3, respectively, and for amikacin were 49.5 ± 12.7, 55.7 ± 14.8, 64.1 ± 19.2 and 73.3 ± 25.3. Klebsiella pneumoniae plazomicin AUC/MIC ratios for 24-h static, -1, -2 and -3 log drop were 34.0 ± 15.2, 46.8 ± 27.8, 67.4 ± 46.5 and 144.3 ±129.8. Plazomicin AUC/MIC ratios >66 and amikacin AUC/MIC ratios >57.7 were associated with suppression of E. coli growth on 4 × or 8 × MIC recovery plates. The equivalent plazomicin AUC/MIC to suppress resistance emergence with K. pneumoniae was >132. The plazomicin AUC/MIC for 24-h static effect and -1 log reduction in E. coli and K. pneumoniae bacterial load was in the range 30-60. Plazomicin AUC/MIC targets aligned with those of amikacin for E. coli.

Amoxicillin effect on bacterial load in group A streptococcal pharyngitis: comparison of single and multiple daily dosage regimens

BackgroundCulture tests have demonstrated that once-daily administration of amoxicillin may be effective in the treatment of group A streptococcal (GAS) pharyngitis. However, culture methods do not allow accurate assessments of bacterial load changes because of the suppressive effect of the antibiotic on bacterial growth. In this study, we used real-time PCR to compare the effectiveness of once-daily and multiple-daily amoxicillin treatment for pediatric patients with GAS pharyngitis.MethodsThe subjects were children (≧3 years of age) diagnosed with GAS pharyngitis. Amoxicillin was administered at a dose of 40–50 mg/kg/day, divided into one (QD), two (BID), or three (TID) daily doses, for 10 days. Throat swabs were collected before treatment (visit 1), 1 to 3 days after treatment (visit 2), and 9 to 11 days after treatment (visit 3), and GAS copies were quantified by real-time PCR. The main compared parameters were the rate of negative PCR results and the number of GAS determined by PCR in throat swabs between each regimen.ResultsSamples were collected from 34 patients (QD, 12; BID, 15; TID, 7) at visit 1, 32 patients (QD, 11; BID, 14; TID, 7) at visit 2, and 25 patients (QD, 7; BID, 11; TID, 7) at visit 3. The rates of negative PCR result for QD, BID, and TID regimens were 18.2, 0, and 14.3% at visit 2, and 85.7, 72.7, and 85.7% at visit 3, respectively. The median values of bacterial load for QD, BID, and TID groups at visit 1 were 1.4 × 106, 8.2 × 105, and 5.4 × 105 copies/μL. At visit 2, they comprised 3.8 × 103, 1.1 × 103, and 2.8 × 103 copies/μL, respectively, whereas at visit 3, GAS copies were mostly undetectable. There was no statistical difference in the negative results and median value of GAS copies between regimens at any stage.ConclusionsOur results obtained by a molecular biology approach indicated that the QD regimen was as effective in eradicating GAS infection as BID or TID.Trial registrationUMIN000036083 / March 12, 2019.

Variation in Bacterial Contamination of Microisolation Cage Tops According to Rodent Species and Housing System.

The Guide recommends sanitizing cage components, including microisolation cage tops (MCT), at a minimum of every 2 wk. Previously published data demonstrated that mouse MCT microbial loads do not increase until at least 2 wk and that sanitation can be delayed past 2 wk. How microbial loads differ on mouse compared with rat MCT, as well as across different ventilation systems, remains unclear. We hypothesized that MCT microbial loads would be higher in tops from rats compared with mice and would differ according to IVC ventilation system. We evaluated bacterial loads on MCT at serial time points to 90 d from static cages housing mice or rats and from rat and mouse cages on several ventilation systems (mice, 6; rats, 4). MCT were determined to have sufficiently elevated bacterial loads to necessitate changing based on either statistically significant changes in bacterial loads or values greater than 50 cfu. Across all ventilation systems, bacterial counts at 14 d were significantly higher on rat MCT compared with mouse MCT. Across the ventilation systems examined, rat MCT cfu remained similarly elevated from 14 d through 90 d. Mouse MCT total cfu were also stable across multiple ventilation systems yet remained lower than 50 cfu until at least 90 d. Patterns of bacterial species isolated from rat MCT were relatively consistent over time and ventilation system, whereas mice showed greater variability in both contexts. We found that 14 d is an appropriate sanitization time point for rat MCT, whereas the interval at which mouse MCT are cleaned can be extended to 90 d at least. Our data highlight interspecies differences in the accumulation of bacteria on MCT and that mouse MCT sanitation intervals for several housing systems can be extended beyond 14 d.

Antibacterial effect of imipenem/relebactam on aerobic Gram-negative bacilli: in vitro simulations of 7 or 14 day human exposures.

We assessed the antibacterial effect of human simulations of dosing with imipenem/relebactam (with or without amikacin) on Enterobacteriaceae or Pseudomonas aeruginosa over 7 or 14 day antibiotic exposures. An in vitro pharmacokinetic model was used to assess changes in bacterial load and population profiles. Imipenem/relebactam produced an initial >4 log drop in viable counts followed by suppression for 7 days for Enterobacteriaceae whether the strain was WT, produced KPC enzymes or produced an AmpC enzyme with porin loss. Similarly, with the P. aeruginosa strains, there was an initial >4 log clearance over the first 24 h irrespective of whether the strain was WT, hyperexpressed AmpC or had OprD mutation with porin loss. However, with three of four strains there was modest regrowth over the 7 days. There were no changes in imipenem/relebactam MICs over the 7 days. Addition of amikacin in 7 day simulations resulted in more suppression of pseudomonal growth. In 14 day simulations with P. aeruginosa there was regrowth to 8 log10 by 14 days with imipenem/relebactam alone and associated increases in MICs. Addition of amikacin resulted in clearance from the model and prevented changes in population profiles. Imipenem/relebactam was highly effective at reducing the bacterial load of Enterobacteriaceae and there was no emergence of resistance. Against P. aeruginosa, the initial bacterial burden was also rapidly reduced, but there was subsequent regrowth, especially after 7 days of exposure. Addition of amikacin increased the clearance of P. aeruginosa and prevented emergence of resistance.