Biology subjects

Boorgula, G. D.

Publications and source records attributed to Boorgula, G. D..

3 recordsLinked to original sources

bioRxiv2026

Novel regimens for treatment of Mycobacterium avium lung disease based on advanced in vitro systems and the mathematics of basis functions

Azithromycin plus ethambutol plus rifabutin (azithromycin-ethambutol-rifabutin) is the standard-of-care (SOC) for Mycobacterium avium-complex lung disease. The SOC achieves sustained sputum culture conversion in only 43-53% of patients, after an average of 18 months of therapy. Recent quantitative analyses ranked omadacycline, ceftriaxone, and minocycline highest for microbial kill. Azithromycin-minocycline-ethambutol, azithromycin-omadacycline-ethambutol, epetraborole-omadacycline-ethambutol, ceftriaxone-omadacycline-rifabutin, and the SOC were compared in the intracellular hollow fiber system model of M. avium lung disease (HFS-MAC). HFS-MAC units were treated once daily for 28 days to mimic the intrapulmonary pharmacokinetics of each drug. The ceftriaxone concentrations measured in the HFS-MAC were only 1% of those achieved in the lung by standard clinical doses. Changes in the bacterial burden were described using basis functions (BF). For liquid cultures, BF 1 (BF1) was described by a linear regression-based slope, with steepest kill slope (95% Confidence interval) of 7.87 (1.52 to14.23) by ceftriaxone-omadacycline-rifabutin versus 1.04 (-0.84 to 2.92) for SOC. For the CFU/mL readout, the BF1 steepest non-linear kill slope was for ceftriaxone-omadacycline-rifabutin of 0.55 (0.35 to 0.98) log10 CFU/mL/day versus 0.16 (0.07 to 0.25) log10 CFU/mL/day for the SOC. Thus, ceftriaxone-omadacycline-rifabutin is potentially better than the SOC, even though further ceftriaxone dose optimization is required. BF2 described rebound growth and drug-resistant subpopulation growth, and demonstrated that contrary to popular belief, SOC rebound was best explained by ethambutol-resistance (r2>0.99, p=0.01) and not by azithromycin-resistance (r2=0.27, p=0.32), questioning ethambutols role in the SOC. The BF framework is potentially easy to adapt for modeling other anti-infective agents across many infectious diseases.

microbiology↗

bioRxiv2025

Sulbactam-Durlobactam Plus Ceftriaxone Dosing and Novel Treatment Regimens for Mycobacterium abscessus Lung Disease

BackgroundIDSA guideline-based therapy achieves sputum culture conversion rates in 20-34% of patients with Mycobacterium abscessus (MAB) lung disease (LD). Double-{beta}-lactam combinations have been proposed to improve cure, based on time-kill curves. MethodsWe performed minimum inhibitory concentrations (MICs) experiments followed by hollow fiber system model of MAB-LD (HFS-MAB) exposure-effect studies with sulbactam-durlobactam administered every 8h (q8h), q12h, and q24h, to identify target exposures. Next, the sulbactam-durlobactam target exposure plus ceftriaxone was administered in the HFS-MAB inoculated with three different MAB isolates, as was the sulbactam-durlobactam-ceftriaxone combination with epetraborole and omadacycline (SDCEO).{gamma} -slopes (kill-speed) were calculated for all regimens. The minimal sulbactam-durlobactam clinical doses that achieved target exposure were identified using Monte Carlo experiments. ResultsCeftriaxone reduced sulbactam-durlobactam MICs by 8-tube dilutions. In the HFS-MAB, sulbactam-durlobactam microbial kill and antimicrobial resistance were linked to % time concentration persists above MIC (%TMIC), with target exposure of 50%. Sulbactam-durlobactam killed 3.85 log10 CFU/mL below day 0 burden (B0) with regrowth. Sulbactam-durlobactam plus ceftriaxone killed without regrowth and demonstrated Bliss additivity.{gamma} of bacterial population in >95% of virtual subjects were 2.28 (0.97-4.80) log10 CFU/mL/day for sulbactam-durlobactam-ceftriaxone and 2.91 (1.65-4.93) log10 CFU/mL/day for SDCEO. The optimal sulbactam-durlobactam dose co-administered with ceftriaxone was 2G q8h for creatinine clearance >90 mL/min, 2G q12h for 60-90 mL/min, 1G q12h for [≥]30 to <60 mL/min, and 1G q24h for <30 mL/min. ConclusionSulbactam-durlobactam-ceftriaxone achieved the highest microbial kill encountered so far in the HFS-MAB. Sulbactam-durlobactam-ceftriaxone should be tested as the backbone for novel treatment shortening regimens.

pharmacology and toxicology↗

bioRxiv2025

A mechanistic understanding of the effect of Staphylococcus aureus VraS histidine kinase single point mutation on antibiotic resistance

Bacterial genomic mutations in Staphylococcus aureus (S. aureus) have been detected in isolated resistant clinical strains, yet their mechanistic effect on the development of antimicrobial resistance remains unclear. The resistance-associated regulatory systems acquire adaptive mutations under stress conditions that may lead to a gain of function effect and contribute to the resistance phenotype. Here, we investigate the effect of a single-point mutation (T331I) in VraS histidine kinase, part of the VraSR two-component system in S. aureus. VraSR senses and responds to environmental stress signals by upregulating gene expression for cell wall synthesis. A combination of enzyme kinetics, microbiological, and transcriptomic analysis revealed the mechanistic effect of the mutation on VraS and S. aureus. Michaelis Mentens kinetics show that the VraS mutation caused an increase in the autophosphorylation rate of VraS and enhanced its catalytic efficiency. The introduction of the mutation through recombineering coupled with CRISPR-Cas9 counterselection to the Newman strain wild-type (WT) genome doubled the minimum inhibitory concentration of three cell wall-targeting antibiotics. The mutation caused an enhanced S. aureus growth rate at sub-lethal doses of the antibiotics, confirming the causative effect of mutation on bacterial persistence. Transcriptomic analysis showed a genome-wide alteration in gene expression levels and protein-protein interaction network of the mutant compared to the WT strain after exposure to vancomycin. The results suggest that vraS mutation causes several mechanistic changes at the protein and cellular levels that favor bacterial survival under antibiotic stress and cause the mutation-harboring strains to become the dominant population during infection. ImportanceRising antimicrobial resistance (AMR) is a global health problem. Mutations in the two- component system have been linked to drug- resistance in Staphylococcus aureus, yet the exact mechanism through which these mutations work is understudied. We investigated the T331I mutation in the vraS gene linked to sensing and responding to cell wall stress. The mutation caused changes at the protein level by increasing the catalytic efficiency of VraS kinase activity. Introducing the mutation to the genome of an S. aureus strain resulted in changes in the phenotypic antibiotic susceptibility, growth kinetics, and genome-wide transcriptomic alterations. By a combination of enzyme kinetics, microbiological, and transcriptomic approaches, we highlight how small genetic changes can significantly impact bacterial physiology and survival under antibiotic stress. Understanding the mechanistic basis of antibiotic resistance is crucial to guide the development of novel therapeutic agents to combat AMR.

microbiology↗