Enhancing wastewater treatment efficiency: A hybrid technology perspective with energy-saving strategies.

The study aimed to investigate how hybrid technology, combined with various intermittent aeration (IA) strategies, contributes to reducing the energy costs of wastewater treatment while simultaneously ensuring a high treatment efficiency. Even with IA subphases lasting half as long as those without aeration, and oxygen levels reduced from 3.5 to 1.5 mg O2/L, pollutants removal efficiency remains robust, allowing for a 1.41-fold reduction in energy consumption (EO). Hybrid technology led to a 1.34-fold decrease in EO, along with improved denitrification efficiency from 74.05 ± 4.71 to 81.87 ± 2.43 % and enhanced biological phosphorus removal from 35.03 ± 4.25 to 87.32 ± 3.64 %. The high nitrification efficiency may have been attributed to the abundance of Pseudomonas, Acinetobacter, and Rhodococcus, which outcompeted the genera of autotrophic nitrifying bacteria, suggesting that the hybrid system is favorable for the growth of heterotrophic nitrifiers.

The Contribution of Efflux Systems to Levofloxacin Resistance in Stenotrophomonas maltophilia Clinical Strains Isolated in Warsaw, Poland.

Levofloxacin is considered an alternative treatment option of Stenotrophomonas maltophilia infections to trimethoprim/sulfamethoxazole. The fluoroquinolone resistance in S. maltophilia is usually caused by an overproduction of efflux pumps. In this study, the contribution of efflux systems to levofloxacin resistance in S. maltophilia clinical isolates was demonstrated using phenotypic (minimal inhibitory concentrations, MICs, of antibiotics determination ± efflux pump inhibitors, EPIs) and molecular (real-time polymerase-chain-reaction and sequencing) methods. Previously, the occurrence of genes encoding ten efflux pumps was shown in 94 studied isolates. Additionally, 44/94 isolates demonstrated reduction in susceptibility to levofloxacin. Only 5 of 13 isolates (with ≥4-fold reduction in levofloxacin MIC) in the presence of EPIs showed an increased susceptibility to levofloxacin and other antibiotics. The overexpression of smeD and smeV genes (in five and one isolate, respectively) of 5 tested efflux pump operons was demonstrated. Sequencing analysis revealed 20-35 nucleotide mutations in local regulatory genes such as smeT and smeRv. However, mutations leading to an amino acid change were shown only in smeT (Arg123Lys, Asp182Glu, Asp204Glu) for one isolate and in smeRv (Gly266Ser) for the other isolate. Our data indicate that the overproduction of the SmeVWX efflux system, unlike SmeDEF, plays a significant role in the levofloxacin resistance.

Phenotypic and Molecular Characteristics of the MDR Efflux Pump Gene-Carrying Stenotrophomonas maltophilia Strains Isolated in Warsaw, Poland.

An increase of nosocomial infections caused by Stenotrophomonas maltophilia strains has recently been observed all over the world. The isolation of these bacteria from the blood is of particular concern. In this study we performed the phenotypic and genotypic characterization of 94 S. maltophilia isolates, including isolates from patients hospitalized in a tertiary Warsaw hospital (n = 79) and from outpatients (n = 15). All isolates were found to be susceptible to trimethoprim-sulfamethoxazole and minocycline, while 44/94 isolates demonstrated a reduction in susceptibility to levofloxacin. A large genetic variation was observed among the isolates tested by pulsed-field gel electrophoresis. A clonal relationship with 100% similarity was observed between isolates within two sub-pulsotypes: the first included nine bloodstream isolates and the second involved six. Multilocus sequence typing showed two new sequence types (ST498 and ST499) deposited in public databases for molecular typing. Moreover, the presence of genes encoding ten different efflux pumps from the resistance-nodulation-division family and the ATP-binding cassette family was shown in the majority of the 94 isolates. The obtained knowledge about the prevalence of efflux pump genes in clinical S. maltophilia strains makes it possible to predict the scale of the risk of resistance emergence in strains as a result of gene overexpression.

Modification of the susceptibility of gram-negative rods producing ESßLS to ß-lactams by the efflux phenomenon.

The production of ß-lactamases is the most important mechanism of Gram-negative rod resistance to ß-lactams. Resistance to ceftazidime and cefepime in clinical isolates of Enterobacteriaceae (especially ESßL-positive E. coli and K. pneumoniae) and P. aeruginosa is life-threatening. However, all strains of the above mentioned species possess chromosomally encoded RND efflux pump systems in addition to ß-lactamase production. The main goal of this study was to assess the role of efflux pump systems in cefepime and/or ceftazidime resistant phenotypes of ESßL-positive clinical strains of Enterobacteriaceae and P. aeruginosa. The influence of the efflux pump inhibitor PAßN on the minimum inhibitory concentration (MIC) values of tested cephalosporins was species-dependent. Generally, a significant reduction (at least four-fold) of ß-lactam MICs was observed in the presence of PAßN only in the case of P. aeruginosa clinical isolates as well as the ESßL-producing transformant PAO1161 ΔampC. The usage of this agent resulted in the restoration of susceptibility to cefepime and/or ceftazidime in the majority of the P. aeruginosa ESßL-positive strains with low and moderate resistance to the above cephalosporins. Moreover, an outer membrane permeabilizing effect in the presence of PAßN was identified. Strain-dependent ß-lactamase leakage upon PAßN or ß-lactam treatment was demonstrated. The most important observation was the restoration of susceptibility of P. aeruginosa WUM226 to cefepime (MIC decrease from 32 to 4 mg/L) and ceftazidime (MIC decrease from 128 to 4 mg/L) in the presence of PAßN, which occurred despite an almost complete lack of ß-lactamase leakage from bacterial cells. In conclusion, these data indicate that RND efflux pumps can modify the susceptibility to ß-lactams in Gram-negative rods producing ESßLs. However, this phenomenon occurs only in P. aeruginosa strains and was not observed among E. coli and K. pneumoniae strains, representing the Enterobacteriaceae family.