Ana C. Reis

Biodegradation of sulfamethoxazole and other sulfonamides by Achromobacter denitrificans PR1.

This study aimed to isolate and characterize a microbial culture able to degrade sulfonamides. Sulfamethoxazole (SMX)-degrading microorganisms were enriched from activated sludge and wastewater. The resultant mixed culture was composed of four bacterial strains, out of which only Achromobacter denitrificans PR1 could degrade SMX. This sulfonamide was used as sole source of carbon, nitrogen and energy with stoichiometric accumulation of 3-amino-5-methylisoxazole. Strain PR1 was able to remove SMX at a rate of 73.6 ± 9.6 μmol SMX/gcell dryweighth. This rate more than doubled when a supplement of amino acids or the other members of the mixed culture were added. Besides SMX, strain PR1 was able to degrade other sulfonamides with anti-microbial activity. Other environmental Achromobacter spp. could not degrade SMX, suggesting that this property is not broadly distributed in members of this genus. Further studies are needed to shed additional light on the genetics and enzymology of this process.

Insights into solar TiO2-assisted photocatalytic oxidation of two antibiotics employed in aquatic animal production, oxolinic acid and oxytetracycline

In this study, solar driven TiO2-assisted heterogeneous photocatalytic experiments in a pilot-plant with compound parabolic collectors (CPCs) were carried out to study the degradation of two authorized veterinary antibiotics with particular relevance in finfish aquaculture, oxolinic acid (OXA) and oxytetracycline (OTC), using pure solutions of individual or mixed antibiotics. Firstly, the influence of natural solar photolysis was assessed for each antibiotic. Secondly, photocatalytic degradation kinetic rate constants for individual and mixed antibiotics were compared, using a catalyst load of 0.5 g L(-1) and an initial pH around 7.5. Thirdly, for individually photocatalytic-treated OXA and OTC in the same conditions, the growth inhibition of Escherichia coli DSM 1103 was followed, and the mineralization extent was assessed by the residual dissolved organic carbon (DOC), low-molecular-weight carboxylate anions and inorganic ions concentration. Finally, the effect of inorganic ions, such as chlorides, sulfates, nitrates, phosphates, ammonium and bicarbonates, on the photocatalytic degradation of individual solutions of OXA and OTC was also evaluated and the formation of different reactive oxygen species were probed using selective scavengers. The removal profiles of each antibiotic, both as single component or in mixture were similar, being necessary 2.5 kJ L(-1) of solar UV energy to fully remove them, and 18 kJ(UV) L(-1) to achieve 73% and 81% mineralization, for OXA and OTC, respectively. The remaining organic carbon content was mainly due to low-molecular-weight carboxylate anions. After complete removal of the antibiotics, the remaining degradation by-products no longer showed antibacterial activity. Also, 10% and 55% of the nitrogen content of each antibiotic was converted to ammonium, while no conversion to nitrite or nitrate was detected. The presence of phosphates hindered considerably the removal of both antibiotics, whereas the presence of other inorganic ions did not substantially altered the antibiotics photocatalytic degradation kinetics.

Relação entre Sintomatologia Psicopatológica, Adesão ao Tratamento e Qualidade de Vida na Infecção HIV e AIDS

The study shows evidence of statistical association among psychopathological symptoms (BSI), treatment adherence (CEAT-VIH) and quality of life (WHOQOL-Bref) in 125 HIV-positive/AIDS patients followed at Porto Hospital (Portugal). The psychopathological symptoms present a negative correlation with treatment adherence and quality of life. On the other hand, adherence was positively correlated with quality of life. The model of adherence to the antiretroviral treatment using multiple regression analysis includes absence of psychopathological symptoms, an adherence behavior (i.e. to get the medication at the hospitals pharmacy) and the experience of side effects because of medication (R2 = 0.30). Besides, psychopathological symptoms have a mediation effect between adherence and quality of life in people with HIV/AIDS.

Solar photocatalytic oxidation of recalcitrant natural metabolic by-products of amoxicillin biodegradation.

The contamination of the aquatic environment by non-metabolized and metabolized antibiotic residues has brought the necessity of alternative treatment steps to current water decontamination technologies. This work assessed the feasibility of using a multistage treatment system for amoxicillin (AMX) spiked solutions combining: i) a biological treatment process using an enriched culture to metabolize AMX, with ii) a solar photocatalytic system to achieve the removal of the metabolized transformation products (TPs) identified via LC-MS, recalcitrant to further biological degradation. Firstly, a mixed culture (MC) was obtained through the enrichment of an activated sludge sample collected in an urban wastewater treatment plant (WWTP). Secondly, different aqueous matrices spiked with AMX were treated with the MC and the metabolic transformation products were identified. Thirdly, the efficiency of two solar assisted photocatalytic processes (TiO2/UV or Fe(3+)/Oxalate/H2O2/UV-Vis) was assessed in the degradation of the obtained TPs using a lab-scale prototype photoreactor equipped with a compound parabolic collector (CPC). Highest AMX specific biodegradation rates were obtained in buffer and urban wastewater (WW) media (0.10 ± 0.01 and 0.13 ± 0.07 g(AMX) g(biomass)(-1) h(-1), respectively). The resulting TPs, which no longer presented antibacterial activity, were identified as amoxicilloic acid (m/z = 384). The performance of the Fe(3+)/Oxalate/H2O2/UV-Vis system in the removal of the TPs from WW medium was superior to the TiO2/UV process (TPs no longer detected after 40 min (QUV = 2.6 kJ L(-1)), against incomplete TPs removal after 240 min (QUV = 14.9 kJ L(-1)), respectively).

Bioaugmentation of membrane bioreactor with Achromobacter denitrificans strain PR1 for enhanced sulfamethoxazole removal in wastewater

Achromobacter denitrificans strain PR1, previously found to harbour specific degradation pathways with high sulfamethoxazole (SMX) degradation rates, was bioaugmented into laboratory-scale membrane bioreactors (MBRs) operated under aerobic conditions to treat SMX-containing real domestic wastewater. Different hydraulic retention times (HRTs), which is related to reaction time and loading rates, were considered and found to affect the SMX removal efficiency. The availability of primary substrates was important in both bioaugmented and non-bioaugmented activated sludge (AS) for cometabolism of SMX. High HRT (24 h) resulted in low food to microorganism ratio (F/M) and low SMX removal, due to substrate limitation. Decrease in HRT from 24 h to 12 h, 6 h and finally 4 h led to gradual increases in primary substrates availability, e.g. organic compounds and ammonia, resulted in increased SMX removal efficiency and degradation rate, and is more favorable for high-rate wastewater treatment processes. After inoculation into the MBRs, the bioaugmentation strain was sustained in the reactor for a maximum of 31 days even though a significant decrease in abundance was observed. The bioaugmented MBRs showed enhanced SMX removal, especially under SMX shock loads compared to the control MBRs. The results of this study indicate that re-inoculation is required regularly after a period of time to maintain the removal efficiency of the target compound.

Biodegradation of sulfamethoxazole by a bacterial consortium of Achromobacter denitrificans PR1 and Leucobacter sp. GP

In the last decade, biological degradation and mineralization of antibiotics have been increasingly reported feats of environmental bacteria. The most extensively described example is that of sulfonamides that can be degraded by several members of Actinobacteria and Proteobacteria. Previously, we reported sulfamethoxazole (SMX) degradation and partial mineralization by Achromobacter denitrificans strain PR1, isolated from activated sludge. However, further studies revealed an apparent instability of this metabolic trait in this strain. Here, we investigated this instability and describe the finding of a low-abundance and slow-growing actinobacterium, thriving only in co-culture with strain PR1. This organism, named GP, shared highest 16S rRNA gene sequence similarity (94.6–96.9%) with the type strains of validly described species of the genus Leucobacter. This microbial consortium was found to harbor a homolog to the sulfonamide monooxygenase gene (sadA) also found in other sulfonamide-degrading bacteria. This gene is overexpressed in the presence of the antibiotic, and evidence suggests that it codes for a group D flavin monooxygenase responsible for the ipso-hydroxylation of SMX. Additional side reactions were also detected comprising an NIH shift and a Baeyer–Villiger rearrangement, which indicate an inefficient biological transformation of these antibiotics in the environment. This work contributes to further our knowledge in the degradation of this ubiquitous micropollutant by environmental bacteria.