Xpert MTB/XDR assay: rapid TB drug resistance detection

PURPOSE

To assess the Xpert MTB/XDR assay's efficiency in promptly detecting resistance to isoniazid, fluoroquinolones, ethionamide, and second-line injectable drugs among tuberculosis (TB) patients.

METHODS

From August 2020 to July 2021, TB suspected patient samples were enrolled at a tertiary care center for our study. We conducted mycobacterial culture, phenotypic DST using proportion method in liquid culture at WHO-recommended concentrations, and the line probe assay (LPA). Simultaneously, the Index test, Xpert MTB/XDR, was performed following the manufacturer's instructions.

RESULTS

Among 360 samples, 107 were excluded due to incomplete information. Resistance to isoniazid, levofloxacin and moxifloxacin was found in 45/251, 21/251 and 20/251 samples, respectively by phenotypic DST. The diagnostic accuracy of Index test, taking phenotypic DST as a reference standard, was 95.8%, 99.04%, and 99.05% for isoniazid, levofloxacin, and moxifloxacin, respectively. The Index test assay demonstrated a specificity of 99.1% for detecting SLID resistance, yielding a diagnostic accuracy of 99.2. Comparing the Index test with LPA revealed a significant enhancement in sensitivity for detecting isoniazid resistance (86.7% vs. 82.2%).

CONCLUSIONS

The Index test exhibited promising outcomes in identifying resistance to isoniazid and fluoroquinolones, surpassing the performance of the LPA. This could be valuable for promptly initiating treatment in cases of drug-resistant tuberculosis.

Genomic Characterization of mcr-1-Carrying Foodborne Salmonella enterica serovar Typhimurium and Identification of a Transferable Plasmid Carrying mcr-1, bla CTX-M-14 , qnrS2, and oqxAB Genes From Ready-to-Eat Pork Product in China

Salmonella enterica resistant to colistin, third-generation cephalosporins (3GCs), and fluoroquinolones (FQs) has been deemed a high-priority pathogen by the World Health Organization (WHO). The objective of this study was to characterize 11 mcr-1-harboring Salmonella enterica serovar Typhimurium isolates from raw pork and ready-to-eat (RTE) pork products in Guangzhou, China. All isolates were multi-drug resistant and contained 6–24 antibiotic-resistant genes. The mcr-1 gene was localized in the most conserved structure (mcr-1-orf ) in eight isolates and in mobile structure (ISApl1-mcr-1-orf ) in three isolates. One raw pork isolate SH16SF0850, co-harbored mcr-1, bla_CTX−M−14, and oqxAB genes. One isolate 17Sal008 carried mcr-1, bla_CTX−M−14, qnrS2, and oqxAB genes located on a 298,622 bp IncHI2 plasmid pSal008, which was obtained from an RTE pork product for the first time. The pSal008 was closely related to a plasmid in an S. typhimurium isolate from a 1-year-old diarrheal outpatient in China and was found to be transferable to Escherichia coli J53 by conjugation. Genome sequence comparisons by core-genome Multi Locus Sequence Typing (cgMLST) based on all S. typhimurium isolates from China inferred highly probably epidemiological links between selected pork isolates and no possible epidemiologically links between RTE pork isolate 17Sal008 and other isolates. Our findings indicate that raw pork and pork products are potential reservoirs of mcr-1-harboring S. typhimurium and highlight the necessity for continuous monitoring of colistin, 3GCs, and FQs resistant S. typhimurium from different origins.

Quantitative analysis of FQs antibiotics content in FMF using THz spectral and imaging technology

Rapid and accurate detection of fluoroquinolones (FQs) antibiotics residues in food substrate are of great significance to food safety. In this study, terahertz spectroscopy was employed to conduct the spectral and imaging analysis to explore its feasibility for detection concentrations of FQs in fish meal feeds (FMF). Four methods (frequency of maximum difference in frequency-domain, characteristic absorption peak, successive projections algorithm and stepwise regression) were used to selected characteristic frequencies of sample. Terahertz imaging was formed at selected characteristic frequency and back propagation neural network was used to establish quantitative evaluation models to select optimal characteristic imaging frequency. Finally, relationship between concentrations of FQs and their gray values was revealed, and each data had a small range of error bar. The results showed that terahertz spectral and imaging technique can visualize norfloxacin and enrofloxacin concentrations in FMF precisely. This study explored a brand-new visualization method for quantitative detection of FQs in FMF based on terahertz spectral and imaging technology.

Interactions of fluoroquinolone antibiotics with sodium hypochlorite in bromide-containing synthetic water: Reaction kinetics and transformation pathways

Seven popular fluoroquinolone antibiotics (FQs) in synthetic marine aquaculture water were subject to sodium hypochlorite (NaClO) disinfection scenario to investigate their reaction kinetics and transformation during chlorination. Reactivity of each FQ to NaClO was following the order of ofloxacin (OFL) > enrofloxacin (ENR) > lomefloxacin (LOM) > ciprofloxacin (CIP) ~ norfloxacin (NOR) >> pipemedic acid (PIP), while flumequine did not exhibit reactivity. The coexisting chlorine ions and sulfate ions in the water slightly facilitated the oxidation of FQs by NaClO, while humic acid was inhibitable to their degradation. The bromide ions promoted degradation of CIP and LOM, but restrained oxidation of OFL and ENR. By analysis of liquid chromatography with tandem mass spectrometry (LC-MS/MS), eight kinds of emerging brominated disinfection byproducts (Br-DBPs) caused by FQ_S were primarily identified in the chlorinated synthetic marine culture water. Through density functional theory calculation, the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) characteristic as well as the charge distribution of the FQs were obtained to clarify transformation mechanisms. Their formation involved decarboxylation, ring-opening/closure, dealkylation and halogenation. Chlorine substitution occurred on the ortho-position of FQs's N4 and bromine substitution occurred on C8 position. The piperazine ring containing tertiary amine was comparatively stable, while this moiety with a secondary amine structure would break down during chlorination. Additionally, logK_ow and logBAF of transformation products were calculated by EPI-Suite^TM to analyze their bioaccumulation. The values indicated that Br-DBPs are easier to accumulate in the aquatic organism relative to their chloro-analogues and parent compounds.

Uptake and depuration of eight fluoroquinolones (FQs) in common carp (Cyprinus carpio)

Fluoroquinolones (FQs) are extensively used in humans and animals, which have aroused wide attention due to the emergence of FQ resistant bacteria and frequent detection in water, sediment and organism. However, little information is available about the bioconcentration and tissue distribution of FQs in fish. In the present study, we investigated the uptake and depuration of eight FQs (balofloxacin (BAL), enoxacin (ENO), enrofloxacin (ENR), fleroxacin (FLE), lomefloxacin (LOM), moxifloxacin (MOX), ofloxacin (OFL), sparfloxacin (SPA)) in common carp under controlled laboratory conditions. The results showed that all target FQs could accumulate in fish tissues, and had a similar tendency over time during the whole uptake and depuration periods. The uptake rate constant (k₁), depuration rate constant (k₂) and half-lives (t_1/2) were in the ranges of 0.007-3.599 L/(kg·d), 0.051-0.283 d^-1 and 2.4-10.7 d, respectively. The ranges of bioconcentration factors (BCFs) were 0.24-39.55 L/kg, 0.21-24.97 L/kg and 0.04-1.07 L/kg in liver, kidney and muscle, respectively. BCFs of eight FQs decreased in the order: MOX > ENR > ENO ≈ BAL ≈ FLE ≈ OFL ≈ LOM ≈ SPA, which may be correlated with the substituents at positions 7 and 8 of the basic quinolone nucleus and the metabolic capacity. Besides, BCFs were relative with pH-adjusted distribution coefficient (log D), suggesting that molecular status of ionizable compounds strongly influenced the bioconcentration processes. The present study provides important insights for understanding the bioconcentration and tissues distribution of FQs.

Effect of copper on the accumulation and elimination kinetics of fluoroquinolones in the zebrafish (Danio rerio)

Fluoroquinolones (FQs) have attracted wide concerns due to their pseudo-persistent and universal presence in natural water. Here we exposed zebrafish separately to two FQs (enrofloxacin (ENR) and ofloxacin (OFL)) in different copper (Cu) concentrations for 20 days (d) in a flow-through system, followed by a 11 d depuration period in clean water to investigate compound specific bioaccumulation and tissue distribution. Two FQs could accumulate in zebrafish, and the high concentration was observed in liver. Moreover, the levels of FQs in different treatment groups were higher than the corresponding control fish group. The uptake rates (k₁), elimination rates (k₂), BCF value, and half-lives (t_1/2) of FQs ranged from 0.02 to 3.28 d^-1, 0.01 to 0.97 d^-1, 0.33 to 109.33, 9.90 to 69.31 d, respectively. With Cu exposure concentration's increasing, k₁ values in three tissues (liver, skin and gill) obviously decreased. The exposure concentration affected the BCF value significantly, but didn't change their relative compositions in liver, gill, skin, and muscle after long time exposure. BCF values of ENR were always a little bit higher than those of OFL in almost all the tissues (liver, skin and gill) in the low Cu concentration treatments, whereas, in the high Cu concentration treatments the bioconcentration factors (BCF) values of ENR were lower than the values of OFL. The exposure of Cu played an important role in the FQs bioconcentration and BCF. These results are meaningful for improved understanding and prediction of the behavior and fate of metallic and antibiotics in aqueous environments.

Emergence of quinolone resistance in the microbiota of hospitalized patients treated or not with a fluoroquinolone

BACKGROUND

Quinolone resistance is a major global clinical problem. It primarily emerges in microbiota under selective pressure. Studies evaluating the incidence and risk factors for carrying quinolone-resistant bacteria in hospitalized patients treated with fluoroquinolones (FQs) are lacking.

METHODS

We prospectively included hospitalized patients treated with FQs. Nasal, throat and rectal swabs were performed before FQ treatment, at the end of FQ treatment and 30 days later. A 'reference group' of patients not receiving FQs was also included to determine the rates of quinolone resistance acquisition not linked to FQ treatment. Prevalence and incidence of quinolone-resistant strains of nasal coagulase-negative staphylococci (CoNS) and Staphylococcus aureus, pharyngeal α-haemolytic streptococci and faecal Escherichia coli, and risk factors for emergence of quinolone resistance in FQ-treated patients were assessed.

RESULTS

Four-hundred and fifty-one FQ-treated patients were included, as well as 119 subjects in the 'reference group'. Emergence of quinolone resistance occurred in 110/213 (51.6%), 50/336 (14.9%), 53/290 (18.3%) and 46/336 (13.7%) of FQ-treated patients for CoNS, S. aureus, α-haemolytic streptococci and E. coli, respectively, significantly more than for reference patients for CoNS (23/65; P < 0.05), S. aureus (5/91; P < 0.02) and E. coli (4/84; P < 0.05), but not for α-haemolytic streptococci (15/70; P = 0.55). Emergence of resistance was not associated with the type of FQ received, the duration of therapy or the duration of hospital stay, but was associated with host factors such as immunosuppression and altered performance status.

CONCLUSIONS

FQs received during hospitalization account for high rates of emergence of resistance to FQs in clinically relevant bacteria from human microbiota, reflecting the important ecological impact of FQs. Host factors outweighed treatment or hospitalization characteristics as risk factors for carrying quinolone-resistant strains.

Light-induced catalytic transformation of ofloxacin by solar Fenton in various water matrices at a pilot plant: mineralization and characterization of major intermediate products

This work investigated the application of a solar driven advanced oxidation process (solar Fenton), for the degradation of the antibiotic ofloxacin (OFX) in various environmental matrices at a pilot-scale. All experiments were carried out in a compound parabolic collector pilot plant in the presence of doses of H2O2 (2.5 mg L(-1)) and at an initial Fe(2+) concentration of 2 mg L(-1). The water matrices used for the solar Fenton experiments were: demineralized water (DW), simulated natural freshwater (SW), simulated effluent from municipal wastewater treatment plant (SWW) and pre-treated real effluent from municipal wastewater treatment plant (RE) to which OFX had been spiked at 10 mg L(-1). Dissolved organic carbon removal was found to be dependent on the chemical composition of the water matrix. OFX mineralization was higher in DW (78.1%) than in SW (58.3%) at 12 mg L(-1) of H2O2 consumption, implying the complexation of iron or the scavenging of hydroxyl radicals by the inorganic ions present in SW. On the other hand, the presence of dissolved organic matter (DOM) in SWW and RE, led to lower mineralization per dose of H2O2 compared to DW and SW. The major transformation products (TPs) formed during the solar Fenton treatment of OFX, were elucidated using liquid chromatography-time of flight-mass spectrometry (LC-ToF-MS). The transformation of OFX proceeded through a defluorination reaction, accompanied by some degree of piperazine and quinolone substituent transformation while a hydroxylation mechanism occurred by attack of the hydroxyl radicals generated during the process leading to the formation of TPs in all the water matrices, seven of which were tentatively identified. The results obtained from the toxicity bioassays indicated that the toxicity originates from the DOM present in RE and its oxidation products formed during the photocatalytic treatment and not from the TPs resulted from the oxidation of OFX.