Laser-Printed Paper-Based Microfluidic Chip Based on a Multicolor Fluorescence Carbon Dot Biosensor for Visual Determination of Multiantibiotics in Aquatic Products

Excessive use of antibiotics in aquaculture severely endangers human health and ecosystems, which has raised significant concerns in recent years. However, conventional laboratory-based approaches regularly required time or skilled manpower. Herein, we propose a point-of-care-testing (POCT) biosensor detection device for the simultaneous determination of multiantibiotics without complex equipment or professional operators. A laser-printed paper-based microfluidic chip loaded with multicolor fluorescence nanoprobes (mCD-μPAD) was developed to rapidly detect sulfamethazine (SMZ), oxytetracycline (OTC), and chloramphenicol (CAP) on-site. These "fluorescence off" detection probes composed of carbon dots (CDs) conjugated with aptamers (donor) and MoS₂ nanosheets (acceptor) (CD-apt-MoS₂) were based on Förster resonance energy transfer. Upon the addition of target antibiotics, the significantly recovered fluorescence signal on the μPAD can be sensitively perceived by employing a 3D-printed portable detection box through a smartphone. Under optimal conditions, this μPAD allowed for a rapid response of 15 min toward SMZ, OTC, and CAP with considerable sensitivities of 0.47, 0.48, and 0.34 ng/mL, respectively. In shrimp samples, the recoveries were 95.2-101.2, 96.4-105, and 96.7-106.1% with RSD below 6%. This paper-based sensor opens an avenue for on-site, high-throughput, and rapid detection methods and can be widely used in POCT in food safety.

Antibiotic allergy in children with cystic fibrosis: A retrospective case-control study

Antibiotic allergy is a big problem that may affect the treatment and life quality of patients with cystic fibrosis (CF).

AIM

To evaluate predictive factors for confirmed antibiotic hypersensitivity in children with CF.

METHODS

In this case-controlled study, we examined 15 patients with CF who had been confirmed with antibiotic allergy. Additionally, we included a control group of age- and gender-matched 45 CF patients with no antibiotic allergy. The diagnosis of antibiotic allergy was confirmed in the presence of a compatible history and a positive response in the drug skin test or provocation test. Multiple drug hypersensitivity was classified according to the temporal relationship of antibiotics: (i) distant, (ii) simultaneous, and (iii) sequential. The data were analyzed by conditional logistic regression.

RESULTS

β-lactam allergy was confirmed in eight patients (ceftazidime n = 5, piperacillin-tazobactam n = 3) and non-β-lactam allergy was confirmed in two patients (ciprofloxacin n = 1, azithromycin n = 1). Additionally, multiple drug hypersensitivity in five patients (distant n = 4, sequential n = 1), among whom two patients showed hypersensitivity against ceftazidime/piperacillin-tazobactam+ ciprofloxacin/levofloxacin, two patients showed hypersensitivity against ceftazidime+ ciprofloxacin n = 2, and one patient showed hypersensitivity against piperacillin-tazobactam+ amikacin+ trimethoprim-sulfamethoxazole. All patients (n = 13) with confirmed β-lactam allergy were meropenem tolerant. Multivariate analysis indicated that immediate reactions (, p < 0.001) and allergic evaluation in the first six months after the reaction (p = 0.036) were significant risk factors for the prediction of antibiotic hypersensitivity.

CONCLUSION

Beta-lactam antibiotic allergy is the most commonly confirmed drug allergy in children with CF. However, unlike normal children, ceftazidime and piperacillin-tazobactam account for the majority.

Rapid Simultaneous Testing of Multiple Antibiotics by the MALDI-TOF MS Direct-on-Target Microdroplet Growth Assay

Accelerating antimicrobial susceptibility testing (AST) is a priority in the development of novel microbiological methods. The MALDI-TOF MS-based direct-on-target microdroplet growth assay (DOT-MGA) has recently been described as a rapid phenotypic AST method. In this proof-of-principle study, we expanded this method to simultaneously test 24 antimicrobials. An Enterobacterales panel was designed and evaluated using 24 clinical isolates. Either one or two (only for antimicrobials with the EUCAST “I” category) breakpoint concentrations were tested. Microdroplets containing bacterial suspensions with antimicrobials and growth controls were incubated directly on the spots of a disposable MALDI target inside a humidity chamber for 6, 8 or 18 h. Broth microdilution was used as the standard method. After 6 and 8 h of incubation, the testing was valid (i.e., growth control was successfully detected) for all isolates and the overall categorical agreement was 92.0% and 92.7%, respectively. Although the overall assay performance applying short incubation times is promising, the lower performance with some antimicrobials and when using the standard incubation time of 18 h indicates the need for thorough standardization of assay conditions. While using “homebrew” utensils and provisional evaluation algorithms here, technical solutions such as dedicated incubation chambers, tools for broth removal and improved software analyses are needed.

The RNA Chaperone Hfq Participates in Persistence to Multiple Antibiotics in the Fish Pathogen Yersinia ruckeri

Yersinia ruckeri causes outbreaks of enteric redmouth disease in salmon aquaculture all over the world. The transient antibiotic tolerance exhibited by bacterial persisters is commonly thought to be responsible for outbreaks; however, the molecular factors underlying this behavior have not been explored in Y. ruckeri. In this study, we investigated the participation of the RNA chaperone Hfq from Y. ruckeri in antibiotic persistence. Cultures of the hfq-knockout mutant (Δhfq) exhibited faster replication, increased ATP levels and a more reductive environment than the wild type. The growth curves of bacteria exposed to sublethal concentrations of ampicillin, oxolinic acid, ciprofloxacin and polymyxin B revealed a greater susceptibility for the Δhfq strain. The time-kill curves of bacteria treated with the antibiotics mentioned above and florfenicol, using inoculums from exponential, stationary and biofilm cultures, demonstrated that the Δhfq strain has significant defects in persister cells production. To shed more light on the role of Hfq in antibiotic persistence, we analyzed its dependence on the (p)ppGpp synthetase RelA by determining the persister cells production in the absence of the relA gene. The ΔrelA and ΔrelAΔhfq strains displayed similar defects in persister cells formation, but higher than Δhfq strain. Similarly, stationary cultures of the ΔrelA and ΔrelAΔhfq strains exhibited comparable levels of ATP but higher than that of the Δhfq strain, indicating that relA is epistatic over hfq. Taken together, our findings provide valuable information on antibiotic persistence in Y. ruckeri, shedding light on the participation of Hfq in the persistence phenomenon.

Antibiotics Application Strategies to Control Biofilm Formation in Pathogenic Bacteria

BACKGROUND

The establishment of a biofilm by most pathogenic bacteria has been known as one of the resistance mechanisms against antibiotics. A biofilm is a structural component where the bacterial community adheres to the biotic or abiotic surfaces by the help of Extracellular Polymeric Substances (EPS) produced by bacterial cells. The biofilm matrix possesses the ability to resist several adverse environmental factors, including the effect of antibiotics. Therefore, the resistance of bacterial biofilm-forming cells could be increased up to 1000 times than the planktonic cells, hence requiring a significantly high concentration of antibiotics for treatment.

METHODS

Up to the present, several methodologies employing antibiotics as an anti-biofilm, antivirulence or quorum quenching agent have been developed for biofilm inhibition and eradication of a pre-formed mature biofilm.

RESULTS

Among the anti-biofilm strategies being tested, the sub-minimal inhibitory concentration of several antibiotics either alone or in combination has been shown to inhibit biofilm formation and down-regulate the production of virulence factors. The combinatorial strategies include (1) combination of multiple antibiotics, (2) combination of antibiotics with non-antibiotic agents and (3) loading of antibiotics onto a carrier.

CONCLUSION

The present review paper describes the role of several antibiotics as biofilm inhibitors and also the alternative strategies adopted for applications in eradicating and inhibiting the formation of biofilm by pathogenic bacteria.