METHODS: A. baumannii was confirmed in clinical specimens by the detection of the blaOXA-51-like gene. Biofilm production was tested by microtitre plate assay and virulence genes were detected by real-time PCR.
RESULTS: A. baumannii was isolated from a total of 307 clinical specimens. The isolate which showed the highest number of A. baumannii was an endotracheal tube specimen (44.95%), then sputum (19.54%), followed by pus (17.26%), urine (7.49%) and blood (5.86%), and <2 per cent from body fluids, catheter-tips and urogenital specimens. A resistance rate of 70-81.43 per cent against all antibiotics tested, except colistin and tigecycline, was noted, and 242 (78.82%) isolates were multidrug-resistant (MDR). Biofilm was detected in 205 (66.78%) with a distribution of 54.1 per cent weak, 10.42 per cent medium and 2.28 per cent strong biofilms. 71.07 per cent of MDR isolates produce biofilm (P<0.05). Amongst virulence factor genes, 281 (91.53%) outer membrane protein A (OmpA) and 98 (31.92%) biofilm-associated protein (Bap) were detected. Amongst 100 carbapenem-resistant A. baumannii, the blaOXA-23-like gene was predominant (96%), the blaOXA-58-like gene (6%) and none harboured the blaOXA-24-like gene. The metallo-β-lactamase genes blaIMP-1 (4%) and blaVIM-1(8%) were detected, and 76 per cent showed the insertion sequence ISAba1.
INTERPRETATION CONCLUSIONS: The majority of isolates studied were from lower respiratory tract specimens. The high MDR rate and its positive association with biofilm formation indicate the nosocomial distribution of A. baumannii. The biofilm formation and the presence of Bap were not interrelated, indicating that biofilm formation was not regulated by a single factor. The MDR rate and the presence of OmpA and Bap showed a positive association (P<0.05). The isolates co-harbouring different carbapenem resistance genes were the predominant biofilm producers, which will seriously limit the therapeutic options suggesting the need for strict antimicrobial stewardship and molecular surveillance in hospitals.
METHODS: In this study, we characterized niosomes, PEG-b-PCL, and their combination loaded with KRe and tested the effect of these NPs on Acanthamoeba triangularis stages. KRe-loaded PEG-b-PCL, KRe-loaded niosome, and KRe-loaded PEG-b-PCL plus niosome were synthesized and characterized regarding particle size and charge, yield, encapsulation efficiency (EE), and drug loading content (DLC). The effect of these KRe-loaded NPs on trophozoite and cystic forms of A. triangularis was assessed through assays of minimal inhibitory concentration (MIC), using trypan blue exclusion to determine the viability. The effect of KRe-loaded NPs was also determined on A. triangularis trophozoite for 24-72 h. Additionally, the anti-adhesion activity of the KRe-loaded niosome on trophozoites was also performed on a 96-well plate. Cytotoxicity activity of KRe-loaded NPs was assessed on VERO and HaCaT cells using MTT assay.
RESULTS: KRe-loaded niosome demonstrated a higher yielded (87.93 ± 6.03%) at 286 nm UV-Vis detection and exhibited a larger size (199.3 ± 29.98 nm) and DLC (19.63 ± 1.84%) compared to KRe-loaded PEG-b-PCL (45.2 ± 10.07 nm and 2.15 ± 0.25%). The EE (%) of KRe-loaded niosome was 63.67 ± 4.04, which was significantly lower than that of the combination of PEG-b-PCL and niosome (79.67 ± 2.08). However, the particle charge of these NPs was similar (-28.2 ± 3.68 mV and -28.5 ± 4.88, respectively). Additionally, KRe-loaded niosome and KRe-loaded PEG-b-PCL plus niosome exhibited a lower MIC at 24 h (0.25 mg/mL), inhibiting 90-100% of Acanthamoeba trophozoites which lasted 72 h. KRe-loaded niosome affected adherence by around 40-60% at 0.125-0.25 mg/mL and removed Acanthamoeba adhesion on the surface by about 90% at 0.5 mg/mL. Cell viability of VERO and HaCaT cells treated with 0.125 mg/mL of KRe-loaded niosome and KRe-loaded PEG-b-PCL plus niosome exceeded 80%.
CONCLUSION: Indeed, niosome and niosome plus PEG-b-PCL were suitable nanocarrier-loaded KRe, and they had a greater nanoparticle property to test with high activities against A. triangularis on the reduction of adherence ability and demonstration of its low toxicity to VERO and HaCaT cells.
METHODS: In this study, A. triangularis amoebas were treated with a sublethal dose of curcumin under nutrient starvation and nutrient-rich condition and the surviving amoebas was investigated. Cysts formation and vacuolization were examined by microscopy and transcriptional expression of autophagy-related genes and other encystation-related genes were evaluated by real-time PCR.
RESULTS: A. triangularis cysts were formed under nutrient starvation. However, in the presence of the autophagy inhibitor, 3-methyladenine (3-MA), the percentage of cysts was significantly reduced. Interestingly, in the presence of curcumin, most of the parasites remained in the trophozoite stage in both the starvation and nutrient-rich condition. In vacuolization analysis, the percentage of amoebas with enlarged vacuole was increased upon starvation. However, the percentage was significantly declined in the presence of curcumin and 3-MA. Molecular analysis of A. triangularis autophagy-related (ATG) genes showed that the mRNA expression of the ATG genes, ATG3, ATG8b, ATG12, ATG16, under the starvation with curcumin was at a basal level along the treatment. The results were similar to those of the curcumin-treated amoebas under a nutrient-rich condition, except AcATG16 which increased later. On the other hand, mRNA expression of encystation-related genes, cellulose synthase and serine proteinase, remained unchanged during the first 18 h, but significantly increased at 24 h post treatment.
CONCLUSION: Curcumin inhibits cyst formation in surviving trophozoites, which may result from its effect on mRNA expression of key Acanthamoeba ATG-related genes. However, further investigation into the mechanism of curcumin in A. triangularis trophozoites arrest and its association with autophagy or other encystation-related pathways is needed to support the future use of curcumin.