Characterization of Fungal Surface Contaminants of the Small Maltese June Pear, Pyrus communis var. bambinella

ABSTRACT

Fungal pathogens cause surface contamination and potential premature fruit spoilage of bambinella, a fruit endemic to the Maltese islands, leading to the loss of fruit during the postharvest phase. The objective of this study was to isolate, quantify, and characterize fungal contaminants of the small Maltese June Pear and describe their growth kinetics. In total, 284 fungicide-free fruits were collected over three consecutive summers (2014, 2015, 2016). The isolated fungi were identified by using forward and reverse colonial morphology. Species identification was determined using PCR-based methods. The number of CFU per square centimeter of bambinella outer skin was calculated. Mycelium diameter growth rate studies of the isolates were also carried out at seven different temperatures, ranging from 5 to 35°C. Fungi isolated from bambinella included Cladosporium ramotenellum, Alternaria arborescens, Penicillium lanosum, Penicillium expansum, and Aspergillus sydowii, listed from the most abundant to the least abundant. The Rosso model was fitted to the growth kinetic data and showed that the optimal temperatures for growth of all five fungi were in the range of 20 to 22°C, whereas growth was slower at temperatures below 10°C and above 30°C. As observed in the diameter studies, the order of highest to lowest germination rate was found to be P. expansum, A. sydowii, P. lanosum, C. ramotenellum, and A. arborescens. Germination studies showed that the highest germination rate was observed for P. lanosum, followed by A. arborescens, C. ramotenellum, P. expansum, and A. sydowii, in descending order. The highest germination lag time was observed for A. arborescens, followed by C. ramotenellum, P. expansum, P. lanosum, and A. sydowii, in ascending order.

HIGHLIGHTS

Assessing the anti-fungal efficiency of filters coated with zinc oxide nanoparticles

Air filters support fungal growth, leading to generation of conidia and volatile organic compounds, causing allergies, infections and food spoilage. Filters that inhibit fungi are therefore necessary. Zinc oxide (ZnO) nanoparticles have anti-fungal properties and therefore are good candidates for inhibiting growth. Two concentrations (0.012 M and 0.12 M) were used to coat two types of filters (melt-blown and needle-punched) for three different periods (0.5, 5 and 50 min). Rhizopus stolonifer and Penicillium expansum isolated from spoiled pears were used as test organisms. Conidial suspensions of 105 to 103 spores ml-1 were prepared in Sabouraud dextrose agar at 50°C, and a modified slide-culture technique was used to test the anti-fungal properties of the filters. Penicillium expansum was the more sensitive organism, with inhibition at 0.012 M at only 0.5 min coating time on the needle-punched filter. The longer the coating time, the more effective inhibition was for both organisms. Furthermore, it was also determined that the coating process had only a slight effect on the Young's Moduli of the needle-punched filters, while the Young's Moduli of the melt-blown filters is more susceptible to the coating method. This work contributes to the assessment of the efficacy of filter coating with ZnO nanopaticles aimed at inhibiting fungal growth.

The effect of NitrAdine on the Candida levels of maxillary removable appliances

OBJECTIVE

Candida colonization is a consequence of orthodontic treatment and can lead to oral candidosis as a complication of maxillary removable appliance treatment. During orthodontic treatment, it is important to minimize colonization to prevent active infection that could consequently interfere with treatment. Hygiene is the most important factor in managing colonization; in this study, the efficacy of NitrAdine to reduce Candida was tested.

METHOD AND MATERIALS

A randomized, double-blind, placebo-controlled trial was performed. Ninety-two patients 11 to 14 years of age were recruited at the Children's and the University Dental Clinics at Mater Dei Hospital, Tal-Qroqq, Msida, Malta. Forty-four patients used the product with NitrAdine, while 48 patients used a placebo. Sampling employing the imprint technique was performed before and after the product was used. Brilliance Candida agar was used for cultures and identification. Further identification was performed using Auxacolor 2 when required.

RESULTS

The control group had a statistically significant increase in Candida during treatment, while the experimental group had a nonstatistically significant decrease.

CONCLUSION

It was concluded that NitrAdine may reduce the Candida burden in maxillary removable appliances. Larger sample sizes are needed to achieve statistical significance.

Randomized, double-blind, placebo-controlled trial to test the efficacy of nitradine tablets in maxillary removable orthodontic appliance patients

OBJECTIVE

to evaluate the efficiency of NitrAdine (MSI Laboratories) tablets in the reduction of oral Candida levels, biofilm formation, and appliance odor in maxillary removable orthodontic appliance wearers.

METHOD AND MATERIALS

seventy children between 11 and 15 years of age undergoing maxillary removable appliance treatment were assigned via a double-blind randomized method to the experimental or placebo arm of the study. One milliliter of unstimulated saliva was collected at the beginning of the experiment and 6 weeks later after treatment of the maxillary removable appliance with NitrAdine tablets. Samples were cultured on chromogenic Candida agar, and the number of colony-forming units per mL of saliva (CFU mL-1) was determined.

RESULTS

there was no significant difference in salivary Candida levels before or after treatment with NitrAdine tablets. There was a significant drop in plaque accumulation on the appliance and a significant amelioration in appliance odor. There was a small, nonsignificant drop in individuals exhibiting counts of 400 CFU mL-1 or more in the experimental group and a nonsignificant increase in the number of new species in the placebo group.

CONCLUSIONS

NitrAdine tablets are effective in reducing plaque accumulation and appliance odor during maxillary removable appliance treatment. Further in vivo studies are required to determine the efficacy and exact protocol for NitrAdine tablets in appliance disinfection.