Journal of microorganism control最新文献

The growth of acid-fast bacteria often hinders the detection of Legionella in water samples on agar plates by the plate culture method. We studied whether anti-tubercular agents inhibit acid-fast bacteria growth on agar plates. First, the antimicrobial activities of isoniazid, ethionamide, and ethambutol were evaluated against Mycobacterium and Legionella. We found that ethambutol at ≥ 100 μg/mL completely inhibited Mycobacterium growth, but ethambutol at 1,000 μg/mL did not inhibit Legionella growth. Next, the effect of ethambutol dissolved in acid buffer was examined. Cell suspensions of L. pneumophila and Mycobacterium spp. were mixed, and ethambutol-acid buffer was added. After 5 min, mixtures were inoculated on GVPC agar plates and incubated at 36℃ for 6 d. We found that ethambutol inhibited Mycobacterium growth on agar plates, but the Legionella colonies recovered. The effect of ethambutol was also significant in the evaluation using bathwaters. Comparing 1,302 bathwaters, the addition of ethambutol reduced the detection rate of acid-fast bacteria from 30.6% to 0% and increased the detection rate of Legionella from 7.1% to 7.5%. Ethambutol, which selectively inhibited acid-fast bacteria growth, enhanced the detection of Legionella on agar plates and will contribute to improving the accuracy of Legionella testing by the plate culture method.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry（ MALDI-TOF MS） is a bacterial typing tool that was approved as a medical device in 2011. However, external accuracy control examination of bacterial typing using mass spectrometry is still only performed on a small scale. In this study, E. faecium and S. maltophilia were selected and tested according to established procedures using Score Values at 228 institutions. The Score Values for MALDI Biotyper were 2.43±0.08 for E. faecium and 2.38±0.08 for S. maltophilia; and those for VITEK MS/PRIME were 99.9±0.0 for E. faecium and S. maltophilia. These results suggest that it is useful to evaluate external accuracy control with Score Values using the procedures we have developed.

Cutibacterium acnes is an opportunistic pathogen in acne vulgaris. C. acnes produces autoinducer-2 (AI-2）, a signaling molecule used for communication known as quorum sensing (QS）. In C. acnes, QS reportedly upregulates biofilm formation leading to resistance against bactericidal agents. In this study, we analyzed how heparinoid affected QS and biofilm formation of the opportunistic pathogen C. acnes. We also verified whether heparinoid would suppress biofilm formation and enhance the efficacy of the bactericidal agent 4-isopropyl-3-methylphenol (IPMP) against C. acnes biofilms. We ran an AI-2 bioassay using Vibrio harveyi ATCC BBA-1121. Heparinoid exhibited inhibitory activity against AI-2 at concentrations of 0.003-0.005%, suggesting an AI-2 analog-derived or C. acnes culture supernatant-derived inhibition of the AI-2 activity. To evaluate how heparinoid suppresses biofilm formation in C. acnes, we completed a biofilm assay in 96-well plates. We also evaluated the bactericidal activity of IPMP against the C. acnes biofilm prepared with or without heparinoid. Heparinoid inhibited C. acnes biofilm formation and IPMP bactericidal efficacy increased upon heparinoid-mediated suppression of biofilm formation. In this study, we clarified that heparinoid inhibits the AI-2-mediated QS of C. acnes, thereby suppressing biofilm formation and increasing IPMP bactericidal efficacy, potentially suppressing acne vulgaris.

An air washer-type humidifier has two useful functions: humidification, and air purification, and it applies to large indoor spaces. In this study, the efficacy of an air washer-type humidifier fed with 24 L of weakly acidic electrolyzed water（WAEW) at pH 5.0 and 30 mg/L in disinfecting attached bacteria and airborne microorganisms was studied in a 480 ^m3 indoor space. The humidifier was operated at a shower volume of 9.0 L/min of WAEW and at an air flow rate of 29 ^m3/min. Volatilization of gaseous hypochlorous acid（HOCl_(g)) proceeded according to first-order kinetics during the 60 min of operation. Fresh WAEW was supplied to the humidifier every 60 min, and the HOCl_(g) concentration in the indoor space was maintained within the range of 25-52 ppb for at least 180 min of operation. The number of viable bacterial cells on wet agar plates placed on the floor at a distance of 5-20 m away from the humidifier decreased by 2.0-3.0 log after 30 min of operation, and no viable cells were detected after 60 min of operation. A logarithmic reduction of more than 2.7 was achieved within 15 min against bacteria-attached plates placed at a 1.5 m-height position where the outlet airflow from the humidifier was directly exposed. This indicates that the disinfection efficacy of HOCl_(g) volatilized from the humidifier depends on the rate of outlet airflow reaching the bacteria-attached plates. The number of viable airborne microorganisms decreased by approximately 54% after 180 min of operation. This study demonstrated that an air-washer-type humidifier can spread HOCl_(g) evenly throughout a large indoor space and is effective in disinfecting attached bacteria and airborne microorganisms.

Fungal contamination in the indoor air of prefabricated temporary houses at the site of the Great East Japan Earthquake revealed extremely high levels compared to those found in conventional residences. We experimentally investigated fungal growth levels on different interior materials to support fungal overgrowth in prefabricated temporary houses. Three species each of allergenic fungi and invasive fungi observed in temporary housing were selected for inoculation tests with various interior materials. The experiments with fungal inoculation were conducted in conformance with standards for industrial products described in the Japanese" JIS Z 2911:2018 Methods of test for fungus resistance" with small modifications. After incubation, visual and stereomicroscopic assessments were performed to determine fungal growth levels. The viability of the fungi varied according to the interior material type. Our findings demonstrate the importance of antifungal measures in indoor environments and the need for additional research on the growth levels of fungal species on various interior materials.

Aquaculture is part of the crucial industry that supplies food, especially for the global human population that is gradually increasing annually. Innovations of culture techniques have been improved throughout the years but aquaculture is regularly susceptible to bacterial and viral diseases. Numerous factors could contribute to occurrence of disease and usually they are from environmental or human stressors on the cultured animals. Synthetic chemicals in commercial treatments may yield fast results however, the side effects are usually unknown until it has taken effect. Therefore, biological control methods to treat diseases in aquaculture are preferred. This mini review provides an overview of different potential biocontrol practices for treatment of bacterial and viral diseases. Bacteriophage causes death of pathogenic bacteria by killing the cell and continue to multiply until all targeted pathogenic bacteria are eliminated. Probiotic, prebiotic, synbiotic, biofloc, and immunostimulants are beneficial products from the respective organisms that are effective in inhibiting pathogens. Vaccines introduce inactivated pathogen into the body to stimulate the immune system, while genetic modifications involve alteration and selection of disease resistant genetics.

Cutibacterium acnes is an opportunistic pathogen recognized as a contributing factor to acne vulgaris. The accumulation of keratin and sebum plugs in hair follicles facilitates C. acnes proliferation, leading to inflammatory acne. Although numerous antimicrobial cosmetic products for acne-prone skin are available, their efficacy is commonly evaluated against planktonic cells of C. acnes. Limited research has assessed the antimicrobial effects on microorganisms within keratin and sebum plugs. This study investigates whether an antibacterial toner can penetrate keratin and sebum plugs, exhibiting bactericidal effects against C. acnes. Scanning electron microscopy and next-generation sequencing analysis of the keratin and sebum plug suggest that C. acnes proliferate within the plug, predominantly in a biofilm-like morphology. To clarify the potential bactericidal effect of the antibacterial toner against C. acnes inside keratin and sebum plugs, we immersed the plugs in the toner, stained them with LIVE/DEAD BacLight Bacterial Viability Kit to visualize microorganism viability, and observed them using confocal laser scanning microscopy. Results indicate that most microorganisms in the plugs were killed by the antibacterial toner. To quantitatively evaluate the bactericidal efficacy of the toner against C. acnes within keratin and sebum, we immersed an artificial plug with inoculated C. acnes type strain and an isolate collected from acne-prone skin into the toner and obtained viable cell counts. The number of the type strain and the isolate inside the artificial plug decreased by over 2.2 log and 1.2 log, respectively, showing that the antibacterial toner exhibits bactericidal effects against C. acnes via keratin and sebum plug penetration.

Although recent propagation of carbapenemase-producing Enterobacterales (CPE) has become a problem worldwide, the picture of CPE infection in Japan has not fully been elucidated. In this study, we examined clinical and microbiological characteristics of invasive CPE infection occurring at 8 hospitals in Minami Ibaraki Area between July 2001 to June 2017. Of 7294 Enterobacterales strains isolated from independent cases of bacteremia and/or meningitis, 10 (0.14%) were CPE (8 Enterobacter cloacae-complex, 1 Escherichia coli, and 1 Edwardsiella tarda）, all of which had the bla_IMP-1 gene and susceptible to gentamicin and trimethoprim/sulfamethoxazole. These strains were isolated from 7 adult and 2 infant bacteremia (1 infant patient developed CPE bacteremia twice) after 2007. The most common portal of entry was intravenous catheters. All of the adult patients were recovered, while the infant patients eventually died. Genomic analyses showed that the 8 E. cloacae-complex strains were classified into 5 groups, each of which was exclusively detected in specific facilities at intervals of up to 3 years, suggesting persistent colonization in the facilities. This study showed that invasive CPE infection in the area was rare, caused by IMP-1-type CPE having susceptibility to various antibiotics, and nonfatal among adult patients.

Mechanical bead disruption is an efficient DNA extraction method from spore cells for subsequent quantification of the spore population by quantitative polymerase chain reaction（qPCR）. In this study, to validate spore DNA localization and extraction efficiencies, the fractionated DNA included the total DNA（tDNA）extracted from spore cells and intracellular（iDNA）and extracellular DNA（eDNA）extracted from fractionated spores through chemical decoating and alkaline lysis buffers, each followed by bead disruption. Furthermore, alkaline lysis buffer-treated spore cells were intensively washed three and five times after each centrifugation to determine how the amount of DNA is affected by repeated centrifugation. This process was achieved through fractionated spore pellet and suspension treatments with propidium monoazide xx（PMAxx）before mechanical bead disruption. Three fractionated and extracted DNAs were assessed with qPCR. The amount of eDNA was higher than that of iDNA, and closer to tDNA levels in the qPCR assay. These results indicted the following: 1）amount of eDNA was more than iDNA and responsible for majority of amount of tDNA through the combination method involving alkaline lysis buffer and bead disruption, 2）lysis buffer partially eliminated the eDNA fragments through multiple washing steps, but it was not largely independent of the number of times centrifugation was performed.

Plasmid-mediated antibiotic-resistant bacteria's transmission is fatal and a major threat to public health. This study aimed to clarify the presence of plasmid-mediated quinolone resistance（PMQR）genes in extended-spectrum β-lactamase（ESBL）-producing or/and mcr-harbouring colistin（COL）-resistant Escherichia coli（ESBL-COL-EC）isolates from Vietnamese and Japanese chicken meat. Resistance towards ciprofloxacin（CIP）was examined in 308 ESBL-COL-EC isolates; CIP-resistant ESBL-COL-EC isolates were examined for the PMQR gene. Approximately, 71.1% and 38.1% of ESBL-COL-EC and ESBLproducing E. coli isolates from Vietnamese and Japanese chicken meat were CIP-resistant, respectively. Multiplex PCR led PMQR detection showed that 35.2% of CIP-resistant ESBL-COL-EC isolates from Vietnamese food contained PMQR gene, whereas CIP-resistant ESBL-COL-EC isolates from Japanese chicken meat did not. Conjugation assays showed that the transmission of qnrS gene carried by E. coli to Salmonella. In conclusion, ESBL-COL-EC isolates from Vietnamese food are associated with a high frequency of fluoroquinolone resistance and a high distribution of the qnrS gene.