Virulence Genes, Antimicrobial Resistance, and Genotypes of Campylobacter jejuni Isolated from Chicken Slaughterhouses in South Korea

Campylobacter jejuni represents one of the leading causes of bacterial gastroenteritis in humans and is primarily linked to chicken meat contamination. In the present study, we analyzed the virulence and survival genes, antimicrobial resistance, and the clonal distribution of 50 C. jejuni isolates obtained from various sources in 14 chicken slaughterhouses across 8 provinces in South Korea from 2019 to 2022. Furthermore, we determined their genetic relatedness to human-derived isolates registered in PubMLST using multilocus sequence typing (MLST). All isolates harbored various virulence and survival genes (flhA, cadF, cdtA, cdtC, cmeA, and sodB) out of 17 tested genes, as confirmed via polymerase chain reaction analysis. Adherence factor gene virB11 was not detected in any isolate. All isolates harbored 12 or more virulence and survival genes. Antimicrobial susceptibility testing indicated that ciprofloxacin resistance was the most prevalent (84.0%), followed by nalidixic acid (82.0%) and tetracycline (52.0%) resistance. MLST analysis of the isolates revealed 18 sequence types (STs), including four new ones. Overlapping STs between chicken slaughterhouse and human-derived isolates included ST42, ST45, ST50, ST137, ST354, and ST464. Our study identified 11 clonal complexes (CCs), with CC-21 being the most prevalent in both human and chicken slaughterhouse-derived isolates. This study provides comprehensive insights into recent C. jejuni isolates from chicken slaughterhouses, including data on quinolone resistance and virulence factors. The MLST-based genetic relatedness between isolates from humans and chicken slaughterhouses in this study suggests the potential of C. jejuni transmission from chickens to humans through the food chain. This study suggests the need for improved management practices in chicken slaughterhouses to reduce the transmission of chicken slaughterhouse-derived C. jejuni to humans.

Biodegradation and valorization of feather waste using the keratinase-producing bacteria and their application in environmentally hazardous industrial processes

Poultry feathers are widely discarded as waste worldwide and are considered an environmental pollutant and a reservoir of pathogenic bacteria. Therefore, developing sustainable and environmentally friendly methods for managing feather waste is one of the important environmental protection requirements. In this study, we investigated a rapid and eco-friendly method for the degradation and valorization of feather waste using keratinase-producing Pseudomonas geniculata H10, and evaluated the applicability of keratinase in environmentally hazardous chemical processes. Strain H10 completely degraded chicken feathers within 48 h by producing keratinase using them as sources of carbon, nitrogen, and sulfur. The culture contained a total of 402.8 μM amino acids, including 8 essential amino acids, which was higher than the chemical treatment. Keratinase was a serine-type metalloprotease with optimal temperature and pH of 30 °C and 9, respectively, and showed relatively high stability at 10-40 °C and pH 3-10. Keratinase was also able to degrade various insoluble keratins such as duck feathers, wool, human hair, and nails. Furthermore, keratinase exhibited more efficient depilation and wool modification than chemical treatment, as well as novel functionalities such as nematicidal and exfoliating activities. This suggests that strain H10 is a promising candidate for the efficient degradation and valorization of feather waste, as well as the improvement of current industrial processes that use hazardous chemicals.

Prevalence of asymptomatic infections of Chlamydia psittaci in psittacine birds in Korea

Avian chlamydiosis is an acute or chronic bacterial disease of birds. Chlamydia psittaci is the primary agent of the disease. It is also an important zoonotic pathogen. Chlamydia avium and Chlamydia gallinacea have also been recognized as potential causative agents of the disease. Clinical signs of this disease can vary in severity. Asymptomatic infections of Chlamydia have commonly been reported in various birds worldwide. In this study, we investigated the distribution of Chlamydia species in healthy psittacine birds in Korea. A total of 263 samples (pharyngeal/cloacal swabs and faeces) were collected from psittacine birds of 26 species in five zoos, five parrot farms and seven parrot cafes between 2020 and 2021. Ages of these birds had a wide range (1 month to 30 years). During sample collection, no bird showed any clinical signs indicating diseases such as chlamydiosis. Samples were tested for the presence of Chlamydia spp. using real-time PCR assays. Chlamydia spp. were detected in 168 (63.9%) samples and C. psittaci was detected in 96 (36.5%) samples. However, C. avium and C. gallinacea were not detected. There were no significant differences in the prevalence of asymptomatic infections in birds among three types of housing environments. Regarding ompA genotypes, 87 C. psittaci-positive samples had genotype A based on sequence analysis (n = 28) and genotype-specific real-time PCR (n = 59). Other positive samples were untyped (n = 9). Overall findings showed high prevalence of asymptomatic infections of C. psittaci in psittacine birds in Korea, posing a significant hazard to public health.

Characterization and applicability of novel alkali-tolerant carbonatogenic bacteria as environment-friendly bioconsolidants for management of concrete structures and soil erosion

Cracking and erosion are critical factors that reduce the mechanical properties and stability of concrete structures and soil, respectively. They are recognized worldwide as severe disasters causing the collapse of many structures including stone heritage and dams, and landslides. Therefore, it is essential to propose effective and environment-friendly management methods to prevent them. Carbonatogenesis has recently received considerable attention as a reliable biological process for remediating cracks in calcareous structures, stabilizing loose soils, and sequestering CO₂ in the environment. Isolating and characterizing carbonatogenic bacteria with excellent performance is crucial for applying this process to the field of environmental and civil engineering. The aim of this study was to isolate new CaCO₃-precipitating bacteria and investigate various properties for their use as bioconsolidants. Furthermore, the possibility of restoring damaged structures and stabilizing loose sandy soil using isolated strain was investigated. Strain LC13 with urease and CaCO₃-precipitating activity was isolated from limestone cave soil in Korea and identified as Arthrobacter sulfureus by phenotypic characterization and 16S rRNA gene analysis. Although cell growth was observed after an adaptation period at pH 11, strain LC13 grew well at pH 7-11, indicating alkali tolerance. The optimal conditions for CaCO₃ precipitation were 1.0% yeast extract, 2.5% urea, 0.35% NaHCO₃, and 400 mM CaCl₂, with an initial pH of 6.5 at 30 °C. Under optimized conditions, maximal CaCO₃ (22.92 ± 0.14 g/l) precipitated after 3 days, which was 10.8-fold higher than the value in a urea-CaCl₂ medium. CaCO₃ precipitation by strain LC13 was associated with an increased pH due to ureolysis and protein deamination. Using an optimized medium as a cementation solution, strain LC13 completely remediated 340-760 μm wide cracks over 3 days, and also restored the spalling of concrete surfaces. Furthermore, the sand treated with LC13 solidified with a surface strength of 14.9 kPa. Instrumental analysis confirmed that the crystals precipitated were a mixture of CaCO₃ polymorphs composed of rhombohedral calcite and spherical vaterite. These results suggest that A. sulfureus LC13 may be useful for implementing sustainable biorestoration and environmental management technologies such as the in situ remediation of structural cracks and in situ prevention of soil erosion.

A multiplex real-time PCR assay for differential identification of avian Chlamydia

Avian chlamydiosis is an acute or chronic disease of birds after infection by Chlamydia. Although Chlamydia psittaci is the primary agent of the disease, two additional species, Chlamydia avium and Chlamydia gallinacea, have also been recognized as potential disease agents. Therefore, the diagnosis of avian chlamydiosis requires differential identification of these avian Chlamydia species. The objective of the present study was to develop a multiplex real-time polymerase chain reaction (PCR) assay to rapidly differentiate between these three species of avian Chlamydia (C. psittaci, C. avium, and C. gallinacea) as well as the genus Chlamydia. Specific genetic regions of the three species were identified by comparative analysis of their genome sequences. Also, the genus-specific region was selected based on 23S rRNA sequences. PCR primers and probes specific to the genus and each species were designed and integrated in the multiplex real-time PCR assay. The assay was highly efficient (94.8-100.7%). It detected less than 10 copies of each target sequence of the genus and each species. Twenty-five Chlamydia control and field DNA samples were differentially identified while 20 other bacterial strains comprising 10 bacterial genera were negative in the assay. This assay allows rapid, sensitive, and specific detection of the genus and the three species of avian Chlamydia in a single protocol that is suitable for routine diagnostic purposes in avian diagnostic laboratories.

Comparative Characteristics and Zoonotic Potential of Avian Pathogenic Escherichia coli (APEC) Isolates from Chicken and Duck in South Korea

Avian pathogenic Escherichia coli (APEC) causes colibacillosis, which is an economically important disease in the poultry industry worldwide. The present study investigated O-serogroups, phylogenetic groups, antimicrobial resistance, and the existence of virulence-associated genes (VAGs) and antimicrobial resistance genes in 125 APEC isolates between 2018 and 2019 in Korea. The phylogenetic group B2 isolates were confirmed for human-related sequence types (STs) through multi-locus sequence typing (MLST). O-serogroups O2 (12.5%) and O78 (10.3%) and phylogenetic group B1 (36.5%) and A (34.5%) were predominant in chicken and duck isolates, respectively. Out of 14 VAGs, iucD, iroN, hlyF, and iss were found significantly more in chicken isolates than duck isolates (p < 0.05). The resistance to ampicillin, ceftiofur, ceftriaxone, and gentamicin was higher in chicken isolates than duck isolates (p < 0.05). The multidrug resistance (MDR) rates of chicken and duck isolates were 77.1% and 65.5%, respectively. One isolate resistant to colistin (MIC 16 μg/mL) carried mcr-1. The B2-ST95 APEC isolates possessed more than 9 VAGs, and most of them were MDR (82.4%). This report is the first to compare the characteristics of APEC isolates from chickens and ducks in Korea and to demonstrate that B2-ST95 isolates circulating in Korea have zoonotic potential and pose a public health risk.

A comparative study of disinfection efficiency and regrowth control of microorganism in secondary wastewater effluent using UV, ozone, and ionizing irradiation process

Ionizing radiation technology was suggested as an alternative method to disinfection processes, such as chlorine, UV, and ozone. Although many studies have demonstrated the effectiveness of irradiation technology for microbial disinfection, there has been a lack of information on comparison studies of disinfection techniques and a regrowth of each treatment. In the present study, an ionizing radiation was investigated to inactivate microorganisms and to determine the critical dose to prevent the regrowth. As a result, it was observed that the disinfection efficiency using ionizing radiation was not affected by the seasonal changes of wastewater characteristics, such as temperature and turbidity. In terms of bacterial regrowth after disinfection, the ionizing radiation showed a significant resistance of regrowth, whereas, on-site UV treatment is influenced by the suspended solid, temperature, or precipitation. The electric power consumption was also compared for the economic feasibility of each technique at a given value of disinfection efficiency of 90% (1-log), showing 0.12, 36.80, and 96.53 Wh/(L/day) for ionizing radiation, ozone, and UV, respectively. The ionizing radiation requires two or three orders of magnitude lower power consumption than UV and ozone. Consequently, ionizing radiation can be applied as an effective and economical alternative technique to other conventional disinfection processes.

Enhanced Biodegradability of Pharmaceuticals and Personal Care Products by Ionizing Radiation

The radiolytic degradation of antibiotic compounds, including lincomycin (LMC), sulfamethoxazole (SMX), and tetracycline (TCN), and the change of biodegradability of the radiation-treated target compounds were evaluated. As a result, the degradation of target antibiotics by hydrolysis, biodegradation, and gamma irradiation showed a compound-dependent manner. However, the biodegradability of all target compounds was enhanced by the gamma irradiation. The enhanced biodegradability after gamma irradiation (2 kGy) followed the trend of LMC (18.89%)<SMX (28.33%)<TCN (36.62%), indicating that gamma irradiation might transform nonbiodegradable compounds into biodegradable. Consequently, the effective degradation of nonbiodegradable antibiotics can be accomplished by ionizing radiation followed by biodegradation. This result indicated that ionizing radiation technology would be useful to enhance biodegradability of the recalcitrant pollutants and can facilitate further degradation of residuals or intermediates in the effluent when discharged into surface water.

Gamma radiolysis of alachlor aqueous solutions in the presence of hydrogen peroxide

The enhanced effect of gamma irradiation with hydrogen peroxide (H(2)O(2)) for alachlor degradation in an aqueous solution was first investigated in this study. The combination of gamma irradiation and H(2)O(2) led to an enhanced effect, which remarkably increased the degradation efficiency of alachlor and the total organic carbon (TOC) removal. At a dose of 200 Gy, the degradation degree of the alachlor solution reached 81.7 and 99.2% under H(2)O(2) concentrations of 0 and 0.1 μM, respectively. In addition, the TOC removal efficiencies of the alachlor under initial H(2)O(2) concentrations of 0, 0.5 and 1.0 μM were 59.5, 74.8 and 83.8%, respectively, at an absorbed dose of 20 k Gy. However, for higher H(2)O(2) concentrations (greater than 1 μM), the alachlor degradation was reduced because OH radicals were scavenged by the H(2)O(2). The biodegradability of alachlor solutions prior to and after treatment by gamma irradiation was also assessed using the Closed Bottle Test (CBT). The results showed enhanced biodegradability of alachlor with increasing absorbed doses.

Influence of glycerol on production and structural-physical properties of cellulose from Acetobacter sp. V6 cultured in shake flasks

Cost-effective production of bacterial cellulose (BC) by Acetobacter sp. V6 was investigated in shake culture using glycerol as carbon source and its structural and physical properties were determined. In medium containing 3% (w/v) glycerol, BC production was 4.98+/-0.03g/l after 7 days. This value was 3.8-fold higher than the yield in the glucose medium. FT-IR spectra revealed that all the BC samples were highly crystalline and were cellulose type capital I, Ukrainian. The crystallinity index value of the BC produced was 9% higher in the glycerol medium than in the glucose medium. Scanning electron micrographs showed that BC from the glycerol medium was more compact than that from the glucose medium. Water-holding capacity and viscosity of BC from the glycerol medium had 61.3% and 22.4% lower values than those from the glucose medium. These results suggest that glycerol could be a potential low-cost substrate for BC production by Acetobacter sp. V6, leading to the reduction in the production cost.