• Microbiology and Biotechnology Letters
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• v.41 no.1
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• pp.96-104
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• 2013

Staphylococcus aureus is a major human pathogen that produces a wide array of toxins, leading to a number of adverse symptoms. We examined 275 strains of Staphylococcus aureus isolated from various foods between 2006 and 2008 for antimicrobial susceptibility. At least 259 (94.2%) of the tested strains showed antibiotic resistant properties, and 106 (40.7%) of them showed multiple antibiotic resistance. Eleven of the tested strains were resistant to oxacillin and mec A-positive. Moreover, oxacillin-resistant strains were significantly more likely to be multi-drug resistant (p < 0.01). Of the 275 isolates tested, 24.4% were noted as being positive for slime production and 30.5% were positive for biofilm assay. Antibiotic resistance was not associated with a significantly higher prevalence of biofilm formation. Twenty strains were classified using the DiversiLab system. Most of the strains could be classified into 2 clusters and 4 unique types. All 10 mec A-positive strains (cluster I) were grouped together into the same sub-cluster. Cluster II (6 strains) was not found to be resistant to oxacillin in this study. Although the prevalence of methicillin-resistant S. aureus in food is currently low, the risk of its transmission through the food chain cannot be disregarded.

• Journal of Digital Convergence
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• v.14 no.4
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• pp.371-378
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• 2016

An aim of current study was to investigate the prevalence and the mechanism of quinolone-resistance in E. coli isolates obtained from chicken cecum in Korea. In addition, multilocus sequence typing (MLST) was also performed for the molecular characterization of E. coli isolates. In an antimicrobial susceptibility test by the disk diffusion method, the 63.5% (54/85) of E. coli isolates showed the resistance to quinolone group of antimicrobial agents. All of the 54 E. coli isolates showing resistant to quinolone group had sense mutations in gyrA gene and point mutations at the $57^{th}$, $80^{th}$, or $84^{th}$ residues in parC gene were detected in 90.7% of the isolates. Interestingly, E. coli ST was closely related to amino acid substitutions in parE gene. Our results indicated that the long-term use of antimicrobial agents in food-producing animals was strongly associated with a prevalence of antimicrobial resistance in commensal Enterobacteriaceae, suggesting the need for continuous surveillance and monitoring of antimicrobial resistant determinants in bacterial isolates from food animals.

• Korean Journal of Microbiology
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• v.48 no.1
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• pp.22-28
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• 2012

Vibrio parahaemolyticus is one of the major agents responsible for food poisoning during summer in Korea, which is transmitted via seawater or seafoods. Recently, distribution of the bacteria in the marine environment has been increased due to global warming. Great concern also has been raised regarding public hygiene as well as marine culture by the emergence of pathogens with antibiotic resistance. Therefore, distribution of V. parahaemolyticus and antibiotic resistance of the isolates were monitored in 7 coastal areas of Kyonggi Province and Incheon by sampling seawater, fishes and clams monthly. V. parahaemolyticus was detected from 47.7% of 966 samples (seawater 61.9%, seafoods 41.8%) analyzed using $CHROMagar^{TM}$ and TCBS agar plates as well as multiplex PCR. Among 13 antibiotics tested, resistance to vancomycin and ampicillin was observed in 97.3% and 87.3% of the isolates, respectively, and the ratios of them resistant to cephalothin (48.8%) and rifampin (46.1%) were also high. The isolates were most highly sensitive to chloramphenicol (91.7%) and trimethoprim-sulfamethoxazole (91.8%). The ratio of sensitivity for other antibiotics was also high in the descending order of gentamycin (82.3%), tobramycin (74.8%), nalidixic acid (71.6%), tetracyclin (69.4%), cefotaxime (63.0%). About 69% of the isolates showed multiple drug resistance toward 3 antibiotics including vancomycin and ampicillin. Two of them exhibited resistance for 11 antibiotics used in this study. Plasmid profile analysis of the isolates with antibiotic resistance revealed that 55.1% of them retained plasmids of 24 different types. However, no clear inter-relationship between the resistance and the plasmid profile has been observed.

• Food Science of Animal Resources
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• v.30 no.3
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• pp.479-486
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• 2010

Tolerance against heat, sanitizers, and antibiotics of 112 Cronobacter isolates classified by desiccation was determined to permit effective biocontrol in powdered foods. The isolates were classified into three groups: dry-tolerant (n=37), dry-sensitive (n=7), and dry-intermediate (n=68). The strains that were highly tolerant to drying also showed high heat tolerance that they seemed to have high tolerance to heat after dry stress in powdered foods like infant formula. Sodium hypochlorite and benzalkonium chloride concentrations necessary to achieve a 5-log reduction in viable counts (CFU/mL) were 15-25 ppm and 5-15 ppm, respectively. However, there was little difference of the efficacy of these sanitizers between dry-sensitive and -tolerant strains for planktonic cells suspended in 3% albumin. The minimal inhibition concentration (MIC) of $\beta$-lactam ampicillin was 64-128 ppm for 90% of the strains. The isolates were consistently sensitive to kanamycin and naldixic acid (MIC=4 ppm). Dry-tolerant strains displayed more antibiotic resistance than dry-sensitive strains. The results indicate that dry-tolerant Cronobacter isolates often possess heat and antibiotic resistance, indicated the need for potent sterilization treatments of powdered foods.

• Korean Journal of Food Science and Technology
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• v.38 no.2
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• pp.313-316
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• 2006

To obtain antibiotic resistant profiles of Bifidobacterium, minimum inhibitory concentrations (MIC) of 14 antibiotics for 93 Bifidobacterium isolates from Korean intestine origin were determined. All strains tested were sensitive to chloramphenicol, rifampicin, and amoxicillin, whereas resistant to aminoglycoside family, nalidixic acid, and vancomycin. Among vancomycin-resistant strains, 34% were resistant at more than $100\;{\mu}g/mL$, and showed variant resistances toward tetracycline, erythromycin, and penicillin. Their resistances against penicillin, cephalothin, and tetracycline were higher than ten years ago. MIC of ten isolates from commercial yoghurt products were very similar to those of strains from Korean intestine origin, and 20% strains showed resistance at higher than $100\;{\mu}g/mL$ vancomycin. These results indicated patterns of antibiotic resistance against Bifidobacterium from Korean intestine origin and commercial yoghurts were very similar,and prevalence of vancomycin resistance for Bifidobacterium was 20%. To develop new probiotic, antibiotic resistance of vancomycin and risks involved should be evaluated.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.5
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• pp.714-720
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• 2012

To evaluate the antibiotic risk of $Enterococcus$ in fermented soy paste, $Enterococcus$ spp. were isolated and identified from 31 $Cheongkukjang$ and 17 $Doenjang$, samples. Exactly 123 $Enterococcus$ spp., 119 from $Cheongkukjang$ and four from $Doenjang$, were ultimately isolated. The most frequently collected $Enterococcus$ isolates in $Cheongkukjang$ were 69 strains of $E.$ $faecium$ and 20 strains of $E.$ $faecalis$. All four $Enterococcus$ spp. from $Deonjang$ were identified as $E.$ $faecium$. All isolates were sensitive to ampicillin, chloramphenicol, penicillin, and tetracyclin $E.$ However, they showed broad spectra from sensitivity to resistance to erythromycin, ripampin, and streptomycin. Vancomycin minimum inhibition concentration (MIC) of $Enterococcus$ spp. from $Cheongkukjang$ ranged from 0.25 to 8 ${\mu}g/mL$. Almost all strains were sensitive to vancomycin, but eight strains showed intermediate resistance to vancomycin. Seventeen strains showing the highest MIC of 8 ${\mu}g/mL$ among all isolates were evenly distributed among $E.$ $faecalis$, $E.$ $faecium$, $E.$ $gallinarum$, and $E.$ $casselifalvus$, in which the strong resistant genes of $van$A and $van$B for vancomycin were not detected. Overall antibiotic resistance of $Enterococcus$ isolates was relatively low and particularly low vancomycin resistance was similar to those of $Enterococcus$ isolates obtained from other foods. Therefore, the antibiotics resistance of $Enterococcus$ and especially vancomycin-resistant $Enterococcus$ spp. from $Cheongkukjang$ and $Doenjang$, is not hazardous.

• The Korean Journal of Ecology
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• v.27 no.5
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• pp.283-289
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• 2004

This study was conducted to evaluate the annual population variation and identification of antibiotic-resistant bacteria in the lower artificial Lake Geumgang from January to December, 2002. Samples were taken from the surface waters at 3 stations near the estuarine barrage. The results were as follows; the population densities of heterotrophic bacteria varied from 4.1±1.0×10² to 6.7±1.1×10³ cfu ml/sup -1/ during the investigation periods. The population densities of antibiotic-resistant bacteria ranged from 1.5±0.7×10 to 4.3±0.3×10³ cfu ml/sup -1/ for ampicillin; from 0 to 6.4±0.4× 10² cfu ml/sup -1/ for chloramphenicol; from 0 to 2.8±0.3×10³ cfu ml/sup -1/ for gentamicin; from 0 to 4.5±1.0×10³ cfu ml/sup -1/ for kanamycin; and from 1.0±0.4 × 10 to 2.3±0.5×10³ cfu ml/sup -1/ for streptomycin, respectively. Of the sixty isolates, 90% were Gram negative. Dominant genera by 16S rDNA analysis were identified Aeromonas spp. (14 strains), Bacillus spp. (6 strains), Enterobacter spp. (4 strains), and Stenotrophomonas spp. (6 strains). These strains were clustered into 12 groups based on relatedness by average linkage method. Of the 60 isolates, 85% had the resistance to ampicilin and 32% were shown resistance to more than 2 kinds of antibiotics.

• Korean Journal of Microbiology
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• v.40 no.4
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• pp.286-294
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• 2004

Between 1997 and 1998 in Korea, 56 isolates of Escherichia coli were obtained from pig suffering diarrhea. Among those, 38 isolates that showed the hemolytic activity, antimicrobial resistance, and toxin production were studied. Among 38 isolates, thirty-six isolates $(94.7\%)$ were resistant to tetracycline, 27 isolates $(71.0\%)$ were resistant to ampicillin, 26 isolates $(68.4\%)$ were resistant to chloramphenicol, and 21 isolates $(55.2\%)$ were resistant to trimethoprim, while none was resistant to aztreonam, amikacin, and norfloxacin. Among these iso­lates, 21 isolates $(55.3\%)$ were multiple drug resistant to at least four different class antimicrobial agents. Extended spectrum $\beta-lactamase$ producing isolates were not detected in the double disk synergy test. In these hemolytic Escherichia coli, heat-stable enterotoxin $(89.5\%)$ was the most prevalent toxin, followed by vero­toxins $(47.4\%),$ and then heat-labile enterotoxin $(31.6\%).$ Except 8 isolates $(21.0\%)$ which produced ST only, 12 isolates $(31.6\%)$ produced ST and LT, 13 isolates $(34.2\%)$ produced ST, VT, and VTe, and 5 isolates $(13.2\%)$ produced VT and VTe. However, none produced all 4 types of toxin, simultaneously. The predominant serotype could not be determined by the agglutination method. Sixteen isolates $(42.1\%)$ were strongly adhered to T-24 bladder cell and 17 isolates $(44.7\%)$ were to Caco-2 intestinal cell. Especially, 11 strains $(28.9\%)$ were evaluated as strongly adhesive to both T-24 cells and Caco-2 cells. Genes for toxin and the antimicrobial resistance were transferred to clinical isolates of Escherichia coli from human urine by the filter mating method. Results suggest the possibility that antimicrobial resistance and toxin can be transferred from animals to humans by direct con­tact of resistant bacteria as well as gene transfer, although there was no correlation between toxin production, adherent activity, and antimicrobial resistance among hemolytic E. coli isolated from pig suffering diarrhea.

• Journal of Veterinary Clinics
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• v.20 no.3
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• pp.302-307
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• 2003

Although, in human medicine, strains of methicillin-resistant staphylococi have become the most important causative agents of nosocomial infections, studies on the small animals are very. limited. The aim of this study was to determine mecA gene and susceptibility to antibiotics of staphylococci strains isolated from clinically ill or healthy dogs and cats, during the period August 2002-July 2003. A total of 136 staphylococci (87 coagulase-positive and 49 coagulase-negative) were investigated for antibiotic resistance, using disk diffusion and minimum inhibitory concentration (MIC) test. The mecA gene was detected using the polymerase chain reaction. The isolates belonged to the species S. aureus (53 isolates), S. intermedius (34 isolates), S. epidermidis (26 isolates) and other coagulase-negative staphylococci (CNS, 23 isolates). Of the 136 isolates, 43 (31.6%) were mecA-positive and the frequency of the ,presence of mecA gene varied among the different species. All S. aureus strains were mecA-negative and were found to be susceptible, with an oxacillin MIC $\leq$1 $\mu\textrm{g}$/ml. Five (13.6%) isolates of 36 that exhibited oxacillin resistance on the MIC testing were found to be mecA-negative, suggesting not all mecA-positive strains may be an oxacillin resistant. However, the mecA presence of the strains was correlated with high oxacillin resistance: 71.4% (10 isolates of 14; P < 0.001) for mecA-positive S. intermedius and 72.4% (21 isolates of 29; P < 0.001) for mecA-positive CNS isolates. About 69% (94 isolates of 136) showed resistance to at least one drug, and 22.8% (31 isolates) were resistant to four or more different drug classes. Resistance (36 isolates, 71.7%) to penicillin G was a common finidng. This study suggest that the mecA-positive staphylococci are prevalent in small animals, and selection of antibiotics to treat infections caused by mecA-positive staphylococci may be very limited because of multi-drug resistance.

• Journal of Food Hygiene and Safety
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• v.30 no.1
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• pp.51-58
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• 2015

Thirty one of Staphylococcus aureus isolated from perilla leaf cultivation areas in Miryang were investigated on the characteristics, such as enterotoxin genes and antibiotic susceptibility. Five toxin genes (sea, seb, sec, sed, and see) were examined by PCR method. Disc diffusion method was used to examine the antibiotic susceptibility of S. aureus by using 18 types of antibiotic discs with different concentrations. Among enterotoxin-encoding genes, sea and sed genes were co-detected from 4 isolates (12.9%), sed gene was founded in 9 isolates (29.0%), and see gene was founded in 1 isolate (3.2%). However seb and sec and tsst were not detected in any isolates. As a result of antibiotic susceptibility test, 7 isolates (22.6%) were resistant to 12 antibiotics (penicillin, ampicillin, oxacillin, amoxicillin-clavulanic acid, cefazolin, cephalothin, imipenem, gentamicin, tetracycline, ofloxacin, norfloxacin, and erythromycin). 2 isolates (6.5%) were resistant to 5 antibiotics (penicillin, ampicillin, amoxicillin-clavulanic acid, gentamycin, and telithromycin). MRSA (Methicilline Resistant Staphylococcus aureus) was founded in packing vinyl, hands, and perilla leaves.