• Tuberculosis and Respiratory Diseases
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• v.60 no.2
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• pp.228-234
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• 2006

Background : Acinetobacter baumannii is an important pathogen associated with nosocomial infections in intensive care units, and is responsible for nosocomial pneumonia, UTI, bacteremia, etc. The main concern is that this pathogen is often resistant to many antimicrobial agents, particularly to carbapenem. This study compared the clinical those of ICU admitted patients with the carbapenem resistant A. baumannii isolated from the sputum with characteristics of patients with carbapenem sensitive A. baumannii. Methods : A total of 49 patients with A. baumannii from a sputum culture who were admitted to the ICU from January to December 2003 were enrolled in this study. This study evaluated the demographic variables, mortality, APACHE II score, comorbidity, antibiotics used, hospital and ICU stay, Clinical Pulmonary Infection Score, and mechanical ventilation. A retrospective analysis was made by a review of the patients' medical records. Results : Carbapenem sensitive and resistant A. baumannii was isolated from 23 patients and 26 patients respectively. Univariate analysis revealed renal disease, the use of carbapenem and aminoglycoside to be statistically significant factors for carbapenem resistance. Multivariate analysis revealed carbapenem use(p=0.024; OR, 8.17; CI 1.32 to 50.68) to be positively associated with carbapenem resistance, and aminoglycoside use(p=0.026; OR, 0.18; CI, 0.04 to 0.82) to be negatively associated with carbapenem resistance. There was no significant difference in mortality between the carbapenem sensitive and resistant group(30 vs 42%. P=0.39). Conclusion : The occurrence of carbapenem resistant A. baumannii is positively associated with carbapenem use and negatively associated with aminoglycoside use. Carbapenem resistance in the sputum culture did not affect the mortality rate.

• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.1154-1162
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• 2015

The emergence of carbapenem resistance among Pseudomonas aeruginosa is an increasing problem in many parts of the world. In particular, metallo-$\beta$-lactamases (MBLs) and AmpC $\beta$lactamases are responsible for high-level resistance to carbapenem and cephalosporin. We studied the diversity and frequency of $\beta$-lactamases and characterized chromosomal AmpC $\beta$lactamase from carbapenem-resistant P. aeruginosa isolates. Sixty-one carbapenem-resistant P. aeruginosa isolates were collected from patients in a tertiary hospital in Daejeon, Korea, from January 2011 to June 2014. Minimum inhibitory concentrations (MICs) of four antimicrobial agents were determined using the agar-dilution method. Polymerase chain reaction and sequencing were used to identify the various $\beta$-lactamase genes, class 1 integrons, and chromosomally encoded and plasmid-mediated ampC genes. In addition, the epidemiological relationship was investigated by multilocus sequence typing. Among 61 carbapenem-resistant P. aeruginosa isolates, 25 isolates (41.0%) were MBL producers. Additionally, 30 isolates producing PDC (Pseudomonas-derived cephalosporinase)-2 were highly resistant to ceftazidime (MIC₅₀ = $256{\mu}g/ml$) and cefepime (MIC₅₀ = $256{\mu}g/ml$). Of all the PDC variants, 25 isolates harboring MBL genes showed high levels of cephalosporin and carbapenem resistance, whereas 36 isolates that did not harbor MBL genes revealed relatively low-level resistance (ceftazidime, p < 0.001; cefepime, p < 0.001; imipenem, p = 0.003; meropenem, p < 0.001). The coexistence of MBLs and AmpC $\beta$-lactamases suggests that these may be important contributing factors for cephalosporin and carbapenem resistance. Therefore, efficient detection and intervention to control drug resistance are necessary to prevent the emergence of P. aeruginosa possessing this combination of $\beta$-lactamases.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.406-413
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• 2018

The emergence of carbapenem resistance among Pseudomonas aeruginosa has become an increasing problem worldwide. In particular, $metallo-{\beta}-lactamases$ (MBLs) are responsible for the high-level resistance to carbapenem. Sequence type 235 (ST235) has been found internationally in a multidrug-resistant clone and is involved in the dissemination of genes encoding IMP-6 and VIM-2. This study examined the prevalence of MBLs and the epidemiological relationship in carbapenem-resistant P. aeruginosa (CRPA) isolates obtained from a tertiary hospital in Daejeon, Korea, between March 2008 and June 2014. The antimicrobial susceptibilities were determined using the disk-diffusion method and PCR and DNA sequencing were used to identify the MBL genes. In addition, an epidemiological relationship was investigated by multilocus sequence typing (MLST). Among the 110 CRPA isolates, 32 isolates (29.1%) were MBL-producers; the major type was IMP-6 (29 isolates, 90.6%). VIM-2 was identified in 3 isolates (9.4%) of ST357. IMP-6-producing isolates were multidrug-resistant (MDR) and belonged to ST235. ST235 (55 isolates, 50.0%) was the clone most frequently detected and has gradually emerged during a seven-year period. To prevent the spread of MDR ST235 P. aeruginosa isolates, the current widespread use of carbapenems needs to be curtailed, and novel continuous monitoring strategies should be developed as soon as possible.

• Biomedical Science Letters
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• v.25 no.3
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• pp.288-292
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• 2019

In vitro antimicrobial activities of hot water extracts of Camellia sinensis (L.) O. Kuntze, for carbapenem-resistant Enterobacteriaceae (CRE) were compared to commonly used conventional antimicrobial agents. CRE was not only resistant to imipenem, meropenem or ertapenem, but also to various antimicrobial agents, such as amikacin (> $128{\mu}g/mL$). The hot water extracts of Camellia sinensis (L.) O. Kuntze had the lowest MIC ($0.06{\sim}0.5{\mu}L/mL$) of the carbapenem-resistant E. coli, K. pneumoniae, and Enterobacter spp. tested, and it was possible more potent than various conventional antimicrobial agents. Synergistic combinations of the extract with used commonly antimicrobial agents might even improve its antimicrobial chemotherapy property.

• Journal of Microbiology and Biotechnology
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• v.31 no.10
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• pp.1383-1392
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• 2021

Carbapenem-resistant Enterobacteriaceae (CRE) that produce Klebsiella pneumoniae carbapenemase are increasingly reported worldwide and have become more and more resistant to nearly all antibiotics during the past decade. The emergence of K. pneumoniae strains with decreased susceptibility to carbapenems, which are used as a last resort treatment option, is a significant threat to hospitalized patients worldwide as K. pneumoniae infection is responsible for a high mortality rate in the elderly and immunodeficient individuals. This study used Lactobacillus fermentum as a candidate probiotic for treating CRE-related infections and investigated its effectiveness. We treated mice with L. fermentum originating from the vaginal fluid of a healthy Korean woman and evaluated the Lactobacilli's efficacy in preventive, treatment, nonestablishment, and colonization mouse model experiments. Compared to the control, pre-treatment with L. fermentum significantly reduced body weight loss in the mouse models, and all mice survived until the end of the study. The oral administration of L. fermentum after carbapenem-resistant Klebsiella (CRK) infection decreased mortality and illness severity during a 2-week observation period and showed that it affects other strains of CRK bacteria. Also, the number of Klebsiella bacteria was decreased to below 5.5 log₁₀ CFU/ml following oral administration of L. fermentum in the colonization model. These findings demonstrate L. fermentum's antibacterial activity and its potential to treat CRE infection in the future.

• Biomedical Science Letters
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• v.27 no.2
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• pp.59-68
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• 2021

Multidrug-resistant strain of Acinetobacter baumannii (MDRAB) is an emerging pathogen in health care facilities, preventing MDRAB is a public health concern. We conducted this experiment on a clinical isolate of A. baumannii with two main goals: the role of the efflux pump system in the stress provision of carbapenem and the response to the transcription level of the efflux pump gene. A total of 34 strains of A. baumannii was isolated from the Yangsan Hospital of Pusan National University. First, when we compared and observed the expression of the efflux pump gene and antibacterial resistance to carbapenem, a strong correlation was observed between carbapenem resistance and overexpression of adeB (P=0.0056). Second, a correlation between the efflux pump and concentration gradient and tolerance to carbapenem stress at the AdeABC efflux pump genes transcription level was confirmed. Our results revealed that the expression of the AdeABC efflux pump is an important resistance determinant in obtaining antibiotic resistance of the carbapenem group in A. baumannii.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.389-398
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• 2020

The prevalence of carbapenem-resistant Enterobacteriaceae (CRE) is increasing globally, resulting in high mortality rates. Although CRE is a relatively recent problem in Korea (the first case was not diagnosed until 2010), it is responsible for serious morbidities at an alarming rate. In this study, we carried out a molecular genetic analysis to determine the incidence of CRE and carbapenemase-producing Enterobacteriaceae (CPE) at a general hospital in Korea between August 2017 and August 2019. Forty strains of CPE were isolated from various clinical specimens and analyzed via antimicrobial susceptibility testing, polymerase chain reaction to detect β-lactamase genes, deoxyribonucleic acid sequencing, multilocus sequence typing, curing testing, and conjugal transfer of plasmids. The results demonstrated that all 40 isolates were multidrug-resistant. The fluoroquinolone susceptibility test showed that 75% of the Enterobacteriaceae isolates were resistant to ciprofloxacin, whereas 72.5% were resistant to trimethoprim-sulfamethoxazole. Further, conjugation accounted for 57.5% of all resistant plasmid transfer events, which is 4.3-fold higher than that observed in 2010 by Frost et al. Finally, the high detection rate of transposon Tn4401 was associated with the rapid diffusion and evolution of CPE. Our results highlight the rapid emergence of extensively drugresistant strains in Korea and emphasize the need for employing urgent control measures and protocols at the national level.

• Pediatric Infection and Vaccine
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• v.18 no.1
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• pp.97-102
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• 2011

The Multidrug-resistant Acinetobactor baumanii (MDRAB) is an opportunistic pathogen. Patients with long periods of hospital stay and/or under intensive care unit (ICU) receiving invasive management are more susceptible to this pathogen. In this report, four children with MDRAB infection are reviewed and described their clinical characteristics. There had been concurrent outbreaks of MDRAB infection in adult patients in the ICU at this period of time. The first child had received a craniotomy and epidural hematoma evacuation. The second child was admitted for status epilepticus with hydrocephalus. The third child had pneumonia with status epilepticus with hydrocephalus. The fourth child had poor activity due to hypoxic ischemic encephalopathy and convulsive disorder. Except the fourth child, all had not been exposed to carbapenem prior to infection of MDRAB. That imply the cause of MDRAB infections may be associated with invasive management and prolonged hospitalization together with the previous exposure to carbapenem in our cases. We would like to emphasize the importance and minimizing the spread of hospital infection in patients under prolonged intensive care management regardless of the use of carbapenem.

• Tuberculosis and Respiratory Diseases
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• v.72 no.4
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• pp.360-366
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• 2012

Background: Carbapenem-resistance is rapidly evolving among the pathogenic microbes in intensive care units (ICUs). This study aimed to determine annual trend of carbapenem-resistance in the ICU for 4 years, since the opening of a university-affiliated hospital in South Korea. Methods: From 2005 to 2008, microbial samples from consecutive 6,772 patients were screened in the ICU. Three hundred and ninety-seven patients (5.9%) and their first isolates of carbapenem-resistant pathogens were analyzed. Results: The percentage of patients infected with carbapenem-resistant organisms increased constantly during the initial three years (2.3% in 2005, 6.2% in 2006, 7.8% in 2007), then it declined to 6.5% in 2008. Acute Physiology and Chronic Health Evaluation (APACHE) III score at admission was $58.0{\pm}23.5$, the median length of the ICU stay was 37 days, and the mortality rate was 37.5%. The sampling sites were endotracheal suction (67%), catheterized urine (17%), wound (6%) and others (10%). Bacteria with carbapenem-resistance were Pseudomonas aeruginosa (247 isolates, 62%), Acinetobacter baumannii (117 isolates, 30%), Enterobacteriaceae (12 isolates, 3%), and others (21, 5%). Of note, peak isolation of carbapenem-resistant microorganisms in medical ICU was followed by the same epidemic at surgical ICU. Conclusion: Taken together, carbapenem-resistant pathogens are of growing concern in the ICU.

• Journal of Korean Academy of Nursing
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• v.50 no.4
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• pp.621-630
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• 2020

Purpose: This study was aimed to evaluate the external validity of a carbapenem-resistant Enterobacteriaceae (CRE) acquisition risk prediction model (the CREP-model) in a medium-sized hospital. Methods: This retrospective cohort study included 613 patients (CRE group: 69, no-CRE group: 544) admitted to the intensive care units of a 453-beds secondary referral general hospital from March 1, 2017 to September 30, 2019 in South Korea. The performance of the CREP-model was analyzed with calibration, discrimination, and clinical usefulness. Results: The results showed that those higher in age had lower presence of multidrug resistant organisms (MDROs), cephalosporin use ≥ 15 days, Acute Physiology and Chronic Health Evaluation II (APACHE II) score ≥ 21 points, and lower CRE acquisition rates than those of CREP-model development subjects. The calibration-in-the-large was 0.12 (95% CI: - 0.16~0.39), while the calibration slope was 0.87 (95% CI: 0.63~1.12), and the concordance statistic was .71 (95% CI: .63~.78). At the predicted risk of .10, the sensitivity, specificity, and correct classification rates were 43.5%, 84.2%, and 79.6%, respectively. The net true positive according to the CREP-model were 3 per 100 subjects. After adjusting the predictors' cutting points, the concordance statistic increased to .84 (95% CI: .79~.89), and the sensitivity and net true positive was improved to 75.4%. and 6 per 100 subjects, respectively. Conclusion: The CREP-model's discrimination and clinical usefulness are low in a medium sized general hospital but are improved after adjusting for the predictors. Therefore, we suggest that institutions should only use the CREP-model after assessing the distribution of the predictors and adjusting their cutting points.