• Korean Journal of Clinical Laboratory Science
• /
• v.43 no.2
• /
• pp.68-74
• /
• 2011

Pseudomonas aeruginosa is an aerobic, Gram-negative, glucose-nonfermenting bacterium, which has emerged as a serious opportunistic pathogen. Recently, outbreaks of carbapenem resistant P. aeruginosa give rise to significant therapeutic challenges for treating nosocomial infections. The genes of metallo-${\beta}$-lactamase (MBL), a powerful carbapenemase, are carried as a part of the mobile gene cassettes inserted into integrons playing an important role in rapid dissemination of antibiotic resistance genes among bacterial isolates. In this study, we investigated the prevalence of integron in imipenem resistant P. aeruginosa isolates. A total of 61 consecutive, non-duplicate, and imipenem resistant P. aeruginosa strains were isolated from a university hospital in the Chungcheong province of Korea. We employed repetitive extragenic palindromic sequence-based PCR (rep-PCR) method for the selection of clonally different P. aerusinosa strains. PCR and DNA sequencing were conducted for the detection of integrons. Twenty-one clonally different P. aeruginosa strains were isolated. Only one (P28) of the strains harbored $bla_{VIM-2}$ that was found as gene cassettes in class 1 integrons. Four of 21 carbapenem resistant P. aeruginosa strains harbored class 1 integron containing aminoglycoside resistance determinant. All of the integrons detected in the study contained more than one resistance gene cassette, which can mediate resistance to multiple antibiotics. To prevent further spreading of the multi-drug resistant P. aeruginosa, conseguent monitoring and clinical polices are required.

• Korean Journal of Clinical Laboratory Science
• /
• v.49 no.4
• /
• pp.413-419
• /
• 2017

Four imipenem-resistant bacteria were isolated from the clinical specimens of a patient with pneumonia. To identify the isolates, we used the GN card of Vitek II system and performed a phylogenetic analysis based on 16S rRNA gene sequence. The isolates were identified as P. aeruginosa (2 strains), P. monteilii (1 strain), and P. putida (1 strain), and were tested for antibiotic resistance after determining the MIC of imipenem to be $${\geq_-}8{\mu}g/mL$$ using the AST-N225 card of Vitek II system. The imipenem-resistant genotypes were determined using PCR products amplified using specific ${\beta}-Lactamase$ gene primers. The MBL gene was identified in all four isolates. One strain of P. aeruginosa exhibited the VIM and SHV-1 type genes, while the other strain exhibited both VIM and OXA group II genes. According to the antimicrobial susceptibility test, the bacteria were more susceptible to amikacin than other antibiotics. DNA fingerprint analysis using ERIC-PCR to analyze the epidemiological relationship between strains estimated that both the P. aeruginosa isolates were similar, but exhibited different DNA band types. It is uncommon to find four strains of imipenem-resistant bacteria with different DNA band types in a single patient.

• Journal of Life Science
• /
• v.20 no.8
• /
• pp.1214-1220
• /
• 2010

Imipenem-resistant bacteria were isolated from clinical specimens taken from hospitalized patients in Suncheon, Korea. Fifty-four isolates were phylogenetically analyzed based on 16S rRNA gene and gyrB gene sequence comparisons. Isolates were affiliated with Pseudomonas aeruginosa (30 strains; 55.6%), Acinetobacter baumannii (21; 38.9%), Enterobacter hormaechei (2) and Pseudomonas putida (2). Twenty-two isolates produced metallo-$\beta$-lactamase (MBL); 12 Acinetobacter baumannii strains, 7 Pseudomonas aeruginosa strains, 2 P. putida strains and 1 Enterobacter hormaechei strain. Antibiotic susceptibility of the isolates was determined using the disc diffusion method and Vitek system. Strains producing metallo-$\beta$-lactamase (type IMP & VIM) were more resistant to antibiotics ceftazidime, aztreonam, amikacin and gentamicin than to strains producing OXA and SHV type of $\beta$-lactamase.

• Korean Journal of Clinical Laboratory Science
• /
• v.42 no.2
• /
• pp.71-80
• /
• 2010

Pseudomonas aeruginosa are important nosocomial pathogens. Their resistance to carbapenem is increasing and causing concerns in Korea. An increasing prevalence of carbapenem resistance mediated by acquired carbapenemase is being reported. Over a 10 month-period from July 2007 to April 2008, 32 strains of imipenem-nonsusceptible P. auruginosa were isolated from Kangwon National University Hospital. To determine the prevalence and genotypes of the carbapenemase-producing clinical isolates, the antibiotic susceptibility was determined by Microscan Walkaway 96 SI System and the carbapenem activity was detected by the modified Hodge test and the imipenem-EDTA-SMA double-disk synergy test. The metallo-${\beta}$-lactamase gene and OXA-type ${\beta}$-lactamase gene reported in Korea were detected by PCR. As for the result of PCR, 30 isolates of P. aeruginosa were found to have $bla_{IMP-1}$-like and 1 isolate was found to have $bla_{IMP-1}$-like and $bla_{IMP-2}$. No clinical isolates were found to have $bla_{SIM-1}$, $bla_{OXA-23}$-like and $bla_{OXA-24}$-like. Random amplified polymorphic DNA (RAPD)-PCR and dendrogram for genetical similarity to band patterns of each clinical isolates were examined. P. aeruginosa were grouped into 7 clusters of up to 50% of similarity index. In the P. aeruginosa group, PS3 was resistant to the most antibiotics, PS1 was susceptible to the most antibiotics. PS7 was resistant to aztreonam unlike other groups. This is the first report of prevalence of carbapenemase in Chuncheon.

• Journal of Life Science
• /
• v.22 no.9
• /
• pp.1268-1276
• /
• 2012

The emergence and dissemination of carbapenem-resistant bacteria have resulted in limitations of antibiotic treatment and potential outbreaks of metallo-${\beta}$-lactamase (MBL) producing Pseudomonas aeruginosa resistant to carbapenems. In this study, we conducted molecular characterization of the MBL genes of the ${\beta}$-lactam drug-resistant P. aeruginosa and prepared basic data for treatment and prevention of proliferation of antimicrobial-resistant bacterial infections. Forty-two P. aeruginosa isolates of 254 were resistant to imipenem or meropenem. Among the 42 isolates, 28 isolates were positive for the Hodge test, and 23 isolates were positive for the EDTA-disk synergy test (EDST). MBLs were detected in 59.5% (25/42) of P. aeruginosa isolates. Eight isolates harbored $bla_{IMP-6}$, whereas 17 isolates harbored $bla_{VIM-2}$. The $bla_{IMP-6}$ gene was in a class 1 integron containing five gene cassettes: $bla_{IMP-6}$, qac, aacA4, $bla_{OXA-1}$, and aadA1. Some strains that produce IMP-6 and VIM-2 showed epidemiological relationships. The $bla_{IMP-6}$ gene in carbapenem-resistant P. aeruginosa showed an identical pattern to a gene cassette that was reported at a hospital in Daegu, Korea. Therefore, MBL-producing P. aeruginosa is already endemic in the community. We are concerned that the existence of carbapenem-resistant bacteria containing the blaMBL gene may increase pressure on antibiotic selection when treating infections. We believe that we should select appropriate antibiotics based on the antibiotic susceptibility test and continue the research to prohibit the emergence and spread of antibiotics resistant bacteria.

• Journal of Korean Academy of Nursing
• /
• v.36 no.7
• /
• pp.1204-1214
• /
• 2006

Purpose: This retrospective study was done to evaluate the status of nosocomial urinary tract infections and to determine the risk factors and transmission route of causal IRPA through molecular epidemiology. Method: Two hundred ninety-nine of 423 patients admitted to the internal medicine and surgery ICU at a university hospital incity B had a positiveurine culture. Twelve of the 299 patients who had a urinary tract infection had IRPA strains. The data was collected from November 1, 2004 to January 31, 2005. The following results were obtained after the data was analyzed using percentile and UPGMA. Result: The rate of nosocomial urinary tract infections in the ICU was 10.8%. Therewere 16.8 cases of infection based on the period of hospitalization. There were 16.9 cases of infection based on the use of a foley catheter. The rate of nosocomial urinary tract infection in the ICU and urinary tract infections related to IRPA were higher in patients with the following characteristics: men, old age, admission through the emergency room, longer than seven days admission, severity of admitting causes, disturbance of consciousness, hydration less than 300cc in 24hours, a long course of antibiotics, a long period of foley catheterization and perineal care. Most of the microorganisms that caused the urinary tract infection were gram negative bacilli, among which P. aeruginosa was found in 70 patients (18.5%) and IRPA in 12 (4.0%). Among the 12 IRPA strains that were tested with PFGE, eight showed a dice coefficient higher than 80%, suggesting a genetic relationship. They were related with the period of hospitalization in the same ICU. These patients all received direct care for a urinary tract infection. Conclusion: Through these results, IRPA can be consideredas a contributing factors to urinary tract infections thus, active preventative measures are needed by the medical staff.

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

• Journal of Microbiology
• /
• v.45 no.4
• /
• pp.358-363
• /
• 2007

Multi-drug resistant Pseudomonas aeruginosa has been implicated in a variety of serious therapeutic problems in clinical environments. Among the 968 P. aeruginosa isolates obtained from two hospitals in Daegu, Korea, we acquired 17 isolates that were resistant to all available tested antimicrobial agents, with the exception of colistin (colistin-only sensitive). We characterized the antimicrobial susceptibilities, $metallo-{\beta}-lactamases$, and epidemiological relatedness among the colistin-only sensitive P. aeruginosa isolates. All colistin-only sensitive isolates were positive in the modified Hodge test and imipenem-EDTA synergy test, thereby indicating the production of $metallo-{\beta}-lactamases$. 11 isolates from the secondary hospital and six isolates from the tertiary teaching hospital harbored $bla_{VIM-2}$ and $bla_{IMP-1}$, respectively. The pulsed-field gel electrophoretic analysis of the SpeI-digested DNA from P. aeruginosa isolates indicated that two different clones of colistin-only sensitive P. aeruginosa originated from each hospital, and had spread within the hospital environment. Overall, colistin-only sensitive P. aeruginosa was detected in Korea for the first time, but no pan-drug resistant bacteria were identified. Nationwide surveillance is required in order to monitor the emergence of colistin-only sensitive or pan-drug resistant bacteria.

• Korean Journal of Microbiology
• /
• v.44 no.4
• /
• pp.339-345
• /
• 2008

This study was to detect MBL (metallo-${\beta}$-lactamase) among glucose non-fermenting Gram-negative bacilli isolated from clinical specimen and to search antimicrobial combination therapy against MBL producing Pseudomonas aeruginosa. Among fifty one isolates of Gram-negative bacilli with reduced imipenem susceptibility ($MIC{\ge}8{\mu}g/ml$), nine isolates have shown positive results in MBL detection test. They were seven Achromobacter xylosoxidans subsp. xylosoxidans and two P. aeruginosa. The results from EDTA-DDST coin-cided with those of PCR and nucleotide sequence analysis which showed the presence of $bla_{VIM-2}$. The combination of aztreonam (AZT) and piperacillin-tazobactarn (TZP) or AZT and amikacin (AN) screened by one disk synergy test showed no synergistic effect. Triple antibiotic combination therapy with AZT, TZP and AN, however, was shown to be effective and the most synergistic after 8 hrs of exposure. This result strongly suggest that the triple combination therapy of AZT, TZP, and AN could be useful for the treatment of infection caused by MBL producing Gram-negative bacilli.

• Biomedical Science Letters
• /
• v.25 no.4
• /
• pp.321-330
• /
• 2019

Carbapenem is recently considered as the last resort of the therapeutics for gram negative bacterial infection. Increasing of organisms producing metallo-β-lactamase (MBL), we have difficulty in choosing the antimicrobial agents. Among 345 clinical isolates of Pseudomonas spp., 61 isolates (17.7%) were positive for the modified imipenem or meropenem-Hodge test and 55 isolates (15.9%) were positive for the imipenem-EDTA + SMA double disk synergy test (DDS). PCR and sequencing of bla_VIM-2-allele and bla_IMP-1-allele showed that 17 isolates of Pseudomonas aeruginosa, 9 isolates of Pseudomonas taiwnensis and 2 Pseudomonas plecoglossicida had bla_VIM-2, and 22 isolates of P. aeruginosa and one Pseudomonas otitidis had bla_IMP-6. These MBL genes were all in class 1 integron. The size of class 1 integron with bla_VIM-2 ranged from 3.5 kb to 5.5 kb in clinical isolates of Pseudomonas spp. including P. aeruginosa. bla_VIM-2 was most often located first in the class 1 integron, sometimes in the second or third position, and these integrons often had aacA4 or aadA1. Strict infection control measures are needed to more effectively prevent further spread of these MBL-producing Pseudomonas spp. In addition, MBL-producing Pseudomonas spp. is expected to continue to spread in various countries and regions.