Chung Jong Kim

Prevalence of Plasmid-Mediated Quinolone Resistance Determinants over a 9-Year Period

ABSTRACT Recently, several plasmid-mediated quinolone resistance (PMQR) genes conferring low levels of quinolone resistance have been discovered. To evaluate the temporal change in the prevalence of PMQR genes over a decade in a tertiary hospital in the Republic of Korea, we selected every fifth isolate of Escherichia coli and Klebsiella pneumoniae and every third isolate of Enterobacter cloacae between 1998 and 2001 and between 2005 and 2006 from a collection of blood isolates. Six PMQR genes [qnrA, qnrB, qnrC, qnrS, aac(6′)-Ib-cr, and qepA] were screened by multiplex PCR and then confirmed by direct sequencing, and the aac(6′)-Ib-positive PCR products were digested with BtsCI to identify the aac(6′)-Ib-cr variant. Of 461 isolates, 37 (8%) had one of the six PMQR genes; 13 (5%) of 261 E. coli strains, 13 (10%) of 135 K. pneumoniae strains, and 11 (17%) of 65 E. cloacae strains. qnrB was the most common PMQR gene and was found as early as 1998, whereas qnrS, aac(6′)-Ib-cr, and qepA emerged after 2000. None of the isolates carried qnrA or qnrC. Ciprofloxacin resistance increased over time (P < 0.001), and the overall prevalence of PMQR genes tended to increase (P = 0.20). PMQR-positive isolates had significantly higher ciprofloxacin resistance and multidrug resistance rates (P = 0.005 and P < 0.001, respectively). The increasing frequency of ciprofloxacin resistance in Enterobacteriaceae was associated with an increasing prevalence of PMQR genes, and this change involved an increase in the diversity of the PMQR genes and also an increase in the prevalence of the mutations in gyrA, parC, or both in PMQR-positive strains but not PMQR-negative strains.

Evidence-Based Guidelines for Empirical Therapy of Neutropenic Fever in Korea

Neutrophils play an important role in immunological function. Neutropenic patients are vulnerable to infection, and except fever is present, inflammatory reactions are scarce in many cases. Additionally, because infections can worsen rapidly, early evaluation and treatments are especially important in febrile neutropenic patients. In cases in which febrile neutropenia is anticipated due to anticancer chemotherapy, antibiotic prophylaxis can be used, based on the risk of infection. Antifungal prophylaxis may also be considered if long-term neutropenia or mucosal damage is expected. When fever is observed in patients suspected to have neutropenia, an adequate physical examination and blood and sputum cultures should be performed. Initial antibiotics should be chosen by considering the risk of complications following the infection; if the risk is low, oral antibiotics can be used. For initial intravenous antibiotics, monotherapy with a broad-spectrum antibiotic or combination therapy with two antibiotics is recommended. At 3-5 days after beginning the initial antibiotic therapy, the condition of the patient is assessed again to determine whether the fever has subsided or symptoms have worsened. If the patients condition has improved, intravenous antibiotics can be replaced with oral antibiotics; if the condition has deteriorated, a change of antibiotics or addition of antifungal agents should be considered. If the causative microorganism is identified, initial antimicrobial or antifungal agents should be changed accordingly. When the cause is not detected, the initial agents should continue to be used until the neutrophil count recovers.

Clinical and Epidemiological Factors Associated with Methicillin Resistance in Community-Onset Invasive Staphylococcus aureus Infections: Prospective Multicenter Cross-Sectional Study in Korea

Successful empirical therapy of Staphylococcus aureus infections requires the ability to predict methicillin resistance. Our aim was to identify predictors of methicillin resistance in community-onset (CO) invasive S. aureus infections. Sixteen hospitals across Korea participated in this study from May to December 2012. We prospectively included cases of S. aureus infection in which S. aureus was isolated from sterile clinical specimens ≤72 hours after hospitalization. Clinical and epidemiological data were gathered and compared in methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) cases. Community-associated (CA) infections were defined as in previous studies. In total, there were 786 cases of community-onset S. aureus infection, 102 (13.0%) of which were CA-MRSA. In addition to known risk factors, exposure to 3rd generation cephalosporins in the past 6 months [odds ratio (OR), 1.922; 95% confidence interval (CI), 1.176–3.142] and close contact with chronically ill patients in the past month (OR, 2.647; 95% CI, 1.189–5.891) were independent risk factors for MRSA infection. However, no clinical predictors of CA-MRSA were identified. Methicillin resistance, CO infection, and appropriateness of empirical antibiotics were not significantly related to 30-day mortality. MRSA infection should be suspected in patients recently exposed to 3rd generation cephalosporins or chronically-ill patients. There were no reliable predictors of CA-MRSA infection, and mortality was not affected by methicillin resistance.

Impact of Vancomycin MIC on Treatment Outcomes in Invasive Staphylococcus aureus Infections

ABSTRACT There are conflicting data on the association of vancomycin MIC (VAN-MIC) with treatment outcomes in Staphylococcus aureus infections. We investigated the relationship between high VAN-MIC and 30-day mortality and identified the risk factors for mortality in a large cohort of patients with invasive S. aureus (ISA) infections, defined as the isolation of S. aureus from a normally sterile site. Over a 2-year period, 1,027 adult patients with ISA infections were enrolled in 10 hospitals, including 673 (66%) patients with methicillin-resistant S. aureus (MRSA) infections. There were 200 (19.5%) isolates with high VAN-MIC (≥1.5 mg/liter) by Etest and 87 (8.5%) by broth microdilution (BMD). The all-cause 30-day mortality rate was 27.4%. High VAN-MIC by either method was not associated with all-cause 30-day mortality, and this finding was consistent across MIC methodologies and methicillin susceptibilities. We conclude that high VAN-MIC is not associated with increased risk of all-cause 30-day mortality in ISA infections. Our data support the view that VAN-MIC alone is not sufficient evidence to change current clinical practice.

Infected Aortic Aneurysm caused by Mycobacterium bovis after Intravesical Bacillus Calmette-Guérin Treatment for Bladder Cancer

A 70-year-old man presented with lower back pain and cyanotic changes in his left lower extremity. He was diagnosed with infected aortic aneurysm and infectious spondylitis. He had received intravesical Bacillus Calmette-Guérin (BCG) therapy up to 1 month before the onset of symptoms. The aneurysm was excised and an aorto-biiliac interposition graft was performed. Mycobacterium tuberculosis complex was cultured in the surgical specimens. Real-time polymerase chain reaction (PCR) targeting the senX3-regX3 region, and multiplex PCR using dual-priming oligonucleotide primers targeting the RD1 gene, revealed that the organism isolated was Mycobacterium bovis BCG. The patient took anti-tuberculosis medication for 1 year, and there was no evidence of recurrence at 18 months follow-up.

Pseudomonas aeruginosa bacteremia in patients with liver cirrhosis: a comparison with bacteremia caused by Enterobacteriaceae

BackgroundThis study was performed to detect risk factors for Pseudomonas aeruginosa bacteremia in patients with liver cirrhosis.MethodsA retrospective case–control study was designed to identify risk factors for P. aeruginosa bacteremia in cirrhotic patients. The cases were cirrhotic patients with P. aeruginosa bacteremia and the controls were cirrhotic patients with Enterobacteriaceae bacteremia.ResultsSixty-one cases and the same number of controls were enrolled. In a multivariate analysis, younger age {adjusted odds ratio (aOR) per one year: 0.96, 95% confidence interval: 0.93 - 0.99}, nosocomial acquisition (aOR 3.87, 95% confidence interval: 1.50 - 9.94), preexisting biliary disease (aOR 4.79, 95% confidence interval: 1.92 - 10.47), and recent exposure to immunosuppressive agent (aOR 3.10, 95% confidence interval: 1.23 - 7.82) were associated with P. aeruginosa bacteremia. In the case group the frequency of appropriate initial antibiotic regimens was considerably lower than in the control group: 29.5% vs. 65.6% (P <0.01). However, thirty day mortality did not differ significantly between cases and controls (19.7% vs. 24.6%).ConclusionsNosocomial acquisition, preexisting biliary disease, and recent use of immunosuppressive agents are strong predictive factors for P. aeruginosa bacteremia in cirrhotic patients.

Serotype Distribution and Antimicrobial Susceptibilities of Invasive Streptococcus pneumoniae Isolates from Adults in Korea from 1997 to 2012

In Republic of Korea, a 7-valent pneumococcal conjugated vaccine (PCV7) was licensed for use in infants in 2003, and 13-valent PCV (PCV13) replaced it since 2010. We investigated trends in serotype distribution and antibiotic susceptibility of pneumococcal isolates from adult patients with invasive pneumococcal diseases (IPD). Invasive pneumococcal isolates from adult patients of ≥ 16 years of age were collected from 1997 to 2012. Serotypes of the isolates were determined by the Quellung reaction. Distribution of serotypes was analyzed according to the vaccine types. Antibiotic susceptibility was tested by using E-test strips. A total of 272 invasive pneumococcal isolates were included. The most common serotypes were serotype 19F (8.5%, 23/272), and serotype 3 (8.1%, 22/272), and 24.6% (67/272) of the isolates were of non-vaccine serotypes. Of the 272 isolates, 2.6% (7/272) were penicillin MICs of ≥ 4 µg/mL. The proportion of the PCV13 serotypes decreased from 63.3% (50/79) in 1997-2003 to 48.6% (17/35) in 2011-2012, whereas that of non-vaccine serotypes was 26.6% (21/79) and 25.7% (9/35), respectively, for the same periods. The proportion of the PCV13 serotypes showed a decreasing trend among adult patients with IPD over the study period.

Low Compliance with National Guidelines for Preventing Transmission of Group 1 Nationally Notifiable Infectious Diseases in Korea

Purpose This study was performed to evaluate the compliance with, and adequacy of, the Korean national guidelines which had been recommended until 2011 for isolation of patients with group 1 nationally notifiable infectious diseases (NNIDs), namely cholera, typhoid fever, paratyphoid fever, shigellosis, and enterohemorrhagic Escherichia coli (EHEC) infection. Materials and Methods We evaluated the clinical and microbiological characteristics of confirmed cases of group 1 NNIDs and compliance with the guidelines in 20 Korean hospitals nationwide in 2000-2010. We also compared the Korean guidelines with international guidelines. Results Among 528 confirmed cases (8 cases of cholera, 232 of typhoid fever, 81 of paratyphoid fever, 175 of shigellosis, and 32 EHEC infections), strict compliance with the Korean guideline was achieved in only 2.6% to 50.0%, depending on the disease. While the Korean guidelines recommend isolation of all patients with group 1 NNIDs, international guidelines recommend selective patient isolation and screening for fecal shedding, depending on the type of disease and patient status. Conclusion Compliance with the previous national guidelines for group 1 NNIDs in Korea was generally very low. Further studies are needed to evaluate whether compliance was improved after implementation of the new guideline in 2012.

Particle Hemodynamics on the bypassed and bifurcated geometry of Abdominal and Iliac Arteries

Proposed near-wall deposition probability (NWDP) index for platelets was applied to the bypassed and bifurcated arterial model of abdominal and iliac arteries to assess the reliability of the index as a hemodynamic index for the prediction of atherosclerotic disease development. NWDP index was evaluated by integrating the contribution of all the particle trajectories with time. The motion of every single particle (platelet; dp∼3µm) in pulsatile blood flow was calculated by using the one-way coupled Lagrangian method. The particle was assumed to be a solid sphere, and particle motions were also assumed not to influence the flow. Interactions with other particles were also neglected. The forces considered in the equation of motion for the particles were the drag, pressure gradient, and collision forces only. The ordinary differential equations were solved along the particle trajectory for the three components of the particle velocity and location vector by using the Rosenbrock method. The Rosenbrock method was more easily integrated than the Runge-Kutta method. The bypassed and bifurcated arterial model was compared with the normal arterial model in terms of NWDP and platelet trajectories. The results of this study indicated that localizations or sharp changes of the NWDP index were in good agreements with the constricted region of arteries or reattachment point in the recirculation zone where have been known to be geometrical lesion-prone.

Analysis of Volumetric Residence Time of Blood Elements in Stenosed Arteries

Blood flow in arteries is known to be closely related to atherosclerosis. Presence of recirculation zones, and low, high, and oscillatory wall shear stresses have been suggested to be important fluid dynamic factors causing development and progress of atherosclerosis. Our study was motivated to develop fluid mechanical indices between residence time of blood particles in arteries and atherosclerosis. In rigid models of stenosed arteries with 75% area reduction, trajectories of blood particles were numerically computed and used to determine local volumetric residence time (VRT) of platelets. The motion of particles in the model artery was computed by considering viscous drag forces between blood particles and presolved transient flow field from computational fluid dynamics (CFD). Many cardiac cycles were considered in the computation to reflect temporally accumulative characteristics of VRT in the recirculation zones. Our results showed that VRT in the recirculation zone was relatively low in the first cardiac cycle. However it increased in the subsequent cycles as more particles were trapped in the same zone. The results suggested that VRT contour calculated in the present study would be an effective indicator of the presence of atherosclerosis.Copyright