Korean Nationwide Surveillance of Antimicrobial Resistance of Bacteria in 1998

Comparing the Phylogenetic Distribution of Multilocus Sequence Typing, Staphylococcal Protein A, and Staphylococcal Cassette Chromosome Mec Types in Methicillin-Resistant Staphylococcus Aureus (MRSA) in Korea from 1994 to 2020

Staphylococcus aureus (S. aureus) bacteremia is one of the most frequent and severe bacterial infections worldwide. Methicillin-resistant Staphylococcus aureus (MRSA) is a serious human pathogen that can cause a wide variety of infections. Comparative genetic analyses have shown that despite the existence of a vast number of genotypes, genotypes are restricted to certain geographical locations. By comparing multilocus sequence typing (MLST) and SCCmec types from 1994 to 2020, the present study intended to discover which genotype genes were related to MRSA infections. MLST, Staphylococcus aureus protein A (spa), and SCCmec typings were performed to determine their relationship during those years. Results revealed that MRSA isolates in the Republic of Korea were distributed among all major staphylococcal cassette chromosome mec (SCCmec) types. The majority of SCCmec isolates belonged to SCCmec type II and type IV. The majority of MLST had the sequence type (ST) 72, 239, 8, or 188. By contrast, minorities belonged to ST22 (SCCmec IV), ST772 (SCCmec V), and ST672 (SCCmec V) genotypes. The SCCmec type was determined for various types. The spa type was dispersed, seemingly regardless of its multidrug resistance property. The MLST type was found to be similar to the existing typical type. These results showed some correlations between resistance characteristics and types according to the characteristics of the MLST types distributed, compared to previous papers. Reports on genotype distribution of MLST and SCCmec types in MRSA are rare. These results show a clear distribution of MLST and SCCmec types of MRSA from 1994 to 2020 in the Republic of Korea.

Current status of multidrug-resistant bacteria

Background: The dissemination of multidrug-resistant (MDR) pathogen is of major public health concern as it leads to increased mortality rate, length of hospital stays, and medical expenses.Current Concepts: Korean Government enacted an Infectious Disease Control and Prevention Act in 2009, and 6 MDR bacteria including methicillin-resistant Staphylococcus aureus, vancomycin-resistant S. aureus (VRSA), vancomycin-resistant enterococci, multidrug-resistant Pseudomonas aeruginosa, multidrug-resistant Acinetobacter baumannii, and carbapenem-resistant Enterobacterales (CRE) have been legally declared as infectious diseases. According to the amendment of the Infectious Disease Control and Prevention Act in 2020, CRE and VRSA were classified as class 2 infectious diseases, and all cases of CRE and VRSA should be reported to the Korea Disease Control and Prevention Agency (KDCA). Methicillin-resistant S. aureus, vancomycin-resistant enterococci, multidrug-resistant P. aeruginosa, and multidrug-resistant A. baumannii were classified as class 4 infectious diseases, and cases that occur need to be monitored at KDCA-designated sentinel hospitals to prevent further dissemination.Discussion and Conclusion: In this review, the current antimicrobial resistance status of six types of MDR bacteria, legally declared as infectious diseases, was investigated.. The Korean government is operating national antimicrobial resistance surveillance systems such as the Korean Antimicrobial Resistance Monitoring System and Korean Global Antimicrobial Surveillance System, as a foundation for preventing the spread of antimicrobial resistance. Certain steps need to be taken, such as establishing a surveillance system for antimicrobial usages, strengthening antimicrobial stewardship and infection control systems, and developing new antimicrobials in order for us to achieve the national goal.

Impact of COVID-19 on Antimicrobial Consumption and Spread of Multidrug-Resistance in Bacterial Infections

The spread of COVID-19 pandemic may have affected antibiotic consumption patterns and the prevalence of colonized or infected by multidrug-resistant (MDR) bacteria. We investigated the differences in the consumption of antibiotics easily prone to resistance and the prevalence of MDR bacteria during the COVID-19 pandemic (March 2020 to September 2021) compared to in the pre-pandemic period (March 2018 to September 2019). Data on usage of antibiotics and infections caused by methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Acinetobacter baumannii (CRAB), and carbapenem-resistant Pseudomonas aeruginosa (CRPA) were obtained from hospitalized patients in four university hospitals. The consumption of penicillin with β-lactamase inhibitors (3.4% in ward, 5.8% in intensive care unit (ICU)), and carbapenems (25.9% in ward, 12.1% in ICU) increased during the pandemic period. The prevalence of MRSA (4.7%), VRE (49.0%), CRE (22.4%), and CRPA (20.1%) isolated in clinical samples from the ward and VRE (26.7%) and CRE (36.4%) isolated in clinical samples from the ICU were significantly increased, respectively. Meanwhile, only the prevalence of CRE (38.7%) isolated in surveillance samples from the ward increased. The COVID-19 pandemic is associated with increased consumption of antibiotics and has influenced the prevalence of infections caused by MDR isolates.

New epidemiology of Staphylococcus aureus infection in Asia

Not only is Asia the most populous region in the world, but inappropriate therapy, including self-medication with over-the-counter antimicrobial agents, is a common response to infectious diseases. The high antibiotic selective pressure among the overcrowded inhabitants creates an environment that is suitable for the rapid development and efficient spread of numerous multidrug-resistant pathogens. Indeed, Asia is among the regions with the highest prevalence rates of healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) and community-associated methicillin-resistant S. aureus (CA-MRSA) in the world. Most hospitals in Asia are endemic for multidrug-resistant methicillin-resistant S. aureus (MRSA), with an estimated proportion from 28% (in Hong Kong and Indonesia) to >70% (in Korea) among all clinical S. aureus isolates in the early 2010s. Isolates with reduced susceptibility or a high level of resistance to glycopeptides have also been increasingly identified in the past few years. In contrast, the proportion of MRSA among community-associated S. aureus infections in Asian countries varies markedly, from <5% to >35%. Two pandemic HA-MRSA clones, namely multilocus sequence type (ST) 239 and ST5, are disseminated internationally in Asia, whereas the molecular epidemiology of CA-MRSA in Asia is characterized by clonal heterogeneity, similar to that in Europe. In this review, the epidemiology of S. aureus in both healthcare facilities and communities in Asia is addressed, with an emphasis on the prevalence, clonal structure and antibiotic resistant profiles of the MRSA strains. The novel MRSA strains from livestock animals have been considered to constitute a public health threat in western countries. The emerging livestock-associated MRSA strains in Asia are also included in this review.

Vancomycin intermediate-resistant Staphylococcus aureus (VISA) isolated from a patient who never received vancomycin treatment

BACKGROUND

With the abuse of antibiotics, the methicillin-resistant Staphylococcus aureus (MRSA) strain became prevalent. Furthermore, Staphylococcus aureus with a character of vancomycin intermediate-resistance (VISA) has been found globally since the first report in Japan. The main objectives of this study were to report a case of VISA isolated from a Chinese patient who had never undergone Vancomycin treatment, and to determine its molecular character.

METHODS

A total of 9 strains were recovered from a patient during the therapeutic process. Antimicrobial susceptibility testing was performed to determine their antibiotic susceptibility patterns. To detect the VISA strain's molecular epidemiological features, growth and morphological characters, we used multilocus sequence typing, autolysis assay and transmission electric microscope tests. Pulsed-field gel electrophoresis (PFGE) was performed to characterize the heterogeneities of all isolates.

RESULTS

One isolate was found to exhibit vancomycin intermediated-resistant with MIC of 8 μg/ml. It was ST239-T030-agr-1, had thickened cell wall, and displayed a slower growth rate and reduced susceptibility to Triton X-100-induced autolysis than other strains. All 9 strains exhibited the same PFGE pattern.

CONCLUSION

This is the first report of VISA found in central China from a patient who had never received vancomycin treatment.

Management of healthcare-associated methicillin-resistantStaphylococcus aureus

Healthcare-associated methicillin-resistant Staphylococcus aureus is a major cause of nosocomial infections worldwide, with significant attributable morbidity and mortality in addition to pronounced healthcare costs. Treatment results with vancomycin--the current recommended antibiotic for serious methicillin-resistant S. aureus infections--have not been impressive. The recent availability of effective antimicrobial agents other than glycopeptides, such as linezolid and daptomycin, as well as the anticipated approval of newer agents with diverse mechanisms of action, has somewhat ameliorated the threat posed by this organism. However, these drugs are expensive, and there is still no overall satisfactory strategy for reducing the incidence of healthcare-associated methicillin-resistant S. aureus in endemic regions. Although early results with the Society for Healthcare Epidemiology of America guidelines give cause for cautious optimism, long-term experience is lacking, and it is likely that these guidelines will have to be adapted according to local conditions and resources before implementation. Trends to keep in mind when considering the problem of healthcare-associated methicillin-resistant S. aureus include the advent of community-associated methicillin-resistant S. aureus, and the propensity of S. aureus to evolve and acquire resistance determinants over time. This was last vividly demonstrated by the handful of vancomycin-resistant S. aureus isolated recently, which had acquired the vancomycin resistance gene from vancomycin-resistant enterococci.

Mutations in thegyrAandparCGenes in Ciprofloxacin-Resistant Clinical Isolates ofAcinetobacter baumanniiin Korea

Mutation with Ser-83-->Leu in gyrA gene was associated with the principal mutation for ciprofloxacin resistance in clinical isolates of Acinetobacter baumannii. Double mutation, Ser-83-->Leu in gyrA gene and Ser-80-->Leu in parC gene, was the most frequently detected among ciprofloxacin-resistant isolates. A novel mutation with Ser-80-->Trp in parC gene, in addition to mutation in gyrA gene, was associated with a high-level ciprofloxacin resistance. These results suggested that the presence of an additional mutation in the parC gene contributed to a higher-level of ciprofloxacin resistance than a single mutation in the gyrA gene (geometric mean MICs of ciprofloxacin, 44.1 versus 16 microg/ml, P < 0.05).

Alterations of gyrA, gyrB, and parC and Activity of Efflux Pump in Fluoroquinolone-resistant Acinetobacter baumannii

Objectives

This study investigated the fluoroquinolone-resistant mechanism of 56 clinical cases of A baumannii infection from 23 non-tertiary hospitals, collected between 2004 and 2006.

Methods

Susceptibility testing was performed by broth microdilution and Epsilometer test. Analyses of quinolone resistance-determining region (QRDR) were done by sequencing. The activity of the efflux pump was measured using inhibitors.

Results

The sequences from selected 56 isolates were divided into seven groups (I-VII) on the basis of mutations in gyrA (S83L), parC (S80L, S80W and S84K) and gyrB (containing the novel mutations E679D, D644Y and A677V). The 27 isolates with triple mutations in gyrA, gyrB and parC (groups IV-VII) showed higher levels of resistance to ciprofloxacin (minimal inhibitory concentration [MIC] of 16-256 μg/mL) than the 26 isolates with double mutations in gyrA and parC (groups II and III, MIC of 8-64 μ g/mL; p < 0.05). Alterations in the efflux pump were observed in four isolates with the parC S80L mutation (group II) or E84K mutation (group VII), but no effect was observed in an isolate with the parC S80 W mutation (group III).

Conclusion

These results suggest that triple mutations in clinical isolates of A baumannii contribute to the development of high levels of resistance to fluoroquinolones and that mutations in parC S80L or E84K (groups II and VII) may contribute to alterations in efflux pump activity in A baumannii.

Trend of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia in an institution with a high rate of MRSA after the reinforcement of antibiotic stewardship and hand hygiene

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) infections are a concern across the worldwide.

METHODS

Antibiotic stewardship and hand hygiene programs were reinforced in a 2,000-bed tertiary hospital in South Korea where the methicillin resistance rate of Staphylococcus aureus is about 65%. The computerized prescription restriction was implemented in August 2008. "Hand hygiene program," consistent with World Health Organization guideline, was reinforced in December 2008. We assessed the effect of the infection control programs on the incidence of MRSA bloodstream infection (BSI) from January 2006 through November 2011.

RESULTS

Incidence of MRSA BSI was reduced from 0.171 per 1,000 patient-days in 2009 to 0.116 per 1,000 patient-days in 2011 (P = .009). Monthly mean antibiotic consumption decreased from 690.54 ± 28.33 defined daily dose per 1,000 patients-days in 2008 to 652.47 ± 20.77 (P = .015) in 2011. The rates of performance in hand hygiene increased from 43% in 2008 to 83% in 2011 (P = .043).

CONCLUSION

Although we did not implement all components of "MRSA bundle," efforts to reinforce antibiotic stewardship and hand hygiene program for 3 years had beneficial effects on the decrease in MRSA BSI in this institute with high rate of MRSA.

Sccmec type II gene is common among clinical isolates of methicillin-resistant Staphylococcus aureus in Jakarta, Indonesia

Background

Community Acquired Methicillin Resistant Staphylococcus aureus (CA-MRSA) is a strain of MRSA that can cause infections in patients in the community, in which these patients had no previous risk factors for MRSA infection and the patient received 72 hours prior to infection when admitted to hospital. This study aims to determine and compare the characteristics of epidemiological, clinical, and molecular biology of CA-MRSA with HA-MRSA.

Methods

A total of 11 clinical strains of Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-sensitive Stapylococcus aureus (MSSA) were collected from 2 hospitals in Jakarta, Indonesia in 2012. SCCmec typing was performed by multiplex polymerase chain reaction (PCR) and the presence of six genes (vraR, vraG, vraA, vraF,fruA, and fruB) associated with vancomycin resistance was examined by simple PCR analysis.

Results

We found three strains of community-acquired MRSA with SCCmec type II and one strain of hospital-acquired MRSA with SCCmec type IV. The other seven strains did not contain mecA genes and SCCmec. Plasmid pUB110 was found in one strain of community-acquired MRSA and two strains of hospital-acquired MRSA. vraA genes were present in 9 of the 11 strains, vraF in 4, vraG in 5, and vraR in 4. Note worthily, three quarters of strains without pUB110 contained vraR and vraF, and 70% contained vraA, whereas 60% of strains with pUB110 contained vraG.

Conclusion

Based on these results, we should be concerned about the possibility of transition from MRSA strains sensitive to vancomycin in VISA strains of MRSA strains obtained in clinical trials. But first we need to look the existence of natural VISA or hVISA among these MRSA strains.

Early use of imipenem/cilastatin and vancomycin followed by de-escalation versus conventional antimicrobials without de-escalation for patients with hospital-acquired pneumonia in a medical ICU: a randomized clinical trial

Introduction

Although early use of broad-spectrum antimicrobials in critically ill patients may increase antimicrobial adequacy, uncontrolled use of these agents may select for more-resistant organisms. This study investigated the effects of early use of broad-spectrum antimicrobials in critically ill patients with hospital-acquired pneumonia.

Methods

We compared the early use of broad-spectrum antimicrobials plus subsequent de-escalation (DE) with conventional antimicrobial treatment (non-de-escalation, NDE) in critically ill patients with hospital-acquired pneumonia (HAP). This open-label, randomized clinical trial was performed in patients in a tertiary-care center medical intensive care unit (MICU) in Korea. Patients (n = 54) randomized to the DE group received initial imipenem/cilastatin plus vancomycin with subsequent de-escalation according to culture results, whereas patients randomized to the NDE group (n = 55) received noncarbapenem, nonvancomycin empiric antimicrobials.

Results

Between November 2004 and October 2006, 109 MICU patients with HAP were enrolled. Initial antimicrobial adequacy was significantly higher in the DE than in the NDE group for Gram-positive organisms (100% versus 14.3%; P < 0.001), but not for Gram-negative organisms (64.3% versus 85.7%; P = 0.190). Mean intensive care unit (ICU) stay, and 14-day, 28-day, and overall mortality rates did not differ in the two groups. Among culture-positive patients, mortality from methicillin-resistant Staphylococcus aureus (MRSA) pneumonia was higher in the DE group, even after early administration of vancomycin. Multidrug-resistant organisms, especially MRSA, were more likely to emerge in the DE group (adjusted hazard ratio for emergence of MRSA, 3.84; 95% confidence interval, 1.06 to 13.91).

Conclusions

The therapeutic advantage of early administration of broad-spectrum antimicrobials, especially with vancomycin, was not evident in this study.

Expression of Sme efflux pumps and multilocus sequence typing in clinical isolates of Stenotrophomonas maltophilia

BACKGROUND

Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen, which causes infections that are often difficult to manage because of the inherent resistance of the pathogen to a variety of antimicrobial agents. In this study, we analyzed the expressions of smeABC and smeDEF and their correlation with antimicrobial susceptibility. We also evaluated the genetic relatedness and epidemiological links among 33 isolates of S. maltophilia.

METHODS

In total, 33 S. maltophilia strains were isolated from patients in a tertiary hospital in Daejeon. Minimum inhibitory concentrations (MICs) of 11 antimicrobial agents were determined by using agar dilution method and E-test (BioMérieux, France). Real-time PCR analysis was performed to evaluate the expression of the Sme efflux systems in the S. maltophilia isolates. Additionally, an epidemiological investigation was performed using multilocus sequence typing (MLST) assays.

RESULTS

The findings of susceptibility testing showed that the majority of the S. maltophilia isolates were resistant to β-lactams and aminoglycosides. Twenty-one clinical isolates overexpressed smeABC and showed high resistance to ciprofloxacin. Moreover, a high degree of genetic diversity was observed among the S. maltophilia isolates; 3 sequence types (STs) and 23 allelic profiles were observed.

CONCLUSIONS

The smeABC efflux pump was associated with multidrug resistance in clinical isolates of S. maltophilia. In particular, smeABC efflux pumps appear to perform an important role in ciprofloxacin resistance of S. maltophilia. The MLST scheme for S. maltophilia represents a discriminatory typing method with stable markers and is appropriate for studying population structures.

Spread of methicillin-resistant Staphylococcus aureus between the community and the hospitals in Asian countries: an ANSORP study

OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) is highly prevalent in hospitals in many Asian countries. Recent emergence of community-associated (CA) MRSA worldwide has added another serious concern to the epidemiology of S. aureus infections. To understand the changing epidemiology of S. aureus infections in Asian countries, we performed a prospective, multinational surveillance study with molecular typing analysis.

METHODS

We evaluated the prevalence of methicillin resistance in S. aureus isolates in CA and healthcare-associated (HA) infections, and performed molecular characterization and antimicrobial susceptibility tests of MRSA isolates.

RESULTS

MRSA accounted for 25.5% of CA S. aureus infections and 67.4% of HA infections. Predominant clones of CA-MRSA isolates were ST59-MRSA-SCCmec type IV-spa type t437, ST30-MRSA-SCCmec type IV-spa type t019 and ST72-MRSA-SCCmec type IV-spa type t324. Previously established nosocomial MRSA strains including sequence type (ST) 239 and ST5 clones were found among CA-MRSA isolates from patients without any risk factors for HA-MRSA infection. CA-MRSA clones such as ST59, ST30 and ST72 were also isolated from patients with HA infections.

CONCLUSIONS

Our findings confirmed that MRSA infections in the community have been increasing in Asian countries. Data also suggest that various MRSA clones have spread between the community and hospitals as well as between countries.

Comparison of antibiogram, staphylococcal enterotoxin productivity, and coagulase genotypes among Staphylococcus aureus isolated from animal and vegetable sources in Korea

Staphylococcal food poisoning is caused by enterotoxin-producing Staphylococcus aureus. We investigated the prevalence of such organisms in samples of bovine mastitic milk (n = 714), raw meat (n = 139), and vegetables (n = 616). We determined the degrees of relatedness of isolates as indicated by antibiogram, staphylococcal enterotoxin (SE) productivity, and coagulase gene restriction fragment length polymorphism analysis. We examined 297 S. aureus isolates and found SE production in 57 (31.8%), 4 (7.8%), and 49 (73.1%) isolates from raw milk, raw meat, and vegetables, respectively. A high proportion of the isolates obtained from milk produced more than two types of toxins (mainly SEA, SEB, and/or SEC), whereas isolates from raw meat and vegetables primarily produced SEA alone. Most isolates were sensitive to cephalothin (97.6%), gentamicin (80.8%), erythromycin (79.5%), and tetracycline (72.7%), but were resistant to penicillin (90.2%) and ampicillin (88.9%). The proportion of antibiotic-resistant isolates differed according the source of the bacteria; the milk and vegetable isolates were more resistant to penicillin and ampicillin than were the meat isolates (P < 0.05), whereas tetracycline resistance was limited to the milk and vegetables isolates. The coagulase genotypes (I to XII) varied with the source of the organism, and only a few genotypes prevailed in each source: II (42.4%) and IV (24%) types in isolates from milk, IX (35.3%) and XI (45%) from raw meat, and III (40.3%) and XII (32.8%) from vegetables. These findings suggest that remarkable differences exist in antibiogram, SE productivity, and coagulase genotypes, resulting in limited clonal transmission of S. aureus into various food sources. As enterotoxin production only occurs when S. aureus grows to high numbers, staphylococcal food poisoning can be prevented by proper refrigeration.

In vitro activities of CG400549, a novel FabI inhibitor, against recently isolated clinical staphylococcal strains in Korea

The in vitro activities of CG400549, a novel FabI inhibitor, were compared to those of linezolid and commonly used antimicrobials against recent bacterial isolates. CG400549 had an MIC(90) of 0.5 microg/ml for Staphylococcus aureus strains and was more potent than either linezolid or vancomycin.

Clinical outcomes in methicillin-resistant Staphylococcus aureus-colonized neonates in the neonatal intensive care unit

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) colonization can persist for prolonged periods, and patient-related factors are associated with persistent carriage in adults. However, such knowledge is lacking among neonates.

OBJECTIVES

To better understand the outcome of MRSA-colonized neonates in the neonatal intensive care unit (NICU), we prospectively followed all colonized neonates until decolonization over 39 months and determined the incidence, duration of colonization, clinical outcomes and risk factors associated with prolonged carriage of MRSA.

METHODS

Nasal and inguinal cultures were obtained from all newly admitted neonates following an outbreak of MRSA. Weekly and 1-2 monthly cultures were obtained from all hospitalized and discharged neonates colonized with MRSA, respectively, until 2 consecutive cultures were negative.

RESULTS

152 of 1,456 (10.4%) neonates became colonized. The mean time to acquire MRSA colonization was 17.1 +/- 40.7 (range 1-471) days. The median time to decolonization was 36 days. About 20% of decolonized patients had been colonized for a prolonged period of >or=160 days. 47.5% of colonized patients were sent home colonized, and none with prolonged carriage developed MRSA-related infections in the following 6 months in contrast to 6 infants (3.9%) who developed MRSA sepsis during hospitalization. The only risk factor associated with prolonged carriage was the concurrent colonization of both the inguinal and nasal areas on admission.

CONCLUSION

Nearly all neonates with acquired colonization became decolonized either prior to or after discharge from NICU. A significant percentage failed to decolonize prior to hospital discharge, but almost all decolonized by 30 months in the community without evidence of systemic or local infections.

Community-associated Methicillin-resistant Staphylococcus aureus: Overview and Local Situation

Introduction: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged worldwide. In contrast to healthcare-associated MRSA (HA-MRSA), CA-MRSA isolates are usually susceptible to multiple non-beta-lactam antibiotics and cause a distinct spectrum of infections in epidemiologically disparate populations – in particular, cutaneous abscesses, necrotising fasciitis and necrotising pneumonia. They arise from a broader genetic background, and possess differing virulence genes. We aim to describe the distribution of different molecular subtypes of CA-MRSA among various regions and discuss briefly the implications of CA-MRSA from a local perspective. Methods: Literature review of articles on CA-MRSA, focusing mainly on reports where the genetic background of isolates had been analysed using multi-locus sequence typing (MLST). Singapore data were obtained from the local CA-MRSA database. Results: MLST analysis demonstrated the presence of epidemic subtypes of CA-MRSA within most geographic areas. In parts of the United States, community MRSA infections currently exceed those caused by their methicillin-susceptible counterparts. In Singapore, CA-MRSA infections are increasing, predominantly as a result of the spread of ST30 clones. Conclusion: Available evidence suggests that the emergence of MRSA from the community is not going to be a transient phenomenon. Local guidelines for dealing with this phenomenon at both therapeutic and preventive levels are needed prior to the potential development of a situation mirroring that of meso-endemic HA-MRSA in local hospitals or CA-MRSA epidemics in parts of USA. Key words: Bacterial typing, Epidemic, Epidemiology, Infection control

In vitro activities of DA-7867, a novel oxazolidinone, against recent clinical isolates of aerobic and anaerobic bacteria

In vitro activities of DA-7867, a novel oxazolidinone, were compared to those of linezolid and commonly used antimicrobials. DA-7867 had the lowest MIC for 90% of the aerobic gram-positive bacterial strains tested, </=0.25 micro g/ml, and it was more potent than linezolid.

Nationwide surveillance for Staphylococcus aureus with reduced susceptibility to vancomycin in Korea

Methicillin-resistant Staphylococcus aureus (MRSA) accounts for more than 70% of S. aureus isolates from tertiary hospitals in Korea. Clinical isolates of S. aureus were collected from eight provincial, university-affiliated hospitals during the period from June 1999 to January 2001 for nationwide surveillance. All isolates were screened for reduced susceptibility to vancomycin by using brain heart infusion agar containing 4 micro g of vancomycin per milliliter. Population analysis and the determination of the MIC of vancomycin were done for the isolates which grew on the screening agar plates. Of 682 total isolates, MRSA accounted for 64% (439 of 682). Of 27 (4%) isolates that grew on the screening agar plates, none showed the heteroresistance phenotype. No strains with reduced susceptibility to vancomycin were identified.

Evaluation of efficiency of screening extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in hospitals where the bacteria are increasingly prevalent

The disk screening methods for extended-spectrum beta-lactamase-producing strains were evaluated. The confirmatory work is reduced significantly in settings such as those in this study, by changing the cefpodoxime breakpoint to < or =20 mm and by not testing cefoxitin-resistant isolates. Cefotaxime and ceftazidime disk screening is reliable, and the laboratory-prepared cefotaxime- and ceftazidime-clavulanic acid disks are stable at -20 degrees C for 12 weeks.

Present situation of antimicrobial resistance in Korea

Resistance of bacteria to antimicrobial agents is a worldwide concern. In Korea, resistant bacteria are more prevalent than in other industrialized countries. Methicillin-resistant Staphylococcus aureus, erythromycin-resistant Streptococcus pyogenes, penicillin non-susceptible pneumococci, beta-lactamase-producing gonococci, extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae, class C beta-lactamase-producing E. coli, fluoroquinolone-resistant E. coli, and aminoglycoside-resistant Acinetobacter baumannii and Pseudomonas aeruginosa are examples of resistant bacteria prevalent in Korea, and their presence suggests a high level of antimicrobial selective pressure and the nosocomial spread of resistant bacteria. Recently observed rapid increases in the incidence of vancomycin-resistant Enterococcus faecium and carbapenem-resistant P. aeruginosa present new threats in Korea.