High prevalence of ceftazidime-resistant Klebsiella pneumoniae and increase of imipenem-resistant Pseudomonas aeruginosa and Acinetobacter spp. in Korea: a KONSAR program in 2004

Analysis of Clinical Factors Associated with Medical Burden and Functional Status in Pyogenic Spine Infection

Background and purpose: Pyogenic spinal infection (PSI) has recently been on the rise due to aging and increasing degenerative spinal disease related procedures. PSI requires long-term antibiotic treatment and is followed by sustained functional disability even after successful treatment. This study aimed to analyze the clinical factors associated with medical burden and functional status of PSI. Methods: This retrospective study involved patients with non-postoperative PSI of thoraco-lumbo-sacral area in a single tertiary hospital. The length/cost of hospitalization with an antibiotic therapy and severity of back pain using the short form 36 (SF-36) were defined as the medical burden and functional status, respectively. We analyzed the clinical factors associated with medical burden and functional status. Results: We enrolled 142 patients (91 males and 51 females). The length and cost of hospitalization were 55.56 ± 27.09 (7–172) days and $14,070.17 ± 9289.39 (1611.87–48,722.35), respectively. A recurrence rate of 7.7% (11/142) and significant improvement of SF-36 at six months after completion of antibiotic treatment were noted (p < 0.05). Procedure-related (OR 2.702), C-reactive protein (CRP; OR 1.062), bacteremia (OR 4.966), additional surgical treatment (OR 6.524), recurrence (OR 12.453), and paraspinal abscess (OR 5.965) for above-average length of hospitalization were observed; female (OR 4.438), CRP (OR 1.071), bacteremia (OR 4.647), additional surgical treatment (OR 6.737), recurrence (OR 22.543), and extent of lesion (OR 1.431) for above-average cost of hospitalization; leg weakness (OR 15.966), white blood cell (WBC; OR 1.116), Charlson’s comorbidity index (CCI, OR 1.485), and identification of causative bacteria (OR 2.913) for below-average initial SF-36 were observed; leg weakness (OR 7.975) and WBC (OR 1.094) for below-average 6-month SF-36 were the statistically significant clinical factors in the multivariable logistic regression analysis (p < 0.05). Conclusion: Recurrence and leg weakness were identified as the most important clinical factors for medical burden and functional status in PSI, respectively. We think that it is necessary to actively suppress recurrence and manage neurological deficits for decreasing medical burden and achieving favorable functional outcome in the treatment of PSI.

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.

A hospital based surveillance of metallo-beta-lactamase producing gram negative bacteria in Nepal by imipenem-EDTA disk method

BACKGROUND

A rising threat of the rapid spread of acquired metallo-beta-lactamases (MBLs) among major Gram-negative pathogens is a matter of public health concern worldwide. Hence, for a low income nation like Nepal, surveillance data on MBL producing clinical isolates via a cost effective technique is necessary to prevent their dissemination as well as formulation and regulation of antimicrobial stewardship policy.

METHODS

The prospective study was conducted at Nepal Medical College, Kathmandu from May to October, 2014 to assess the prevalence of MBL production among ceftazidime-resistant Gram-negative rods (GNRs) isolates. The samples were processed according to standard microbiological procedure following the Manual of clinical Microbiology. Isolated GNRs were subjected to susceptibility testing against the selected panel of antibiotics by Kirby- Bauer disc diffusion method and interpretation made in conformity with the Clinical and Laboratory Standards Institute (CLSI) guidelines. Ceftazidime-resistant isolates were subjected to the detection of MBL production by imipenem-EDTA combined disc (CD) method.

RESULTS

Among the Gram-negative isolates, 5.80% (21/362) were found to be MBL positive with Acinetobacter spp. showing the highest prevalence i.e. 85.71% (18/21), followed by P. aeruginosa i.e. 14.29% (3/21). None of the other cefazidime resistant gram negative bacteria tested were found to be positive for MBL production with all the positive isolates determined to be Multidrug resistant (MDR) strains.

CONCLUSION

This study demonstrated a higher rate of resistance among P. aeruginosa and Acinetobacter spp. to a wide variety of antibiotic categories with an additional burden of MBL production within them, warranting a need for strict surveillance and rapid detection of MBL production among the GNRs.

Trimethoprim/sulfamethoxazole for Acinetobacter spp.: A review of current microbiological and clinical evidence

Clinicians nowadays are confronted with an epidemic of multidrug-resistant (MDR) Acinetobacter infections and are forced to consider every treatment alternative, including older antibiotic agents, not conventionally used. This review aimed to evaluate the published evidence on the antimicrobial activity and clinical effectiveness of trimethoprim/sulfamethoxazole (TMP-SMX) against Acinetobacter spp. Selected in vitro studies included antimicrobial surveillance reports, microbiological studies regarding the activity of TMP-SMX against MDR Acinetobacter isolates, and clinical studies published after the year 2000. Non-susceptibility rates for Acinetobacter spp. in surveillance studies ranged from 4% to 98.2%; in 23 of 28 studies, non-susceptibility to TMP-SMX was >50% and in a subset of 15 studies non-susceptibility was >70%. In studies regarding MDR Acinetobacter spp., non-susceptibility rates ranged from 5.9% to 100%; however, 19 of 21 studies reported >70% non-susceptibility. Extensively drug-resistant Acinetobacter baumannii complex had total (100%) resistance in five of six studies. Carbapenem-resistant Acinetobacter spp. had non-susceptibility rates to TMP-SMX of >80% in 22 of 26 studies. One study on polymyxin-resistant A. baumannii showed a susceptibility rate of 54.2% (13/24). Only seven case reports evaluated TMP-SMX for Acinetobacter spp. infections, mainly in combination with other agents; all cases were deemed therapeutic successes. Although TMP-SMX is not usually active against Acinetobacter spp., it might be considered in cases where there are no other options.

Epidemiology of carbapenem resistant Enterobacteriaceae (CRE) during 2000-2012 in Asia

BACKGROUND

Over the past decade, the worldwide emergence of carbapenem resistance in Enterobacteriaceae has become a severe public health issue. This meta-analysis aims to describe the epidemiology of carbapenem resistant Enterobacteriaceae (CRE) during the years of 2000-2012 in Asian area.

METHODS

PubMed and Embase databases were searched to identify the qualified papers. Random or fixed-effect model was used to deal with the data.

RESULTS

Over all the 49 Asian countries (or regions), only 37.5% [19] of them contributed epidemiology data of CRE, and the rest ones provided either only case reports or no information at all. In Asia, the prevalence of CRE was still low during the study period with average resistance rates of 0.6% (95% CI, 0.6-0.8%, imipenem) and 0.9% (95% CI, 0.7-1.2%, meropenem). Resistance rates to imipenem and meropenem in Enterobacteriaceae exhibited stably escalating trend. Similar trend can also be observed among each Enterobacteriaceae genus, such as E. coli, Klebsiella spp. and Enterobacer spp. Klebsiella spp. accounted for the largest proportion among the isolates resistant to imipenem, and then followed by E. coli and Serratia. The rank order of resistance rates to imipenem among Enterobacteriaceae genus during the period of 2000-2012 was as follows: Serratia spp. (1.8%) > Proteus spp. (1.6%) > Klebsiella spp. (0.8%) = Citrobacter spp. (0.8%) > Enterobacer spp. (0.7%) > E. coli (0.2%).

CONCLUSIONS

Given the fact that the prevalence of CRE was increasing during the past decade, it is urgent for us to establish regional surveillance worldwide, carry out more effective antibiotic stewardship and infection control measures to prevent further spread of carbapenem resistance in Enterobacteriaceae.

Penicillin-Resistant trend of Streptococcus pneumoniae in Asia: A systematic review

The high prevalence of resistance to penicillin by Streptococcus pneumoniaeis considered as a great concern, particularly in Asian countries. The aim of this study was to investigate the changing trend of penicillin-resistant S. pneumoniae (PRSP) in Asia over a 20 years period. A review of the literature was conducted using the PubMed database, Google Scholar, Scopus, two Persian scientific search engines "Scientific Information Database" (www.sid.ir), and "Mag Iran" (www.magiran.com) through 1993 to 2013. Our study provides a unique chance to investigate the changing trend in PSSP in Asia over a 20 years period. Susceptibility rates among different centers in each country varied widely. In Malaysia, the PSSP rate decreased from 97.2% in 1995-1996 to 69% in 2000. In Singapore, PSSP levels decreased from 72.6% in 1997 to 30.5% in 2007-2008. In Iran, PSSP ranged from 0% to 100%. In Taiwan, the rate of PSSP was 60.3% in 1995 and <50% in other years. In Lebanon, the rate of PSSP was less than 50% (ranging from 30.1% to 50%) in all published data. In Hong Kong, the level of penicillin susceptibility decreased from 71.1% during 1993-1995 to less 42% in 2007. Continuous surveillance of resistance data from clinical isolates as well as implementation of strict infection control policies is recommended. More studies are needed for better evaluation PSSP rate in some Asian countries such as Vietnam, Singapore, Philippines, Pakistan, Nepal, Kuwait, Korea and Indonesia.

High burden of antimicrobial drug resistance in Asia

The rapid development of antimicrobial resistance among micro-organisms is a serious public health concern. Moreover, the dissemination of antibiotic-resistant bacteria makes this issue a global problem, and Asia is no exception. For example, since New Delhi metallo-β-lactamase (NDM)-producing Enterobacteriaceae were identified in India, further spread of NDM has become a worldwide threat. However, the epidemiology of antibiotic-resistant bacteria in Asia may be different to other regions, and clinical condition may be worse than in western countries. Antibiotic-resistant bacteria, including community-acquired and hospital-acquired meticillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate S. aureus (VISA), vancomycin-resistant enterococci, macrolide- and penicillin-resistant Streptococcus pneumoniae, extend-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae, carbapenem-resistant Enterobacteriaceae, and multidrug-resistant Pseudomonas aeruginosa and Acinetobacter spp., are becoming prevalent in many countries in Asia. Moreover, the prevalence of each antibiotic-resistant bacterium in each country is not identical. This review provides useful information regarding the critical condition of antibiotic resistance in Asia and emphasises the importance of continuous surveillance of resistance data.

A 2011-2012 survey of doctors' perceptions of korean guidelines and empirical treatment of community-acquired pneumonia

Background

The causative pathogens of and prevalence of antibiotic resistance in community-acquired pneumonia (CAP) varies across countries. We evaluated the patterns of antibiotic prescriptions for adult CAP patients, and physician satisfaction with the form and content of the 2009 Korean CAP treatment guidelines.

Materials and Methods

We designed an online survey for clinical physicians who treat CAP (infectious disease specialists, pulmonologists, and other physicians). We e-mailed the online survey to physicians and gathered results from December 2011 to January 2012, and then analyzed their responses.

Results

A total of 157 physicians responded to our survey: 61 (38.9%) infectious disease specialists, 33 (21.0%) pulmonologists, and 63 (40.1%) other physicians. Two-thirds (96/157, 61.2%) had positions in tertiary and secondary hospitals; the others (61, 38.8%) worked in primary clinics (hospitals and private clinics). One hundred and eight (68.8%) were aware of the Korean CAP clinical guidelines; of these, 98 (62.4%) applied the guidelines to their practice. Among physicians using them, 86.7% (85/98) reported the guidelines to be most useful for empirical selection of antibiotics, and 75.2% (118/157) said the guidelines were useful and satisfactory. Sixty-eight (43.3%) respondents indicated that they had not used aminoglycosides as an initial empirical CAP treatment, while 51 (32.5%) had combined aminoglycosides with other antibiotics to treat patients with CAP. Seventy-three (46.5%) physicians often combined macrolides with β-lactam antibiotics for empirical treatment of CAP, and 21 (13.4%) reported using macrolide monotherapy (which is not recommended in the 2009 Korean CAP treatment guidelines) for CAP patients. The most commonly used β-lactams were third-generation cephalosporins (72, 45.9%) and ampicillin/sulbactam or amoxicillin/clavulanate (28, 17.8%).

Conclusions

Some physicians remain unaware of the 2009 Korean treatment guidelines for CAP and do not use them in clinical practice. In addition, aminoglycoside combination therapy is frequently and inappropriately used in practice. In some cases, CAP is treated with macrolide monotherapy. Thus, the Korean CAP clinical guidelines must be more aggressively and continuously publicized.

Characteristics of carbapenem-resistant Acinetobacter spp. other than Acinetobacter baumannii in South Korea

Although many studies have been performed on carbapenem-resistant Acinetobacter baumannii, only a few studies have addressed carbapenem resistance in Acinetobacter spp. other than A. baumannii (non-baumannii Acinetobacter). Amongst 287 Acinetobacter spp. isolates from patients with bacteraemia in a South Korean hospital collected between 2003 and 2010, 160 (55.7%) were non-baumannii Acinetobacter spp. Antimicrobial susceptibility testing was performed and the effect of efflux pump inhibitors was examined. Antimicrobial resistance genes were identified and pulsed-field gel electrophoresis (PFGE) analysis was performed. OprD expression was also evaluated by quantitative real-time polymerase chain reaction (qRT-PCR), and CarO disruption was investigated by PCR. Seventeen non-baumannii Acinetobacter isolates (10.6%) were resistant to imipenem or meropenem, comprising eight Acinetobacter pittii (or Acinetobacter genomospecies 3), four Acinetobacter nosocomialis (or Acinetobacter genomospecies 13TU), two Acinetobacter genomospecies 'close to 13TU', two Acinetobacter bereziniae (or Acinetobacter genomospecies 10) and one Acinetobacter genomospecies 16. bla(IMP-1) genes were detected in seven and two carbapenem-resistant A. pittii and A. bereziniae isolates, respectively. PFGE showed that A. pittii isolates carrying bla(IMP-1) belonged to the same clone. In addition, bla(SIM-1) and bla(PER-1) genes were simultaneously identified in two A. nosocomialis isolates. In four isolates (one each of A. pittii, A. nosocomialis, Acinetobacter genomospecies 'close to 13TU' and Acinetobacter genomospecies 16), efflux pumps were implicated in the increase in carbapenem minimum inhibitory concentrations. No decreased expression of OprD was identified in any carbapenem-resistant non-baumannii Acinetobacter isolates, and disruption of carO was also not detected. Clonal spread of carbapenem-resistant A. pittii carrying bla(IMP-1), which contributes to a high resistance rate in this species, was identified. The bla(IMP-1) and bla(SIM-1) genes were first identified in A. bereziniae and A. nosocomialis, respectively. Since no carbapenem resistance mechanisms could be identified, further efforts to find the resistance mechanism should be made.

Changes in antimicrobial susceptibility and major clones of Acinetobacter calcoaceticus-baumannii complex isolates from a single hospital in Korea over 7 years

Acinetobacter species have emerged as opportunistic nosocomial pathogens in intensive care units. Epidemic spread and outbreaks of multidrug-resistant or carbapenem-resistant Acinetobacter baumannii infections have been described worldwide. Species distribution, antimicrobial resistance and genotypes were investigated for Acinetobacter species isolates collected from a single institution in Korea over 7 years. Two hundred and eighty-seven Acinetobacter species isolates were collected from patients with bloodstream infections in one Korean hospital from 2003 to 2010. Most of them belonged to the Acinetobacter calcoaceticus-baumannii complex (94.4 %). The most frequently isolated species was A. baumannii (44.2 %), followed by Acinetobacter nosocomialis (formerly Acinetobacter genomic species 13TU) (34.1 %). The proportion of A. baumannii increased significantly from 2008 to 2010 (40.4 to 50.0 %). From 2008, imipenem and meropenem resistance rates increased significantly compared with 2003-2007 (12.9 % and 20.5 %, respectively, to 41.4 % and 41.5 %, respectively). An increased carbapenem resistance rate between the two periods was identified more clearly amongst A. baumannii isolates. Polymyxin-resistant A. baumannii isolates emerged in 2008-2010, despite the availability of few isolates. The increase of carbapenem resistance in A. baumannii might be due to the substitution of main clones. Although ST92 and ST69 were the most prevalent clones amongst A. baumannii in 2003-2007 (47.8 % and 15.9 %, respectively), ST75 and ST138 had increased in 2008-2010 (39.7 % and 25.9 %, respectively). Although ST92 showed moderate resistance to carbapenems, most ST75 and ST138 isolates were resistant to carbapenems. All ST75 and ST138 isolates, but only one ST92 isolate, contained the bla(OXA-23-like) gene. Increased carbapenem resistance in Acinetobacter species and A. baumannii isolates might be due to the expansion of specific carbapenem-resistant clones.

Impact of de-escalation therapy on clinical outcomes for intensive care unit-acquired pneumonia

Introduction

De-escalation therapy is a strategy currently used for the management of nosocomial pneumonia. In this study, we evaluated clinical outcomes and risk factors related to de-escalation therapy in patients with intensive care unit (ICU)-acquired pneumonia.

Methods

This was a retrospective observational cohort study of ICU patients who developed pneumonia more than 48 hours after admission to the ICU at Samsung Medical Center from September 2004 to December 2007.

Results

The 137 patients comprised 44 (32.1%) who received de-escalation therapy and 93 in the non-de-escalation group. The de-escalation group showed a lower pneumonia-related mortality rate than the non-de-escalation group by day 14 (2.3% vs. 10.8%, respectively; P = 0.08) and by day 30 (2.3% vs. 14%, respectively; P = 0.03) after the diagnosis of pneumonia. The variables independently associated with ICU-acquired pneumonia-related mortality included the Acute Physiology and Chronic Health Evaluation II (APACHE II) score and the modified Clinical Pulmonary Infection Score (CPIS) after 5 days with pneumonia. The non-de-escalation group had significantly higher APACHE II score and modified CPIS after 5 days with ICU-acquired pneumonia compared to the de-escalation group. Among all patients, 20.4% (28 of 137) had negative cultures for pathogens, and 42.9% (12 of 28) received de-escalation therapy. The latter 12 patients received de-escalation therapy and survived 30 days after the diagnosis of pneumonia.

Conclusions

Patients in the de-escalation group showed a significantly lower mortality rate compared to patients in the non-de-escalation group. De-escalation therapy can be safely provided to patients with ICU-acquired pneumonia if they are clinically stable by day 5, even in those whose respiratory specimen cultures yield no specific pathogens.

Increase of ceftazidime- and fluoroquinolone-resistant Klebsiella pneumoniae and imipenem-resistant Acinetobacter spp. in Korea: analysis of KONSAR study data from 2005 and 2007

PURPOSE

Antimicrobial resistance monitoring could be a useful source of information for treating and controlling nosocomial infections. We analyzed antimicrobial resistance data generated by Korean Hospitals and by a commercial laboratory in 2005 and 2007.

MATERIALS AND METHODS

Susceptibility data for 2005 and 2007 were collected from 37 and 41 hospitals, respectively, and from one commercial laboratory. Intermediate susceptibility was not included in the calculation of resistance rates.

RESULTS

Methicillin-resistant Staphylococcus aureus (MRSA) (64%), third-generation cephalosporin-resistant Klebsiella pneumoniae (29%), fluoroquinolone-resistant Escherichia coli (27%), Pseudomonas aeruginosa (33%), and Acinetobacter spp. (48%), and amikacin-resistant P. aeruginosa (19%) and Acinetobacter spp. (37%) were prevalent in hospitals in 2007. A gradual increase of vancomycin-resistant Enterococcus faecium and imipenem-resistant Acinetobacter spp. was observed. Higher incidences of thirdgeneration cephalosporin-resistant E. coli and K. pneumoniae and imipenemresistant P. aeruginosa were found in the commercial laboratory than in the hospitals.

CONCLUSION

Methicillin-resistant S. aureus, third-generation cephalosporin- resistant K. pneumoniae, and fluoroquinolone-resistant E. coli, P. aeruginosa and Acinetobacter spp. remain prevalent in Korea, while the incidence of vancomycin-resistant E. faecium and imipenem-resistant Acinetobacter spp. has increased gradually. The higher prevalences of third-generation cephalosporinresistant E. coli and K. pneumoniae, and imipenem-resistant P. aeruginosa in the commercial laboratory are a new concern.

Prevalence and diversity of carbapenemases among imipenem-nonsusceptible Acinetobacter isolates in Korea: emergence of a novel OXA-182

Increase in multidrug-resistant Acinetobacter poses a serious problem in Korea. In this study, 190 imipenem (IPM)-nonsusceptible (NS) Acinetobacter isolates from 12 Korean hospitals in 2007 were used to determine species, prevalence, and antimicrobial susceptibility of OXA carbapenemase- and metallo-β-lactamase (MBL)-producing isolates. bla(OXA)-₂₃-like and ISAba1-asssociated bla(OXA)-₅₁-like genes were detected in 80% and 12% of 178 IPM-NS Acinetobacter baumannii isolates, respectively. A novel bla(OXA)-₁₈₂ was detected in 12 IPM-NS A. baumannii isolates. Twelve out of 14 MBL-producing isolates were non-baumanniiAcinetobacter. A. baumannii isolates with OXA carbapenemase were more often resistant to aminoglycosides, ciprofloxacin, and tigecycline than non-baumannii Acinetobacter isolates with MBL. Identical pulsed- field gel electrophoresis patterns were observed in 89% of A. baumannii isolates with bla(OXA)-₂₃-like gene. In conclusion, extremely rapid increase of IPM-NS A. baumannii in previous Korean studies was mainly due to clonal spread of OXA-23-producing A. baumannii isolates. A novel OXA-182 emerged in Korea.

A single clone of Acinetobacter baumannii, ST22, is responsible for high antimicrobial resistance rates of Acinetobacter spp. isolates that cause bacteremia and urinary tract infections in Korea

We investigated the characteristics of a total of 96 Acinetobacter spp. isolates that were shown to cause bacteremia and urinary tract infections (UTIs) from 10 university hospitals located in various regions of Korea from November 2006 to August 2007. The antimicrobial susceptibilities of these isolates were determined using a broth microdilution method, and the species were identified using molecular identification. In addition, we performed multilocus sequence typing for Acinetobacter baumannii subgroup A isolates. A. baumannii subgroup A was the most prevalent in patients with both bacteremia (32 isolates, 53.3%) and UTIs (20 isolates, 55.6%), followed by Acinetobacter genomic species 13TU (15.0% and 27.8% in bacteremia and UTIs, respectively). A. baumannii subgroup B and Acinetobacter junii were found exclusively in isolates causing bacteremia (seven and five isolates, respectively). Among 96 Acinetobacter spp. isolates, 19.8% were resistant to imipenem and 25.0% were resistant to meropenem. Most carbapenem-resistant A. baumannii isolates contained PER or oxacillinase-23-like enzymes (65.2% and 78.3%, respectively). In addition, 13.5% were resistant to polymyxin B and 17.7% were resistant to colistin. A. baumannii subgroup A isolates (52 isolates, 54.2%) showed higher resistance rates to most antimicrobial agents than other species, but not to colistin. Among A. baumannii subgroup A isolates, ST22 was the most prevalent genotype (33 isolates, 63.5%) and showed higher resistance rates to all antimicrobial agents than the other genotypes. In addition, four out of five polymyxin-resistant A. baumannii group A isolates belonged to ST22. Thus, dissemination of the main clone of A. baumannii, ST22, may contribute to the high resistance rates of Acinetobacter isolates to antimicrobials, including carbapenems, in Korea.

Comparative in vitro activities of torezolid (DA-7157) against clinical isolates of aerobic and anaerobic bacteria in South Korea

Resistance of Gram-positive pathogens to first-line antimicrobial agents has been increasing in many parts of the world. We compared the in vitro activities of torezolid with those of other antimicrobial agents, including linezolid, against clinical isolates of major aerobic and anaerobic bacteria. Torezolid had an MIC(90) of ≤0.5 μg/ml for the Gram-positive bacterial isolates tested and was more potent than either linezolid or vancomycin.

Change in antibiotic resistance of Helicobacter pylori strains and the effect of A2143G point mutation of 23S rRNA on the eradication of H. pylori in a single center of Korea

BACKGROUND

The current prevalence of primary antibiotic resistance of H. pylori is not known in Korea. This study was done to evaluate the prevalence of primary antibiotic resistance of H. pylori, and to evaluate the effect of point mutations of 23S rRNA on the rate of eradication of H. pylori.

METHODS

H. pylori were isolated from gastric mucosal biopsy specimens obtained from 222 Koreans. The susceptibilities of the H. pylori isolates to amoxicillin, clarithromycin, metronidazole, tetracycline, ciprofloxacin, and levofloxacin were examined using the agar dilution method. DNA sequencing was carried out to detect H. pylori 23S rRNA mutations.

RESULTS

The resistance to clarithromycin, tetracycline, ciprofloxacin, and levofloxacin increased during the period of 2007 to 2009 compared with 2003 to 2005 (P<0.05). However, amoxicillin and metronidazole resistance slightly decreased. The rates of eradication were 95.5% for the clarithromycin-sensitive strains, which was higher than the 67.9% for the clarithromycin-resistant strains (P=0.001). By contrast, the eradication rate was 100% in patients with amoxicillin-resistant H. pylori. Among 26 clarithromyin-resistant strains, 6 (23%) had A2143G mutations, and all of the cases in which these mutations were present were not eradicated by proton pump inhibitor-based triple therapy (P=0.0004). By contrast, none of the 26 clarithromyin-sensitive strains had A2143G mutations. The T2183C and A2223G mutations were frequently found in the sensitive strains and in the resistant strains.

CONCLUSIONS

Clarithromycin resistance of H. pylori, which determined the efficacy of H. pylori eradication of proton pump inhibitor triple regimen, was found to be increased in a single center study. A2143G was an important 23S rRNA mutation associated with clarithromycin resistance and affected the H. pylori eradication efficacy.

Loss of the 29-kilodalton outer membrane protein in the presence of OXA-51-like enzymes in Acinetobacter baumannii is associated with decreased imipenem susceptibility

Carbapenem resistance in Acinetobacter baumannii is increasing these days. We investigated the roles of outer membrane proteins and efflux pumps in carbapenem resistance of A. baumannii which showed no carbapenemase activity in modified Hodge test. Among 58 carbapenem-resistant isolates collected from the Korea University Medical Center between January 2002 and March 2006, 17 isolates showed negative results in modified Hodge test. In outer membrane protein analysis, loss of the 29-kDa protein band was related with higher imipenem minimum inhibitory concentrations especially in the presence of OXA-51-like enzymes. Efflux pump-mediated carbapenem resistance was found in one out of the 17 isolates (5.9%). All of the 58 carbapenem-resistant strains and 5 of the 10 carbapenem-susceptible strains had OXA-51-like carbapenemase genes, suggesting that OXA-51-like enzymes may be naturally existing in A. baumannii and have very weak carbapenem hydrolyzing activity.

DNA microarray-based identification of bacterial and fungal pathogens in bloodstream infections

The accurate and rapid identification of pathogens in blood is a major challenge in clinical pathogen diagnostics because of the high mortality of sepsis. Here we report the development of DNA microarray for the identification of pathogens causing bloodstream infections. Species-specific and bacteria- and fungi-broad-ranged probes were designed to identify 50 bacteria and 7 fungi. The specificities and sensitivities of the selected probes were successfully validated by applying reference strains. To assess the performance of the DNA microarray in a clinical setting, blind tests were performed using 112 blood culture specimens that showed preliminary presence of pathogenic microorganisms by culture-based method, resulting in the correct identification of pathogens in 104 samples showing the sensitivity of 93%. In addition, closely-related species could be discriminated by the distinct hybridization patterns. This DNA microarray-based pathogen diagnosis takes approximately 10 h starting from a positive blood culture, considerably reducing time required to sufficiently identify pathogens by subsequent agar-culture and biochemical tests which requires altogether at least 1-3 days. Also, the amount of sample required for the identification of pathogens is much less than that required for biochemical assays. Thus, the DNA microarray reported here should be useful for the effective identification of microbial pathogens in blood cultures from septicemic patients.

Two distinct clones of carbapenem-resistant Acinetobacter baumannii isolates from Korean hospitals

We investigated the characteristics of 48 carbapenem-resistant Acinetobacter baumannii isolates collected from 5 tertiary care hospitals in Korea by multilocus sequencing typing, pulsed-field gel electrophoresis, and polymerase chain reaction amplification of the antimicrobial resistance determinants. We identified 2 distinct main clones of carbapenem-resistant A. baumannii isolates, which showed different antimicrobial resistance profiles and are also differentiated by the kinds of oxacillinase (OXA) carbapenemases and Acinetobacter-derived cephalosporinase (ADC) beta-lactamases. One main clone, ST22:A, had 27 carbapenem-resistant isolates (56.3%), showed high polymyxin B and colistin resistances (33.3% and 37.0%, respectively), and contained both bla(OXA-51-like) and bla(OXA-23-like) genes and the bla(ADC-29) or bla(ADC-30) gene. In contrast, the other main clone, ST28:B, included 15 isolates (31.3%), showed complete susceptibilities to polymyxin B and colistin, and contained only the bla(OXA-51-like) gene and bla(ADC-31) or bla(ADC-32) genes. The distribution of these main carbapenem-resistant A. baumannii clones did not relate to locality, indicating that they are widespread in Korean hospitals. In addition, we found new types of PER beta-lactamases, PER-6.

[Microbiological and epidemiological characteristics of vancomycin-dependent enterococci]

BACKGROUND

Vancomycin-dependent enterococci (VDE) are clinically equivalent to vancomycin-resistant enterococci (VRE), but more difficult to detect. This study was purposed to characterize VDE microbiologically and epidemiologically.

METHODS

The patients from whom VDE were detected from April 2007 to March 2008 were investigated. For available isolates, minimal inhibitory concentrations (MICs) of and the levels of dependence on vancomycin and teicoplanin were measured by E test (AB Biodisk, Sweden), and a test for reversion of VDE to non-dependent VRE (NDVRE) and pulsed field gel electrophoresis (PFGE) were performed. Patients' demographic and clinical findings were reviewed via electronic medical records.

RESULTS

VDE were recovered from 6 (2.2%) of 272 patients carrying VRE during this study period. All patients were already colonized or infected by VRE and treated with vancomycin for 13 to 107 days. VDE were isolated from pleural fluid (one), urine (four), and stool (one). All isolates carried vanA with vancomycin MICs of >256 microg/mL, but two of them had intermediate susceptibilities to teicoplanin. Because 4 VDE isolates were reverted to NDVRE with single passage, vancomycin dependence was measurable for only two isolates as equal and above 0.064 and 0.5 microg/mL respectively, and was reverted after 5 and 7 passages, respectively. Six VDE isolates showed no related clones in PFGE analysis, and 3 of 4 available pairs of initial VRE isolates and subsequent VDE isolates were identical clones.

CONCLUSIONS

VDE were not rare and seemed to emerge independently from VRE with a prolonged use of vancomycin. Vancomycin-dependence was reverted within several passages.

Comparison of genotypes and enterotoxin genes between Staphylococcus aureus isolates from blood and nasal colonizers in a Korean hospital

In this study, we investigated the genetic background of 70 Staphylococcus aureus isolates (36 methicillin-resistant S. aureus [MRSA] and 34 methicillin-susceptible S. aureus [MSSA]) obtained from blood at a Korean tertiary-care hospital, using spa typing, multilocus sequence typing, and SCCmec typing. In addition, the prevalence of enterotoxin (sea, seb, sec, sed, see, seg, seh, sei, and sek), tst, and pvl genes among the samples was assessed via polymerase chain reaction, and the results were compared with those of 95 isolates of S. aureus obtained from nasal swabs. All MRSA isolates from blood, except one, belonged to three major clones: sequence type (ST)5-MRSA-II, ST72-MRSA-II (or IVA), and ST239-MRSA-III, among which ST5-MRSA-II was the predominant clone. The prevalence of enterotoxin genes in the S. aureus isolates obtained from blood differed significantly from those from the nasal swabs for the sea, seb, sec, and seh gene. In particular, the seb and sec genes were detected exclusively in the MRSA isolates of ST5 or spa-CC002, thereby suggesting the co-adaptation of virulence genes with the genetic background and their contribution to biological fitness.

Metallo-beta-lactamase-producing Pseudomonas spp. in Korea: high prevalence of isolates with VIM-2 type and emergence of isolates with IMP-1 type

PURPOSE

Two Korean nationwide studies showed that metallo-beta-lactamases (MBLs)-producing-Pseudomonas spp. are not rare. The aim of this study was to assess the trends of MBL-producing isolates among imipenem-resistant isolates of Pseudomonas spp.

MATERIALS AND METHODS

Imipenem-resistant clinical isolates were collected from 23 hospitals and one commercial laboratory participating in the KONSAR program in 2005. Polymerase chain reaction (PCR) was used to detect MBL genes.

RESULTS

Alleles of MBL genes were detected in 10.8% of 415 Pseudomonas aeruginosa and 66.7% of 12 P. putida isolates from 18 of 24 hospitals/laboratory. Among the 14 IMP-1-like and 39 VIM-2-like MBLs, emergence of IMP-6 was detected for the first time.

CONCLUSION

Prevalence of MBL-producing P. aeruginosa has not significantly increased, but IMP-6 emerged in P. aeruginosa.

Antibiotic susceptibility of conjunctival bacterial isolates from refractive surgery patients

PURPOSE

To determine the in vitro antibiotic susceptibility patterns of conjunctival bacterial flora isolated before surgery from patients undergoing refractive surgery.

DESIGN

In vitro laboratory investigation.

PARTICIPANTS

One hundred five eyes from 105 patients scheduled for refractive surgery at Balgensesang Ophthalmology Clinic between September 2005 and January 2006 were studied. Among 105 patients, 71 (67.6%) underwent LASIK using a femtosecond laser, 24 (22.9%) underwent LASIK using an automated microkeratome, 8 (7.6%) underwent LASEK, and 2 (1.9%) patients underwent phakic intraocular lens implantation.

METHODS

Preoperative conjunctival swab samples were inoculated directly in culture media at the bedside before topical anesthetic or antibiotic application. Blood agar, chocolate agar, thioglycolate broth, Sabouraud dextrose agar, and Ogawa media were used for bacterial, fungal, and mycobacterial cultures.

MAIN OUTCOME MEASURES

Minimum inhibitory concentrations (MICs) of ofloxacin (OFX), levofloxacin (LEV), gatifloxacin (GAT), moxifloxacin (MOX), gemifloxacin (GEM), and other commonly used antibiotics were determined using an E test.

RESULTS

From 105 patients, 73 (85%) coagulase-negative staphylococci (CNS), 2 (2.3%) Staphylococcus aureus, 1 (1.2%) Streptococcus pneumoniae, and 5 (4.8%) gram-negative bacilli were isolated. No fungi or mycobacteria were isolated. The MIC that would inhibit the growth of 90% of the tested bacterial isolates (MIC(90)) of OFX, LEV, GAT, MOX, and GEM for methicillin-susceptible CNS (n = 46) were 0.5 microg/ml, 0.19 microg/ml, 0.094 microg/ml, 0.047 microg/ml, and 0.023 microg/ml, respectively. The MIC(90) values for methicillin-resistant CNS (n = 27) were 32 microg/ml, 4 microg/ml, 1 microg/ml, 0.5 microg/ml, and 0.25 microg/ml, respectively (P<0.001).

CONCLUSIONS

The most effective against conjunctival bacteria isolated from refractive surgery patients were GEM, MOX, and GAT; however, resistance to earlier-generation fluoroquinolones (OFX and LEV) is increasing among methicillin-resistant CNS. It may be a therapeutic option to use newer fluoroquinolones in patients undergoing refractive eye surgery to reduce such infections as methicillin-resistant CNS.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Therapeutic challenges in the era of antibiotic resistance

Multidrug microbial resistance poses major challenges to the management of infection, particularly with the paucity of new drugs with activity against these bacteria. Since the turn of this century a few new antibiotics have been licensed, including linezolid, daptomycin and tigecycline. This supplement reports data presented at the 13th International Congress of Infectious Diseases held in Kuala Lumpur in June 2008. Dr R. Isturiz reviews the data on global resistance trends and the potential impact on empirical therapy; Dr J.-H. Song reviews new agents on the antimicrobial horizon; and the final paper in the supplement, by Dr L.R. Peterson, reviews the role of tigecycline in the management of complicated intra-abdominal and skin and soft tissue infections.

Wide dissemination of OXA-type carbapenemases in clinical Acinetobacter spp. isolates from South Korea

Carbapenem-resistant Acinetobacter spp. are being increasingly reported worldwide, including in South Korea, where we examined 144 representative isolates collected in a nationwide hospital survey in 2005. Metallo-beta-lactamases were detected in only 19.4% of isolates, none of which were Acinetobacter baumannii, whereas 74.3% of isolates (mostly A. baumannii) expressed bla(OXA) carbapenemase genes. Among the latter, 47 had bla(OXA-23)-like genes and 56 had upregulated bla(OXA-51)-like variants, including bla(OXA-66), (-83), (-109) and (-115); bla(OXA-115) was a novel variant, detected in two isolates. bla(OXA-72) (bla(OXA-40)-like) was detected in only a single Acinetobacter baylyi isolate, whilst three Acinetobacter calcoaceticus isolates had both bla(VIM-2)-like and bla(OXA-58) genes. Pulsed-field gel electrophoresis (PFGE) suggested the spread of A. baumannii clones with OXA carbapenemases within and between hospitals. In conclusion, the recent increase in imipenem-resistant Acinetobacter spp. from South Korea is mostly due to OXA-type carbapenemases.

[Microorganisms isolated from blood cultures and their antimicrobial susceptibility patterns at a university hospital during 1994-2003]

BACKGROUND

Blood culture is important for the determination of the etiologic agent of bacteremia. Analysis of blood culture results and antimicrobial susceptibility trend can provide clinicians with relevant information for the empirical treatment of patients.

METHODS

The species and antimicrobial susceptibility of the isolates from blood cultures at the Severance Hospital during 1994-2003 were analysed. Blood specimens were cultured for 7 days using tryptic soy broth and thioglycollate medium. Identification of organism was based on conventional methods or commercial kit systems. Antimicrobial susceptibility was tested by a disk diffusion method.

RESULTS

Of 536,916 blood specimens cultured, 24,877 (4.6%) from 13,102 patients were positive. Among the isolates, 93.1% were aerobic or facultative anaerobic bacteria, 3.3% anaerobes, and 3.6% fungi. Escherichia coli was isolated most frequently, followed by Staphylococcus aureus, alpha-hemolytic Streptococcus, Enterococcus spp., and Klebsiella pneumoniae. The proportion of patients with Enterococcus faecium and K. pneumoniae gradually increased during this study. Enterococcus, S. aureus and alpha-hemolytic Streptococcus were frequently isolated from the age group of less than 2 yr. E. coli, Enterococcus spp., K. pneumoniae and S. aureus from the age group of over 50 yr. Oxacillin-resistant S. aureus decreased, whereas vancomycin-resistant E. faecium and imipenemresistant Pseudomonas aeruginosa and Acinetobacter baumannii increased.

CONCLUSIONS

E. coli was the most common cause of bacteremia and S. aureus, alpha-hemolytic Streptococcus, and K. pneumoniae were frequently isolated pathogens. The bacteremia due to Enterococcus, K. pneumoniae, fungi, vancomycin-resistant E. faecium, and imipenem-resistant P. aeruginosa and A. baumannii gradually increased during this period.

Acinetobacter baumannii: emergence of a successful pathogen

Acinetobacter baumannii has emerged as a highly troublesome pathogen for many institutions globally. As a consequence of its immense ability to acquire or upregulate antibiotic drug resistance determinants, it has justifiably been propelled to the forefront of scientific attention. Apart from its predilection for the seriously ill within intensive care units, A. baumannii has more recently caused a range of infectious syndromes in military personnel injured in the Iraq and Afghanistan conflicts. This review details the significant advances that have been made in our understanding of this remarkable organism over the last 10 years, including current taxonomy and species identification, issues with susceptibility testing, mechanisms of antibiotic resistance, global epidemiology, clinical impact of infection, host-pathogen interactions, and infection control and therapeutic considerations.

Five-year report of national surveillance of antimicrobial resistance in Pseudomonas aeruginosa isolated from non-tertiary care hospitals in Korea (2002-2006)

A nationwide surveillance of the antimicrobial resistance of Pseudomonas aeruginosa isolates from non-tertiary care hospitals was conducted in Korea from 2002 to 2006. Resistance to almost all antimicrobial agents decreased significantly from 2003 (P < 0.01). Resistance rates to the major antipseudomonal agents, ceftazidime, imipenem, meropenem, and aztreonam, were 18.8%, 20.5%, 18.7%, and 19.7%, respectively, in 2003. However, they had all decreased to below 10% in 2006. The proportion of multidrug-resistant isolates that were resistant to at least 3 of 5 major antipseudomonal agent decreased from 33.5% in 2003 to 23.1% in 2006 (P < 0.05). In this study, we found a decreasing trend in resistance rates and low resistance rates in P. aeruginosa from non-tertiary care hospitals compared with those from general hospitals, including tertiary care hospitals, in Korea. Our data provide valuable information for the selection of reliable empiric therapies for P. aeruginosa infections in non-tertiary care hospital patients, including outpatients.

Species distribution and susceptibility to azole antifungals of Candida bloodstream isolates from eight university hospitals in Korea

PURPOSE

The incidence of Candida bloodstream infections (BSI) has increased over the past two decades. The rank order of occurrence and the susceptibility to antifungals of the various Candida species causing BSI are important factors driving the establishment of empirical treatment protocols; however, very limited multi-institutional data are available on Candida bloodstream isolates in Korea.

MATERIALS AND METHODS

We investigated the susceptibility to azole antifungals and species distribution of 143 Candida bloodstream isolates recovered from eight university hospitals over a six-month period. Minimal inhibitory concentrations (MICs) of fluconazole, itraconazole, and voriconazole for each isolate were determined by the broth microdilution method of the Clinical and Laboratory Standards Institute (CLSI).

RESULTS

The Candida species recovered most frequently from the blood cultures was C. albicans (49%), followed by C. parapsilosis (22%), C. tropicalis (14%), and C. glabrata (11%). The MIC ranges for the Candida isolates were 0.125 to 64 microg/mL for fluconazole, 0.03 to 2 microg/mL for itraconazole, and 0.03 to 1 microg/mL for voriconazole. Overall, resistance to fluconazole was found in only 2% of the Candida isolates (3/143), while the dose-dependent susceptibility was found in 6% (8/143). The resistance and dose-dependent susceptibility of itraconazole were found in 4% (6/143) and 14% (20/143) of the isolates, respectively. All bloodstream isolates were susceptible to voriconazole (MIC, < or = 1 microg/mL).

CONCLUSION

Our findings show that C. albicans is the most common cause of Candida-related BSI, followed by C. parapsilosis, and that the rates of resistance to azole antifungals are still low among bloodstream isolates in Korea.