BACKGROUND: Cefroxadine is an oral first-generation cephalosporin, which has been used for several years. But, the susceptibility data of cefroxadine were rarely reported in Korea. The current study attempted to determine the antibacterial activity of cefroxadine against the major clinical isolates. METHODS: According to the NCCLS recommendations, antibacterial activities of cefroxadine were measured against total 500 major clinical isolates. MICs were determined by the agar dilution method, a series of doubling dilutions from 128 to 0.03 /mL, on Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Citrobacter freundii, Serratia marcescens, Proteus mirabilis, and Staphylococcus spp. In case of Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis, broth microdilution method, a series of doubling dilutions from 16 to 0.015 /mL, was performed. RESULTS: Cefroxadine had variable activity against Enterobacteriaceae. MIC cumulative curves showed that cefroxadine had relatively low MIC distributions against E. coli, K. pneumoniae and P. mirabilis, showing MIC50 were 4, 4, and 8 /mL, respectively. Against E. cloacae, C. freundii, and S. marcescens, cefroxadine 's MIC50 values ranged from 128 to >128 /mL. For clinical isolates of methicillin-susceptible Staphylococcus aureus and methicillin-susceptible Staphylococcus epidermidis, cefroxadine had MIC90 values were 4 /mL and 8 /mL, respectively. Cefroxadine had MIC50 values of 1 /mL and >16 /mL for penicillin-susceptible and penicillin-not-susceptible strains of S. pneumoniae, respectively. Cefroxadine had MIC50 values of 8 /mL and 4 /mL against H. influenzae and M. catarrhalis, respectively. CONCLUSION: Cefroxadine had good activity against gram-positive bacteria, except penicillin-resistant S. pneumoniae, and showed moderate antimicrobial activity against M. catarrhalis, E. coli, P. mirabilis, and K. pneumonaie. Cefroxadine had variable activity against Enterobacteriaceae other than the above-mentioned species.
Agar ; Citrobacter freundii ; Cloaca ; Enterobacter cloacae ; Enterobacteriaceae ; Escherichia coli ; Gram-Positive Bacteria ; Haemophilus influenzae ; Influenza, Human ; Klebsiella pneumoniae ; Korea ; Mirabilis ; Moraxella (Branhamella) catarrhalis ; Pneumonia ; Proteus mirabilis ; Serratia marcescens ; Staphylococcus ; Staphylococcus aureus ; Staphylococcus epidermidis ; Streptococcus pneumoniae

BACKGROUND: beta-lactam antibiotics are one of the most frequently used antimicrobial agents. However, with the increase of beta-lactamase-producing bacteria, penicillins arid 1 st generation cephalosporins have become less useful. Cefatrizine and clavulanic acid combination (CTCA) was developed to restore the activity. The aim of this study was to determine the activities of CTCA against major recent clinical isolates. METHODS: Aerobic and anaerobic bacteria tested were isolated from clinical specimens in Severance Hospital during 1996 to 1999. Antimicrobial susceptibility was determined by the NCCLS agar dilution methods. RESULTS: MICs of cefatrizine (CT) and CTCA were similar for methicillin-susceptible Staphylococcus aureus, Streptococcus pyogenes and S. pneumoniae. For Moraxella (Branhamella) catarrhalis, MIC90 CTCA was 1 microgram/mL, which was 1/8-fold lower than that of cefatrizine. MIC90S of CTCA for Escherichia coli and Klebsiella pneumoniae were 4 microgram/mL and 8 microgram/mL, respectively, which were 1/4- to 1/16-fold lower than those of CT. However, it was less active against Citrobacter freundii, Enterobacter cloacae and Serratia marcescens. Against Bacteroides fragilis group organisms, it showed good activities similar to those of other beta-lactam and beta-lactamase inhibitor combinations. CONCLUSIONS: CTCA showed good antimicrobial activities against M. (B.) catarrhalis, Haemophilus influenzae, Neisseria gonorrhoeae, extended spectrum beta-lactamase-producing E. coli and K. pneumoniae, Proteus vulgaris and B. fragilis. In conclusion, it would be useful for the treatment of infections due to those organisms, and for the empirical treatment of respiratory and urinary tract infections.
Agar ; Anti-Bacterial Agents ; Anti-Infective Agents ; Bacteria* ; Bacteria, Anaerobic ; Bacteroides fragilis ; beta-Lactamases ; Cefatrizine ; Cephalosporins ; Citrobacter freundii ; Clavulanic Acid ; Enterobacter cloacae ; Escherichia coli ; Haemophilus influenzae ; Klebsiella pneumoniae ; Moraxella (Branhamella) catarrhalis ; Neisseria gonorrhoeae ; Penicillins ; Pneumonia ; Proteus vulgaris ; Serratia marcescens ; Staphylococcus aureus ; Streptococcus pyogenes ; Urinary Tract Infections

BACKGROUND: Recent clinical isolates of bacteria often produce various beta-lactamases, for example, extended spectrum beta-lactamase (ESBL) by some species of Enterobacteriaceae, TEM beta-lactamase by Haemophilus influenzae, and penicillinase by methicillin-susceptible Staphylococcus aureus (MSSA). Cefminox, a commonly used cephamycin, is stable to various beta-lactamases, but its activity against recent clinical isolates has not been evaluated. The aim of this study was to determine the activities of cefminox against recent clinical isolates of Enterobacteriaceae, H. influenzae, and MSSA. METHODS: The organisms, isolated from Severance Hospital patients during 1997 to 1998, were kept frozen until the test. Antimicrobial susceptibility was determined by the NCCLS agar dilution method. RESULTS: All 30 isolates of Escherichia coli and 90% of 30 Klebsiella pneumoniae isolates were susceptible to cefminox, cefotetan and amikacin. All of the Enterobacter cloacae and Serratia marcescens, and 86% of Citrobacter freundii isolates were susceptible to amikacin. All of the 15 isolates each of Proteus mirabilis, P. vulgaris and Morganella morganii were susceptible to cefminox, cefotetan, cefotaxime, ceftazidime, and aztreonam, while all of the Providencia spp. were susceptible to ceftazidime and aztreonam. All of the 29 H. influenzae isolates were susceptible to cefminox, cefotaxime, and levofloxacin, while all MSSA isolates were susceptible to cefoxitin and cotrimoxazole. CONCLUSION: Cefminox is more active than the other beta-lactams against Enterobacteriaceae including, ESBL- producing E. coli, and K. pneumoniae.
Agar ; Amikacin ; Aztreonam ; Bacteria ; beta-Lactamases ; beta-Lactams ; Cefotaxime ; Cefotetan ; Cefoxitin ; Ceftazidime ; Citrobacter freundii ; Enterobacter cloacae ; Enterobacteriaceae* ; Escherichia coli ; Haemophilus influenzae* ; Haemophilus* ; Humans ; Influenza, Human ; Klebsiella pneumoniae ; Levofloxacin ; Morganella morganii ; Penicillinase ; Pneumonia ; Proteus mirabilis ; Providencia ; Serratia marcescens ; Staphylococcus aureus* ; Staphylococcus* ; Trimethoprim, Sulfamethoxazole Drug Combination

BACKGROUND: At antimicrobial susceptibility testing (AST), clinical isolates may appear susceptible sometimes to the antibiotics that are clinically ineffective or due to technical errors in the testing. So an interpretive reading of AST should be done, but most hospitals do not perform it routinely. Here, we developed and evaluated a computerized expert system to interpret AST of Enterobacteriaceae to beta-lactam antibiotics. METHODS: We made a rule-based expert system according to the natural resistance of the members of Enterobacteriaceae and the common phenotypes of resistance mechanisms for Enterobacteriacae. Antimicrobial suceptibility testings were performed using the disk diffusion method with 12 beta-lactam antibiotics for a total of 1, 016 clinical isolates. Then we compared the raw and expert results of AST. RESULTS: An overall discrepancy rate due to natural resistance was 5.9%; 10.4% for Klebsiella spp. and Citrobacter diversus, 15.0% for Enterobacter spp., 2.6% for Serratia marcescens, 31.6% for Morganella morganii and Providencia stuartti. Accoriding to acquired antimicrobial resistant mechanisms, overall resistant discrepancy was 21.8%; 18.8% for Escherichia coli, Proteus mirabilis, Salmonella and Shigella spp., 25.9% for Citrobacter diversus and Klebsiella spp., 21.6% for Citrobacter freundii and Enterobacter spp., 45.6% for Morganella morganii, 10.0% for Proteus vulgaris, 12.2% for Serratia spp.. CONCLUSIONS: These results indicate that the application of the expert system for interpretation of antimicrobial susceptibility test may provide more reliable data for the treating physician. Additional information should be applied on the software for new resistant mechanisms or some misinterpretive readings.
Anti-Bacterial Agents ; beta-Lactams* ; Citrobacter freundii ; Citrobacter koseri ; Diffusion ; Enterobacter ; Enterobacteriaceae* ; Escherichia coli ; Expert Systems* ; Immunity, Innate ; Klebsiella ; Morganella morganii ; Phenotype ; Proteus mirabilis ; Proteus vulgaris ; Providencia ; Reading ; Salmonella ; Serratia ; Serratia marcescens ; Shigella

To use in the identification of Legionella pneumophila isolates, one Legionella genus-specific, an two L. pneumophila species-specific monoclonal antibodies (MAbs) were produced. Reactivities of the MAbs with Legionella species and non-Legionella strains were tested by immunoblot. MAb 7D8-F1, MAb 7D8-A9, and MAb 1G12-C11 reacted only with protein. MAb 7D8-F1 recognized a genus-specific epitope in the protein ranged from 28 to 34 kDa in the tested 40 species with 61 serogroups. MAb 7D8-A9 and MAb 1G12-C11 reacted strongly with 49 kDa and 70 kDa protein from 18 L. pneumophila serogroups but did not react with 39 non-L. pneumophila species, respectively. In addtion, 17 non-Legionella strains, including Coxiella burnetii, Klebsiella pneumoniae, Mycoplasma pneumoniae, Pseudomonas areoginosa, Francisella tularensis, and Staphylococcus pneumoniae did not show cross-reacivities with the three MAbs. The MAbs reacted with 28 environmemtal isolates and three clinical isolates previously identified as L. pneumophila. When the immunoblot patterns were divided into four types (type I~IV) by using MAb 7D8-F1, all the 31 isolates belonged to the type II. These results indicate that the MAbs were highly specific to Legionella and can be used for the identification of L. pneumophila isolates on the genus and species levels.
Antibodies, Monoclonal* ; Coxiella burnetii ; Francisella tularensis ; Klebsiella pneumoniae ; Legionella pneumophila ; Legionella* ; Mycoplasma pneumoniae ; Pneumonia ; Pneumonia, Mycoplasma ; Pseudomonas ; Staphylococcus

BACKGROUND: In 2010, the Clinical and Laboratory Standards Institute (CLSI) revised breakpoints for cephalosporins and carbapenems and indicated that extended-spectrum beta-lactamase (ESBL) testing is no longer necessary for Enterobacteriaceae. We compared the results of the CLSI 2010 and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) MIC breakpoints for Enterobacteriaceae producing ESBL and/or plasmid-mediated AmpC beta-lactamase (PABL). METHODS: A total of 94 well-characterized clinical isolates of Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Proteus mirabilis, Salmonella spp., Shigella spp., Citrobacter freundii, Enterobacter aerogenes, Enterobacter cloacae, and Serratia marcescens were analyzed. Of them, 57 were ESBL producers, 24 were PABL producers, and 13 were ESBL plus PABL co-producers. Broth microdilution MIC tests were performed for cefotaxime, ceftazidime, aztreonam, cefepime, and imipenem. RESULTS: Among the 94 isolates containing ESBL and/or PABL, the number of isolates that were susceptible to cefotaxime, ceftazidime, aztreonam, cefepime, and imipenem according to the CLSI 2010 vs. the EUCAST breakpoints were 4 (4.3%) vs. 4 (4.3%); 26 (27.7%) vs. 8 (8.5%); 37 (39.4%) vs. 14 (14.9%); 71 (75.5%) vs. 31 (33.0%); and 76 (80.9%) vs. 90 (95.7%), respectively. Of the 18 isolates that were not susceptible to imipenem according to the CLSI 2010 breakpoints, 13 isolates (72.2%) were P. mirabilis. CONCLUSION: The CLSI 2010 MIC breakpoints without tests to detect ESBL and/or PABL for Enterobacteriaceae could be unreliable. Thus, special tests for ESBLs and AmpC beta-lactamases are required to detect the resistance mechanisms involved.
Aztreonam ; Bacterial Proteins ; beta-Lactamases ; beta-Lactams ; Carbapenems ; Cefotaxime ; Ceftazidime ; Cephalosporins ; Citrobacter freundii ; Enterobacter aerogenes ; Enterobacter cloacae ; Enterobacteriaceae ; Escherichia coli ; Imipenem ; Klebsiella oxytoca ; Klebsiella pneumoniae ; Proteus mirabilis ; Salmonella ; Serratia marcescens ; Shigella

BACKGROUND: We compared the performance of the modified Hodge test (MHT), Triton Hodge test (THT), Carba NP test (CNPt), simplified Carba NP test (CNPt-direct), blue-Carba NP test (BCT), and carbapenem inactivation method (CIM) for rapid and accurate carbapenemase detection. METHODS: The methods were evaluated by using 256 gram-negative isolates, including 197 Enterobacteriaceae (79 Enterobacter spp., 74 Klebsiella spp., 33 Escherichia coli, 10 Citrobacter spp., and 1 Serratia marcescens), 51 Acinetobacter baumannii, and 8 Pseudomonas aeruginosa strains. The collection included 117 non-carbapenemase, 18 Klebsiella pneumoniae carbapenemases (KPC) producers, 46 New Delhi metallo-β-lactamases (NDM) producers, 11 imipenemases (IMP) producers, and 51 oxacillinases (OXA) producers, and 13 strains harboring two different carbapenemase genes. RESULTS: The specificity of the THT (91.5%) was significantly lower than other methods, each of which had 100% specificity (P<0.003). This can be attributed to the false detection of Ampler class C β-lactamases (AmpC) carriers. The CNPt-direct and CIM yielded the highest sensitivities (P<0.003), which were comparable (92.8% vs 93.5%, P>0.999). Because of improved detection of NDM carriers, THT showed significantly higher sensitivity than the MHT (84.9% vs 75.5%, P<0.001). However, poor performances in detecting OXA still influenced the sensitivities of the CNPt (66.2%) and BCT (82.0%), as well as the MHT and THT. CONCLUSIONS: CNPt-direct and CIM demonstrated the best performance for the efficient detection of carbapenemase among the six evaluated methods. Except the MHT and THT, the detection of carbapenemase-producing Enterobacteriaceae by all the other methods was acceptable, when the OXA-type carbapenemase was not prevalent.
Acinetobacter baumannii ; Citrobacter ; Enterobacter ; Enterobacteriaceae ; Escherichia coli ; Gram-Negative Bacteria* ; Klebsiella ; Klebsiella pneumoniae ; Methods* ; Neptune ; Pseudomonas aeruginosa ; Sensitivity and Specificity ; Serratia

BACKGROUND: Recently a novel plasmid-mediated resistant mechanism that conferred high-level resistance to aminoglycoside via methylation of 16S rRNA was reported. The aims of this study were to determine the prevalence of the 16S rRNA methylase genes and to characterize the coresistance to other antibiotics in Gram-negative bacilli. METHODS: Consecutive non-duplicate Gram-negative bacilli were isolated from clinical specimens at a Korean secondary- and tertiary-care hospital from July 2006 to June 2007. The antimicrobial susceptibility was tested by the CLSI agar dilution method,and PCR was performed to detect the 16S rRNA methylase genes in the arbekacin-resistant isolates. RESULTS: In Gram-negative bacilli, the proportions of 16S rRNA methylase gene-positive isolates were 5% (75/1,471) in the secondary-carehospital and 4% (48/1,251) in the tertiary-care hospital, and the positive rates by species were 1% Escherichiae coli 16% (10/1,062), Klebsiella pneumoniae 16% (75/460), K. oxytoca 2% (1/44), Citrobacter spp. 9% (7/82), Enterobacter spp. 2% (4/181), Serratia marcescens 6% (6/100), Proteus miriabilis 4% (2/57), Achromobacter xylosoxidans 20% (1/5), Pseudomonas aeruginosa < 1% (1/505), Acinetobacter spp. 10% (11/112), and Stenotrophomonas maltophilia 2% (1/66), respectively. Among 16S rRNA methylase-positive isolates from secondary- and tertiary-care hospitals, 93% (70/75) and 90% (43/48), respectively, were armA positive, and others, except one rmtA positive isolate, were positive for the rmtB gene, according to PCR results. The rates of ESBL-positive and cefoxitin-resistant K. pneumoniae were 59% and 92%,s respectively. In addition, 91% of 16S rRNA methylase-producing K. pneumoniae were positive for qnrB. There were no MBL producers among 16S rRNA methylase-producing Pseudomonas and Acinetobacter species. CONCLUSION: The novel aminoglycoside-resistant mechanisms involving16S rRNA methylase were prevalent and widely distributed among Gram-negative bacilli in Korea, and other resistance mechanisms were commonly associated with 16S rRNA methylase-mediated resistance in Korea.
Achromobacter denitrificans ; Acinetobacter ; Agar ; Anti-Bacterial Agents ; Citrobacter ; Enterobacter ; Escherichia ; Klebsiella pneumoniae ; Korea ; Methylation ; Methyltransferases ; Pneumonia ; Polymerase Chain Reaction ; Prevalence ; Proteus ; Pseudomonas ; Pseudomonas aeruginosa ; Serratia marcescens ; Stenotrophomonas maltophilia

BACKGROUND: Moxifloxacin is a newly developed drug which is more potent and safe compared to previous fluoroquinolones. This drug effectively eradicates organisms such as beta-lactamase-producing or other resistant bacteria. Moxifloxacin is known to be effective in treating respiratory infections such as Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Chlamydia pneumoniae, Legionella spp. and Mycoplasma pneumoniae. METHODS: In a multicenter, randomized, open, comparative study, the efficacy and safety of oral moxifloxacin taken 400 mg once a day and clarithromycin taken 500 mg twice daily for 7 days were compared for the treatment of Korean patients with acute exacerbations of chronic bronchitis. RESULTS: A total of 170 patients were enrolled, and they were divided into two groups:87 in the moxifloxacin group and 83 in the clarithromycin group. Of those enrolled, 76 (35 for bacteriologic efficacy) in the moxifloxacin group and 77 (31 for bacteriologic efficacy) in the clarithromycin group were included in the efficacy analysis. All were included in the safety analysis. Clinical success was noted in 70 (92.1%) of 76 moxifloxacin-treated patients and 71 (92.2%) of 77 clarithromycin-treated patients. Bacteriologic success rate seemed to be higher in moxifloxacin group (73.5%) than in clarithromycin group (54.8%), but statistically insignificant (p=0.098). Drug susceptibility among organisms initially isolated was higher in moxifloxacin group on Streptococcus pneumoniae, Pseudomonas aeruginosa, Klebsiella pneumoniae(p<0.001). Adverse events were reported by 12.8% of 86 patients receiving moxifloxacin and 21.7% of 83 patients receiveing clarithromycin. Headache (4.7% vs 4.8%, moxiflosacin group vs clarithromycin group, respectively) and indigestion (2.3% vs 6.0%, moxifloxacin group vs clarithromycin group, respectively) were the most frequent side effects in the two groups. CONCLUSION: This study demonstrated that for the treatment of acute exacerbations of chronic bronchitis a 7-days course of moxifloxacin 400 mg od was clinically equivalent and microbiologically superior to clarithromycin 500 mg bid.
Bacteria ; Bronchitis, Chronic* ; Chlamydophila pneumoniae ; Clarithromycin* ; Dyspepsia ; Fluoroquinolones ; Haemophilus influenzae ; Headache ; Humans ; Klebsiella ; Legionella ; Moraxella (Branhamella) catarrhalis ; Mycoplasma pneumoniae ; Pneumonia, Mycoplasma ; Pseudomonas aeruginosa ; Respiratory Tract Infections ; Streptococcus pneumoniae

BACKGROUND: A rapid increase in antimicrobial-resistant bacteria has become a serious problem in many countries including Korea, but the rate and pattern of antimicrobial resistance may vary significantly depending on countries and even on hospitals. The aim of this study was to determine the nationwide prevalence of resistance among frequently isolated bacterial pathogens in Korea. METHODS: Routine susceptibility data for medically important bacterial pathogens from 12 university hospital and general hospital laboratories in Korea were analysed by patient group. These pathogens had been isolated during the period from April to November in 2004. RESULTS: The proportion of methicillin-resistant Staphylococcus aureus (MRSA) was 67%. Van-comycin-resistance rate of Enterococcus faecalis was 1% and that of E.faecium was 20%. The resistance rates of Streptococcus pneumoniae to penicillin and Haemophilus influenzae to ampicillin were 70% and 54%, respectively. The resistant rates of Escherichia coli and Klebsiella pneumoniae were 7-10% and 26-31% to the 3rd generation cephalosporin, respectively. The resistance rates to 3rd generation cephalosporin were 22-30% in Citrobacter freundii, 35-44% in Enterobacter cloacae and 15-22 % in Serratia marcescens. Imipenem resistance rates of Pseudomonas aeruginosa and Acinetobacter baumannii were 26% and 17%. Cotrimoxazole and levofloxacin resistance rates of Stenotrophomonas maltophilia were 46% and 44%, respectively. CONCLUSION: Antimicrobial resistance rates of clinically important pathogens in Korea were still high and were generally higher among the bacteria isolated from the intensive care unit patients. Strict infection control and continuous nationwide surveillance program will be required to manage the antimicrobial resistance problem.
Acinetobacter baumannii ; Ampicillin ; Bacteria* ; Citrobacter freundii ; Enterobacter cloacae ; Enterococcus faecalis ; Escherichia coli ; Haemophilus influenzae ; Hospitals, General ; Humans ; Imipenem ; Infection Control ; Intensive Care Units ; Klebsiella pneumoniae ; Korea* ; Levofloxacin ; Methicillin-Resistant Staphylococcus aureus ; Penicillins ; Prevalence ; Pseudomonas aeruginosa ; Serratia marcescens ; Stenotrophomonas maltophilia ; Streptococcus pneumoniae ; Trimethoprim, Sulfamethoxazole Drug Combination