To determine the epidemiologic features and clinical outcomes of bloodstream infections caused by extended-spectrum ␤-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae isolates, cases of bacteremia caused by these organisms in children were analyzed retrospectively. Among the 157 blood isolates recovered from 1993 to 1998 at the Seoul National University Children's Hospital, the prevalence of ESBL production was 17.9% among the E. coli isolates and 52.9% among the K. pneumoniae isolates. The commonest ESBLs were SHV-2a and TEM-52. A novel ESBL, TEM-88, was identified. Pulsed-field gel electrophoresis analysis of the ESBL-producing organisms showed extensive diversity in clonality. The medical records of 142 episodes were reviewed. The risk factors for bloodstream infection with ESBL-producing organisms were prior hospitalization, prior use of oxyimino-cephalosporins, and admission to an intensive care unit within the previous month. There was no difference in clinical severity between patients infected with ESBL-producing strains (the ESBL group) and those infected with ESBL-nonproducing strains (the non-ESBL group) at the time of presentation. However, the overall fatality rate for the ESBL group was significantly higher than that for the non-ESBL group: 12 of 45 (26.7%) versus 5 of 87 (5.7%) (P ‫؍‬ 0.001). In a subset analysis of patients treated with extended-spectrum cephalosporins with or without an aminoglycoside, favorable response rates were significantly higher in the non-ESBL group at the 3rd day (6 of 17 versus 33 of 51; P ‫؍‬ 0.035), the 5th day (6 of 17 versus 36 of 50; P < 0.05), and the end of therapy (9 of 17 versus 47 of 50; P < 0.001). In conclusion, the ESBL production of the infecting organisms has a significant impact on the clinical course and survival of pediatric patients with bacteremia caused by E. coli and K. pneumoniae.Escherichia coli and Klebsiella pneumoniae are leading causes of serious infections in neonates, neutropenic cancer patients, and other patients with underlying diseases. These bacteria had been uniformly susceptible to oxyimino-␤-lactam antimicrobials. However, since the initial description of extended-spectrum ␤-lactamase (ESBL) production by K. pneumoniae strains in 1983 (18) and E. coli strains in 1987 (3), strains of E. coli and K. pneumoniae that are resistant to broadspectrum cephalosporins are increasingly being recognized (6, 14). There have been many reports of outbreaks caused by these organisms in cancer centers, pediatric and geriatric wards, and hospitalized nursing home patients. However, epidemiologic descriptions of bloodstream infections caused by ESBL-producing E. coli and K. pneumoniae are limited (32,36), and clinical data regarding treatment are further limited (2,31,35,36). At present, carbapenems are recommended for the treatment of infections caused by ESBL-producing organisms. However, this recommendation is primarily based on the in vitro effect (12), the results of animal experiments (33), and only very limited clinical da...

We evaluated the clinical characteristics, cytokine/chemokine concentrations, viral shedding and antibody kinetics in 30 patients with Middle East respiratory syndrome (MERS), including 6 non-survivors admitted to 3 MERS-designated hospitals. Old age, low albumin, altered mentality and high pneumonia severity index score at admission were risk factors for mortality. In addition, severe signs of inflammation at initial presentation (at hospital days 1-4), such as high inducible protein-10 (p=0.0013), monocyte chemoattractant protein-1 (p=0.0007) and interleukin 6 (p=0.0007) concentrations, and poor viral control (high viral load at hospital days 5-10, p<0.001) without adequate antibody titres (low antibody titre at hospital days 11-16, p=0.07) during the course of disease, were associated with mortality.

Cases of bacteremia caused by AmpC-type-␤-lactamase-producing Klebsiella pneumoniae isolates were retrospectively studied to determine the epidemiologic features and clinical outcomes of bloodstream infections. Among 389 blood isolates recovered from 1998 to 2002, 65 isolates (16.7%) were found to be extended-spectrum ␤-lactamase (ESBL) or AmpC ␤-lactamase producers. The ␤-lactamases from 61 of the 65 isolates were characterized; 28 of 61 isolates produced AmpC-type enzymes (14 isolates each produced DHA-1 and CMY-1-like enzymes), 32 isolates produced TEM or SHV-related ESBLs, and 1 isolate produced a CTX-M-14-like enzyme. To compare the clinical features and outcomes of bloodstream infections caused by AmpC producers with those caused by TEM-or SHV-related ESBL producers, 27 patients infected with isolates producing AmpC-type enzymes (AmpC group) and 25 patients infected with isolates producing TEM-or SHV-related enzymes (ESBL group) were analyzed. There was no significant difference between the AmpC and the ESBL groups in terms of risk factors. When the initial response was assessed at 72 h after antimicrobial therapy, the treatment failure rate for the AmpC group was 51.9% (14 of 27 patients) and the 7-and 30-day mortality rates were 14.8 and 29.6%, respectively, which were similar to those for the ESBL group. When the mortality rate for the patients who received extended-spectrum cephalosporins as definitive treatment was assessed, all four patients in the DHA-1 group and one of three patients in the CMY-1-like group died. In summary, the prevalence of AmpC enzyme-producing K. pneumoniae was high at the Seoul National University Hospital, and the clinical features and outcomes for the patients infected with AmpC-producing organisms were similar to those for the patients infected with TEM-or SHV-related ESBL producers.

In order to define the contributions of the mechanisms for carbapenem resistance in clinical strains of Pseudomonas aeruginosa, we investigated the presence of OprD, the expressions of the MexAB-OprM and MexEF-OprN systems, and the production of the ␤-lactamases for 44 clinical strains. All of the carbapenemresistant isolates showed the loss of or decreased levels of OprD. Three strains overexpressed the MexABOprM efflux system by carrying mutations in mexR. These three strains had the amino acid substitution in MexR protein, Arg (CGG) 3 Gln (CAG), at the position of amino acid 70. None of the isolates, however, expressed the MexEF-OprN efflux system. For the characterization of ␤-lactamases, at least 13 isolates were the depressed mutants, and 12 strains produced secondary ␤-lactamases. Based on the above resistance mechanisms, the MICs of carbapenem for the isolates were analyzed. The MICs of carbapenem were mostly determined by the expression of OprD. The MICs of meropenem were two-to four-fold increased for the isolates which overexpressed MexAB-OprM in the background of OprD loss. However, the elevated MICs of meropenem for some individual isolates could not be explained. These findings suggested that other resistance mechanisms would play a role in meropenem resistance in clinical isolates of P. aeruginosa.Pseudomonas aeruginosa is a clinically important pathogen with intrinsic resistance to various antimicrobial agents. This intrinsic multidrug resistance results from the synergy between broadly specific drug efflux pumps and a low degree of outer membrane permeability. For the carbapenem antimicrobials, the resistance is mostly mediated by OprD loss, which primarily confers a resistance to imipenem but also confers a low grade resistance to meropenem (12,16). But the multidrug efflux systems which mediate the resistance to quinolone, chloramphenicol, and many other antimicrobial agents, also contribute to the carbapenem resistance. The strains which overexpress the MexAB-OprM system or express the MexEFOprN system exhibit the carbapenem resistance by pumping the drug out or repressing the transcription of oprD, respectively (13,20,25). On the other hand, the NfxB mutants which expressed MexCE-OprJ became more susceptible to imipenem, bipenem, and some ␤-lactams (22). In addition to the OprD loss or drug efflux pumps, chromosomal AmpC ␤-lactamase plays an important role in carbapenem resistance in P. aeruginosa (16,21). Although the contributions of the OprD loss, the efflux systems, and ␤-lactamase in the carbapenem resistance have been well characterized in the laboratory strains, little data is available for how such factors play together in the clinical isolates of P. aeruginosa (2,4,31).Based on the carbapenem susceptibility patterns, the clinical isolates of carbapenem-resistant P. aeruginosa could be divided into three groups as the imipenem-resistant and meropenemsensitive group, the imipenem-sensitive and meropenem-resistant group, and the imipenem-resistant and meropenem-resistant group (2,4,17)...

CTX-M-14 ␤-lactamase was identified in a stool isolate of Shigella sonnei and in blood isolates of Escherichia coli (one isolate) and Klebsiella pneumoniae (two isolates) from different parts of Korea. The amino acid sequence differed by one amino acid from CTX-M-9 (Ala-2313 Val) and was identical to that of ␤-lactamases recently found in China and Japan.Because resistance is more than locally relevant with increasingly mobile populations and since unique resistance mechanisms may evolve anywhere antibiotics are used, we have investigated several unusually resistant clinical isolates from Korea.One strain of Escherichia coli and two strains of Klebsiella pneumoniae that had high levels of resistance to cefotaxime were isolated from the blood of patients in Seoul National University Children's Hospital in 1995 and 1996. One strain of Shigella sonnei isolated from a pediatric patient on Cheju Island in 2000 also had a high level of cefotaxime resistance. By disk susceptibility testing, the strains were resistant to amoxicillin, cephalothin, and cefotaxime but were susceptible to ceftazidime, cefoxitin, and amoxicillin-clavulanic acid. Isoelectric focusing showed that the four strains produced a ␤-lactamase with an isoelectric point (pI) of 8.0. PCR with SHVspecific primers (3) was negative for all strains. Cefotaxime resistance was transferred by conjugation (9) from K. pneumoniae strain 95151 along with a plasmid of 160 kb to E. coli J53 Azi r (met pro azide resistant) to produce E. coli J53 Azi r / pMG267. The ␤-lactamase gene was cloned from plasmid pMG267 with EcoRI as an 8-kb insert into vector plasmid pBC SK (Stratagene, La Jolla, Calif.) carrying chloramphenicol resistance to produce plasmid pMG268. For sequencing, a Tn7-based transposon carrying a kanamycin resistance gene was inserted into purified pMG268 using the GPS-1 Genome Priming System-1 kit (New England BioLabs, Beverly, Mass.), and the resulting derivative was introduced into E. coli DH10B (Gibco BRL, Rockville, Md.) by electroporation. After selection with 50 g of kanamycin per ml and 30 g of chloramphenicol per ml, colonies were screened for loss of resistance to 100 g of ampicillin per ml. In ampicillin-susceptible colonies, the transposon was assumed to have been inserted into the ␤-lactamase gene. With primers (primerN and primerS) that matched nucleotides at the extremities of the inserted transposon, cycle sequencing (Perkin-Elmer Cetus, Norwalk,