Aims: Isolates obtained from various regions in Korea in 2002 were identified and their susceptibility to extendedspectrum cephalosporins, monobactams and/or cephamycins was studied along with any production of extended-spectrum b-lactamases (ESBLs). Methods and Results: Bacteria identified by the conventional techniques and Vitek GNI card were Klebsiella pneumoniae and Escherichia coli. Using disk diffusion and double-disk synergy tests, we found that 39AE2% of strains produced ESBLs. About 52% of isolates transferred resistance to ceftazidime by conjugation. Banding patterns of PCR amplification with the designed primers showed that 837-and 259-bp fragments specific to bla TEM genes were amplified in 63AE3% of strains. 929-and 231-bp fragments (bla SHV ), 847-and 520-bp fragments (bla CMY ), 597-and 858-bp fragments (bla CTX-M ) were amplified in 61AE5, 17AE3 and 7AE7% of strains respectively. About 51AE9% of strains contained more than two types of b-lactamase genes. Especially, one strain contained bla TEM , bla CMY and bla CTX-M genes. Significance: Resistance mechanisms to b-lactams, comprising mostly ESBL production, lead to the resistance against even recently developed b-lactams in enterobacteria, which is now a serious threat to antibiotic therapy. The high prevalence of bla CMY genes and multidrug-resistant genes may also make therapeutic failure and lack of eradiation of these strains by extended-spectrum cephalosporins or cephamycins.

The bla(CMY-10) gene responsible for β-lactam resistance was located on a new complex class 1 integron within a conjugative plasmid. The sul1-type class 1 integron, containing an aadA2a gene cassette, was identified upstream of bla(CMY-10). A unique gene array (yqgF-yqgE-gshB-orf97--orf105) was identified downstream of bla(CMY-10.).

Abstract-Single-pass VDD pacemakers have been used as a result of simple implantation procedures and generally reliable atrial tracking. However, there is a controversy over their reliabilities of atrial tracking. As a new sensing method for reliable atrial tracking, a simple automatic pacemaker sensing algorithm was implemented and evaluated to validate its benefits in sensing depolarization waves of single-pass VDD atrial electrograms . The automatic sensing algorithm had a predetermined sensing dynamic range and the sensitivity level was controlled as 50 % of the average of two most recently sensed intrinsic amplitudes. The behavior of the automatic sensing algorithm in the single-pass VDD atrial electrograms was analyzed and characterized. It was observe d that the automatic sensing algorithm was more effective than a conventional fixed threshold method to accurately detect and track p-waves in SVDD electrograms. Keywords -Automatic sensing algorithm, pacemakers, singlepass VDD, electrogram I. INTRODUCTIONSingle-pass VDD (SVDD) pacemaker systems have been used as a result of simple implantation procedures and generally reliable atrial tracking [1][2]. However, since in the single lead electrode the atrial sensing poles are floating, the signal amplitude may vary considerably. An optimal sensitivity level can not be determined using amplitude measurements of acute atrial electrograms because of the significant amplitude variations [3][4]. I ndividual patients may experience serious P -wave undersensing that may require sensing sensitivity reprogramming or may cause asynchronous pacing.There are several studies that suggest a highest sensitivity for P-wave sensing to compensate the amplitude variation, while there are contradictory studies that concern possible oversensing problems by the highest sensitivities [5][6][7].In this study, a sensing method that adapts its sensitivity level to previous intrinsic amplitude variations, an automatic sensing algorithm, is implemented and evaluated to validate its benefits in atrial electrograms from SVDD leads. The automatic sensing algorithm had been developed for sensing of automatic implantable cardioverter defibrillator (AICD or ICD), and has been adopted by pacemakers recently [8][9]. It is expected that the automatic sensing algorithm in pacemakers will improve the sensing performance and remove the human intervention for choosing an optimal sensitivity level.The purpose of this study is to characterize the behavior of an automatic sensing algorithm during SVDD P -wave sensing and compare its sensing performance to that of a conventional fixed sensitivity method. II. METHODOLOGYA simple automatic sensing algorithm was applied to 9 patients SVDD atrial electrograms obtained by Phymos™ 830-s lead (Medico), during several different body postures, deep respiration, and walking. The algorithm had a predetermined sensing dynamic range of 0.25 -2.25 mV and controlled the sensitivity level beat by beat as 50% of the average of two most recently sensed intrinsic amplit ude...