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Background Extended-spectrum β-lactamase (ESBL)-producing bacteria coexpressing AmpC type β-lactamase (ACBL) are associated with the laboratory issue of false susceptibility to third-generation cephalosporins. This study was to evaluate laboratory tests and clinical significance of bacteremic isolates of Escherichia coli and Klebsiella pneumoniae with both ESBL and ACBL [dual-type lactamases (DTL)]. Methods From 2006 to 2009, 78 E coli and 12 pneumoniae bacteremic isolates with reduced susceptibility to cefotaxime (CTX) or ceftazidime (CAZ) were identified and relevant patients' data were collected for analysis. Phenotypic and genotypic characterizations of these selected isolates were determined by inhibitor-based assays and polymerase chain reaction–based genetic analyses, respectively. Results Among the 90 isolates, 47 had DTL production. There was an increasing annual prevalence from 29% in 2006 to 56% in 2009 ( p =0.02). Phenotypic assays had a sensitivity and specificity of 57% (43/76) and 93% (13/14) for ESBL detection and 95% (58/61) and 34% (10/29) for ACBL, respectively. Among the DTL-producing isolates, phenotypic assays yielded a higher false negative rate of ESBL detection than that of ACBL detection (70% versus 6%), while all false negative ESBL results were associated with ESBL genes other than bla CTx-M . The majority of the DTL-producing isolates were in the category of resistance to CTX (47/47, 100%) and CAZ (44/47, 94%) by the Clinical and Laboratory Standards Institute (CLSI) 2010 interpretive criteria, of which many were considered intermediate or fully susceptible to CTX (25/47, 53%) and CAZ (15/47, 32%) by the previous ones (CLSI-2009). The DTL-producing isolates exhibited a lower susceptibility rate to fluoroquinolones, aztreonam, and β-lactam/lactamase inhibitors than those with either ESBL or ACBL alone. The use of indwelling catheters or nasogastric tubes was associated with bacteremia due to the DTL isolates, but the mortality rates were not different among those due to isolates with ESBL, ACBL, or both. By multivariate analysis, Pittsburg bacteremia score and Charlson comorbidity index were the significant predictors for all-cause mortalities. Conclusion Bacteremic episodes due to DTL-producing E coli and K pneumoniae became increasingly prevalent and were often associated with coresistance to antibiotics other than β-lactams, but they were not associated with a worse prognosis than those due to ESBL- or ACBL-producing bacteria.

Chronic otitis media was the cause of septicemia in two hospitalized men. The organisms involved, K pneumoniae and B fragilis, are not usually associated with primary infections of the middle ear and would not have been traced to this site had proper cultures not been performed. In adults, the true incidence of bacteremia arising from the middle ear may be higher than suspected.

We have constructed wide host range plasmids in vitro carrying the K. pneumoniae (Kp) regulatory genes nifA and nifL or nif promoters fused to lacA, the gene for β-galactosidase. We reported recently that constitutively-produced nifA activates nif gene expression in two species of Azotobacter (1).

Many authors have studied the phagocytosis of mono-cultures by leucocytes (1,2,3,5). In a clinical setting infections caused by mixed culture could occur. We were thus interested in studying phagocytic activity of human granulocytes against cultures containing gram-negative and gram-positive organisms.

OSTEOMYELITIS due to Klebsiella pneumoniae would seem to be extremely uncommon. The literature has disclosed reports on a total of 11 cases, all of them in adults. 1-5 No case of Klebsiella osteomyelitis has been described in children, infants or the newborn, and reviews of osteomyelitis in children do not mention Klebsiella as a possible causative agent. 6-10 This is surprising, since gram-negative bacteria (especially the gram-negative enteric flora) have become increasingly important both in prevalence and severity in neonatal infection. 11-13 Recently, reports have appeared describing osteomyelitis in infants due to organisms that were considered to be rare as factors in this disease 14-18; these reports emphasize the need for awareness of the expanding range of etiological possibilities in osteomyelitis in infancy. We hereby report the case of a 25-day-old girl who developed multiple bone lesions due to K pneumoniae . To the best of our knowledge this is the first case

Background Klebsiella pneumoniae is a Gram-negative bacterial species well known for its capacity to cause infections in humans, and to carry and spread a wide variety of resistance genes including extended-spectrum beta-lactamase genes, carbapenem resistance genes, and colistin resistance genes. Recently, our real-time laboratory-based surveillance system MARSS (the Marseille Antibiotic Resistance Surveillance System) allowed us to observe a intringing dramatic decrease in the beta-lactam resistance level of the K. pneumoniae strains routinely isolated from patients hospitalized in our settings since 2013. Here we study the evolution of the prevalence of K. pneumoniae infections in Marseille university hospitals, France, from January 2012 to July 2015, and study their antibiotic resistance profiles.

The infection incidences from MDR strains in our ICU are in accordance with the results of respective studies in other ICUs of our country. Our aim is to identify potential risk factors for the development of MDR infection in ICU patients.