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Phenotypic detection of extended-spectrum β-lactamase (ESBL) is important for public health and infection control; however, plasmid-mediated AmpC β-lactamases (pAmpCs) can interfere with the ESBL phenotyping. We focused on Enterobacteriaceae strains that were susceptible to cefepime but had a mildly elevated minimum inhibitory concentration (MIC) of ceftazidime and studied the effect of pAmpC on the ESBL phenotyping in this population. Genotyping of ESBL and pAmpC was performed on 528 clinical isolates of Escherichia coli, Klebsiella spp., and Proteus spp. with a ceftazidime MIC of ≥2 μg/mL and cefepime MIC≤8 μg/mL; these isolates were collected at Nagasaki University Hospital from January 2005 to March 2011. In this sample, 145 isolates (27.5%) tested positive for pAmpC (pAmpC group). The concordance rates of phenotypic and genotypic detection of ESBLs were 69.2% in the pAmpC group and 88.8% in the non-pAmpC group (P=0.04). pAmpC was more commonly detected in isolates with non-CTX-M genes (5/53, 9.4%) than in isolates with CTX-M genes (8/121, 6.6%). Our data suggest that the presence of pAmpC increases the false negative detection of ESBL. When ESBL phenotyping is used, the underestimation of the prevalence of ESBL producers should be taken into account.

Meropenem-susceptible and -resistant Aeromonas dhakensis isolates from blood cultures of a fatal case of septicemia were analyzed. The two isolates were homologous and gene expression of metallo-β-lactamase in the resistant strain was upregulated. Physicians should be aware of the possibility of the induction of carbapenem-resistance, following the use of carbapenems in the treatment of Aeromonas infection.

The Cica Fungi Test Candida is a novel immunoassay test that is used in Japan to detect Candida mannan antigens. A total of 130 samples from 89 cases in which the β-D-glucan assay (MK method) was positive were collected between July 2007 and August 2008 at Nagasaki University Hospital, and the Cica Fungi Test Candida and Cand-Tec were performed. Diagnosis of candidemia was based on a positive culture for Candida spp. from blood or other sterile clinical specimens. A total of 19 samples from 16 cases with candidemia, and 111 samples from 73 cases without microbiological evidence of candidemia, were obtained. The sensitivity and specificity of the Cica Fungi Test and Cand-Tec were 63.2 and 95.5%, and 52.6 and 50.5%, respectively. The Cica Fungi Test showed significantly higher specificity than Cand-Tec (P<0.01). The β-D-glucan assay values were significantly higher in the candidemia samples than in the non-candidemia samples (P=0.0003), a result that was well correlated with the Cica Fungi Test (P=0.0005). The Cica Fungi Test was thus found to be more reliable and specific than Cand-Tec, and the combined evaluation with the β-D-glucan assay was more efficient for diagnosis of candidemia.

The mechanisms of severe pneumonia caused by co-infection of bacteria and influenza A virus (IAV) have not been fully elucidated. We examined apoptosis and inflammatory responses in a murine model for pneumococcal pneumonia during IAV infection. Inflammation, respiratory epithelium apoptosis, and inflammatory-cell infiltration increased in a time dependent manner in the lungs of mice co-infected with Streptococcus pneumoniae and IAV, in comparison with those infected with either S. pneumoniae or IAV. According to appearance of terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling positive cells, caspases-3 and -8 were activated 24 h after S. pneumoniae infection, and caspase-3 activation decreased after 48 h, whereas inflammatory cytokine levels continued to increase in co-infected mice. In contrast, in mice infected with either IAV or S. pneumoniae, apoptosis and activation of factors related to caspase-3 peaked at 48 h. Furthermore, Fas-associated death domain was significantly expressed in the lungs of co-infected mice 24 h after S. pneumoniae infection. These data suggest that early onset of apoptosis and its related factors play important roles in fulminant pneumonia resulting from bacterial pneumonia complicated by co-infection with influenza virus.

Platelet-activating factor (PAF) is a critical mediator of severe inflammatory diseases such as pneumonia, and the PAF-receptor (PAFR) is known to be an anchor for Streptococcus pneumoniae attachment to lung epithelial cells. We conducted a DNA microarray analysis to detect critical factors that mediate fulminant pneumonia due to influenza virus and S. pneumoniae co-infection in mice. Among the factors detected, levels of PAF-acetyl hydrolase (PAF-AH), which functions as inactivated PAF, were significantly increased, and PAFR was expressed in co-infected mouse lungs, as compared to the respective levels in mice infected with either S. pneumoniae or virus alone. Significantly elevated PAF-AH enzymatic activity was observed in the co-infected mouse lung, suggesting that co-infection activated PAF-related factors. These findings suggest that PAF and related molecules play important roles in fulminant pneumonia due to influenza virus infection, especially when severe bacterial pneumonia is complicated by co-infection with influenza virus.

We report a rare case of Legionella pneumophila pneumonia followed by invasive aspergillosis (IA). Legionellosis was ameliorated by the administration of ciprofloxacin, erythromycin, and corticosteroid as adjunctive therapy. Although intravenous administration of the corticosteroid was effective at reducing severe inflammation due to legionellosis, IA occurred at 12 days after admission. Combination therapy with micafungin and voriconazole was effective in this case; however, it remains necessary to exercise caution when making decisions regarding indications for corticosteroid use and observation in the treatment of severe pneumonia patients.