[Two cases of Mycoplasma pneumoniae bronchopneumonia diagnosed with LAMP (loop-mediated isothermal amplification) as a rapid assay].

Mycoplasma pneumoniae is one of the common pathogens of the community-acquired pneumonia in adults and children. Macrolide antibiotics are considered to be the first-choice drug for M. pneumoniae infections. However, macrolide-resistant M. pneumoniae was first detected from Japanese pediatric patients in 2000,and it has been increasing over the past decade. On the other hand, the Immunocard Mycoplasma IgM test is widely used as a rapid and easy diagnostic method for M. pneumoniae pneumonia, but false-positive or false-negative cases have been reported in adults. Therefore new methods have been developed recently. Using the LAMP assay, the results are available rapidly and accurately. We report herein on two cases of M. pneumoniae bronchopneumonia in which the LAMP assay was useful in the diagnosis and treatment.

Increased prevalence and clonal dissemination of multidrug-resistant Pseudomonas aeruginosa with the blaIMP-1 gene cassette in Hiroshima.

OBJECTIVES: The aim of this study was to evaluate the dissemination of metallo-beta-lactamase (MBL)-encoding genes among multidrug-resistant (MDR) Pseudomonas aeruginosa isolates recovered from major hospitals in the Hiroshima region. METHODS: During July to December from 2004 to 2006, a surveillance of eight major hospitals in the Hiroshima region identified 387 non-duplicate isolates resistant to imipenem (MIC >or= 16 mg/L). They were screened for resistance to amikacin (MIC >or= 64 mg/L) and ciprofloxacin (MIC >or= 4 mg/L) and MBL-encoding genes. The structure of the variable regions of the integrons was determined using PCR mapping. Clonality was assessed using PFGE and multilocus sequence typing (MLST). RESULTS: The frequency of MBL-positive isolates in MDR P. aeruginosa isolates significantly increased from 42.3% in 2004 to 81.4% in 2006. Most of the MBL-positive isolates produced IMP-1 followed by VIM-2. The bla(IMP-1) and bla(VIM-2) genes were present in class 1 integrons. Characterization of the variable regions of the integron showed the presence of six different gene cassette arrays in bla(IMP-1) cassettes and a single array in bla(VIM-2) cassettes. The IMP-1 producers belonged to two clonal lineages using PFGE and MLST analyses and the integron variations correlated well with the clonal complexes. Among them, strains positive for a newly identified In113-derived bla(IMP-1) gene cassette array were most widely distributed in Hiroshima. CONCLUSIONS: This study shows a dramatic increase in MBL genes, primarily bla(IMP-1), in MDR P. aeruginosa isolates in Hiroshima during these 3 years. In addition, MDR P. aeruginosa with the newly discovered In113-derived bla(IMP-1) gene cassette array appears to be clonally expanding.

Increased resistance to cationic antimicrobial peptide LL-37 in methicillin-resistant strains of Staphylococcus aureus.

OBJECTIVES: The susceptibility of clinical isolates of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), to host-derived cationic antimicrobial peptides was investigated. METHODS: We examined the susceptibility of 190 clinical strains of methicillin-susceptible S. aureus (MSSA) and 304 strains of MRSA to two different classes of cationic antimicrobial peptides: LL-37 and human beta-defensin-3 (hBD3). Out of the total 494 clinical strains, a random selection of 54 S. aureus strains was examined to establish the relationship between the net charge, or zeta potential, of each strain and its susceptibility to hBD3 or LL-37. To further confirm bacterial susceptibility to either hBD3 or LL-37, we concurrently measured: (i) percentage survival after in vitro bacterial exposure and (ii) MBCs for both MRSA and MSSA strains. RESULTS: Of the 54 randomly selected S. aureus strains, those MRSA strains resistant to LL-37 showed significantly higher zeta potentials than those susceptible to LL-37 (P < 0.05). In contrast, there was no difference in bacterial zeta potentials for MRSA strains that showed either resistance or susceptibility to hBD3. In addition, resistance to LL-37, but not to hBD3, as determined by either percentage survival or MBC, was significantly elevated in highly methicillin-resistant strains of S. aureus when compared with MSSA strains (P < 0.01). CONCLUSIONS: Clinical strains of MRSA, but not MSSA, that demonstrated an increased net charge also showed elevated resistance to LL-37, but not to hBD3.

Pharmacokinetics and pharmacodynamics of biapenem in critically ill patients under continuous venovenous hemodiafiltration.

To characterize the PK/PD of biapenem (BIPM) in critically ill patients under continuous venovenous hemodiafiltration (CVVHDF), we conducted a prospective, open-label study in nine adult CVVHDF patients with acute renal failure at the Critical Care Medical Center, Hiroshima Prefectural Hospital. Plasma and filtrate samples were obtained at six time points. The concentrations of BIPM in plasma and filtrate were determined by HPLC. PK parameters were analyzed using Monte Carlo simulation with MIC data. BIPM concentrations in the plasma and CVVHDF filtrate peaked at the end of infusion, and the values were similar. The drug clearance by CVVHDF and non-CVVHDF was 1.28 +/- 0.14 and 9.05 +/- 4.05 L/h, respectively. Monte Carlo simulation showed that the more administration times, there were the higher the probability. In conclusion, a dosing regimen of 300 mg BIPM q8h had a higher probability of therapeutic efficacy than q12h in patients with severe sepsis under CVVHDF.

Molecular characterization of imipenem-resistant Pseudomonas aeruginosa in Hiroshima, Japan.

Pseudomonas aeruginosa showing resistance to imipenem were found in 100 of 1,058 strains (9.5%) from six hospitals (a-f) in Hiroshima City, Japan. Of the 100 strains, 14 (14%) were double disk synergy test positive using sodium mercaptoacetic acid disks, and 18 (18%) were bla(IMP-1) or bla(VIM-2) allele positive by polymerase chain reaction (PCR). Among 100 imipenem-resistant strains, 32 were categorized into multi-drug resistant strains, in which 13 were positive for the metallo-beta-lactamase gene. Fifty-one strains (51%) among the 100 imipenem-resistant strains had elevated RND efflux pump activity against levofloxacin. But only 6 of 51 strains were classified as multi-drug resistant strains. The pulsed field gel electrophoresis analysis of the Spe I-digested DNA from the 100 isolates suggested not only clonal spread but spread of heterogeneous clones started to contribute to the prevalence of metallo-beta-lactamase producing P. aeruginosa strains in Japanese hospitals.

[Antimicrobial susceptibility of Pseudomonas aeruginosa isolated from urine at one hospital to mainly carbapenem and fluoroquinolone drugs].

We tested the drug susceptibility to 8 anti-pseudomonal agents of 97 strains of Pseudomonas aeruginosa isolated from urine between January 1998 and May 2004. The results were as follows. 1. Antimicrobial activity was, in order of superiority to biapenem (BIPM), meropenem (MEPM), ciprofloxacin (CPFX), imipenem (IPM), pazufloxacin (PZFX), amikacin (AMK), ceftazidime (CAZ), piperacillin (PIPC). 2. The resistance rate (intermediate+resistance) to carbapenem drugs was 10.3% for BIPM and MEPM, and 13.4% for IPM. Many of the IPM-resistant strains showed crossover resistance with BIPM and MEPM. 3. The resistance rate (intermediate+resistance) to fluoroquinolone drugs was 23.7% for CPFX and 20.6% for PZFX. 4. One strain showed simultaneous resistance to IPM = 16 microg/mL, CPFX = 4 microg/mL, and AMK = 32 microg/mL, and produced IMP-1 metallo-beta-lactamase. Susceptibility of P. aeruginosa isolated from urine developed resistance to fluoroquinolone drugs. It is important to promote appropriate use of antimicrobial agents and continue to survey emerging resistance in the clinical isolates.