Identification and characterization of a novel aac(6')-Iag associated with the blaIMP-1-integron in a multidrug-resistant Pseudomonas aeruginosa.

In a continuing study from Dec 2006 to Apr 2008, we characterized nine multi-drug resistant Pseudomonas aeruginosa strains isolated from four patients in a ward at the Hiroshima University Hospital, Japan. Pulsed-field gel electrophoresis of SpeI-digested genomic DNAs from the isolates suggested the clonal expansion of a single strain; however, only one strain, NK0009, was found to produce metallo-ß-lactamase. PCR and subsequent sequencing analysis indicated NK0009 possessed a novel class 1 integron, designated as In124, that carries an array of four gene cassettes: a novel aminoglycoside (AG) resistance gene, aac(6')-Iag, blaIMP-1, a truncated form of blaIMP-1, and a truncated form of aac(6')-Iag. The aac(6')-Iag encoded a 167-amino-acid protein that shows 40% identity with AAC(6')-Iz. Recombinant AAC(6')-Iag protein showed aminoglycoside 6'-N-acetyltransferase activity using thin-layer chromatography (TLC) and MS spectrometric analysis. Escherichia coli carrying aac(6')-Iag showed resistance to amikacin, arbekacin, dibekacin, isepamicin, kanamycin, sisomicin, and tobramycin; but not to gentamicin. A conjugation experiment and subsequent Southern hybridization with the gene probes for blaIMP-1 and aac(6')-Ig strongly suggested In124 is on a conjugal plasmid. Transconjugants acquired resistance to gentamicin and were resistant to virtually all AGs, suggesting that the In124 conjugal plasmid also possesses a gene conferring resistance to gentamicin.

[Nationwide surveillance of parenteral antibiotics containing meropenem activities against clinically isolated strains in 2009].

The antibacterial activity of meropenem (MEPM) and other parenteral antibiotics against clinical isolates of 2655 strains including 810 strains of Gram-positive bacteria, 1635 strains of Gram-negative bacteria, and 210 strains of anaerobic bacteria obtained from 30 medical institutions during 2009 was examined. The results were as follows; (1) MEPM was more active than the other carbapenem antibiotics tested against Gram-negative bacteria, especially against enterobacteriaceae and Haemophilus influenzae. MEPM was also active against most of the species tested in Gram-positive and anaerobic bacteria, except for multidrug resistant strains including methicillin-resistant Staphylococcus aureus (MRSA). (2) MEPM maintained potent and stable antibacterial activity against Pseudomonas aeruginosa. The proportion of MEPM-resistant strains to ciprofloxacin-resistant strains or imipenem-resistant strains were 53.1% and 58.0% respectively. (3) The proportion of extended-spectrum beta-lactamase (ESBL) strains was 3.1% (26 strains) in enterobacteriaceae. And the proportion of metallo-beta-lactamase strains was 2.0% (6 strains) in P. aeruginosa. (4) Of all species tested, there were no species except for Bacteroides fragilis group, which MIC90 of MEPM was more than 4-fold higher than those in our previous study. Therefore, there is almost no significant decrease in susceptibility of clinical isolates to meropenem. In conclusion, the results from this surveillance study suggest that MEPM retains its potent and broad antibacterial activity and therefore is a clinically useful carbapenem for serious infections treatment at present, 14 years passed after available for commercial use in Japan.

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.

Antimicrobial susceptibility of respiratory tract pathogens in Japan during PROTEKT years 1-5 (1999-2004).

Susceptibility to a range of antimicrobial agents was determined among isolates of Streptococcus pneumoniae, Streptococcus pyogenes, and Haemophilus influenzae collected in 12 centers throughout Japan during years 1-5 (the respiratory seasons of 1999-2004) of the longitudinal Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin study. The most frequent source of isolates of S. pneumoniae was from patients with community-acquired pneumonia (CAP) (25.3%). Reduced susceptibility to penicillin or erythromycin resistance was common among S. pneumoniae isolates (30.9-44.5% and 77.2-81.9%, respectively). The macrolide MIC(50) for S. pneumoniae was >or=128 microg/ml (azithromycin and erythromycin) and >or=64 microg/ml (clarithromycin). The erm(B) genotype accounted for the most erythromycin-resistant isolates in each study year. H. influenzae isolates were most commonly derived from patients with CAP (26.2%). The proportion of H. influenzae isolates that were beta-lactamase positive ranged between 4.3% and 9.7%. The prevalence of beta-lactamase-negative ampicillin-resistant isolates increased from 0.4% to 2.6% between years 1 and 4 then to 19.7% in year 5. S. pyogenes isolates were highly susceptible to most antimicrobial agents except macrolides and tetracycline. Telithromycin was highly active against all three pathogens examined throughout the study.

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.

[Nationwide surveillance of parenteral antibiotics containing meropenem activities against clinically isolated strains in 2004].

The antibacterial activity of meropenem (MEPM) and other parenteral antibiotics against clinical isolates of 907 strains of Gram-positive bacteria, 1790 strains of Gram-negative bacteria, and 192 strains of anaerobic bacteria obtained from 30 medical institutions during 2004 was measured. The results were as follows; 1. MIC90 of MEPM for almost all of enterobacteriaceae and Haemophilus influenzae were 4-fold to 32-fold lower than those of other carbapenems. MEPM was more active than other carbapenem antibiotics against Gram-negative bacteria, especially against enterobacteriaceae and H. influenzae. MEPM were active against most of the species tested in Gram-positive and anaerobic bacteria, except for multi-drug resistant strains including methicillin-resistant Staphylococcus aureus. 2. As for Pseudomonas aeruginosa, imipenem (IPM) showed high cross-resistant rate againt meropenem-resistant P. aeruginosa (87.9%). MEPM showed low cross-resistant rate both againt IPM-resistant P. aeruginosa (49.2%) and ciprofloxacin-resistant P. aeruginosa (38.0%). 3. The proportion of extended-spectrum beta-lactamase (ESBL) strains was 3.1% (4 strains) in Escherichia coli, 8.0% (2 strains) in Citrobacter koseri, 2.5% (3 strains) in Klebsiella pneumoniae, 2.5% (2 strains) in Enterobacter cloacae, 0.9% (1 strains) in Serratia marcescens, and 2.2% (2 strains) in Proteus mirabilis. The proportion of metallo-beta-lactamase strains was 1.6% (5 strains) in P. aeruginosa. 4. Of all species tested, Peptostreptococcus spp. was the only species, which MIC90 of MEPM was more than 4-fold higher than that in our previous study using clinical isolates during 2002 (0.25 microg/ml --> 1 microg/ml). Therefore, there is almost no siginificant decrease in susceptibility of clinical isolates to meropenem. In conclusion, the results from this surveillance study suggest that MEPM retains its potent and broad antibacterial activity and therefore is a clinically useful carbapenem at present, 9 years after available for commercial use.

[Pharmaceutical and pharmacological evaluation of Burow's solution (aluminum acetate solution), hospital preparation, and development of its rapid preparation method].

Burow's solution, or aluminum acetate solution, is effective in inhibiting various microorganisms including methicillin-resistant Staphylococcus aureus (MRSA) that are commonly observed in chronic suppurative otitis media. It takes several days to prepare Burow's solution using aluminum sulfate, and the pharmaceutical properties of the solution are not fully understood. In this study, the effect of storage (5 months) of Burow's solution prepared according to the Teine-Keijin Hospital manual on its pharmaceutical properties and antibacterial activities was examined. We also attempted to develop a rapid preparation method of aluminum acetate (or 1.7% aluminum) solution using two commercially available compounds of aluminum acetate basic (Al(2)O(CH(3)CO(2))(4), Al(OH)(CH(3)CO(2))(2)). The properties of Burow's solution, pH, osmolarity and antibacterial activity, were the same among different preparations and its storage for 5 months at 4 degrees C had no effect on these properties. The antibacterial potency of Burow's solution was dependent on aluminum concentration and its antibacterial potency against S. aureus and several MRSA strains was of the same magnitude. In a rapid preparation, aluminum acetate basic was mixed with appropriate amounts of tartaric acid and acetic acid, and the suspension was boiled for 2-2.5 hr until dissolved. The rapidly prepared aluminum acetate solution showed the same pharmaceutical properties and antibacterial activities as those of Burow's solution. The newly developed preparation method for aluminum acetate solution is expected to be convenient and feasible for hospital treatment of chronic suppurative otitis media.

[Nationwide surveillance of parenteral antibiotics containing meropenem activities against clinically isolated strains in 2002].

The antibacterial activity of meropenem (MEPM) and other parenteral antibiotics against clinical isolates of 899 strains of Gram-positive bacteria, 1500 strains of Gram-negative bacteria, and 158 strains of anaerobic bacteria obtained from 28 medical institutions during 2002 was measured. The results were as follows; 1. MEPM was more active than other carbapenem antibiotics against Gram-negative bacteria, especially against enterobacteriaceae and Haemophilus influenzae. MIC90 of MEPM against Pseudomonas aeruginosa was the lowest of the drugs tested. MEPM showed low cross-resistant rate against both imipenem-resistant P. aeruginosa and ciprofloxacin-resistant P. aeruginosa. MEPM was active against most of the species tested in Gram-positive and anaerobic bacteria, except for multi-drug resistant strains including methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE). 2. The proportion of extended-spectrum beta-lactamase (ESBL) strains was 3.1% (4 strains) in Escherichia coli and 1.9% (2 strains) in Klebsiella pneumoniae. Carbapenems including MEPM were active against these ESBL strains. In conclusion, the results from this surveillance study suggest that MEPM retains its potent and broad antibacterial activity and therefore is a clinically useful carbapenem; at present, 7 years after available for commercial use.

Changes in intestinal flora after administration of panipenem/betamipron or sulbactam/cefoperazone for treatment of postoperative infections in gastrectomy patients.

To determine the effect of antibiotics used for the treatment of postoperative infections on the normal intestinal flora in patients who have undergone gastroenterological surgery, we performed a prospective randomized study in patients who had undergone distal gastrectomy. Cefazoline was administered up to postoperative day 3 for prophylaxis. For the treatment of postoperative infections, either panipenem/betamipron (PAPM/BP; n = 5) or sulbactam/cefoperazone (SBT/CPZ; n = 5) was adminstered to ten patients with signs of postoperative infections. Feces were examined for bacteria before and 4 and 7 days after the commencement of administration of these therapeutic antibiotics. The anaerobic bacterial count decreased significantly in four of five patients treated with SBT/CPZ, from 1010.2+/-0.36/g before treatment to 105.22+/-3.51/g. In the PAPM/BP-treated group, the anaerobic bacterial count did not change after antibiotic therapy. We also investigated the major genera of colonic anaerobes, and found that the numbers of bifidobacteria were maintained during PAPM/BP administration. However, in the SBT/CPZ group, the number of bifidobacteria decreased to below the detection limit in four of five patients. Little change was observed in the aerobic bacterial count in either group. However, Enterobacteriaceae were replaced by enterococcus or candida in all patients from the SBT/CPZ group and in one of five patients from the PAPM/BP group. Physicians should be alert for the possible clinical consequences of changes in intestinal microflora after antibiotic treatment of postoperative infections.