Efficacy of Photodynamic Anti-Microbial Chemotherapy for Acanthamoeba Keratitis In Vivo.

BACKGROUND AND OBJECTIVES: Acanthamoeba keratitis is a sight-threatening infectious disease that is difficult to treat. The aim of this study was to evaluate TONS504 (cationic chlorin derivative photosensitizer)-mediated photodynamic antimicrobial chemotherapy (PACT) in vivo as a potential treatment for Acanthamoeba keratitis. STUDY DESIGN/MATERIALS AND METHODS: Acanthamoeba keratitis was induced by soft contact lenses incubated with 1 × 105 /ml Acanthamoeba castellanii, which were placed over debrided corneas with temporary tarsorrhaphy. Thirty-eight male Japanese white rabbits were randomly divided into three groups (normal eye, no treatment, and treatment groups). TONS504 was administered as eye drops at 1 mg/ml, followed by light-emitting diode irradiation after the establishment of keratitis at 7 days after infectious contact lens exposure. All animals were evaluated under a slit-lamp microscope every 3 days for 6 days after the treatment. Clinical scores based on corneal epithelial defects detected by fluorescein staining, stromal opacity edema, and vascular infiltration into the cornea were determined. After 6 days, the eyes were enucleated for histopathological analysis. RESULTS: Clinical signs of infection in the treatment group were markedly reduced for up to 6 days after treatment. Histopathology showed a regular arrangement of stromal fibers and a small number of inflammatory cells in 58% of the corneas. However, 42% of corneas in the treatment group showed infiltrating neutrophils and irregular alignment of stromal collagen fibers. CONCLUSIONS: Our TONS504-PACT achieved complete recovery from keratitis in 58% of the rabbit models. Further studies are required to determine the conditions for the maximal effectiveness of our TONS504-PACT for Acanthamoeba keratitis. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Clinical characteristics of liver failure from a systemic cause: A report from an advanced critical care center.

UNLABELLED:  Background/Purpose. In Japan, acute liver failure (ALF) has generally been described using the diagnostic term, "fulminant hepatitis", because of the fact that most cases of ALF has been thought to occur in association with hepatitis mainly due to a hepatitis virus infection. New diagnostic criteria for ALF, including ALF other than fulminant hepatitis, were established in 2011. We therefore examined the prognostic factors of patients with liver failure from a systemic cause, including warfarin users. MATERIAL AND METHODS: Sixty-six patients with ALF that were diagnosed according to the Japanese diagnostic criteria for ALF between 2009 and 2013 were divided into a survivor group and a non-survivor group. The data regarding demography, liver tests, coagulation tests, Sequential Organ Failure Assessment (SOFA) scores, and the use of oral warfarin or aspirin were compared between the two groups. RESULTS: The SOFA score was significantly higher in the non-survivor group (p = 0.025). The proportion of oral warfarin users was significantly higher in the survivor group (p = 0.013) (58.1% vs. 26.1%). A multivariate logistic regression analysis showed the SOFA score (odds ratio: 0.851, 95% confidence interval (CI): 0.728-0.995, p = 0.043) and warfarin use (odds ratio: 3.261, 95% CI: 1.028-10.347, p = 0.045) to be significant factors that were negatively and positively associated with the prognosis, respectively. CONCLUSION: In this study, among the patients with ALF other than fulminant hepatitis, those with a high SOFA score on admission exhibited a poor prognosis. In addition, oral warfarin use prior to disease onset was found to be a factor which indicated a good prognosis.

Complete nucleotide sequence of the IncN plasmid encoding IMP-6 and CTX-M-2 from emerging carbapenem-resistant Enterobacteriaceae in Japan.

We have determined the DNA sequence of Klebsiella pneumoniae multidrug resistance plasmid pKPI-6, which is a self-transmissible IncN-type plasmid. pKPI-6 harboring blaIMP-6 and blaCTX-M-2 confers a stealth-type carbapenem resistance phenotype on members of the family Enterobacteriaceae that is not detectable with imipenem. pKPI-6 is already epidemic in Japan, favoring the dissemination of IMP-6 and CTX-M-2 in members of the family Enterobacteriaceae.

[In vitro combined effects of double antibacterial drugs against multidrug-resistant Pseudomonas aeruginosa isolates: comparison among combinations of colistin, arbekacin, aztreonam, rifampicin and piperacillin].

This in vitro study examined the combined effects of double antibacterial drugs against multidrug-resistant Pseudomonas aeruginosa (MDRP). The tested clinical isolates from Hiroshima University Hospital were 40 strains which met the criteria for MDRP, that is, the minimum inhibitory concentration (MIC) was > or = 16 microg/mL of meropenem, > or = 4 microg/mL of ciprofloxacin and > or = 32 microg/mL of amikacin. Using the original checkerboard plates for colistin (CL), arbekacin (ABK), aztreonam (AZT), rifampicin (RFP) and piperacillin (PIPC), MIC values were determined for single and double combinations. Based on the MIC values, fractional inhibitory concentration index values were calculated and the combined effects (synergy action or additive action) were evaluated. The three strongest drugs among the tested combinations were i) CL + RFP (synergy, 80.0%; additive, 17.5%), ii) RFP + ABK (synergy, 7.5%; additive, 70.0%) and iii) RFP + AZT (synergy, 5.0%; additive, 77.5%). In these cases, the arithmetic mean MIC value of each drug significantly decreased as follows: i) 1.38 microg/mL (alone) and 0.26 microg/mL (with RFP) for CL, 19.85 microg/mL (alone) and 1.85 microg/mL (with CL) for RFP; ii) 19.85 microg/mL (alone) and 7.53 microg/mL (with ABK) for RFP, 8.87 microg/mL (alone) and 2.79 microg/mL (with RFP) for ABK; iii) 19.85 microg/mL (alone) and 10.15 microg/mL (with AZT) for RFP, 28.3 microg/ mL (alone) and 6.65 microg/mL (with RFP) for AZT. Of 40 strains, metallo-beta-lactamase and aminoglycoside 6'-N-acetyltransferase were found in 20 and 37 strains, respectively; however, no significant influence of these factors was observed on the combined effects of i), ii) and iii). The results of this study provide an in vitro rationale for RFP plus CL, ABK or AZT as an effective combination therapy for MDRP infections, although the results should be verified and compared with other antibacterial drugs in further studies.

[Nationwide surveillance of parenteral antibiotics containing meropenem activities against clinically isolated strains in 2012].

The nationwide surveillance of antibacterial susceptibility to meropenem (MEPM) and other parenteral antibiotics against clinical isolates during 2012 in Japan was conducted. A total of 2985 strains including 955 strains of Gram-positive bacteria, 1782 strains of Gram-negative bacteria, and 248 strains of anaerobic bacteria obtained from 31 medical institutions were 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 multi-drug resistant strains including methicillin-resistant Staphylococcus aureus (MRSA). 2. Of all species tested, there were no species, which MIC90 of MEPM was more than 4-fold higher than those in our previous studies in 2009 or 2006. Therefore, the tendency to increase in antimicrobial resistance rates was not observed. 3. MEPM resistance against Pseudomonas aeruginosa was 17.8% (56/315 strains). Compared to our previous results, it was the lowest than that in 2006 and 2009. 4. Carbapenem-resistant Klebsiella pneumoniae, and multi-drug-resistant Acinetobacter species, which emerged in worldwide, were not observed. 5. The proportion of extended-spectrum beta-lactamase (ESBL) strains was 6.2% (59/951 strains) in enterobacteriaceae, which increased compared with that of our previous studies in 2009 or before. Whereas, the proportion of metallo-beta-lactamase strains was 1.6% (5/315 strains) in P. aeruginosa, which was stable. In conclusion, the results from this surveillance suggest that MEPM retains its potent and broad antibacterial activity and therefore is a clinically useful carbapenem for serious infections treatment at present, 17 years passed after available for commercial use in Japan.

Serotonin syndrome treated with cyproheptadine using NPi from a digital pupillometer as a therapeutic indicator: A case report.

RATIONALE: Serotonin syndrome is a potentially life-threatening condition resulting from the use of antidepressants, their interactions with other serotonergic medications, or poisoning. It presents with a triad of psychiatric, dysautonomic, and neurological symptoms and is sometimes fatal. While cyproheptadine is a specific treatment option, the optimal duration of its administration remains unclear. The purpose of this report is to quantitatively assess the endpoints of serotonin syndrome treatment. Based on the hypothesis that neurological pupil index (NPi) on a digital pupil recorder would correlate with the severity of the serotonin syndrome, we administered cyproheptadine using NPi as an indicator. PATIENT CONCERNS: A patient with a history of depression was brought to our hospital after he overdosed on 251 tablets of serotonin and noradrenaline reuptake inhibitors. DIAGNOSES: On day 3, the patient was diagnosed with serotonin syndrome. INTERVENTIONS: Cyproheptadine syrup was administered at 4 mg every 4 hours. The NPi of the automated pupillometer was simultaneously measured. On day 5, the NPi exceeded 3.0 cyproheptadine was discontinued. OUTCOMES: The patient was discharged on day 7. LESSONS: The lack of considerable improvement during the treatment period suggests that the patient may have improved on his own. In this case, the relationship between NPi and the severity of serotonin syndrome could not be determined.

Meropenem resistance in imipenem-susceptible meropenem-resistant Klebsiella pneumoniae isolates not detected by rapid automated testing systems.

Klebsiella pneumoniae showing high resistance to all ß-lactams except imipenem, designated as ISMRK (imipenem-susceptible meropenem-resistant Klebsiella) is emerging in Japan. The carbapenem resistance of ISMRK cannot be screened by the Vitek and the RAISUS rapid automated susceptibility test systems, which may lead to inappropriate antimicrobial therapy, resulting in compromised patient outcomes.

[Hypokalemic myopathy with severe constipation in a patient routinely administered sodium polystyrene sulfonate and the spherical carbon adsorbent].

66-year-old man was hospitalized because of severe abdominal pain. He had been treated for chronic renal failure. Sodium polystyrene sulfonate (SPS) and the spherical carbon adsorbent AST-120 were routinely administered to him. However, after several treatments, his pain did not resolve and his serum creatine kinase concentration was markedly elevated, so he was transferred to our hospital. Before admission to the previous hospital, muscular weakness was noted in his extremities and those symptoms persisted. His serum potassium concentration was 1.6 mEq/L, and he was administered potassium. A lower gastrointestinal endoscopy revealed normal mucosa and SPS powder-like brownish-yellow stool containing AST-120 granules in the colorectum. After massive stool discharge, the patient's pain improved and his serum potassium concentration gradually increased. The patient was diagnosed with hypokalemic myopathy thought to be mainly caused by accumulation of SPS in the colorectum.

Tsunami lung.

We encountered three cases of lung disorders caused by drowning in the recent large tsunami that struck following the Great East Japan Earthquake. All three were females, and two of them were old elderly. All segments of both lungs were involved in all the three patients, necessitating ICU admission and endotracheal intubation and mechanical ventilation. All three died within 3 weeks. In at least two cases, misswallowing of oil was suspected from the features noted at the time of the detection. Sputum culture for bacteria yielded isolation of Stenotrophomonas maltophilia, Legionella pneumophila, Burkholderia cepacia, and Pseudomonas aeruginosa. The cause of tsunami lung may be a combination of chemical induced pneumonia and bacterial pneumonia.

Characteristics of Patients Transported by Doctor-Requested Helicopters After Japan's 2011 Nuclear Incident.

OBJECTIVES: This study examined the characteristics of severe patients after the Great East Japan Earthquake in 2011. METHODS: Cases in the Futaba area were extracted using the dispatch database of the doctor helicopter and flight-nurse records from March 11, 2008, till March 10, 2014. The period before March 11, 2011, was defined as 'pre-earthquake' and the period after March 11, 2011, as 'post-earthquake' to compare the recorded data. RESULTS: Of the 128 total recorded cases, 78 were dispatched during the pre-earthquake period and 50 during the post-earthquake period. The number of patients with physical trauma following the earthquake included 4 patients (33.3%) in 2011, 7 patients (43.7%) in 2012, and 13 patients (59.1%) in 2013. However, the increase in number of requests was not statistically significant (P = 0.33). All 4 incidents of physical trauma in 2011, and 3 out of 7 incidents in 2012, occurred at the power plants. A total of 4 incidents occurred at decontamination worksites in 2013. CONCLUSIONS: It is of primary importance for hospitals to anticipate physical trauma cases during the reconstruction phase following a disaster, and develop a system for patients with physical trauma in the short- and long-term.

1H-magnetic resonance spectroscopy indicates damage to cerebral white matter in the subacute phase after CO poisoning.

OBJECTIVE: The authors examined whether (1)H-magnetic resonance spectroscopy (MRS) can identify damage to the centrum semiovale in the subacute phase after CO exposure. METHODS: Subjects comprised 29 adult patients who were treated with hyperbaric oxygenation within a range of 4-95 h (mean 18.7 h) after CO exposure. Subjects were classified into three groups according to clinical behaviours: Group A, patients with transit acute symptoms only; Group P, patients with persistent neurological symptoms; and Group D, patients with 'delayed neuropsychiatric sequelae' occurring after a lucid interval. MRS of bilateral centrum semiovale was performed 2 weeks after CO inhalation for all patients and 13 healthy volunteers. The mean ratios of choline-containing compounds/creatine ((mean)Cho/Cr) and N-acetylaspartate/Cr ((mean)NAA/Cr) for bilateral centrum semiovale were calculated and compared between the three CO groups and controls. Myelin basic protein (MBP) concentration in cerebrospinal fluid was examined at 2 weeks to evaluate the degree of demyelination in patients. RESULTS: MBP concentration was abnormal for almost all patients in Groups P and D, but was not abnormal for any Group A patients. The (mean)Cho/Cr ratios were significantly higher in Groups P and D than in Group A. No significant difference in (mean)NAA/Cr ratio was seen between the three pathological groups and controls. A significant correlation was identified between MBP and (mean)Cho/Cr ratio. CONCLUSIONS: These results suggest that the Cho/Cr ratio in the subacute phase after CO intoxication represents early demyelination in the centrum semiovale, and can predict chronic neurological symptoms.

[Detection of glimepiride and rosiglitazone from Chinese dietary supplements].

A 79-year-old man with diabetes mellitus developed prolonged hypoglycemia. The patient had ingested two Chinese dietary supplements in addition to his prescribed nateglinide (Fastic). Using liquid chromatography tandem mass spectrometry, glimepiride from sulfonylurea, as well as rosiglitazone from a thiazolidine derivative, were detected in the Chinese dietary supplements, which were then quantitatively analyzed using liquid chromatography with UV detector. Mean values (n=3) of glimepiride contents of the Chinese dietary supplements were 0.75 and 0.86 mg/capsule. Predicted intake of glimepiride in the patient was estimated to be 4.8-8.2 mg/day according to the glimepiride contents and directions of the Chinese dietary supplements. The daily intake of glimepiride in this patient was greater than daily maintenance doses (1-4 mg) of glimepiride for diabetic patients. Therefore, overdose of glimepiride by ingestion of the Chinese dietary supplements appears to be associated with the development of prolonged hypoglycemia.

Development of delayed neurologic sequelae in acute carbon monoxide poisoning cases caused by briquette-based kotatsu: A case-control study.

ABSTRACT: Briquette-based kotatsu, a traditional Japanese heating system, is still used in rural areas and has been linked to the development of acute carbon monoxide (CO) poisoning. This study aimed to investigate the occurrence of delayed neurologic sequelae (DNS) in patients with acute CO poisoning caused by briquette-based kotatsu.This retrospective study included 17 patients treated for acute CO poisoning due to briquette-based kotatsu, between April 2017 and March 2020. Patients were divided into either a sequelae group (3 patients) or a non-sequelae group (14 patients) based on the presence or absence, respectively, of DNS. Demographic data, kotatsu characteristics, clinical findings, and therapies were compared between the 2 groups.Significant differences were noted in patient posture during their initial discovery. Specifically, all non-sequelae patients only had their legs under the kotatsu quilt and all sequelae patients had their entire bodies under the kotatsu quilt (P = .001). There were no statistically significant differences in carbon monoxide levels in hemoglobin (CO-Hb) or the creatine-kinase myocardial band (CK-MB), between the 2 groups; however, troponin-I levels were significantly higher in the sequelae group (P = .026). Abnormal head imaging findings were noted in 2 sequelae-group patients, with a significant difference between the groups (P = .025).We speculate that acute CO poisoning, caused by briquette-based kotatsu, may lead to DNS more frequently in patients in who cover their entire body with the kotatsu quilt and are found in this position. Patients should be warned about the dangers of acute CO poisoning when using briquette-based kotatsu.

Balloon-occluded retrograde transvenous obliteration for gastric varices: the relationship between the clinical outcome and gastrorenal shunt occlusion.

BACKGROUND: The rupture of gastric varices is associated with high mortality rate. Balloon-occluded retrograde transvenous obliteration (B-RTO), a minimally invasive procedure that was introduced in the mid-1990s, has been widely accepted in Japan. Several reports have indicated that B-RTO yields satisfactory results; however, few reports have discussed the recurrence of gastric varices after this therapy. The purpose of this study is to retrospectively evaluate the technical aspects of B-RTO and the recurrence of gastric varices after treatment with this procedure. METHODS: B-RTO was performed in 47 patients with gastric varices, who were at a risk of variceal ruptures and who may or may not have had a history of variceal bleeding. We injected a sclerosing agent into the gastric varices for 30-60 minutes. To evaluate the therapeutic efficacy of the technique, we obtained contrast-enhanced computed tomography (CT) scans 5 days after B-RTO. As a general rule, if the gastric varices did not appear thrombosed, we repeated the procedure 7 days after the first procedure. RESULTS: B-RTO was a technical success in 37 patients. It was performed once in 26 patients, twice in 6 patients, thrice in 2 patients, and 4 times in 3 patients. Contrast-enhanced CT scans obtained after B-RTO showed thrombosed gastrorenal shunts in 29 patients and patent gastrorenal shunts in 8 patients. The gastric varices recurred in 2 patients who had patent gastrorenal shunts. The overall cumulative relapse-free rate of gastric varices was 90% at 5 years after B-RTO. CONCLUSIONS: B-RTO is an effective treatment modality for gastric varices. Moreover, obliteration of the gastrorenal shunt as well as the gastric varices appears to be important for the treatment of gastric varices.

[Susceptibility surveillance of clinical isolates to fluoroquinolone antimicrobial agents from 2003 to 2008: post-marketing study of prulifloxacin].

Yearly changes in the susceptibility of clinical isolates to ulifloxacin (UFX) and other fluoroquinolones were examined through surveys over 3 periods. In the first survey, 534 strains derived from 19 species were collected from clinical specimens during 6 months from December 2003 to May 2004. In the same way, 805 strains were collected from December 2005 to May 2006 in the second survey, and 863 strains were from December 2007 to May 2008 in the third survey. Over these 3 study periods, the susceptibilities of fluoroquinolones against methicillin-susceptible Staphylococcus aureus and Escherichia coli were decreased. The isolation frequency of levofloxacin-nonsusceptible strain was increased from 0% to 11.8% and from 14.6% to 20.8%, respectively. MIC90s of UFX against these pathogens were also increased, but its MIC90 for E. coli was 2 to 4 times lower than that of levofloxacin. On the other hand, the susceptibility of strains of Klebsiella pneumoniae to UFX was increased. Among the fluoroquinolones tested, UFX showed the most potent activity against Pseudomonas aeruginosa, and no changes in the MIC90s occurred during the surveillance. Although one strain of Streptococcus pneumoniae isolated in the third study period showed levofloxacin-resistance (MIC, 8 microg/mL), there were nearly no changes in the MIC90s of any agents tested including UFX against S. pneumoniae during the surveillance. As for other bacterial species, a tendency to increase in resistance to UFX was not observed. The activity of UFX against Salmonella spp. and Shigella spp. was superior/equal to those of fluoroquinolones tested.

[Case followed by delayed loss of consciousness after exposure to hydrogen sulfide that was treated with intermittent administration of sodium nitrite].

A 49-year-old man lost consciousness after being accidentally exposed to what was probably hydrogen sulfide gas while performing maintenance on a machine producing feather meal. He was immediately taken to the hospital. Upon admission, his consciousness level was 14 (E4V4M6) on the Glasgow Coma Scale (GCS), but it subsequently decreased, and the patient was intubated when his respirations became depressed as well. About 5 hours after the initial incident, he was transferred to our department. His consciousness level was GCS 9 (E2V2M5), his blood pressure was 95/78 mmHg, and his heart rate was 90 beats per min. There was no metabolic acidosis. Mechanical ventilation was begun and 10% sodium nitrite was intermittently administered intravenously, with the goal of lowering arterial blood methemoglobin saturation to 20%. Two days following admission, the patient regained full consciousness and sodium nitrite administration was stopped. The following day mechanical ventilation was also discontinued. This patient exhibited severe recurring neurologic symptoms without metabolic acidosis; thus, the manifestations of toxicity in this case might have been due to the direct neurologic toxicity of hydrogen sulfide, hypoxia, or delayed post-ischemic cerebral hypoperfusion syndrome. The patient made a full recovery without any sequelae; therefore we would like to hypothesize that repetitive intravenous administration of sodium nitrite is effective in cases of hydrogen sulfide exposure.

Oral colonisation by antimicrobial-resistant Gram-negative bacteria among long-term care facility residents: prevalence, risk factors, and molecular epidemiology.

BACKGROUND: For residents of long-term care facilities (LTCFs), antimicrobial-resistant bacteria (ARB) are a risk factor, yet their oral colonisation, potentially leading to aspiration pneumonia, remains unclear. This study was undertaken to survey the prevalence, phenotypic characteristics, and molecular epidemiology of antimicrobial-resistant Gram-negative bacteria in the oral cavity of LTCF residents, and to analyse the risk factors for such carriers. METHODS: This study involved 98 residents of a LTCF in Hiroshima City, Japan, aged between 55 and 101 years. Oropharyngeal swabs were collected and plated on screening media for ESBL-producing and carbapenem-resistant bacteria; isolates were identified and tested for antibiotic susceptibility; biofilm formation was tested in vitro; identification of epidemic clones were pre-determined by PCR; resistance genes, sequence types, and whole-genome comparison of strains were conducted using draft genome sequences. Demographic data and clinical characterisations were collected and risk factors analysed. RESULTS: Fifty-four strains from 38% of the residents grew on screening media and comprised predominantly of Acinetobacter spp. (35%), Enterobacteriaceae spp. (22%), and Pseudomonas spp. (19%). All Escherichia coli isolates carried CTX-M-9 group and belonged to the phylogroup B2, O25:H4 ST131 fimH30 lineage. Six Acinetobacter baumannii isolates presented identical molecular characteristics and revealed more biofilm production than the others, strongly suggesting their clonal lineage. One Acinetobacter ursingii isolate displayed extensive resistance to various ß-lactams due to multiple acquired resistance genes. One Pseudomonas aeruginosa isolate showed exceptional resistance to all ß-lactams including carbapenems, aminoglycosides, and a new quinolone, showing a multidrug-resistant Pseudomonas aeruginosa (MDRP) phenotype and remarkable biofilm formation. Genome sequence analysis revealed this isolate was the blaIMP-1-positive clone ST235 in Japan. Strokes (cerebral infarction or cerebral haemorrhage) and percutaneous endoscopic gastrostomy tubes were recognised as risk factors for oral colonisation by ARB in the LTCF residents. CONCLUSIONS: ARB, as defined by growth on screening agar plates, which carried mobile resistance genes or elements or conferred high biofilm formation, were already prevalent in the oral cavity of LTCF residents. Health-care workers involved in oral care should be aware of antimicrobial resistance and pay special attention to transmission prevention and infection control measures to diminish ARB or mobile resistance elements dissemination in LTCFs.

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.