M2 polarization of murine peritoneal macrophages induces regulatory cytokine production and suppresses T-cell proliferation.

Bone-marrow-derived macrophages are divided into two phenotypically and functionally distinct subsets, M1 and M2 macrophages. Recently, it was shown that adoptive transfer of M2-polarized peritoneal macrophages reduced the severity of experimental colitis in mice. However, it is still unclear whether peritoneal macrophages possess the same ability to be polarized to cells with functionally different phenotypes and cytokine production patterns as bone-marrow-derived macrophages. To address this question, we examined the ability of peritoneal macrophages to be polarized to the M1 and M2 phenotypes and determined the specific cytokine profiles of cells with each phenotype. We showed that peritoneal macrophages, as well as bone-marrow-derived macrophages, were differentiated into M1 and M2 phenotypes following stimulation with interferon-γ (IFN-γ) and interleukin-4 (IL-4)/IL-13, respectively. Following in vitro stimulation with lipopolysaccharide, M2-polarized peritoneal macrophages predominantly expressed T helper type 2 (Th2) cytokines and regulatory cytokines, including IL-4, IL-13, transforming growth factor-ß and IL-10, whereas M1-polarized peritoneal macrophages expressed negligible amounts of Th1 and pro-inflammatory cytokines. ELISA showed that M2-polarized peritoneal macrophages produced significantly more IL-10 than M1-polarized peritoneal macrophages. Notably, M2-polarized peritoneal macrophages contributed more to the suppression of T-cell proliferation than did M1-polarized peritoneal macrophages. The mRNA expression of Th2 cytokines, including IL-4 and IL-13, increased in T-cells co-cultured with M2-polarized macrophages. Hence, our findings showed that M2 polarization of peritoneal macrophages induced regulatory cytokine production and suppressed T-cell proliferation in vitro, and that resident peritoneal macrophages could be used as a new adoptive transfer therapy for autoimmune/inflammatory diseases after polarization to the regulatory phenotype ex vivo.

Bloodstream infection caused by Campylobacter lari.

We describe a case of bloodstream infection (BSI) caused by Campylobacter lari in a 58-year-old man diagnosed with lumbar pyogenic spondylitis. Anaerobic blood cultures, taken on the day of admission and on hospital day 4, were positive after 30 h of incubation, although no bacteria were detected by Gram staining. After subculture on 5 % sheep blood agar for 2 days at 35 °C in a 5 % CO2 environment, capnophilic, curved, gram-negative bacteria were recovered. The bacteria were identified as C. lari using a combination of phenotypic identification methods and partial 16S rRNA gene sequencing. The BSI was eradicated following combination therapy with intravenous tazobactam/piperacillin, oral erythromycin, and sulfamethoxazole/trimethoprim. These results suggest that accurate identification, to the species level, is important to determine effective treatment of BSI caused by Campylobacter spp. and can help us to understand the epidemiology.

Genotypes of Candida albicans isolated from healthy individuals and their distribution in patients with oral candidiasis.

For the study of Candida albicans genotypes involved in development of candidiasis, Candida albicans isolates were collected from healthy volunteers and patients with oral candidiasis and genotyped on the basis of 25S rDNA and microsatellite polymorphisms. In the microsatellite analysis using two microsatellite markers (CDC3 and CAI), 63 healthy volunteer isolates were classified into 35 genotypes (allelic relations to CDC3 alleles 1:2/CAI alleles 1:2), among which genotypes II (115:119/23:23), III (115:123/18:27), and V (123:127/32:41) were found at frequencies of 12.7%, 7.9%, and 7.9%, respectively. In 68 oral candidiasis isolates classified into 39 genotypes, genotypes II and III were identified in 4.4% and 20.6% of the isolates, respectively. The frequency of genotype III was higher in the candidiasis isolates than in the healthy isolates (p < 0.05). These results suggest that genotype III C. albicans assigned by CDC3/CAI is related to the development of oral candidiasis.

[Antimicrobial susceptibility of clinical isolates of aerobic gram-positive cocci and anaerobic bacteria in 2008].

The activity of antibacterial agents against aerobic Gram-positive cocci (25 genus or species, 1029 strains) and anaerobic bacteria (21 genus or species, 187 strains) isolated from clinical specimens in 2008 at 16 clinical facilities in Japan were studied using either broth microdilution or agar dilution method. The ratio of methicillin-resistant strains among Staphylococcus aureus and Staphylococcus epidermidis was 59.6% and 81.2%, suggesting that resistant strains were isolated at high frequency. Vancomycin (VCM), linezolid (LZD) and quinupristin/dalfopristin (QPR/DPR) had good antibacterial activity against methicillin-resistant S. aureus and methicillin-resistant S. epidermidis, with MIC90s of < or = 2 microg/mL. The ratio of penicillin (PC) intermediate and resistant strains classified by mutations of PC-binding proteins among Streptococcus pneumoniae was 92.0% that was highest among our previous reports. Cefpirome, carbapenems, VCM, teicoplanin (TEIC), LZD and QPR/DPR had MIC90s of < or = 1 microg/mL against PC-intermediate and resistant S. pneumoniae strains. Against all strains of Enterococcus faecalis and Enterococcus faecium, the MICs of VCM and TEIC were under 2 microg/mL, and no resistant strain was detected, suggesting that these agents had excellent activities against these species. 15.9% of E. faecalis strains and 1.2% of E. faecium strains showed intermediate to LZD. 17.1% of E. faecium strains showed intermediate or resistant to QPR/DPR. Against all strains of Clostridium difficile, the MIC of VCM was under 1 microg/mL, suggesting that VCM had excellent activity. Carbapenems showed good activity against Clostridiales, Bacteroides spp., and Prevotella spp., but one strain of Bacteroides fragilis showed resistant to carbapenems. And so, the susceptibility of this species should be well-focused in the future at detecting continuously.

Population pharmacokinetic and pharmacodynamic analysis of linezolid and a hematologic side effect, thrombocytopenia, in Japanese patients.

Linezolid is an antimicrobial agent to treat infections by Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). While effective, linezolid treatment frequently is associated with hematological side effects, especially thrombocytopenia. However, little is known about the mechanism of this side effect and the exposure-response relationship. The present population pharmacokinetic/pharmacodynamic (PPK/PD) study was undertaken to elucidate the factors that determine linezolid levels, the relationship between exposure to linezolid and a decrease in platelet counts, and appropriate dosage adjustments based on exposure levels. In total, 50 patients (135 plasma samples) were used for the PPK analysis. The PPK analysis revealed that renal function and severe liver cirrhosis (Child Pugh grade C) significantly affect the pharmacokinetics of linezolid according to the equation clearance (liter/h)=2.85×(creatinine clearance/60.9)0.618×0.472CIR (CIR indicates cirrhosis status; 0 for noncirrhosis, 1 for cirrhosis patients). Using 603 platelet counts from 45 patients, a PPK/PD analysis with a semimechanistic pharmacodynamic model described the relationship between linezolid exposure and platelet counts quantitatively, and the newly constructed model was validated using external data (776 platelet counts from 60 patients). Simulation indicated considerable risks in patients with insufficient renal function (creatinine clearance, ≤30 ml/min) or severe liver cirrhosis. For these patients, a reduced dosage (600 mg/day) would be recommended for sufficient efficacy (area under the concentration-time curve over 24 h in the steady state divided by the MIC, >100) and safety.

Detection of carbapenem resistance in clinical mucoid Pseudomonas aeruginosa isolates.

Of 19 isolates of mucoid Pseudomonas aeruginosa, 2 isolates showed imipenem resistance conferred by reduced OprD production. Imipenem resistance was detected by the MicroScan broth microdilution and Etest methods, but minimum inhibitory concentrations could not be determined by the Vitek system for an isolate. In cases where susceptibility cannot be determined by the broth microdilution methods, Etest results would be valuable for effective treatment.

Effect of the inoculum size on carbapenem susceptibilities of beta-lactamase-negative, ampicillin-resistant Haemophilus influenzae.

A higher inoculum size of beta-lactamase-positive Haemophilus influenzae is reported to increase minimum inhibitory concentrations (MICs) for beta-lactams. However, the effect of inoculum size of beta-lactamase-negative, ampicillin-resistant H. influenzae (BLNAR) on MICs for carbapenems has not been investigated. This study evaluated the effect of inoculum size on MICs for carbapenems and other beta-lactams in nine clinical isolates of BLNAR. The MICs were determined by both the standard method described by the Clinical and Laboratory Standards Institute (final inoculum size of 5 x 10(5) colony-forming units [CFU]/ml) and a modified method (final inoculum size of 5 x 10(6) CFU/ml) using viable cell counts. The findings showed that the higher inoculum size increased MICs for imipenem, meropenem, panipenem, biapenem, ampicillin, ceftazidime, and ceftriaxone. The inoculum effect (4 log(2) dilution or a greater increase in the MIC) with imipenem, meropenem, panipenem, and biapenem was found in three, five, two, and two isolates, respectively. The magnitude of the inoculum effect for panipenem significantly increased with the levels of MICs, but correlation between them for the others was not statistically significant. The mutations of penicillin-binding protein genes had little relevance to the reduced susceptibility to carbapenems or to the magnitude of the inoculum effect. These results suggest that MIC determination using turbidity can produce interpretive errors in the antimicrobial susceptibility testing of BLNAR for carbapenems because of their inoculum effect. Thus, accurate adjustment of inoculum size, such as viable cell count, is helpful for confirming the true MICs when the isolates are interpreted as "resistant" by turbidity-based MIC determination.

BK virus nephropathy: clinical experience in a university hospital in Japan.

OBJECTIVES: To review the medical records of patients with BK virus nephropathy (BKVN) following kidney transplantation in our institution. METHODS: We screened patients for decoy cells using urine cytology, assessed serum creatinine levels, and conducted a graft biopsy, as well as assessed the presence of plasma BK virus DNA by quantitative real-time polymerase chain reaction. The treatment of BKVN was based on the decreased use of immunosuppressants. RESULTS: Overall, six male patients were studied (mean age 40.8 years, range 18-58; mean donor age 45.2 years, range 15-67). A positive urine cytology screen led to the subsequent detection of plasma BK virus DNA in the five patients with urine cytology results positive for decoy cells. In the four patients in whom plasma BK virus DNA was detected, a maximum value of DNA of > or = 10 000 copies/mL was observed. Time elapsed from transplantation to BKVN diagnosis ranged from 3 to 62 months. Although the two cadaver grafts were lost, the loss was not due to any effects directly associated with BKVN. The other four grafts are still functioning with a mean creatinine level of 1.8 mg/dL. Most of the patients with BKVN were regarded as being in a state of heightened immunosuppression. BK virus transition to blood was prevented in one patient. CONCLUSIONS: Early diagnosis of BKV infection with reduction of immunosuppression may potentially counter BK viremia and retard progression of BKV nephropathy. Decoy cell screening by urine cytology as well as plasma BK virus DNA screening should be considered in addition to the required graft biopsy in kidney transplant recipients, particularly in those with impaired graft function.

Fluoroquinolone resistance in clinical isolates of Klebsiella oxytoca.

BACKGROUND: Prevalence of fluoroquinolone-resistant Klebsiella oxytoca has been reported worldwide. METHODS: We recovered ten clinical K. oxytoca isolates from patients with acute cystitis, asymptomatic bacteriuria or acute bacillary diarrhea in Japan. Out of ten isolates, one fluoroquinolone-susceptible isolate was included as a control. Fluoroquinolone resistance was characterized genetically by PCR and DNA sequencing methods. Outer membrane protein (OMP) profiles were determined by SDS-PAGE. RESULTS: In nine clinical isolates of levofloxacin-resistant K. oxytoca, nucleotide sequences in the quinolone-resistance-determining regions showed amino acid mutations such as Thr83Ile and Asp87Gly in GyrA and Ser80Ile in ParC. Combined effects of reduced 36-kDa OMP production and amino acid mutations in GyrA and ParC were shown by two K. oxytoca isolates exhibiting higher minimum inhibitory concentrations for fluoroquinolones than other fluoroquinolone-resistant isolates. CONCLUSIONS: In clinical K. oxytoca isolates, the various mechanisms of fluoroquinolone resistance may include reduced 36-kDa OMP production as well as GyrA and ParC mutations.

Molecular characterization of 8-methoxyfluoroquinolone resistance in a clinical isolate of methicillin-resistant Staphylococcus aureus.

BACKGROUND: Activity of gatifloxacin against clinical isolates of fluoroquinolone-resistant Staphylococcus aureus is more potent than that of other fluoroquinolones such as norfloxacin and levofloxacin. To date, few reports have described high-level resistance to gatifloxacin in clinical isolates of S. aureus, although in vitro studies have shown that mutations in both DNA gyrase and topoisomerase IV were required for gatifloxacin resistance in S. aureus. METHODS: Minimum inhibitory concentrations were determined for fluoroquinolones and other antimicrobials in a methicillin-resistant S. aureus isolate that was cultured from blood of a patient with septicemia. Fluoroquinolone resistance was characterized by DNA sequencing and microbiologic assay. RESULTS: The isolate showed high-level resistance to fluoroquinolones including an 8-methoxyfluoroquinolone, gatifloxacin (minimum inhibitory concentration 64 microg/ml). Amino acid mutations of Ser80Tyr and Glu84Lys in GrlA and Ser84Leu and Ser85Pro in GyrA were possibly related to this resistance in methicillin-resistant S. aureus HU2000-062, although efflux may play a minor role in resistance as well. CONCLUSION: GyrA and GrlA mutations mainly conferred to 8-methoxyfluoroquinolone resistance in this isolate.

[Comparison of susceptibilities for fosfomycin determined by various methods in clinical isolates in 2003 -2004].

Antimicrobial susceptibilities for fosfomycin (FOM), cephalexin, cefpodoxime, cefdinir, cefditren, ampicillin, sulbactam/ampicillin, imipenem (IPM), panipenem, meropenem (MEPM), biapenem, levofloxacin (LVFX), gatifloxacin, pazufloxacin, prulifloxacin and sulfamethoxazole/trimethoprim were determined by an agar dilution method using Mueller-Hinton agar (MHA) in Escherichia coli, Klebsiella spp., Serratia marcescens, Citrobacter spp., Enterobacter spp. and Proteus mirabilis, which were isolated from patients in 2003-2004. Those for FOM were determined by the agar dilution methods using MHA containing glucose-6-phosphate (G6P) under aerobic conditions, MHA under anaerobic conditions and nutrient agar under aerobic conditions. Those for FOM, LVFX, IPM and MEPM were also determined by an Etest method. The results by the agar dilution method showed that carbapenems had good antibacterial activities in all isolates, whereas MIC ranges for other antimicrobials were broad. Our results showed that the agar dilution method for FOM using MHA containing G6P under aerobic conditions provided reliable MICs in E. coli, which agreed with data previously reported. The results by the agar dilution method for LVFX, IPM and MEPM showed the high rate of agreement compared with those by the Etest method. In E. coli, the results for FOM by the agar dilution method using MHA containing G6P showed the high rate of agreement compared with the Etest results, although the rate was affected by bacterial species and culture conditions in various ways.

[Nationwide surveillance of parenteral antibiotics containing meropenem activities against clinically isolated strains in 2006].

The antibacterial activity of meropenem (MEPM) and other parenteral antibiotics against clinical isolates of 876 strains of Gram-positive bacteria, 1764 strains of Gram-negative bacteria, and 198 strains of anaerobic bacteria obtained from 30 medical institutions during 2006 was measured. 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. 2. As for Pseudomonas aeruginosa, all of the MEPM-resistant strains were resistant to imipenem (IPM). MEPM showed low cross-resistant rate both againt IPM-resistant P. aeruginosa (41.8%) and ciprofloxacin-resistant P. aeruginosa (33.3%). 3. The proportion of extended-spectrum beta-lactamase (ESBL) strains was 4.3% (6 strains) in Escherichia coli, 1.1% (1 strain) in Citrobacter freundii, 21.7% (5 strains) in Citrobacter koseri, 3.1% (4 strains) in Klebsiella pneumoniae, 3.3% (3 strains) in Enterobacter cloacae, 0.8% (1 strain) in Serratia marcescens, and 4.9% (2 strains) in Providencia spp. The proportion of metallo-beta-lactamase strains was 3.1% (10 strains) in P. aeruginosa. 4. Of all species tested, there were no species, 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 at present, 11 years after available for commercial use.

Digoxin Attenuates Murine Experimental Colitis by Downregulating Th17-related Cytokines.

BACKGROUND: Digoxin, a cardiac glycoside used for the treatment of heart failure, was reported to inhibit the retinoid-related orphan receptor gamma t (RORγt) and attenuate the severity of experimental autoimmune encephalomyelitis and arthritis in mice. However, the effects of digoxin in a mice model of inflammatory bowel disease have not been elucidated. METHODS: Colitis was induced in severe combined immunodeficiency mice by adoptive transfer of CD45RB CD4 T cells. Digoxin or a vehicle was injected into mice with colitis intraperitoneally every other day and changes in body weight were evaluated. After 6 to 8 weeks, the treated mice were killed and evaluated for histological score, T-cell subset, and cytokine messenger RNA (mRNA) expression in the colonic tissue. RESULTS: Wasting disease and histological damage were significantly attenuated in digoxin-treated mice with colitis compared with those in the vehicle-treated mice. In addition, the mRNAs of Th17-related cytokines were downregulated, whereas those of interleukin-10 were upregulated in the colonic mucosa of digoxin-treated mice. However, unexpectedly, the mRNA expression level of tumor necrosis factor alpha did not decrease in the colonic mucosa of digoxin-treated mice with colitis. This observation suggests that digoxin may ameliorate colitis by a tumor necrosis factor alpha-independent pathway. CONCLUSIONS: This study has shown for the first time that treatment with digoxin can ameliorate murine experimental colitis. This finding suggests that the suppression of Th17 using reagents such as digoxin could be effective in treating Crohn's disease refractory to anti-tumor necrosis factor alpha therapy.

Acute peritonitis and salpingitis associated with streptococcal toxic shock syndrome caused by Lancefield group G alpha-haemolytic Streptococcus dysgalactiae subsp. equisimilis.

The authors treated a patient for what appears to be the first reported occurrence of acute peritonitis and salpingitis associated with streptococcal toxic shock syndrome (STSS). This was caused by Lancefield group G alpha-haemolytic Streptococcus dysgalactiae subsp. equisimilis TKCH2004-001. The isolate showed M protein type stc36 and carried the spegg gene. To the best of the authors' knowledge, the present report represents the first case of STSS complicating acute peritonitis and salpingitis caused by Lancefield group G alpha-haemolytic S. dysgalactiae subsp. equisimilis.

Rapid detection of fluoroquinolone resistance by isothermal chimeric primer-initiated amplification of nucleic acids from clinical isolates of Neisseria gonorrhoeae.

To ensure a complete response to fluoroquinolone therapy against Neisseria gonorrhoeae infections, rapid susceptibility determinations are required. We assessed a new approach, an isothermal chimeric primer-initiated amplification of nucleic acids (ICAN)/hybrid-chromatography method to detect rapidly fluoroquinolone resistance in N. gonorrhoeae. Comparison of the amplification results with fluoroquinolone minimum inhibitory concentrations (MICs), which were determined by an agar dilution method, showed that the new method accurately determined fluoroquinolone resistance in all ciprofloxacin- and/or gatifloxacin-resistant isolates, but agreed with results based on MICs in only 6 of 8 (75.0%) ciprofloxacin-susceptible and 7 of 12 (58.3%) gatifloxacin-susceptible isolates. Our results suggest that this method can rapidly and reliably detect point mutations in the gyrA gene as well as fluoroquinolone resistance in resistant isolates of N. gonorrhoeae.

Two patients with all-trans retinoic acid-resistant acute promyelocytic leukemia treated successfully with gemtuzumab ozogamicin as a single agent.

Acute promyelocytic leukemia (APL) cells express a considerable level of CD33, which is the target of gemtuzumab ozogamicin (GO), and a significantly lower level of P-glycoprotein (P-gp). Therefore, GO is predicted to be a successful treatment for APL. In this article, we report on the GO treatment of 2 patients with APL, who had fully relapsed after induction therapy with all-trans retinoic acid (ATRA) following chemotherapy. Both patients had relapsed 3 times and were resistant to reinduction therapy with ATRA. GO (9 mg/m2) was administered on days 1 and 15. After GO treatment, both patients achieved complete hematologic and molecular remission. GO may be another promising agent for the treatment of ATRA-resistant relapsed APL when given as salvage chemotherapy.

Pilot study of arbitrarily primed PCR-single stranded DNA conformation polymorphism analysis for screening genetic polymorphisms related to specific phenotypes.

BACKGROUND: To investigate relationships between phenotypes and genotypes is not simple. We propose a phenotype-to-genotype screening strategy and pooled DNA system. As a pilot study of this strategy, we used arbitrarily primed polymerase chain reaction (AP-PCR) in combination with single-stranded DNA conformation polymorphism (SSCP) to screen for genetic polymorphisms associated with longevity. METHODS: Study subjects were separated into 3 age groups, individuals aged >100 years, 90-99 years and 60-69 years. Genomic DNAs were prepared from each individual, pooled to represent the 5 study groups, and then the pooled genomic DNAs were subjected to AP-PCR-SSCP analysis. RESULTS: We found 1 SNP more frequently in senior citizens with longevity. The genotype frequency of the 82133G>A polymorphism of human chromosome 3 clone RP11-61K12 (AC011199) differed significantly (P=0.0189, Fisher's exact test) between older subjects (>90 years) and younger subjects (<70 years). It is noteworthy that the strategy we describe herein was useful for identifying an SNP that showed statistically significant differences in its distribution across the subject groups. CONCLUSIONS: The pooled DNA strategy and quantitative genotype discrimination can also be applied to screening for the relationship between phenotype and genotype more effectively.

[In vitro susceptibilites to levofloxacin and various antibacterial agents of 11,475 clinical isolates obtained from 52 centers in 2002].

The susceptibilities of bacteria to fluoroquinolones (FQs), especially levofloxacin, and other antimicrobial agents were investigated using 11,475 clinical isolates collected in Japan during 2002. Methicillin susceptible staphylococci, Streptococcus pyogenes, Streptococcus pneumoniae, Moraxella catarrhalis, the family of Enterobactericeae, Haemophilus influenzae and Acinetobacter spp. exhibited stable and high susceptibilities to FQs. The rate of FQs-resistant MRSA was 80 approximately 90%, being markedly higher than that of FQs-resistant MSSA. The FQs-resistance rate of MRCNS was also higher than that of MSCNS, however, it was lower than that of MRSA. No FQs-resistant clinical isolates of Salmonella spp. were detected in any of the surveys. Thirteen of Escherichai coli 696 isolates, 8 of Klebsiella pneumoniae 630 isolates and 33 of Proteus mirabilis 373 isolates produced extended-spectrum beta-lactamase (ESBL), furthermore 6 of 13 in E. coli, 1 of 8 in K. pneumoniae and 14 of 31 ESBL-producing isolates, and in P. mirabilis were FQs resistant. Attention should be focused in the future on the emergence of ESBL in relation to FQs resistance. The rate of FQs-resistant P. aeruginosa isolated from urinary tract infection (UTI) was 40 approximately 60%, while 15 approximately 25% of isolates from respiratory tract infection (RTI) were resistant. IMP-1 type metallo beta-lactamase producing organisms were found in 49 of P. aeruginosa 1,095 isolates, 7 of S. marcescens 586 isolates and 4 of Acinetobacter spp. 474 isolates, respectively. Glycopeptide-resistant enterococci or S. aureus was not found.

[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.

Characterization of Pseudomonas aeruginosa isolates from patients with urinary tract infections during antibiotic therapy.

We characterized susceptibilities and genotypes in a series of Pseudomonas aeruginosa isolates from five cases of urinary tract infections (UTIs) to evaluate clonal shifts of carbapenem resistance. In one case, a series of isolates showed different susceptibility patterns for carbapenems but an identical genotype. In another case, genotypes varied among 4 P. aeruginosa isolates from recurrent UTIs over 9 months. Although the patient had been treated with no antibiotic immediately before isolation, the susceptibility patterns for carbapenems and ceftazidime varied. Further analysis in these two cases of outer membrane protein profiles showed that loss of OprD production resulted in reduced susceptibilities to carbapenems in all of the carbapenem-resistant isolates. Loss of OprD production was likely due to oprD gene inactivation in both of cases, since the carbapenem-resistant isolates showed no cross resistance to levofloxacin and chloramphenicol compared with the carbapenem-susceptible isolates. There was another case in which all isolates showed similar susceptibility patterns for carbapenems and ceftazidime, and an identical genotype during the intermittent use of antibiotics over 5 months. In two cases, a single course of antibiotic therapy resulted in eradication of P. aeruginosa. Our results suggest that clonal shifts of carbapenem resistance in P. aeruginosa may result from loss of OprD during antibiotic treatment. Therefore, it is important for clinicians to monitor susceptibilities to antibiotics, especially carbapenems, in P. aeruginosa isolated during therapy.