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Tuberculosis has attracted increased attention worldwide due to its high morality and its resistance to treatment with traditional antibacterial drugs. The l,d-transpeptidase LdtMt2 confers resistance to traditional β-lactams and is considered a target for anti-Tuberculosis treatment. Carbapenems are proposed to inhibit Mycobacterium tuberculosis by repressing the activity of LdtMt2. The interaction mechanisms between LdtMt2 and carbapenems have been revealed by LdtMt2-carbapenem adduct structures along with various biochemical assays. Interestingly, the lack of the 1-β-methyl group in imipenem may be related to its high binding ability to LdtMt2. However, there is limited evidence on the interaction mode of LdtMt2 and panipenem, another carbapenem lacking the 1-β-methyl group. Herein, we identified the biochemical features of panipenem binding to LdtMt2. We further suggest that the presence of the 1-β-methyl group in carbapenems is indeed related to the ligand affinity of LdtMt2 and that the presence of the Y308 and Y318 residues in LdtMt2 stabilized the conformation of the LdtMt2-carbepenem adduct. Our research provides a structural basis for the development of novel carbapenems against L,D-transpeptidases.

Purpose To reduce Clostridioides difficile infection (CDI), we implemented interprofessional antimicrobial, infection control, and diagnostic stewardship (ipAS) conducted by physicians/pharmacists, infection control nurses, and medical technologists, respectively. As a numerical indicator for ipAS, we used antimicrobial use density (AUD) in an 8-year study to validate its efficacy in CDI reduction. Patients and methods This was an observational study. CDI was defined as stool samples or C. difficile isolates containing toxin A and/or B from a patient with diarrhea occurring three or more times per day. From 2011-2018 at a 10-ward single site the subjects were in-patients with CDI, and the following data were collected: AUDs for 23 antibiotics, and antimicrobial test results. By 2015, we had established ipAS, consisting of culture submission before the administration of broad-spectrum antimicrobials, the promotion of point-of-care testing for diagnosis-based antimicrobials, perioperative prophylactic antibiotics, intervention at positive diagnosis of blood culture, team round for diarrhea, and inspection on contact precautions and disinfection in CDI cases. The study outcomes included annual numbers of CDI patients and blood culture sets. We compared annual AUDs between former (2011-14) and latter (2015-18) periods using Kruskal-Wallis tests and examined the correlation between AUDs and CDI numbers. Results Of a total 50,970 patients, 1,750 patients underwent C. difficile toxin tests, of whom 171 patients (9.8%) were positive for CDI. Between the former and latter periods, AUDs for flomoxef (11.96 to 2.71 by medians), panipenem/betamipron (0.30 to 0.00), and clindamycin (3.87 to 2.19) significantly decreased (P

Carbapenems are among the most commonly used and the most efficient antibiotics since they are relatively resistant to hydrolysis by most β-lactamases, they target penicillin-binding proteins, and generally have broad-spectrum antibacterial effect. In this review, we described the initial discovery and development of carbapenems, chemical characteristics, in vitro/in vivo activities, resistance studies, and clinical investigations for traditional carbapenem antibiotics in the market; imipenem-cilastatin, meropenem, ertapenem, doripenem, biapenem, panipenem/betamipron in addition to newer carbapenems such as razupenem, tebipenem, tomopenem, and sanfetrinem. We focused on the literature published from 2010 to 2016.

Forty clinical isolates of multidrug-resistant Pseudomonas aeruginosa were obtained in a medical setting in Hanoi, Vietnam. Whole genomes of all 40 isolates were sequenced by MiSeq (Illumina), and phylogenic trees were constructed from the single nucleotide polymorphism concatemers. Of these 40 isolates, 24 (60.0%) harbored metallo-β-lactamase-encoding genes, including bla IMP-15 , bla IMP-26 , bla IMP-51 , and/or bla NDM-1 . Of these 24 isolates, 12 harbored bla IMP-26 and belonged to sequence type 235 (ST235). Escherichia coli expressing bla IMP-26 was significantly more resistant to doripenem and meropenem than E. coli expressing bla IMP-1 and bla IMP-15 . IMP-26 showed higher catalytic activity against doripenem and meropenem than IMP-1 and against all carbapenems tested, including doripenem, imipenem, meropenem, and panipenem, than did IMP-15. These data suggest that clinical isolates of multidrug-resistant ST235 P. aeruginosa producing IMP-26 with increased carbapenem-hydrolyzing activities are spreading in medical settings in Vietnam.

Carbapenem-resistant Enterobacteriaceae (CRE) are increasing globally. Particularly, carbapenemase-producing Enterobacteriaceae (CPE) are of concern. Rapid and accurate detection of these strains is critical for appropriate antimicrobial use and hospital infection control. In the present study, criteria for CPE screening were examined using a carbapenem susceptibility disk. Carbapenemase producers showed minimal inhibition zones for faropenem (5 μg): 6-12 mm (mean: 6.9 mm). Some strains with the IMP-6 genotype showed inhibition zones of >30 mm for imipenem (10 μg) and biapenem (10 μg). All strains that formed inhibition zones for FRPM had the IMP-6 genotype. The cut off values of carbapenemase-producers, determined by ROC analysis, were 12 mm for FRPM, 24 mm for meropenem (10 μg), 29 mm for BIPM, 25 mm for doripenem (10 μg), 26 mm for IPM, and 24 mm for panipenem (10 μg). Thus, the sensitivity was the highest (100%) for FRPM. Specificities were 93.44% for MEPM and DRPM and 85.25% for FRPM. Consequently, a drug sensitivity test using FRPM (5 μg) disks facilitates simple and accurate CPE screening.

The present study aimed to investigate the bacterial distribution, changes in drug susceptibility and clinical characteristics in patients with diabetic foot infection (DFI). A retrospective analysis of 216 patients with DFI treated at Xinxiang Central Hospital between 2013 and 2016 was carried out to analyze the bacterial distribution, changes of susceptibility and clinical characteristics. A total of 262 pathogenic strains were isolated from 216 patients with DFI. Among them, 43.13% exhibited Gram-positive (G+) bacteria, 45.04% exhibited Gram-negative (G−) bacteria and 11.83% was other. Between 2013 and 2016, the susceptibility of pathogenic bacteria to common antibacterial drugs showed a declining trend year by year. G+ bacteria had high susceptibility to vancomycin and acetazolamide; while G− bacteria showed high susceptibility to dibekacin, panipenem and biapenem. The main clinical symptoms of the 216 patients included edema (98.61%), purulent secretions (62.96%) and lower extremity sepsis (58.80%). The top three complications of the 216 cases were lower extremity vascular disease (58.80%), peripheral neuropathy (39.81%) and kidney disease (26.39%). Logistic regression analysis showed that age [odds ratio (OR), 2.708; P=0.005], previous use of antibacterial drugs (OR, 3.816; P=0.007) and application of the third generation cephalosporins (OR, 3.014; P=0.008) were the independent risk factors of drug resistance in patients with DFI (P

Introduction Streptococcus pneumoniae is one of the most common bacteria causing otorhinolaryngological infections, such as acute otitis media and upper respiratory tract infection. Our group surveyed the drug susceptibility profile of S. pneumoniae isolates from otorhinolaryngology patients. Materials and methods A total of 41,069 S. pneumoniae isolates were detected at Miyagi Medical Association Health Center between May 2001 and December 2012. Specimens were obtained from patients at 40 otorhinolaryngology outpatient clinics in Miyagi Prefecture, Japan. The minimum inhibitory concentrations (MICs) of 8 antimicrobial agents were measured using the broth microdilution method according to Clinical and Laboratory Standards Institute guidelines. Results In children aged 0–2 years old, the MIC50 values of penicillins decreased after 2010 (PCG: 1 μg/ml (2010) to 0.06 μg/ml (2012); ABPC: 1 μg/ml (2010) to 0.25 μg/ml (2012)). The prevalence of penicillin-resistant S. pneumoniae (PRSP) decreased from 35.2% (2010) to 14.6% (2012) in rhinorrhea specimens and from 43.4% (2010) to 14.3% (2012) in otorrhea specimens. Susceptibility to cephems (ceftriaxone and cefditoren) and carbapenems (panipenem) also showed improvement after 2010. For macrolides (clarithromycin) and lincosamides (clindamycin), MIC50 values increased in all age groups during the study period, and a high level of resistance was seen until 2012. There were no marked changes of susceptibility to fluoroquinolones (LVFX) during the study period. Conclusion Improvement of susceptibility of S. pneumoniae to β-lactams occurred after 2010 in Miyagi Prefecture, Japan.

The efficacy of the antiepileptic drug VPA is decreased by co-administered carbapenems (CBPMs). The mechanism of CBPM selective inhibition of acylpeptide hydrolase (APEH) hydrolysis of VPA-glucuronide (VPA-G) to VPA is unclear due to the lack of APEH structural information. Here we performed homology modeling of the three-dimensional structure of APEH and subsequent docking simulations with a modeled structure to understand this mechanism. Docking simulations indicated that four groups of binding structures were involved in the binding of VPA-G, panipenem, and meropenem to APEH, but only one or two binding structures were involved in the binding of meropenem with an open β-lactam ring structure and other antibiotics involving ampicillin. One of the four VPA-G binding structures was close enough to the APEH catalytic triad to facilitate VPA-G hydrolysis. This binding structure was also the most stable binding structure for panipenem, suggesting potential inhibition of VPA-G hydrolysis by panipenem. Fragment molecular orbital calculations of interaction energies of amino acid residues of APEH with VPA-G, panipenem, and meropenem indicated that the binding structure for panipenem closest to the catalytic triad is stabilized upon APEH interaction. These data suggest that APEH binding characteristics with CBPMs may help explain the selective inhibition of APEH by CBPMs.

The emergence of Gram-negative "superbugs" exhibiting resistance to known antibacterials poses a major public health concern. Low molecular weight Gram-negative antibacterials are believed to penetrate the outer bacterial membrane (OM) through porin channels. Therefore, intracellular exposure needed to drive antibacterial target occupancy should depend critically on the translocation rates through these proteins and avoidance of efflux pumps. We used electrophysiology to study the structure-translocation kinetics relationships of a set of carbapenem antibacterials through purified porin OmpC reconstituted in phospholipid bilayers. We also studied the relative susceptibility of OmpC+ and OmpC- E. coli to these compounds as an orthogonal test of translocation. Carbapenems exhibit good efficacy in OmpC-expressing E. coli cells compared with other known antibacterials. Ertapenem, which contains an additional acidic group compared to other analogs, exhibits the fastest entry into OmpC (k(on) ≈ 2 × 10(4) M(-1) s(-1)). Zwitterionic compounds with highly polar groups attached to the penem-2 ring, including panipenem, imipenem and doripenem exhibit faster k(on) (>10(4) M(-1) s(-1)), while meropenem and biapenem with fewer exposed polar groups exhibit slower k(on) (∼5 × 10(3) M(-1) s(-1)). Tebipenem pivoxil and razupenem exhibit ∼13-fold slower k(on) (∼1.5 × 10(3) M(-1) s(-1)) than ertapenem. Overall, our results suggest that (a) OmpC serves as an important route of entry of these antibacterials into E. coli cells; and (b) that the structure-kinetic relationships of carbapenem translocation are governed by H-bond acceptor/donor composition (in accordance with our previous findings that the enthalpic cost of transferring water from the constriction zone to bulk solvent increases in the presence of exposed nonpolar groups).

Carbapenems are an effective tool to treat complicated bacterial infections. This review aims to summarize the available information on carbapenems in neonates to guide clinicians on drug choice and indications in neonates. Moreover, identification of knowledge gaps may stimulate researchers to design studies to further improve pharmacotherapy in neonates. To do so, a bibliographic search [infant/newborn and meropenem, imipenem, panipenem, ertapenem, doripenem or imipenem] was performed (PubMed, EMBASE) and public clinical trial registries (clinicaltrials.gov, EU registry) were searched to summarize the available information. Carbapenem clearance in neonates is low. Variability relates to maturation (weight, age) and renal function (creatinine clearance), while observations in neonates with renal failure are absent. Pharmacodynamics are almost exclusively limited to meropenem, and the available information will further increase (NeoMero-1-2, necrotizing enterocolitis, meningitis). Finally, there are also some ongoing doripenem pharmacokinetics (PK) studies in neonates. It was concluded that observations on carbapenems in neonates are limited, but studies (NeoMero, doripenem) are ongoing. Until this information becomes available, off label prescription of meropenem seems to be the most reasonable choice when a carbapenem is appropriate. Knowledge gaps relate to PK in neonates with renal failure and to the potential benefit of prolonged compared to short duration of infusion.

It is well known that carbapenem-resistant mutations in penicillin-binding proteins (PBPs) are not observed in most Gram-negative bacteria under either clinical or experimental conditions. To understand the mechanisms involved in carbapenem resistance, this study constructed a mutS- and tolC-deficient Escherichia coli strain, which was expected to have elevated mutation frequencies and to lack drug efflux. Using this mutant, carbapenem-resistant strains with target mutations were successfully and efficiently isolated. The mutations T547I/A, M574I and G601D were identified in the PBP2 gene. Meropenem (MEPM)-resistant strains with the PBP2 T547I mutation showed fourfold increased resistance to 1-β-methyl-substituted carbapenems, such as doripenem, MEPM and biapenem, but not to non-substituted carbapenems such as imipenem and panipenem and other β-lactams. In addition, resistance resulting from the G601D mutation was limited to MEPM, whilst the M574I mutation conferred resistance to MEPM, imipenem and panipenem. This is the first report, to the best of our knowledge, that E. coli also has a carbapenem-resistance mechanism as a result of PBP2 mutations, and it provides insight into the resistance profiles of PBP2 mutations to carbapenems with and without the 1-β-methyl group.

The nasopharyngeal flora is generally thought to be a major reservoir for bacterial pathogens of respiratory tract infections in children. We surveyed the bacterial flora in the nasopharynx of 261 outpatients aged 0 to 6 yeas who visited the Department of Otorhinolaryngology and/or Pediatrics from 2005 through 2010. We obtained 118 Haemophilus influenzae (H. influenzae) isolates, 116 Streptococcus pneumoniae (S. pneumoniae) isolates, 44 Staphylococcus aureus (S. aureus) isolates, and 40 Moraxella catarrhalis isolates, and analyzed them by antibiotic susceptibility testing. The overall carriage rates of the H. influenzae strains and S. pneumoniae strains were 45.2% (118/261) and 44.4% (116/261), respectively. The percentages of ampicillin-resistant H. influenzae strains, penicillin-resistant S. pneumoniae strains and methicillin-resistant S. aureus were 80.5% (95/118), 55.2% (64/116) and 40.9% (18/44), respectively. The H. influenzae strain was susceptible to cefditren pivoxil, minocycline, and levofloxacin, while the S. pneumoniae strain was susceptible to cefditren pivoxil, cefotaxime sodium, and panipenem/betamipron. The percentage of ampicillin-resistant H. influenzae strains was invariably high in all years. On the other hand, the percentage of penicillin-resistant S. pneumoniae strains was highest in 2008, and gradually decreased after that. The recovery of susceptibility to penicillin in clinical isolates of S. pneumoniae may reflect recent enlightenment in the appropriate use of antimicrobial drugs.

An evaluation committee studied the relationship between initial treatment drug and prognosis in 339 of 466 subjects with bacterial meningitis treated at 108 institutions between April 2004 and January 2007, after excluding those with uncertain diagnosis or non-assessable records. Prognosis was considered unfavorable if meningitis sequelae such as quadriplegia, deafness, or epilepsy were present in 3- month follow-up; Based on this definition, 43 (12.7%) had a poor prognosis. No significant relationship was seen between unfavorable prognosis and age or causative pathogen. More had an unfavorable prognosis if treatment was initiated 4 days or later after onset. The percentage with an unfavorable prognosis was 6.4% (4/64) in the group administered combined panipenem/betamipron (PAPM/BP) plus ceftriaxone (CTRX), 10.5% (6/57) administered MEPM plus cefotaxime (CTX), 14.0% (7/50) administered meropenem (MEPM) plus CTRX, and none of the 23 administered CTRX alone. The percentage with an unfavorable prognosis was 26.2% (11/42) in those administered MEPM, significantly higher than that in those administered PAPM/BP plus CTRX, MEPM plus CTX, or CTRX alone (p < 0.05). We concluded that in initial treatment, it would be more desirable to use MEPM combined with another drug than alone.

Bacteria producing extended-spectrum beta lactamase (ESBL) are detected mainly in adult urinary specimens, and are believed to cause hospital-acquired infection due to their resistance to many drugs. The incidence of community-acquired infection due to such bacteria is increasing, but few cases of infant upper urinary tract infection (UUTI) have been reported in Japan. We treated four infants with UUTI caused by ESBL-producing Escherichia coli, as determined by genotyping. Using medical records, we retrospectively evaluated the clinical course, antibiotic use and efficacy, antimicrobial susceptibility results, and the presence of underlying disease. One of the four had been previously hospitalized for occult bacteremia. Two developed UUTI after antibiotic treatment, indicating that previous antibiotic use may have been a risk factor in these cases. We could not identify the infection route in all cases. Two of the four had bilateral vesicoureteral reflux (VUR). Renal scintigraphy was done in three. Although an initial dimercaptosuccinic acid (DMSA) defect was detected in all four, only one had renal scarring. E. coli isolates from all four showed PCR signals for blaCTX-M-; one isolate positive for the blaCTX-M3 group and three positive for blaCTX-M14. Antimicrobial susceptibility test results showed all isolates to be resistant to cephalosporins, but discrepancies existed between antimicrobial susceptibility results and actual clinical efficacy. Clinically, cefazolin (CEZ) was effective in two subjects and ceftazidime (CAZ) effective in one. Panipenem/betamipron (PAPM/BP) was effective in one. None of the four developed sepsis or meningitis. Post hospitalization antibiotic prophylaxis showed that none of the four has had UUTI recur. Japan's ESBL-producing bacterial infection incidence is increasing, so medical professionals should watch for such UUTI even in first-case occurrence in infants.

Here, we describe the case of a 56-year-old female patient who was diagnosed with an anterior mediastinal cyst measuring 26 × 16 mm in size. An endobronchial ultrasound-guided transbronchial needle aspiration was performed, and punctures occurred three times. The patient was then prescribed cefditoren pivoxil. Three days after the procedure, the patient developed infective mediastinitis. Panipenem/betamipron, clindamycin, and human immunoglobulin were administered, and her symptoms improved over 2 weeks. Five months after developing mediastinitis, surgical resection of the cyst was performed with inverted L-shaped mini-sternotomy. The cystic lesion strongly adhered to the surrounding tissues. The final pathological diagnosis was a bronchogenic cyst. Endobronchial ultrasound-guided transbronchial needle aspiration is not a completely sterile procedure and can lead to severe infective complications in the mediastinum. Although this procedure may not be contraindication for use with mediastinal cystic lesions, physicians must take into account the risk of severe infective complications.

Summary Pseudomonas aeruginosa is an opportunistic pathogen, and ubiquitously found in natural environments. However, details on difference between clinical and environmental isolates have not been reported enough. In this study, we defined existence of marine specific genogroup and different drug susceptibility among isolates from clinical, river and coastal seawaters. Pseudomonas aeruginosa were isolated by using cetrimide kanamycin nalidixic acid agar media and incubation at 42°C, which was specific selection method of this bacterium from the natural aquatic samples. Pulse field gel electrophoresis analysis showed that the levels of genetic variation within P. aeruginosa were different among environmental sites. Pulse field gel electrophoresis also showed a lower diversity within P. aeruginosa in the coastal waters; and coastal strains isolated different sampling points were positioned closely in the same cluster. Most of the aquatic isolates were sensitive to most of the drugs tested and ‘intermediate’ to panipenem on the contrast to the clinical isolates, suggesting that the clinical use of antibiotics affect significantly to the emergence of the drug-resistant P. aeruginosa.

A 79-year-old man consulted us because of left chest pain and fever ranging from 38.0 to 38.9 °C. A chest computed tomography scan showed a mass lesion (φ40 mm) in the left lingular segment, and inflammatory markers were elevated. He was admitted with a diagnosis of lung abscess, and panipenem/betamipron was administered at a dose of 2 g/day, after which the symptoms showed slight transient resolution. However, his body temperature increased again, to more than 39.0 °C, on the eighth day of hospitalization, and a chest radiograph suggested pleuritis as a complication. The antibiotics were changed to teicoplanin (TEIC; 400 mg/day) and meropenem (2.0 g/day). Thoracic drainage and pleural lavage were initiated at the same time. Lactobacillus spp. was detected from the pleural effusion by culture and was considered to be the causative organism, and it was resistant to TEIC. Therefore, the antibiotic was changed, to clindamycin, to which the bacteria was susceptible. No subsequent fever or pleural fluid retention was observed. The patient’s course was good, and he was discharged on day 45 of hospitalization. Subsequently, the causative organism was identified as Lactobacillus rhamnosus by the 16s rRNA sequence. Lactobacillus rhamnosus is rarely pathogenic in humans. Lactobacillus rhamnosus infection mostly occurs in immunosuppressed patients, and only a few cases have been reported in immunocompetent patients. In the present case, the patient was not immunodeficient; however, his lung had an impaired local immunosystem, due to emphysema.

Molecular detection and surveillance of the resistance genes harboured byPseudomonas aeruginosaare becoming increasingly important in assessing and controlling spread and colonization in hospitals, and in guiding the treatment of infections. This study analysed the resistance mechanisms of carbapenem-resistant clinical isolates ofP. aeruginosaand identified the associated integron-borne metallo-β-lactamase (MBL)-encoding genes. Twenty-seven imipenem (IPM)-resistant clinical isolates ofP. aeruginosawere divided into three groups according to their resistance levels to carbapenems. Strains bearingblaIMP-10showed extremely high-level resistance to IPM, with MICs of 512–2048 μg ml−1. By comparison, strains bearingblaIMP-1,blaIMP-7andblaVIM-2showed an intermediate level of resistance, with MICs of 32–256 μg ml−1. The non-MBL-producing strains showed a low level of resistance, with MICs of 8–32 μg ml−1. The same trend in resistance levels was also observed when resistance to other carbapenems, such as meropenem and panipenem, was determined. DNA sequencing showed that the MBL-encoding gene cassettes were carried by class 1 integrons. TheblaIMP-1,blaIMP-7andblaIMP-10gene cassettes were preceded by a hybridPantpromoter, TGGACA-N17-TAAACT, and theblaVIM-2gene cassette was preceded by a weak promoter, TGGACA-N17-TAAGCT. Most of the MBL-encoding genes were linked to one or two resistance genes encoding aminoglycoside-modifying enzymes, such asaac(6′)Iae,aac(6′)II,aacA7,aacC4,aadA1,aadA2andaadA6, highlighting the multidrug-resistant properties of these clinical isolates.

We evaluated the beta-lactamase-producing ability and resistance to 20 antibacterial agents of 448 clinically isolated strains of Haemophilus influenzae accumulated from October 2000 to July 2001 (phase 1) and of 376 different strains accumulated from January to June 2004 (phase 2), from institutions that participated in a nationwide Drug-Resistant Pathogen Surveillance Group in Pediatric Infectious Disease. Between phase 1 and phase 2 the proportion of beta-lactamase-negative ampicillin (ABPC)-susceptible (BLNAS) strains declined from 62.9% to 34.3%; the proportions of beta-lactamase-positive ABPC-resistant (BLPAR) strains were 8.3% and 6.4% in phases 1 and 2, but the proportion of beta-lactamase-negative ABPC-resistant (BLNAR) strains increased from 28.8% in phase 1 to 59.3% in phase 2. Comparison of the MIC(90) values of the antibacterial agents for H. influenzae in phase 1 and phase 2 showed that cefcapene, cefpodoxime, ceftriaxone, panipenem, and clarithromycin kept the same level, while cefdinir, faropenem, and rokitamycin showed 2-fold to 8-fold decreases. With the exception of the above antibiotics, all of the other antibacterial agents tested showed 2-fold to 4-fold increases. The MIC(90) values of the beta-lactam drugs for BLNAR were 2-fold to 32-fold higher than the values for BLNAS. The proportion of BLNAR H. influenzae strains rose dramatically over the 3 years between phases 1 and 2. In relation to age, prior administration of antibacterial agents, and attendance at a day nursery as background factors, no significant differences between BLNAS and BLNAR were detected in phase 1. In the phase 2 survey, the proportion of BLNAR strains showed significant differences between children under 3 years and those aged 3 years or more, and there were also significant differences according to whether antibacterial agents, especially beta-lactams, had been administered previously. No significant difference was found in resistant bacteria according to whether or not a child had attended a day nursery.

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.

Among the many different structurally distinct classes of β-lactams, the carbapenem class is regarded as that which is most potent and which has the widest spectrum of antimicrobial activity. Rapidly bactericidal, and demonstrating time-dependent killing, carbapenemes have a spectrum of antimicrobial activity that includes Gram-positive and Gram-negative aerobic and anaerobic pathogens. Their in-vitro activity includes extended-spectrum β-lactamase (ESBL)-producing pathogens and carbapenems are currently considered to be the treatment of choice for serious infections due to ESBL-producing organisms. However, isolates acquiring resistance under treatment have been reported. Imipenem, meropenem and ertapenem are licensed in the European Community and panipenem and biapenem are also available in Japan and South Korea. Other carbapenemes are under development.

Although several high-performance liquid chromatography (HPLC) methods for the determination of serum concentrations of carbapenems have been reported, they are complicated and involve column switching. We established a simple and rapid HPLC method for the determination of serum concentrations of carbapenems, and this method is suitable for routine use in the clinical field. With our HPLC method, the serum concentrations of five commercially available carbapenems could be determined by changing only the methanol/phosphate-buffer ratio in the mobile phase. Serum levels of imipenem, panipenem, and meropenem in mice could be monitored when these carbapenems (20 mg/kg) were administered subcutaneously with cilastatin (20 mg/kg). These results suggest that our simple and rapid HPLC method for the determination of the serum concentrations of carbapenems is useful for pharmacokinetic/pharmacodynamic (PK/PD)-based determination of carbapenem dosage regimens.

We examined the susceptibilities of 100 Neisseria meningitidis strains isolated between 1990 and 2004 to 12 antimicrobial agents, finding the MIC50 to be 0.031 microg/mL and that of MIC90 of benzylpenicillin (PCG), a type of penicillin, to be 0.063 microg/mL. Two strains showed intermediate resistance (MIC of 0.125-0.25 microg/mL). Two strains of the same origin also showed intermediate resistance (0.25-1 microg/mL) to ampicillin (ABPC). For cephems, MIC50 and MIC90 of cefotaxime (CTX) were both 0.004 microg/mL, while the MICs of ceftriaxone (CTRX) were all 0.004 microg/mL, showing the strongest antibacterial spectrum. The three carbapenems surveyed meropenem (MEPM), panipenem (PAPM), and imipenem (IPM) also had a strong antibacterial spectrum in ascending order, with the MIC50 and MIC90 of MEPM, which was lowest, being 0.008 microg/mL and 0.016 microg/mL. Some 97% of MICs for ciprofloxacin (CPFX) were 0.004 microg/mL but 3 strains showed resistance (0.125 microg/mL). No difference was seen between MICs of N. meningitidis strains originated from meningitis patients, patients other than meningitis, and healthy carriers. No difference was seen in MICs by serogroup (A, B, C, Y, W135 and NG).

The serum concentration of valproic acid (VPA) in epilepsy patients decreased by the administration of carbapenem antibiotics, such as meropenem, panipenem or imipenem, to a sub-therapeutic level. Studies to explain the decrease were carried out using almost rats by the following steps: absorption of VPA in the intestine, glucuronidation in the liver, disposition in blood and renal excretion. It is difficult to consider the inhibition of intestinal absorption, because carbapenem antibiotics are intravenously administered and do not reach the intestine at an effective concentration. The liver is the key organ for the decrease of VPA concentration by carbapenem antibiotics, because it has been reported that no decrease of the VPA level by carbapenem was found in hepatectomized rats. The most likely mechanism in liver is the activation of UDP-glucuronosyltransferase by carbapenem antibiotics. We found a 35% increase of VPA-glucuronidation activity by the pre-incubation of human liver microsomes with meropenem. We estimated that this increase fully compensates for the decrease of serum VPA level by carbapenem antibiotics in patients. Meanwhile, we could not find the in vitro activation of CYP2A6, CYP3A4, P-glycoprotein (P-gp, MDR1) and Multidrug resistance-associated protein 2 by pre-incubation with carbapenem antibiotics. Thus, we considered that the activation of VPA glucuronidation by carbapenem antibiotics is a key point in the decrease of plasma VPA level.

In December 2003, a 57-year-old-man was diagnosed as having a hepatic tumor for which he had a hepatectomy. On pathology, the hepatic tumor biopsy specimen was diagnosed as malignant lymphoma. In February 2005, the patient was referred to our hospital because of fever and chest pain. A right pleural effusion was seen on chest X-ray. Microscopic examination of the stained pleural fluid revealed many neutrophils and Gram-negative rods, and Edwardsiella tarda was cultured from the pleural effusion fluid. These findings were consistent with an empyema caused by E. tarda. Therefore, we treated the patient with panipenem/betamipron and thoracic drainage. In this paper, we describe this rare case of empyema caused by E. tarda infection.

We recently reported that the decrease in plasma valproic acid (VPA) level by carbapenem antibiotics (CPs) may partly be due to the increased erythrocyte distribution of VPA. In order to clarify the mechanisms underlying altered VPA distribution in erythrocytes, we examined the role of multidrug resistance-associated proteins (Mrps). The uptake of 2,4-dinitrophenyl-S-glutathione (DNP-SG), a substrate of Mrps, by inside-out vesicles (IOVs) prepared from rat erythrocytes was an ATP-dependent, active process. DNP-SG uptake was mediated by high- and low-affinity transport systems, and was inhibited by various Mrp inhibitors such as probenecid and indomethacin. Glutathione stimulated only the high-affinity transport system. VPA inhibited the low-affinity transport of DNP-SG, while panipenem, a CP, inhibited both high- and low-affinity transport. ATP-dependent, Mrp-mediated transport of methotrexate, another Mrp substrate, in IOVs was also observed, and VPA and various CPs inhibited the transport. The uptake of [(3)H]VPA was examined, and found to be ATP-dependent. ATP-dependent uptake of [(3)H]VPA was inhibited by Mrp inhibitors and panipenem, while the inhibition was not observed in the absence of ATP. These results indicate that VPA and CPs interact with Mrp-mediated transport in erythrocyte membranes, and VPA itself is transported by Mrps, which is inhibited by panipenem. Thus, the increased erythrocyte distribution of VPA by CPs observed under in vivo conditions may partly be explained by their interaction with Mrps in erythrocyte membranes.

Critically ill patients often have complications of acute renal failure induced by severe infection or sepsis. The patients need administration of broad-spectrum antibiotics as well as continuous renal replacement therapy (CRRT). However, there is no uniform pharmacokinetics of antibiotics during the CRRT because CRRT is performed with the various combinations of dialysate flows (Q D ) and ultrafiltrate flows (Q F ). The aims of this study were to estimate the pharmacokinetics of panipenem/beta Mipron (PAPM/BP) and to determine the appropriate treatment regimens for PAPM/BP in critically ill patients undergoing CRRT. In patients with CRRT, the PAPM total clearance (PAPM CL tot ) was calculated as the sum of PAPM clearance dependent on the living body and CRRT and shown as follows: PAPM CL tot (ml/min) = (1.2 CL cre + 66.5) + 0.86 (Q D + Q F ) where CL cre is creatinine clearance. Pharmacokinetic values of PAPM were measured in 4 patients with CRRT. According to these results, the most appropriate treatment regimen regarding PAPM CL tot (ml/min) showed as follows: PAPM CL tot < 80 0.5 g every 12 hours or 1 g every 15 hours PAPM CL tot 80 to 120 0.5 g every 8 hours or 1 g every 12 hours PAPM CL tot 120 to 160 0.5 g every 6 hours or 1 g every 8 hours.

beta-Lactam antibiotics have been suggested to have some degree of convulsive activity and neurotoxicity in experimental animals as well as in clinical situations. We examined the convulsive activities of a new carbapenem antibiotic, (+)-(4R,5S,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-7-oxo-3-[[(3S,5S)-5-[(sulfamoylamino)methyl]-3-pyrrolidinyl]thio]-1-azabicyclo[3.2.0]hept-2-ene-2-carboxic acid monohydrate (doripenem) using several animals and compared them with beta-lactam antibiotics. In intravenous (IV) injection studies, imipenem/cilastatin, at 400/400mg/kg produced seizure discharges on electroencephalogram (EEG) accompanied with clonic convulsions in rats. Meropenem showed only wet dog shaking behavior at 200 and 400mg/kg. Doripenem caused no changes in the EEG and behavior in rats at 400mg/kg. Imipenem/cilastatin IV potentiated the pentylenetetrazol (PTZ)-induced convulsions in mice at 250/250 mg/kg, while meropenem, panipenem/betamipron, cefazolin or doripenem did not cause any marked effects at up to 500 mg/kg. In mouse intracerebroventricular (ICV) injection studies, imipenem, panipenem and cefazolin induced clonic convulsions in a dose-dependent manner in mice. Doripenem and meropenem did not induce convulsions at up to 100 microg/mouse. In dog ICV injection studies, imipenem produced generalized seizure discharge with clonic convulsions at 100 microg/dog. Meropenem also produced spikes or seizure discharges at 100, 300 and 1,000 microg/dog. However, doripenem had no effects on the EEG and behavior in dogs at any doses. In in vitro binding studies, imipenem, panipenem, cefazolin and meropenem inhibited [(3)H]muscimol binding to the GABA(A) receptor in mouse brain homogenates while doripenem did not cause any inhibition at up to 10mM. In addition, doripenem had no influence on the anti-convulsant actions of valproic acid in the PTZ- or bicuculine-induced convulsive model. These results clearly indicate that doripenem has no convulsive activity, suggesting that its neurotoxicity may be negligible in clinical use.

Summary Study objectives We investigated pleural fluid penetration of carbapenem antibiotic agents [imipenem (IPM), panipenem (PAPM), meropenem (MEPM), and biapenem (BIPM)] using an experimental rabbit pleuritis model to clarify the usefulness of the carbapenem agents for the treatment of bacterial pleurisy or pyothorax. Measurements and results Serum and pleural fluid specimens were serially collected at 5, 10, 15, 30, 60, 90, 120, 180, 240, 300, and 360min after antibiotic administration for measurement of antibiotic levels. We investigated each agent alone as well as drug solutions containing each agent and a dehydropeptidase-I-specific inhibitor, cilastatin (CS), to remove the influence of dehydropeptidase-I-related hydrolysis. Groups of animals \( n = 3 \) received each carbapenem agent with or without CS. Serum and pleural fluid antibiotic levels were measured by high-performance liquid chromatography (HPLC). Because C max is not useful for evaluating the antimicrobial effects of carbapenem antibiotic agents due to their dose-dependent antimicrobial activity, we also investigated the AUC, which is correlated with the total drug levels in vivo. Among the drug solutions containing CS, MEPM/CS had the highest pleural fluid AUC 0–360 (1594.8±510.3μgmin/ml), and the highest pleural fluid AUC 0–360 /plasma AUC 0–360 ratio (0.79±0.04). BIPM/CS had the highest plasma AUC 0–360 (3040.1±1525.9μgmin/ml). In pleural fluid AUC 0–360 /plasma AUC 0–360 ratio MEPM/CS was significantly higher than those for the remaining agents. In pleural fluid AUC 0–360 and plasma AUC 0–360 there were no significant differences among these mixed solutions. Conclusions MEPM had the most favorable pleural fluid penetration. Pleural fluid penetration should be examined in infection models and in clinical trials.

Salmonella Enteritidis often causes food poisoning. In this study, an extremely rare case of cervical abscess caused by S. Enteritidis is reported. In January 2003, a 44-year-old man visited our hospital with swelling of the left submandibular region. He had been suffering from a severe diabetic condition but had neglected to seek medical attention. An incision was made at the abscess to drain the pus from which only S. Enteritidis was isolated. This finding led to the discovery that he had suffered from an episode of food poisoning 6 months earlier. However, the organism was not isolated from the stool. The patient recovered with the administration of panipenem/betamipron and gatifloxacin. The S. Enteritidis strain isolated from the pus obtained from this case and that detected from the samples originating from the other patients during the episode of food poisoning 6 months earlier were examined by using pulse-field gel electrophoresis (PFGE). The PFGE patterns of the strains were almost identical. The molecular epidemiological analysis by PFGE was useful in estimating the infection route. In an immuno-compromised host such as those suffering from diabetes mellitus, one must be reminded that unusual bacteria (including S. Enteritidis) may cause a cervical abscess.

A total of 16 isolates of Streptococcus pneumoniae and 18 isolates of Haemophilus influenzae were obtained from the blood of children admitted to the pediatric wards of hospitals in Hokkaido Kamikawa subprefecture between January 2003 and December 2005. The ages of the patients with S. pneumoniae or H. influenzae infection ranged from 2 months to 9 years and from 1 month to 4 years, respectively. The diagnoses of S. pneumoniae infection were as follows: pneumonia in 8 patients, occult bacteremia in 5 patients, and meningitis in 3 patients. The diagnoses of H. influenzae were: meningitis in 6 patients, pneumonia in 4 patients, occult bacteremia in 4 patients, epiglotitis in 2 patients, and facial cellulitis in 2 patients. Out of 16 S. pneumoniae isolates, penicillin-resistant strains with a mutation of 3 genes were observed in 7 children, and penicillin intermediate-resistant strains with a mutation of 1 or 2 genes were observed in 8 children. Out of 18 H. influenzae isolates, the beta-lactamase-negative ampicillin-resistant strain with a substitution of 2 points in the ftsI gene was revealed in 2 children, the beta-lactamase-negative ampicillin-resistant strain with a substitution of 1 point in the ftsI gene was observed in 4 children, the beta-lactamase-positive amoxicillin/clavulanic acid-resistant strain with blaTEM-1 and ftsI with 2 substitutions in the ftsI gene was observed in 3 children, and the beta-lactamase-positive ampicillin-resistant strain with blaTEM-1was not observed. The MBC90s of ampicillin, ceftriaxone, cefotaxime, meropenem, panipenem, and vancomycin against S. pneumoniae were 8 microg/ml, 1 microg/ml, 1 microg/ml 1 microg/ml, 0.25 microg/ml, and 0.5 microg/ml, respectively. Those of ampicillin, piperacillin, ceftriaxone, cefotaxime, meropenem, and panipenem against H. influenzae were128 microg/ml,128 microg/ml, 0.25 microg/mL, 1 microg/ml, 0.12 microg/ml, and 0.5 g/ml, respectively. It is suggest that the minimum bactricidal concentration (MBC) was dissociated from the minimum inhibitory concentration (MIC) in S. pneumoniae and H. influenzae with abnormal pbp genes.

Background: Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa are the main causes of refractory infections that are often resistant to antimicrobial agents. In these cases, combination of agents with antimicrobial activity is being examined. However, few studies have investigated combined effects with antimicrobial agents including carbapenem and aminoglycosides. Methods: We evaluated the effects of panipenem (PAPM) combined with 3 aminoglycosides, arbekacin, amikacin, and netilmicin, and vancomicin (VCM) with an agar dilution checkerboard technique and the fractional inhibitory concentration index against 47 strains of MRSA and 56 strains of P. aeruginosa. Results: PAPM combined with VCM achieved a synergic effect against MRSA in 80.9%. PAPM combined with aminoglycosides showed only additive effects against MRSA and P. aeruginosa. When comparing the activity of Mueller-Hinton agar (MHA) medium with MHA medium diluted 40-fold (1/40 MHA) against P. aeruginosa, the mean minimum inhibitory concentration of PAPM was decreased to 1/16. Conclusions: Combination of PAPM and VCM is effective against MRSA. Combinations of PAPM and aminoglycosides showed additive effects against MRSA and P. aeruginosa.

The isomerization kinetics of panipenem (INN: (+)-(5R,6S)-3-[(S)-1-(acetimidoylpyrrolidin-3-yl)thio]-6-[(R)-hydroxyethyl]-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid, CAS No. 87726-17-8) in aqueous solution were investigated. An equilibrium between the Z-form and E-form was observed, and it was found that the isomerization rates were affected by the pH of the solution. Under acidic conditions, the isomerization rates were small. However, the isomerization rates were increased with the pH value. This phenomenon resulted from the extent of proton dissociation from the acetimidoyl group.

The effect of initial panipenem (CAS No. 87726-17-8) concentration on its degradation in an aqueous solution was investigated. The degradation of panipenem followed pseudo-first-order kinetics at all the pH values tested. However, in an acidic solution, the degradation rate increased with the initial panipenem concentration. On the other hand, in an alkaline solution, the degradation rate was not affected by its initial concentration. In an acidic solution, the plots of the first-order rate constants versus initial panipenem concentrations showed a linear relationship. Theoretically, the first-order rate constant is independent of the initial concentration, and therefore, the results suggested unusualness. We investigated the results obtained under acidic conditions in detail to find a very complex reaction mechanism: panipenem and its degradation products are factors causing the unusual increase in the degradation rate. Moreover, it was shown that the dissociation of the carboxyl group played an important role in the degradation of panipenem.

Four carbapenems have been available clinically in Japan. These are imipenem/cilastatin (IMIP/CS) and panipenem/ betamipron (PANI/BP) of the older compounds and newer carbapenems such as biapem (BIAP) and meropenem (MERO). The latter compounds are relatively stable to dehydropeptidase-1 (DHP-1) and have been reported to have higher antimicrobial activities compared to the earlier carbapenems. The antimicrobial activity of these four carbapenems against fresh urinary isolates showed high activities against Enterobacteriacae such as Serratia marcescens, Enterobacter cloacae, Citrobacter freundii and Escherichia coli containing the class C-beta-lactamase- and extended spectrum beta-lactamase (ESBL)-producing strains compared to piperacillin (PIPC) and ceftazidime (CTAZ). Against Pseudomonas aeruginosa, the carbapenems, with the exception of panipenem showed strong antimicrobial activities compared to PIPC and CTAZ. High activities were also seen against Enterococcus faecalis, Staphylococcus aureus and Staphylococcus epidermidis, but methicillin-resistant strains were not affected. The first generation carbapenems showed better activity against E. faecalis than newer carbapenems. All four carbapenems were similar in clinical effectiveness in double blind trials for complicated urinary tract infections (UTIs). However, PANI/BP is less effective in UTIs caused by P. aeruginosa than IMIP/CS. MERO showed better eradication rate of P. aeruginosa than IMIP/CS. Retrospective analysis of treated cases using carbapenems showed a rapid defervescence in the treatment of febrile complicated UTIs, which were mainly caused by mixed infection of Gram-negative and Gram-positive bacteria, especially those involving P. aeruginosa and E. faecalis.

Introduction Carbapenems are broad-spectrum antibiotics that are often employed as the last line of therapy for patients with nonresponsive nosocomial infections. Consideration of pharmacodynamic principles in dosage regimens for these agents can maximize their antibacterial effectiveness and reduce the number of bacterial strains that survive to mutate or continue infection. Objective The objectives of this review were to highlight examples of the application of pharmacodynamics to the carbapenems (particularly meropenem) and to comment on clinical utility of these dosage regimens. Methods Relevant information was identified through a MEDLINE search of the literature (1980–present) using the terms carbapenem, pharmacodynamic, pharmacokinetic, pharmacoeconomic, meropenem, imipenem, ertapenem, biapenem , and panipenem . Additionally, meeting posters were identified from the International Conference of Antimicrobial Agents and Chemotherapy (years 2001–2003) and the International Conference of the American Thoracic Society (years 2002–2003). All studies demonstrating the pharmacodynamics of the carbapenems by incorporating changes in dosage strategies were included. Results Only relevant data for meropenem were identified in our literature search. The dosage scheme for meropenem may be modified to maximize the percentage of the dosage interval that drug concentrations remain above the minimum inhibitory concentration, an important parameter related to the bacterial kill rate. Only relevant data for meropenem were identified in our literature search. Human volunteer and Monte Carlo simulation studies suggested that in the treatment of susceptible pathogens, higher meropenem doses, increased frequency of administration, or prolonged duration of infusion resulted in improved pharmacodynamics. Conclusion When proper pharmacodynamic principles are applied to dosage strategies for meropenem, clinical and microbiological outcomes can be optimized.

The antibiotic susceptibilities, genotypes of penicillin (PEN)-binding protein genes ( pbp ), and serotype distributions of Streptococcus pneumoniae isolates from meningitis patients were investigated by a nationwide surveillance group in Japan between 1999 and 2002. We analyzed 146 isolates from children (≤17 years old) and 73 from adults (≥18 years old). Isolates with or without abnormal pbp1a , pbp2x , or pbp2b genes identified by PCR were classified into six genotype patterns and 90% MIC (MIC 90 ) values for PEN: (i) strains with three normal genes (17.2% of isolates; MIC 90 , 0.031 μg/ml); (ii) strains with abnormal pbp2x (22.1%, 0.063 μg/ml); (iii) strains with abnormal pbp2b (1.0%, 0.125 μg/ml); (iv) strains with abnormal pbp2x and pbp2b (7.4%, 0.25 μg/ml); (v) strains with abnormal pbp1a and pbp2x (12.7%, 0.25 μg/ml); and (vi) strains with three abnormal PBP genes (39.7%, 4 μg/ml), which are termed genotypic PEN-resistant S. pneumoniae (gPRSP). Panipenem, a carbapenem, showed an excellent MIC 90 (0.125 μg/ml) against gPRSP, followed by meropenem and vancomycin (0.5 μg/ml), cefotaxime and ceftriaxone (1 μg/ml), and ampicillin (4 μg/ml). Strains of gPRSP were significantly more prevalent in children (45.2%) than in adults (27.4%). The most frequent serotypes were 6B, 19F, 23F, 6A, and 14 in children and 23F, 22, 3, 10, 6B, and 19F in adults. Serotypes 6B, 6A, 19F, 23F, and 14 predominated among gPRSP. In children, 7- and 11-valent pneumococcal conjugate vaccines would cover 76.2 and 81.3% of isolates, respectively, although coverage would be lower in adults (43.9 and 56.0%, respectively). These findings suggest the need for early introduction of pneumococcal conjugate vaccines and continuous bacteriological surveillance for meningitis.

Immature renal function in neonates requires antibiotic dosage adjustment. Population pharmacokinetic studies were performed to determine the optimal dosage regimens for three types of antibiotics: an aminoglycoside, arbekacin; a glycopeptide, vancomycin; and a carbapenem, panipenem. Eighty-three neonates received arbekacin ( n = 41), vancomycin ( n = 19), or panipenem ( n = 23). The postconceptional ages (PCAs) were 24.1 to 48.4 weeks, and the body weights (BWs) ranged from 458 to 5,200 g. A one-compartment open model with first-order elimination was applied and evaluated with a nonlinear mixed-effect model for population pharmacokinetic analysis. In the fitting process, the fixed effects significantly related to clearance (CL) were PCA, postnatal age, gestational age, BW, and serum creatinine level; and the fixed effect significantly related to the volume of distribution ( V ) was BW. The final formulas for the population pharmacokinetic parameters are as follows: CL arbekacin = 0.0238 × BW/serum creatinine level for PCAs of arbekacin = 0.0367 × BW/serum creatinine level for PCAs of ≥33 weeks, V arbekacin = 0.54 liters/kg, CL vancomycin = 0.0250 × BW/serum creatinine level for PCAs of vancomycin = 0.0323 × BW/serum creatinine level for PCAs of ≥34 weeks, V vancomycin = 0.66 liters/kg, CL panipenem = 0.0832 for PCAs of panipenem = 0.179 × BW for PCAs of ≥33 weeks, and V panipenem = 0.53 liters/kg. When the CL of each drug was evaluated by the nonlinear mixed-effect model, we found that the mean CL for subjects with PCAs of

A total of 535 Haemophilus influenzae strains from 226 Japanese institutions participating in the Nationwide Surveillance Study Group for Bacterial Meningitis were sent to our laboratory during 1999 to 2003. All strains were analyzed by PCR to identify the beta-lactam resistance genes, and their susceptibilities to beta-lactam agents were determined. These strains were classified into 6 genotype patterns and MIC90 values for ampicillin (ABPC): (i) beta-lactamase nonproducing, ABPC susceptible (BLNAS) strains and lacked all resistance genes (27.7% of isolates; MIC90, 0.5 microg/ml); (ii) beta-lactamase producing, ABPC resistant (BLPAR) strains (12.9%, 16 microg/ml); (iii) beta-lactamase nonproducing, ABPC resistant (Low-BLNAR) strains with a Asn526Lys amino acid substitution in ftsI gene encoding PBP3 (31.2%, 2 microg/ml); (iv) beta-lactamase nonproducing, ABPC resistant (BLNAR) strains with Ser385Thr and Asn526Lys substitutions in ftsI (17.2%, 8 microg/ml); (v) amoxicillin/clavlanic acid resistant (BLPACR I) strains, having beta-lactamase gene and a Asn526Lys amino acid substitution in ftsI (9.2%, 32 microg/ml); and (vi) amoxicillin/clavlanic acid resistant (BLPACR II), having beta-lactamase gene and ftsI substitutions as for BLNAR strains (1.9%, 64 microg/ml). All but 4 strains were serotype b. The prevalence of BLNAR strains has increased exponentially: 0% (n = 0/41) in 1999, 5.8% (n = 4/69) in 2000, 14.1% (n = 19/139) in 2001, 20.1% (n = 32/159) in 2002, and 29.1% (n = 37/127) in 2003. The MIC90s of BLNAR isolates except for ABPC were as follows: piperacillin, 0.125 microg/ml; ceftriaxone, 0.25 microg/ml; meropenem, 0.5 microg/ml; cefotaxime, 1 microg/ml; panipenem, 2 microg/ml; cefozopran, 16 microg/ml; and cefotiam, 64 microg/ml. To prevent such resistance from increasing, expedited vaccination, correct identification of the BLNAR molecularly, and the proper selection of proper antibiotics based on PK/PD must be taken.

A biapenem-tolerant mutant of Pseudomonas aeruginosa was isolated by Tn 1737 KH insertion. The survival of the mutant 3 h after the addition of biapenem was about 1,000 times greater than that of the wild type. The mutant was also tolerant to other biapenems, such as imipenem, panipenem, and meropenem.