Monte Carlo simulation for evaluation of the efficacy of carbapenems and new quinolones against ESBL-producing Escherichia coli.

Extended-spectrum beta-lactamase (ESBL)-producing bacteria are known to be resistant to penicillins, cephalosporins, and monobactams because of their substrate specificity, and these bacteria are sensitive only to a narrow range of antimicrobial agents. The present study was undertaken to evaluate the efficacy of carbapenems and the new quinolones against ESBL-producing Escherichia coli, using a Monte Carlo simulation based on the pharmacokinetic/pharmacodynamic (PK/PD) theory. The time above MIC (TAM, %) served as the PK/PD parameter for carbapenems, with the target level set at 40%. The AUC/MIC served as the PK/PD parameter for the new quinolones, with the target level set at more than 125. In the analysis of drug sensitivity, the MIC50 of all carbapenems other than imipenem was low (0.03 microg/ml), while the MIC50 of the new quinolones was higher (1-2 microg/ml). The probability of achieving the PK/PD target with carba penems after two doses at the usual dose level, as determined by the Monte Carlo simulation, was high for each of the carbapenems tested (99.0% for biapenem, 99.60% for meropenem, and 95.03% for doripenem), except for imipenem. Among the new quinolones, the highest probability of achieving the PK/PD target was obtained with pazufloxacin (42.90%). Thus, the results of the present study have revealed that carbapenems are effective at the regular dose and can be used as the first-choice antibiotics for ESBL-producing E. coli because the resistance ratios for carbapenems are low compared to those of the new quinolones.

Metallo-beta-lactamase-producing gram-negative bacilli: laboratory-based surveillance in cooperation with 13 clinical laboratories in the Kinki region of Japan.

A total of 19,753 strains of gram-negative rods collected during two 6-month periods (October 2000 to March 2001 and November 2001 to April 2002) from 13 clinical laboratories in the Kinki region of Japan were investigated for the production of metallo-beta-lactamases (MBLs). MBLs were detected in 96 (0.5%) of the 19,753 isolates by the broth microdilution method, the 2-mercaptopropionic acid inhibition test, and PCR and DNA sequencing analyses. MBL-positive isolates were detected in 9 of 13 laboratories, with the rate of detection ranging between 0 and 2.6% for each laboratory. Forty-four of 1,429 (3.1%) Serratia marcescens, 22 of 6,198 (0.4%) Pseudomonas aeruginosa, 21 of 1,108 (1.9%) Acinetobacter spp., 4 of 544 (0.7%) Citrobacter freundii, 3 of 127 (2.4%) Providencia rettgeri, 1 of 434 (0.2%) Morganella morganii, and 1 of 1,483 (0.1%) Enterobacter cloacae isolates were positive for MBLs. Of these 96 MBL-positive strains, 87 (90.6%), 7 (7.3%), and 2 (2.1%) isolates carried the genes for IMP-1-group MBLs, IMP-2-group MBLs, and VIM-2-group MBLs, respectively. The class 1 integrase gene, intI1, was detected in all MBL-positive strains, and the aac (6')-Ib gene was detected in 37 (38.5%) isolates. Strains with identical PCR fingerprint profiles in a random amplified polymorphic DNA pattern analysis were isolated successively from five separate hospitals, suggesting the nosocomial spread of the organism in each hospital. In conclusion, many species of MBL-positive gram-negative rods are distributed widely in different hospitals in the Kinki region of Japan. The present findings should be considered during the development of policies and strategies to prevent the emergence and further spread of MBL-producing bacteria.

Production of CTX-M-3 extended-spectrum beta-lactamase and IMP-1 metallo beta-lactamase by five Gram-negative bacilli: survey of clinical isolates from seven laboratories collected in 1998 and 2000, in the Kinki region of Japan.

The aim of this study was to research the distribution in the Kinki region of Japan of Enterobacteriaceae and Pseudomonas aeruginosa that produce extended-spectrum beta-lactamase (ESBL) and metallo beta-lactamase (MBL). One thousand isolates, 200 of each of four enterobacterial species (i.e. Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae and Serratia marcescens) and 200 of P. aeruginosa, were collected from seven different laboratories during two 2 month periods, one in 1998 and one in 2000. A double-disc synergy test (DDST) and 2-mercaptopropionic acid inhibition test (2-MPAT) were used to confirm beta-lactamase-producing isolates. The DDST was positive for one isolate of E. coli, five of K. pneumoniae, two of E. cloacae and 14 of S. marcescens. The 2-MPAT was positive for five isolates of S. marcescens and two of P. aeruginosa. We identified the beta-lactamase type of each isolate by molecular confirmatory tests (isoelectric focusing, PCR and DNA sequencing): CTX-M-3 ESBLs (three isolates of K. pneumoniae, two of E. cloacae and 13 of S. marcescens), CTX-M-2 ESBL (one isolate of K. pneumoniae), SHV-12 ESBLs (one isolate of E. coli and one of S. marcescens), CTX-M-3 and SHV-12 combination ESBL (one isolate of K. pneumoniae) and IMP-1 MBLs (five isolates of S. marcescens and two of P. aeruginosa). In conclusion, many species of Gram-negative bacilli that produce CTX-M-3 ESBLs and IMP-1 MBLs were disseminated widely in different hospitals of the Kinki region of Japan. Therefore, monitoring of laboratory bacterial ecology seems important to stop the spread of these strains through nosocomial outbreaks.

[Resistance to antimicrobiotics and mutation of PBPs in Streptococcus pneumoniae isolated from Kinki region of Japan].

We studied the susceptibility to penicillin G (PCG) and other antimicrobiotics in 235 clinical isolates of Streptococcus pneumoniae. Samples were collected between April 1 and June 30, 2000 from nine medical institutions of the Kinki Region of Japan. We classified the minimum inhibitory concentration (MIC) of PCG according to the National Committee for Clinical Laboratory Standards (NCCLS) criteria. The overall rate of all types of S. pneumoniae resistance was 53.2% (penicillin-susceptible S. pneumoniae (PSSP): 46.8%, penicillin-intermediate S. pneumoniae (PISP): 42.6%, penicillin-resistant S. pneumoniae (PRSP): 10.6%). In other antimicrobiotics, the resistance (R)/intermediate susceptibility (I) rates (R/I%) were as follows: ceftriaxone, 28.9%; cefotaxime, 7.7%; imipenem, 8.9%; meropenem, 9.8%; clarithromycin, 82.6%; clindamycin, 42.1%; levofloxacin, 0.4%; vancomycin, 0%. We used the polymerase chain reaction to study the mutations of the penicillin-binding proteins pbp1 a, pbp2b, and pbp2x in 140 strains of S. pneumoniae in the MIC for PCG was < 0.5 microgram/ml. Among the 109 strains of PSSP, 32 (29.4%) had no mutation and 77 (70.6%) showed mutation of more than one of the pbp mutations. Among the 31 strains of PISP, only 1 strain (3.2%) was not mutated. Since 70.6% of the strains classified as PSSP had pbp mutations, S. pneumoniae clearly can acquire resistance to anti-microbiotics. In the future, a comprehensive surveillance of S. pneumoniae is necessary.

[Antimicrobial susceptibility and beta-lactamase types among clinical isolates during January and February 2000 in the Kinki area of Japan].

We studied antimicrobial susceptibility and beta-lactamase types among clinical isolates in the Kinki area of Japan. Eight hundreds isolates of eight organisms were collected by seven medical institutions during January and February 2000. The rates of beta-lactamase producing by using the chromogenic nitrocephin test were 68.0% against Staphylococcus aureus isolates, 6.0% against Haemophilus influenzae isolates, 98.0% against Moraxella catarrhalis isolates. The rate of beta-lactamase negative ampicillin-resistant H. influenzae was 4.0% (4 out of 100). The result of beta-lactamase producing by using the acid-metric method were as follows the penicillinase and cephalosporinase: 27.0% and 37.0% against Escherichia coli isolates, 37.0% and 1.0% against Klebsiella pneumoniae isolates, 21.8% and 100% against Enterobacter cloacae isolates, 24.2% and 96.0% against Serratia marcescens isolates, 7.0% and 22.0% against Pseudomonas aeruginosa isolates. We identified beta-lactamase type of each isolate detected by polymerase chain reaction: SHV-derived extended-spectrum beta-lactamase (ESBLs) (1 isolate of E. coli and 1 isolate of K. pneumoniae), CTX-M-1-derived ESBLs (1 isolate of K. pneumoniae, 1 of E. cloacae and 4 of S. marcescens), and IMP-1-derived metallo beta-lactamases (2 isolates of S. marcescens).