Bioequivalence, antibacterial activity and therapeutic outcome of a generic meropenem (Mapenem).

BACKGROUND: The authors aimed to compare the bioequivalence and antibacterial activity of a generic meropenem with the original meropenem and studied its preliminary therapeutic outcome. MATERIAL AND METHOD: A randomized, open-label, crossover study was employed to assess the bioequivalence and antibacterial activity. Twenty-six healthy males were recruited at Siriraj Hospital, Thailand and randomized to firstly receive either a single intravenous 30-minute infusion of a generic (Mapenem) or original meropenem (Meronem) and vice versa for the second period. The washout period was one week. Ten milliliters of blood samples were collected before meropenem infusion and at 0, 10, 15, 30, 45, 60, 90, 120, 150, 180, 240, 360, 470 and 480 minutes after the beginning of the drug infusion. Blood samples were coded and separated into plasma and serum samples. Plasma samples were used to determine drug concentrations by HPLC-UV detector and the data were analyzed for Cmax, AUC0-t and AUC0-inf. Serum samples were assayed in triplicate for measuring generic and original meropenems' inhibitory activities of a meropenem-susceptible E. coli ATCC 25922 in the same agar plate. An open-label design was used to preliminarily study of the therapeutic outcome and adverse effects of the generic meropenem in 30 patients. RESULTS: All enrolled twenty-six volunteers completed the whole study. The statistical analysis of 90% confidence interval of Cmax, A UC0-t, and AUC0-inf of the generic and original meropenems were 87.7 to 101.7%, 96.3 to 102.4% and 96.3 to 102.3%, respectively. The results were within the standard range of bioequivalence acceptance criteria (80-125%) and the powers of the test were greater than 80%. Using E. coli ATCC 25922 in the blind assay of serum inhibition activity, the inhibitory zone sizes (mm) of the generic compared to original meropenems were not statistically different with respect to every time points of blood collections (p < 0.05). Correlation of mean values of serum meropenem levels and the widths of inhibitory zone sizes of the same samples collected at the same intervals showed good linear relationship with r = 0.891; R2 = 0.794 (p < 0.01) for the generic meropenem and r = 0.885; R2 = 0.784 (p < 0.01) for the original meropenem. The therapeutic result with the generic meropenem for various indications was successful or improved in 24 cases from 30 cases (80%) and the bacterial cure rate was 23 in 30 clinical isolates (76.7%). Adverse reactions probably related to the study medication were rash and elevated liver enzymes in 1 and 3 patients, respectively, and all resolved spontaneously. CONCLUSION: In the present study, the generic meropenem exhibited indifferent bioequivalence and antibacterial activity compared to the original meropenem. There was also a good correlation between serum levels and inhibitory zone sizes produced by the same serum samples in every periods of blood collection. Clinical efficacy of the generic meropenem was shown to be satisfactory without notable severe adverse reaction.

Prevalence of extended-spectrum beta-lactamase and class 1 integron integrase gene intl1 in Escherichia coli from Thai patients and healthy adults.

Among 120 Escherichia coli isolates from Thai patients, 37 and 9 isolates were extended-spectrum beta-lactamase (ESBL) and suspected ESBL producers respectively while 5 E. coli isolates from 120 Thai healthy adults were suspected ESBL producers. Integrase (intl1) gene was detected in 99% of the clinical and 87% of the non-clinical isolates. Among 37 ESBL producers, percent recovery of bla(TEM), bla(CTX-M), bla(SHV) and bla(VEB) was 78%, 78%, 8% and 8%, respectively. Twenty-five isolates of ESBL producers carried both bla(TEM) and bla(CTX-M), 2 isolates carried 3 genes (bla(TEM), blac(CTX-M), and bla(SHV)) and 3 showed no detectable bla gene. Among the 14 suspected ESBL producers, intl1 and bla(TEM) were detected in 13 isolates. ESBL producers from clinical samples were resistant to most of the tested antimicrobial agents compared to non-ESBL producers and isolates from healthy adults with about half of the latter susceptible to all tested antimicrobial agents. Only one clinical isolate was resistant to imipenem. Susceptibility to trimethoprim/sulfamethoxazole among the clinical isolates in ESBL producer group (27%) and non-producer group (33%) were comparable, whereas the percent susceptibility of the non-clinical isolates was about twice that of the clinical isolates.

Discriminatory powers of molecular typing techniques for methicillin-resistant Staphylococcus aureus in a university hospital, Thailand.

Discriminatory powers of various molecular techniques were evaluated for typing of methicillin-resistant Staphylococcus aureus (MRSA) isolated in Siriraj Hospital, Bangkok, Thailand. Thirty MRSA isolates were randomly selected in this study. They were characterized by pulsed-field gel electrophoresis, Clal-mecA and Clal-Tn554 polymorphisms, ribotyping, and PCR-based methods including SCCmec typing, spa and coa gene polymorphism, and repeat units in hypervariable region downstream of mecA. Individual molecular typing technique distinguished those MRSA isolates into 2 to 5 types. Eleven genetic backgrounds of MRSA isolates were elucidated by combination of typing methods with trimethoprim/sulfamethoxazole (TMP/SXT) susceptibility. Combination of all typing methods including TMP/SXT susceptibility yielded a discriminatory index of 0.94. Combination of PCR-based methods and TMP/SXT susceptibility, with the discriminatory index of 0.89, is a practical typing approach suitable for rapid epidemiological investigation of MRSA isolates in a hospital setting.

Endemic Serratia marcescens in a neonatal intensive care unit.

OBJECTIVE: To study the endemicity of Serratia marcescens in a neonatal intensive care unit (N.I.C.U). MATERIAL AND METHOD: During the first 4 months of 2001, neonates in the N.I.C.U. in a teaching hospital were screened for S. marcescens by serial throat swabs and collections of other appropriate clinical specimens. Environmental cultures were also done in the same period. Isolated S. marcescens were tested for antimicrobial susceptibility and for genotyping by pulsed field gel electrophoresis. RESULTS: During the period, 104 neonates were studied. S. marcescens were isolated in 34.6% of the cases. Environmental cultures were positive for S. marcescens in 1.4%. There were 10 patterns of antibiogram of the 190 strains isolated. All strains belonged to pulsotype A. CONCLUSION: The study confirmed that S. marcescens was endemic in the N.I.C.U. and belonged to one genotype.

Occurrence of extended-spectrum beta-lactamase in clinical isolates of Klebsiella pneumoniae in a University Hospital, Thailand.

The occurrence and antimicrobial susceptibility of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae in patients attending Siriraj Hospital in Bangkok from August 2000 to January 2001 were determined. ESBL-producing isolates were screened with four different methods: disk diffusion according to the National Committee for Clinical Laboratory Standards (NCCLS) guidelines, Etest ESBL (CT/CTL and TZ/TZL), Oxoid combination discs and MIC Etest strip. Antimicrobial susceptibility testing were determined by a microdilution automatic method (VITEX system, bioMerieux). Of 22,178 clinical specimens, 400 (1.8%) K. pneumoniae were isolated Of 26% (104/400) of these isolates were suspected to be ESBL-producing. Rates of detection of ESBL-producing K. pneumoniae were 18.67%, 30% and 23.78% for blood, sputum and urine samples, respectively. Susceptibility testing has revealed that all 70 tested isolates including 53 isolates from blood and sputum and 17 isolates from urine samples were susceptible to imipenem (MIC< or =4 mg/L). None of the tested isolates were susceptible to cephalosporins, cephamycin and aztreonam. Rate of susceptibility to ciprofloxacin, levofloxacin, gentamicin and tobramycin were 60%, 64%, 28% and 9%, respectively, for isolates from blood and sputum; 71%, 71%, 18% and 6% for urinary isolates. The present findings revealed a high occurrence rate of multi-drug resistance ESBL-producing K. pneumoniae in patients attending the university hospital. Imipenem was highly active against ESBL-producing K. pneumoniae.

Antifungal susceptibility and molecular typing of candida albicans isolated from AIDS and non-AIDS Thai patients.

The antifungal susceptibility of Candida albicans isolated from 2 groups of Thai patiens; AIDS patients and non-AIDS patients was investigated. Two hundread and seventeen C. albicans were isolated from the specimens from 54 AIDS patients and 163 non AIDS patients. All isolate were included in the antifungal susceptibility test against amphotericin B, fluconazole, ketoconazole and nystatin. A hundred isolates were randomly selected from both groups for the electrophoretic karyotypes determination. There was not much difference in the value of Mic, MIC50 and MIC90 of all antifungal agent for C. albicans isolates between AIDS and non-AIDS patients. The amphoter B MIC for 61.0% if AIDS isolates and 71.0% of non-AIDS isolates were >0.5 mg/l, while ketoconazole MIC for 94.4% of AIDS and 74.9% of non-AIDS isolates were >0.125 mg/l and fluconazole MIC of 100% of AIDS and non-AIDS isolates were 2.0 mg/l. For nystatin, the MIC for more than 90% of both isolates was <8 mg/l. The MIC50 and MIC90 of all antifungal agents for the two groups of isolates were almost at the same concentration except for fluconazole which showed a two-fold difference of MIC50. The chromosomal DNA karyotypic of C. albicans indicated genetic diversity among all isolates. Twenty-three distinct pulsed-field gel electrophoresis karyotypes and molecular sizes ranging from 3.5 to 0.5 megabases were identified. Most isolates (61%) from both AIDS and non-AIDS isolates belong to type 1 and type 3. Among the AIDS isolates, 38.3% and 29.8% were type 1 and 3, respectivety, and non-AIDS isolates, 20.8% and 33.9% were type 1 and 3, respectively. C. albicans isolates were show to have 8 to 10 chromosomal DNA brands. Most of the isolates (78%) along with C. albicans FC18 control strain had 8 band patterns. The recovery of the common karyotypes in AIDS patients, as well as in non-AIDS patients, suggests that C. albicans infection may develop from a common source by the cross contamination between both groups of patients.

Detection of Clostridium difficile toxin A and B genes from stool samples of Thai diarrheal patients by polymerase chain reaction technique.

The prevalence of Clostridium difficile isolated from stools of Thai adult patients with suspected antibiotic-associated diarrhea (AAD) was 18.64 per cent. The recovery rate of toxin genes (tcdA and tcdB) by polymerase chain reaction (PCR) from stool samples yielded almost the same compared to the recovery rate of the toxin detection by enzyme immunoassay (EIA), which were 44.9 per cent and 46.7 per cent, respectively. Correlation of toxin gene detection by PCR and toxin detection by EIA was 90.6 per cent. All but one stool sample, the tcdA gene was detected together with the tcdB gene. Both genes were always detected together from tox gene-positive strains. Although, there were some discrepancy results for certain samples, the direct PCR-based-detection of C. difficile tox genes in stool samples seems to be the appropriate method for the diagnosis of C. difficile diarrhea. The PCR assay should be a recommended technique to be used routinely in laboratories. Further optimization of the technique to increase the sensitivity of the PCR assays is still needed. However, a quantitative isolation of the organism from stools of suspected antibiotic-associated diarrhea (AAD) or antibiotic-associated colitis (AAC) patients may give some evidence for clinicians in hospitals who cannot perform PCR-based or EIA-based techniques, since 48.6 per cent of the isolates were demonstrated as toxigenic strains.