Antimicrobial Activity Profiles and Potential Antimicrobial Regimens against Carbapenem-Resistant Enterobacterales Isolated from Multi-Centers in Western Thailand.

The spread of carbapenem-resistant Enterobacterales (CRE) constitutes a global health burden. Antimicrobial susceptibility and types of carbapenemase differ by geographic region. This study aimed to (1) examine the minimum inhibitory concentrations (MICs) and antibiotic resistance genes and (2) investigate antibiotic dosing regimens against CRE using Monte Carlo simulation. Clinical carbapenem-resistant Klebsiella pneumoniae (CRKP), Escherichia coli (CREC), and Enterobacter cloacae (CREclo) isolates were collected from various hospitals in western Thailand. Broth microdilution was performed, and the types of carbapenemase and mcr-1 genes were detected using polymerase chain reaction (PCR). Monte Carlo simulation was used to establish optimal antimicrobial dosing regimens meeting the criterion of a cumulative fraction of response (CFR) >90%. A total of 150 CRE isolates from 12 hospitals were included. The proportion of CRKP (76%) was greater than that of CREC (22%) and CREclo (2%). Regional hospitals reported higher rates of resistance than general hospitals. Most isolates were resistant to aztreonam and ceftazidime/avibactam, whereas they were highly susceptible to aminoglycosides. Most carbapenemases were NDM (47.33%), OXA-48 (43.33%) and NDM plus OXA-48 (6.67%); five OXA-48 positive isolates carried mcr-1 genes. Currently, high-dose tigecycline is the only optimal regimen against CRE isolates. Further extensive research on antibiotic synergism or new antibiotics should be conducted.

The sequence of pbp2b from penicillin-resistant Streptococcus pneumoniae in Thailand.

OBJECTIVE: Penicillin resistance in Streptococcus pneumoniae isolates results from altered penicillin-binding proteins (PBPs), especially PBP2, which has a reduced affinity to penicillin. This study evaluated drug resistance and the gene sequence of the conserved motif pbp2b of penicillin-resistant isolates in Thailand. MATERIAL AND METHOD: Penicillin-resistant pneumococci with minimum inhibitory concentrations (MIC) for penicillin > or = microg/ ml and penicillin-susceptible strains were identified from clinical specimens. The pbp2b genes were amplified by polymerase chain reaction (PCR), and the purified PCR product was cloned into E. coli. The recombinant plasmid clones containing pbp2b were sequenced and evaluated for mutations corresponding to penicillin and cefotaxime resistance. RESULTS: Penicillin-susceptible S. pneumoniae isolates were susceptible to 12 other antibiotics tested (range 95-100%) while penicillin-nonsusceptible isolates were resistant to most antibiotics except amoxicillin/clavulanate and levofloxacin. Sequence analysis of pbp2b showed a substitution of A for T451 next to the region of the SSN triad in all six resistant isolates tested and mutations clustered around the KTG triad in two isolates. Using the ClustalW alignment program, Thai isolates differed from those of European countries, but were more similar to those from Japan than Korea. CONCLUSION: Penicillin or cefotaxime resistance in S. pneumoniae in Thailand was due to affinity reduction of PBP2b, similar to changes found in other Asian isolates.

SHV-12 extended spectrum beta-lactamase associated with high-level ceftazidime resistance in Enterobacter cloacae isolated from Thailand.

Four Enterobacter cloacae clinical isolates with reduced susceptibility to ceftazidime from two hospitals in Thailand were studied. Production of extended-spectrum beta-lactamase was confirmed by double disk synergy test and combination disk method. All isolates were highly resistant to ceftazidime but retained susceptibility to imipenem. One isolate was able to hydrolyze cefotaxime, ceftazidime and cefepime, the latter being one of the treatment choices for infection by Enterobacter spp. PCR analysis demonstrated the presence of bla(SHV12) in addition to bla(TEM-1) in all isolates suggesting that SHV-12 was associated with high-level resistance to ceftazidime in the E. cloacae isolates.

Long-term study of Escherichia coli and Klebsiella pneumoniae isolates producing extended-spectrum beta-lactamases.

OBJECTIVE: To evaluate the prevalence and susceptibility pattern of Escherichia coli and Klebsiella pneumoniae isolates producing extended-spectrum beta-lactamases (ESBLs) in Thailand from 2000 to 2005. MATERIAL AND METHOD: Data on the WHONET, from 28 hospitals participated in the National Antimicrobial Resistance Surveillance, Thailand surveillance program, were reviewed and analyzed for the prevalence and susceptibility pattern. RESULTS: During the five-year surveillance from 2000 to 2005, the prevalence of ESBL-producing E. coli detected by ceftazidime screening test was 17%, 21.3%, 23.2%, 20.4%, 23.1%, and 25.0%; as well as detected by cefotaxime screening test was 20.8%, 65.9%, 69.3%, 69.3%, 68.3%, and 33.8%, respectively. The prevalence of ESBL-producing K. pneumoniae detected by ceftazidime screening test was 30.9%, 34.7%, 32.5%, 34.4%, 372%, and 39.2%; as well as detected by cefotaxime screening test 38.4%, 39.3%, 40.1%, 41.0%, 42.8%, and 40.4%, respectively. CONCLUSION: From 2000 to 2005, the prevalence of ESBL-producing organisms in Thailand was high. ESBL-producing E. coli was most commonly isolated from sputum, followed by blood and urine specimens. ESBL-producing K. pneumoniae had not been increasingly isolated from sputum, blood and urine.

Antimicrobial resistance of Escherichia coli isolated from urine in Thailand from 2000 to 2005.

OBJECTIVE: To study the trends of antimicrobial resistance of Escherichia coli in Thailand during 2000 and 2005. MATERIAL AND METHOD: All isolates of E. coli from 28 hospitals across Thailand from 2000 to 2005 were tested for their susceptibility to aminoglycosides, beta-lactams, fluoroquinolones, and trimethoprim-sulfamethoxazole by the disk diffusion method (Kirby Bauer). The relevant data were collected and analyzed by the WHONET software program supported by the World Health Organization. RESULTS: The rate of resistance to ampicillin, ceftriaxone, ceftazidime gentamicin, and ciprofloxacin increased from 79.3% to 85.3%, 12.7% to 28.5%, 10.7% to 15.2%, 25% to 32.9%, and 45.1% to 51% during the 6-year period from 2000 to 2005 among isolates from catheterized urine, respectively. The rate of resistance to gentamicin and ceftriaxone increased from 23.2% to 28.9% and 6.8% to 24.2%, from 2000 to 2005 respectively among isolates in non-intensive care units (non-ICUs). The rate of resistance to gentamicin increased from 18% to 26.1%, and 24.2% to 29.6% among isolates in out-patient department (OPD) and non-OPD, respectively. The rate of resistance to ceftriaxone increased from 2.5% to 15.4%, and 7.9% to 25.9% among isolates in OPD and non-OPD, respectively. The rate of resistance to gentamicin and ceftriaxone increased from 23.2% to 28.9%, and 6.8% to 24.2% among isolates in non-ICU, respectively. The rate of resistance to trimethoprim-sulfamethoxazole decreased from 71.2% to 62.6% among isolates in non-ICUs. Isolates from catheterized urine were significantly associated with imipenem resistance (p > 0.05). CONCLUSION: The present study shows a significant correlation between ciprofloxacin resistance and fluoroquinolone use, and indicates that prior fluoroquinolone use seems to be the most important risk factor for ciprofloxacin-resistant E. coli bacteremia. Isolates from catheterized urine were significantly associated with resistance to imipenem, and the ICU hospitalization and OPD attention during the previous year were significantly associated with ofloxacin resistant E. coli.

Dissemination of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae and Escherichia coli in Thai hospitals.

Fifty clinical isolates of Klebsiella pneumoniae and Escherichia coli with reduced susceptibility to third-generation cephalosporins, collected from 11 hospitals in Thailand, were studied. All isolates were found to produce extended-spectrum beta-lactamase (ESBL), as judged by double-disk synergy and combination disk methods. Most ESBL-producing K. pneumoniae isolates were resistant to ceftazidime (94%) and aztreonam (90%). In contrast, most ESBL-producing E. coli isolates were resistant to ceftriaxone (95%) and cefotaxime (74%). Plasmid DNA was isolated and beta-lactamase genes were identified by PCR and sequencing. We found that SHV-12 and CTX-M-14 were the main ESBLs responsible for resistance in K. pneumoniae and E. coli, respectively. SHV-27, SHV-28, and CTX-M-14 were detected in three, two, and four K. pneumoniae isolates, respectively. A high genetic diversity among ESBL-producing K. pneumoniae and E. coli isolates was observed. In addition, the finding of a few isolates that produced identical restriction patterns on pulsed field gel electrophoresis (PFGE) suggests the clonal spread of resistant bacteria within the hospital.

Antimicrobial susceptibility of Streptococcus pneumoniae isolated from patients with respiratory tract infections in Thailand.

A total of 400 clinical Streptococcus pneumoniae strains from patients with respiratory diseases were collected from January 2002 to December 2005. In this study, an increased prevalence of penicillin-nonsusceptible S. pneumoniae (PNSP) from 63% in 2002-2003 to 69% in 2004-2005 was found. During 2004-2005, 56% were erythromycin-nonsusceptible S. pneumoniae (ENSP) and 54% were both PNSP and ENSP. The PNSP, ENSP and PNSP+ENSP groups showed similar trends, ie, sensitive to amoxicillin/clavulanate (range 97.2-98.5%), levofloxacin (range 90.7-92.4%), ceftriaxone (range 87.1-89.4%), and ofloxacin (range 64.8-66.1%). Lower levels of susceptibility were detected for azithromycin, clarithromycin, cefdinir, cefprozil, clindamycin, co-trimoxazole, chloramphenicol and tetracycline in penicillin and erythromycin-nonsusceptible strains. Of the macrolide-resistant S. pneumoniae, 55% of strains exhibited the M phenotype and 45% the constitutive MLS(B) phenotype. No pneumococci with the inducible MLS(B) phenotype were detected in Thailand.