A pragmatic approach to identify extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in Taiwan: in vitro activity of newer and established antimicrobial agents

Identification of DHA-23, a novel plasmid-mediated and inducible AmpC beta-lactamase from Enterobacteriaceae in Northern Taiwan

Objectives: AmpC β-lactamases are classified as Amber Class C and Bush Group 1. AmpC β-lactamases can hydrolyze broad and extended-spectrum cephalosporins, and are not inhibited by β-lactamase inhibitors such as clavulanic acid. This study was conducted to identify DHA-23, a novel plasmid-mediated and inducible AmpC β-lactamase obtained from Enterobacteriaceae.

Methods: A total of 210 carbapenem-resistant Enterobacteriaceae isolates were collected from a medical center (comprising two branches) in Northern Taiwan during 2009–2012. AmpC β-lactamase genes were analyzed through a polymerase chain reaction using plasmid DNA templates and gene sequencing. The genetic relationships of the isolates were typed using pulsed-field gel electrophoresis following the digestion of intact genomic DNA by using XbaI.

Results: Three enterobacterial isolates (one Escherichia coli and two Klebsiella pneumoniae) were obtained from three hospitalized patients. All three isolates were resistant or intermediately susceptible to all β-lactams, and exhibited reduced susceptibility to carbapenems. These three isolates expressed a novel AmpC β-lactamase, designated DHA-23, approved by the curators of the Lahey website. DHA-23 differs from DHA-1 and DHA-6 by one amino acid substitution (Ser245Ala), exhibiting three amino acid changes compared with DHA-7 and DHA-Morganella morganii; three amino acid changes compared with DHA-3; four amino acid changes compared with DHA-5; and eight amino acid changes compared with DHA-2 (>97% identity). This AmpC β-lactamase is inducible using a system involving ampR.

Conclusion: This is the first report to address DHA-23, a novel AmpC β-lactamase. DHA-type β-lactamases are continuous threat in Taiwan.

Genotypic detection and molecular epidemiology of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in a regional hospital in central Taiwan

This study was conducted to detect the genes encoding extended-spectrum beta-lactamases (ESBLs) and determine the epidemiological relatedness of 69 Escherichia coli and 33 Klebsiella pneumoniae isolates collected from a regional hospital in central Taiwan, mostly from inpatients (E. coli 87.0%; K. pneumoniae 88.0%). The phenotypes of these isolates were examined according to the combination disc method recommended by the Clinical and Laboratory Standards Institute. Most of the ESBL-producing E. coli and K. pneumoniae isolates (98.6% and 97%, respectively) could be detected using cefotaxime discs with and without clavulanate. Genotyping was performed by PCR with type-specific primers. CTX-M-14 type (53.6%) was the most prevalent ESBL among E. coli isolates while SHV type (57.6%) was the most dominant among K. pneumoniae isolates. Six E. coli and three K. pneumoniae isolates did not carry genes encoding ESBLs of types TEM, SHV, CTX-M-3, CTX-M-14, CMY-2 and DHA-1. The co-existence of two or more kinds of ESBL in a single isolate was common, occurring in 40.6% and 72.7% of E. coli and K. pneumoniae isolates, respectively. PFGE analysis revealed that ESBL producers isolated in this setting were genetically divergent.

Identification of a novel cephalosporinase (DHA-3) in Klebsiella pneumoniae isolated in Taiwan

A strain of Klebsiella pneumoniae resistant to cefoxitin and oxyimino-cephalosporins, but susceptible to cefepime, was isolated from an adult patient hospitalised in Taichung, Taiwan. Isoelectric focusing revealed three beta-lactamases with isoelectric points of 5.4, 8.2 and 7.9, respectively. Following PCR with plasmid DNA templates and gene sequencing, these enzymes were shown to correspond to TEM-1, SHV-5 and a novel DHA-1-like enzyme (designated DHA-3). The bla genes for TEM-1 and SHV-5 were transferable, but the bla(DHA-3) gene was non-self-transferable in conjugation experiments. All three bla genes were successfully introduced by electrotransformation into an Escherichia coli recipient (DH5alpha), resulting in a similar resistance profile to that observed in the original donor strain. Other K. pneumoniae strains producing DHA-1-like enzymes have been identified previously in Taiwan, and this report suggests that DHA-type beta-lactamases are continuing to emerge in this country.

Risk Factors for Increasing Multidrug Resistance among Extended-Spectrum -Lactamase-Producing Escherichia coli and Klebsiella Species

BACKGROUND

The importance of infections due to extended-spectrum beta -lactamase-producing Escherichia coli and Klebsiella species (ESBL-EK) has been increasingly recognized in recent years. ESBL-EK infections are of clinical concern, because few antimicrobials are available as therapeutic options. Increased reliance on carbapenems has led to increasing carbapenem resistance. Efforts to maintain current therapeutic options for ESBL-EK infections are essential.

METHODS

We conducted a case-control study to identify risk factors for multidrug resistance (MDR) among ESBL-EK. All patients at our institution who had an inpatient clinical culture result positive for an ESBL-EK during the period of 1 June 1997 through 31 December 2002 were eligible for inclusion. An MDR ESBL-EK was defined as ESBL-EK demonstrating resistance to trimethoprim-sulfamethoxazole, aminoglycosides, and quinolones. All available ESBL-EK isolates were characterized by pulsed-field gel electrophoresis (PFGE).

RESULTS

Of 361 total ESBL-EK isolates, 68 (18.8%) were MDR. During the study period, the prevalence of MDR among ESBL-EK isolates increased from 12.5% to 26.9%. The only independent risk factor for MDR ESBL-EK was the infecting organism (i.e., Klebsiella pneumoniae; adjusted odds ratio, 11.7; 95% confidence interval, 4.77-28.51; P < .001). Prior antibiotic use was not independently associated with MDR ESBL-EK. PFGE patterns from K. pneumoniae isolates indicated close genetic relatedness among a substantial proportion of isolates.

CONCLUSIONS

The emergence of MDR among ESBL-EK has important implications for the future ability to treat these infections. The strong association between the species of infecting organism and MDR suggests that the epidemiology in K. pneumoniae may be unique. PFGE results suggest that horizontal spread is important in the emergence of MDR ESBL-EK.

Surveillance of antimicrobial resistance at a tertiary hospital in Tanzania

BACKGROUND

Antimicrobial resistance is particularly harmful to infectious disease management in low-income countries since expensive second-line drugs are not readily available. The objective of this study was to implement and evaluate a computerized system for surveillance of antimicrobial resistance at a tertiary hospital in Tanzania.

METHODS

A computerized surveillance system for antimicrobial susceptibility (WHONET) was implemented at the national referral hospital in Tanzania in 1998. The antimicrobial susceptibilities of all clinical bacterial isolates received during an 18 months' period were recorded and analyzed.

RESULTS

The surveillance system was successfully implemented at the hospital. This activity increased the focus on antimicrobial resistance issues and on laboratory quality assurance issues. The study identified specific nosocomial problems in the hospital and led to the initiation of other prospective studies on prevalence and antimicrobial susceptibility of bacterial infections. Furthermore, the study provided useful data on antimicrobial patterns in bacterial isolates from the hospital. Gram-negative bacteria displayed high rates of resistance to common inexpensive antibiotics such as ampicillin, tetracycline and trimethoprim-sulfamethoxazole, leaving fluoroquinolones as the only reliable oral drugs against common Gram-negative bacilli. Gentamicin and third generation cephalosporins remain useful for parenteral therapy.

CONCLUSION

The surveillance system is a low-cost tool to generate valuable information on antimicrobial resistance, which can be used to prepare locally applicable recommendations on antimicrobial use. The system pinpoints relevant nosocomial problems and can be used to efficiently plan further research. The surveillance system also functions as a quality assurance tool, bringing attention to methodological issues in identification and susceptibility testing.