Martin Kaase

NDM-2 carbapenemase in Acinetobacter baumannii from Egypt

OBJECTIVES To analyse the mechanisms responsible for carbapenem resistance in one Acinetobacter baumannii isolate recovered from a patient transferred to Germany from an Egyptian hospital. METHODS PCR and sequencing were used to search for β-lactamase and 16S RNA methylase genes. Multilocus sequence typing was used to determine the sequence type (ST) of the isolate. RESULTS Sequencing of the PCR product obtained using primers for bla(NDM-1) revealed a variant of NDM-1 that had a C to G substitution at position 82 resulting in an amino acid substitution of proline to alanine at position 28. This variant was designated NDM-2. Genes encoding extended-spectrum β-lactamases or 16S RNA methylase were not detected. The strain lacked detectable plasmids and bla(NDM-2) was not transferred by conjugation. MLST showed that the isolate belonged to a new ST, ST103. CONCLUSIONS This work further underlines the spread of NDM carbapenemases in A. baumannii, and the spread of the corresponding gene in the Middle East. It also describes the first variant of NDM-1.

Tn125-Related Acquisition of blaNDM-Like Genes in Acinetobacter baumannii

ABSTRACT A multidrug-resistant Acinetobacter baumannii isolate recovered from a patient hospitalized in Switzerland after a transfer from Serbia produced the NDM-1 carbapenemase. The blaNDM-1 gene was part of a chromosomally located Tn125 composite transposon bracketed by two copies of the same insertion sequence, ISAba125. This transposon was also associated with the acquisition and expression of the blaNDM-2 gene in an A. baumannii isolate in Germany. Tn125 appears to be the main vehicle for dissemination of blaNDM genes in that species.

Identification of molecularly defined Staphylococcus aureus strains using matrix-assisted laser desorption/ionization time of flight mass spectrometry and the Biotyper 2.0 database

Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) has recently been introduced for bacterial identification. To our knowledge, this is the first study where the Biotyper 2.0 database (Bruker Daltonics) has been applied for bacterial identification in a local strain collection of molecularly defined Staphylococcus aureus. We showed that the accuracy of the Biotyper 2.0-based identification for 602 molecularly defined strains of S. aureus, irrespective of meticillin resistance, was equivalent to that of the molecularly defined reference even at a score cut-off value of 2. Also, 412 isolates of 20 different species of non-S. aureus staphylococci were all correctly identified to species level compared to the molecularly defined reference. Moreover, the MALDI-TOF MS-based S. aureus identification approach was clearly faster than more time-consuming methods such as a molecular identification approach.

Detection of carbapenemases in Enterobacteriaceae by a commercial multiplex PCR

ABSTRACT A commercial multiplex PCR (hyplex SuperBug ID) was tested with a collection of 132 clinical Enterobacteriaceae strains producing different carbapenemases. The sensitivity for the detection of KPC-, VIM-, NDM-, and OXA-48-encoding genes was 100%, whereas two IMP variants were missed.

Uncomplicated Urinary Tract Infections

BACKGROUND Urinary tract infections (UTIs) are among the most common types of bacterial infection in outpatient medicine. Rising rates of antibiotic resistance and a better understanding of the ecological adverse effects (collateral damage) of antibiotics warrant a reevaluation of the treatment recommendations for uncomplicated UTI. The new S3 guideline contains updated recommendations. METHODS The new S3 guideline is based on a review of publications on uncomplicated UTI retrieved by a systematic search of the Medline and Cochrane Library databases. Guidelines from abroad were also considered in the review. RESULTS Uncomplicated UTI is classified as either uncomplicated cystitis (UC) or uncomplicated pyelonephritis (UP). The choice of a suitable antibiotic is determined by the following main criteria: the patients individual risk profile and prior antibiotic treatment, if any; the spectrum of pathogens and antibiotic susceptibility; the proven efficacy of the antibiotic; the ecological adverse effects (collateral damage) of antimicrobial therapy; the side effects for the patient under treatment. On the basis of these criteria, co-trimoxazole/trimethoprim and fluoroquinolones can no longer be recommended as first-line empirical treatment for UC. Rather, the new recommended treatment of first choice consists of fosfomycin-trometamol, nitrofurantoin, or pivmecillinam. High-dose fluoroquinolones are still recommended, however, as first-line oral treatment for UP. Asymptomatic bacteriuria should only be treated in exceptional situations such as pregnancy or before urological procedures that will probably injure the mucosa of the urinary tract. CONCLUSION The new S3 guideline on uncomplicated UTI incorporates a forward-looking approach to the use of antibiotics in treating this common type of infection. It is intended to bring about a sustained improvement in the quality of care.

An outbreak of carbapenem-resistant OXA-48 – producing Klebsiella pneumonia associated to duodenoscopy

BackgroundCarbapenemase-producing Enterobacteriaceae (CPE) have become a major problem for healthcare systems worldwide. While the first reports from European hospitals described the introduction of CPE from endemic countries, there is now a growing number of reports describing outbreaks of CPE in European hospitals. Here we report an outbreak of Carbapenem-resistant K. pneumoniae in a German University hospital which was in part associated to duodenoscopy.FindingsBetween December 6, 2012 and January 10, 2013, carbapenem-resistant K. pneumoniae (CRKP) was cultured from 12 patients staying on 4 different wards. The amplification of carbapenemase genes by multiplex PCR showed presence of the blaOXA-48 gene. Molecular typing confirmed the identity of all 12 isolates. Reviewing the medical records of CRKP cases revealed that there was a spatial relationship between 6 of the cases which were located on the same wards. The remaining 6 cases were all related to endoscopic retrograde cholangiopancreatography (ERCP) which was performed with the same duodenoscope. The outbreak ended after the endoscope was sent to the manufacturer for maintenance.ConclusionsThough the outbreak strain was also disseminated to patients who did not undergo ERCP and environmental sources or medical personnel also contributed to the outbreak, the gut of colonized patients is the main source for CPE. Therefore, accurate and stringent reprocessing of endoscopic instruments is extremely important, which is especially true for more complex instruments like the duodenoscope (TJF Q180V series) involved in the outbreak described here.

Comparison of phenotypic methods for penicillinase detection in Staphylococcus aureus

Penicillinase testing is required for Staphylococcus aureus isolates with a penicillin MIC of </=0.12 mg/L. This study compared five phenotypic assays with a PCR for blaZ when testing 197 S. aureus isolates. The starch-iodine plate method and nitrocefin tests had low sensitivities of 42.9% and 35.7%, respectively. The cloverleaf assay and the penicillin zone-edge determination method had sensitivities of 67.8% and 71.4%, respectively, and these methods might be appropriate in many circumstances, but were not as sensitive as blaZ PCR.

Fosfomycin Susceptibility in Carbapenem-Resistant Enterobacteriaceae from Germany

ABSTRACT Due to the increase in multidrug-resistant Enterobacteriaceae, the interest in older antimicrobial agents, like fosfomycin, has increased. In this study, we used agar dilution for testing susceptibilities to fosfomycin in a collection of 107 carbapenem-nonsusceptible Enterobacteriaceae isolates, of which 80 produced various types of carbapenemases, including KPC, VIM, NDM, and OXA-48. Overall, 78% of the strains had fosfomycin MICs of ≤32 mg/liter and were thus considered to be susceptible according to the current EUCAST breakpoint. The MIC50 and MIC90 were 8 mg/liter and 512 mg/liter, respectively. Escherichia coli strains had significantly lower fosfomycin MICs than the Klebsiella pneumoniae and Enterobacter cloacae strains. Furthermore, comparisons of the susceptibility testing methods, like Etest and disk diffusion, were performed against agar dilution as the reference method. Essential agreement between Etest and agar dilution was 78.9%, and categorical agreement between the two methods was 92.5%, with 20% very major errors and 2.6% major errors. Disk diffusion was studied with 50-μg and 200-μg fosfomycin disks, but no inhibition zone breakpoint that reduced very major and major errors to an acceptable level was found. Etest and disk diffusion showed poor agreement with fosfomycin agar dilution.

The matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS)-based protein peaks of 4448 and 5302 Da are not associated with the presence of Panton-Valentine leukocidin.

The Panton-Valentine leukocidin (PVL) of Staphylococcus aureus plays an important role in the pathogenesis of necrotizing pneumonia and recurrent skin and soft tissue infections. The gene encoding for PVL, lukS/F-PV, is distributed by prophages and can thus spread between isolates. Molecular methods have normally been used to identify lukS/F-PV-positive strains. Recently, however, a matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS)-based method has been described to identify PVL-positive S. aureus strains. The aim of this study was thus to investigate the association of distinct MALDI-TOF MS peaks to the toxin profile in molecularly characterized methicillin-susceptible (MSSA) and methicillin-resistant S. aureus (MRSA) strains harbouring lukS/F-PV. In contrast to the previous results, the MALDI-TOF MS peaks were detected in all 104 recently described molecularly divergent MRSA irrespective of the presence of PVL. Our result indicates that these described peaks seem to be independent of the presence of PVL.

Detection of the carbapenemase GIM-1 in Enterobacter cloacae in Germany

OBJECTIVES To characterize the mechanisms involved in reduced susceptibility to carbapenems in two Enterobacter cloacae clinical isolates. METHODS Two E. cloacae isolates recovered from different regions in Germany and showing reduced susceptibility to carbapenems were analysed. Susceptibility testing, conjugation, transformation assays, plasmid analysis, sequencing and molecular typing using rep-PCR were performed. RESULTS The two clinical isolates carried the bla(GIM-1) gene and showed resistance to ertapenem, with variable MIC values of imipenem and meropenem. The isolates were clonally unrelated. The bla(GIM-1) gene was located on self-transferable and non-typeable plasmids. Both isolates harboured distinct plasmids and integron structures containing the bla(GIM-1) gene cassette. Interestingly, one of the two plasmids was able to replicate in Pseudomonas aeruginosa, demonstrating its broad host range. CONCLUSIONS This is the first identification in E. cloacae of the bla(GIM-1) gene, which is responsible for reduced susceptibility to carbapenems. We showed that this gene, previously identified in P. aeruginosa, was located in a different genetic background in E. cloacae. The bla(GIM-1) gene might spread quite efficiently in Enterobacteriaceae and P. aeruginosa, as it is difficult to detect and in addition is located on conjugative plasmids.