Lilian Masoud

Orally administered colistin leads to colistin-resistant intestinal flora and fails to prevent faecal colonisation with extended-spectrum β-lactamase-producing enterobacteria in hospitalised newborns.

Colonisation and infection with extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) is an emerging problem. The aim of this study was to investigate whether colistin, which is reported to be effective against multiresistant enterobacteria, prevents ESBL-E colonisation in neonates. For prophylaxis of necrotising enterocolitis, oral gentamicin (15 mg/kg/day) is routinely used in all neonates hospitalised at the Neonatal Intensive Care Unit of University Hospital Graz (Austria). During the study period from May 2005 to September 2007, three ESBL-E outbreaks (total duration 18 months) occurred. During these outbreaks, gentamicin was immediately replaced by oral colistin (8 mg/kg/day) in all hospitalised neonates. All neonates colonised with ESBL-E during the study period were retrospectively analysed with regard to the influence of colistin on ESBL-E colonisation. Genetic relatedness of isolates was assessed by repetitive sequence-based polymerase chain reaction (rep-PCR). During the study period, 30 (4.5%) of 667 neonates were colonised with ESBL-E. Twelve of twenty-one patients colonised with Klebsiella pneumoniae (ESBL-Kp) and one of nine patients colonised with Klebsiella oxytoca (ESBL-Ko) had received oral colistin at time of colonisation with ESBL-E. Amongst ESBL-Kp, the rate of colistin resistance was significantly higher in the colistin group (P=0.0075). Four different clones of ESBL-Kp and three different clones of ESBL-Ko were isolated, indicating the occurrence of patient-to-patient transmission. Colistin-resistant as well as colistin-susceptible isolates were detected within the same clones, indicating induction of resistance. At the dosage used, oral colistin did not prevent colonisation with ESBL-E and appeared to select colistin-resistant strains or to induce colistin resistance.

Occurrence and genotyping using automated repetitive-sequence–based PCR of methicillin-resistant Staphylococcus aureus ST398 in Southeast Austria☆☆☆

In this retrospective study, the occurrence and genetic relatedness of methicillin-resistant Staphylococcus aureus (MRSA) ST398 in Austrian MRSA patients was investigated. From 2002 to 2008, 14 MRSA ST398 were detected. First occurrence of MRSA ST398 was already found in 2004. Spa ribotyping assigned 12 isolates to spa type t011 and 1 each to spa type t034 and spa type t1451. Isolated MRSA ST398 was nontypeable by pulsed-field gel electrophoresis (NT-MRSA) using restriction enzyme SmaI; therefore, genotyping was performed using automated repetitive-sequence-based PCR (rep-PCR) on the DiversiLab system. Rep-PCR results assigned 10 (71%) of the 14 MRSA ST398 into 1 cluster with a similarity >95%; there was 1 cluster consisting of 2 isolates with a similarity >99% and 2 unique MRSA ST398 isolates. In conclusion, MRSA ST398 was continuously detected in Southeast Austria; first in 2004 with up to 5 MRSA ST398 isolates in 2008. Automated rep-PCR proved as a reliable technique in determining genetic relatedness of NT-MRSA ST398 and demonstrates clonal spread of MRSA ST398 in the investigated region.

Virulence and antimicrobial resistance genes in human MRSA ST398 isolates in Austria.

SUMMARY This study determined the genetic background of virulence and resistance genes of MRSA ST398 in Austria. From 2004 up to 2008 a total of 41 human isolates of MRSA ST398 were investigated for virulence and resistance gene patterns using DNA microarray chip analysis. Highly similar virulence gene profiles were found in 29 (70·7%) of the isolates but genes encoding Panton–Valentine leukocidin, enterotoxins, or toxic shock syndrome toxin were not detected. Genes conferring resistance to tetracycline and erythromycin-lincosamide were common as all but one of the isolates exhibited tetM and/or tetK, which are involved in tetracycline resistance, and 12 (29·9%) were positive for ermC, conferring resistance to erythromycin/lincosamide. SplitsTree analysis showed that 40 isolates were closely related. Changes in virulence and resistance gene patterns were minimal over the observed time period.

Antimicrobial resistance of Streptococcus pneumoniae in Southeast Austria, 1997-2008

Antibiotic resistance in Streptococcus pneumoniae has increased worldwide but varies within geographical regions. We conducted a retrospective analysis of resistance in S. pneumoniae over a 12-year period to assess local and temporal trends in antibacterial resistance. From 1997 to 2008, a total of 1814 non-duplicate S. pneumoniae isolates were identified at the Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Austria. Antibiotic resistance was determined by the Clinical and Laboratory Standards Institute (CLSI) disk diffusion test. For penicillin, the minimum inhibitory concentration was determined by Etest. Susceptibility was defined according to CLSI interpretive criteria. For penicillin, resistance rates were consistently low at 0.2% over the 12-year study period. An increase in resistance was remarkable for erythromycin (3.5% in 1997; 14.7% in 2008), clindamycin (1.8% in 1997; 10.6% in 2008) and tetracycline (1.8% in 2000; 11.0% in 2008). For trimethoprim/sulfamethoxazole, resistance increased slightly to 9.2% in 2008. Quinolones showed a low resistance rate of 0.2% that persisted over the whole study period. In contrast to previously published national data, resistance to penicillin was observed to remain at a remarkably low and constant level. Although international surveillance programmes have set up sustainable and interlinked data networks, our results suggest that regional surveillance may still be needed as decision support for appropriate empirical antibiotic therapy in the local health setting.

Multidrug-resistant bacteria in southeastern Austria.

To the Editor: In many parts of the world, the proportions of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci, and extended-spectrum β-lactamase (ESBL)–producing organisms in the family Enterobacteriaceae have increased remarkably during recent years (1). However, proportions of antimicrobial drug resistance vary substantially at national and regional levels. We describe antimicrobial drug resistance data for hospitalized patients and outpatients in southeast Austria. A total of 690,967 clinical samples were collected from hospitalized patients and outpatients and analyzed at the microbiology laboratory of the Medical University of Graz during 1997–2006. Selected for resistance surveillance were nonduplicate isolates of S. aureus, Enterococcus faecium, E. faecalis, Escherichia coli, and Klebsiella spp. Antibiotic susceptibilities were determined by using disk diffusion and the VITEK2 system (bioMerieux, Marcy l’Etoile, France) with specific susceptibility test cards. Etest (AB Biodisk, Solna, Sweden) was used to confirm results. Test results were interpreted according to the recommendations of the Clinical and Laboratory Standards Institute (2). During the study period, the proportion of patients with MRSA remained stable (2.5%–4.9%) (Figure, panel A). The prevalence of MRSA among invasive S. aureus isolates ranges between 0.5% and 44.4% in European countries and has increased in recent years (3). We found MRSA predominantly in samples from hospitalized patients (median 72.1%); however, the incidence of community-acquired MRSA increased slightly during recent years, similar to that of other central European countries (4). Vancomycin resistance was not noted during the study period; however, 4 vancomycin-intermediate MRSA isolates were noted in 2004, 2005, and 2006, in concordance with the sporadic occurrence of MRSA with intermediate susceptibility to glycopeptides recently reported for other European countries (3). The percentage of patients with vancomycin-resistant E. faecium and E. faecalis was low (median 0.4%) (Figure, panel A). In total, 10 E. faecium and 4 E. faecalis isolates with resistance to vancomycin were reported; most were from hospitalized patients. As in most European countries, human infections due to glycopeptide-resistant enterococci remain rare in Austria, although a high proportion of glycopeptide-resistant E. faecium was reported recently from animals used in food production (5). Among E. coli isolates, no ESBL producers were noted in 1997. From 1998 through 2002, proportions of ESBL-producing E. coli were 0.06%–0.13%, which corresponds to 3–6 isolates per year. A subsequent increase of ESBL-producing E. coli isolates was noted, from 19 (0.3%) in 2003 to 148 (2.4%) in 2006 (Figure, panel B). Most (67%) ESBL-producing isolates found during 2003–2006 originated from community-acquired urinary tract infections. Resistance of E. coli to carbapenems was not reported during the study period. Among Klebsiella spp. isolates, 2 (0.2%) ESBL producers were observed during 1997. From 1998 through 2004, the prevalence of ESBLs among Klebsiella spp. ranged between 0.6% and 1.6%. In 2005 and 2006, the rate of ESBL-producing Klebsiella spp. increased to 3.8% (44 isolates) and 4.5% (55 isolates), respectively, and originated mainly from intensive care units (Figure, panel B). In 2005, a single Klebsiella pneumoniae isolate showed reduced susceptibility to imipenem (MIC 2 μg/mL) and to meropenem (MIC 4 μg/mL) and resistance to ertapenem (MIC >16 μg/mL). Nevertheless, production of ESBL by Enterobacteriaceae organisms is still rare in southeast Austria compared with other European countries (6). However, a dramatic increase of ESBL-producing E. coli and Klebsiella spp. has been observed during recent years. The increase of ESBL-producing E. coli isolates in outpatients with urinary tract infections leads to serious treatment problems. Results from a recent study indicate that the increase of ESBL-producers in southeast Austria is caused mainly by the emergence of CTX-M–type ESBLs, which are increasingly being isolated from outpatients (7). The K. pneumoniae isolate found in 2005 represents the first ESBL-producing isolate not susceptible to carbapenems reported from Austria. Development of resistance to carbapenems in Enterobacteriaceae organisms has been reported increasingly, which substantially limits treatment options for persons with multidrug-resistant gram-negative infections (8). Our data show insignificant changes in prevalence of MRSA and vancomycin-resistant enterococci in southeast Austria during the past decade but an alarming increase of multidrug-resistant ESBL-producing E. coli and Klebsiella spp. isolates in recent years. Detection of an ESBL-producing K. pneumoniae isolate with reduced susceptibility to carbapenems shows that pathogens with new mechanisms of resistance are emerging in this region. Figure A) Proportion of methicillin resistance in Staphylococcus aureus and vancomycin resistance in Enterococcus faecium and E. faecalis in southeastern Austria, 1997–2006. B) Proportion of extended-spectrum β-lactamase–producing (ESBL) ...