Mats Walder

Molecular Epidemiology of Metallo-β-Lactamase-Producing Pseudomonas aeruginosa Isolates from Norway and Sweden Shows Import of International Clones and Local Clonal Expansion

ABSTRACT Scandinavia is considered a region with a low prevalence of antimicrobial resistance. However, the number of multidrug-resistant (MDR) Gram-negative bacteria is increasing, including metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa. In this study MBL-producing P. aeruginosa isolates identified in Norway (n = 4) and Sweden (n = 9) from 1999 to 2007 were characterized. Two international clonal complexes (CC), CC111 (n = 8) and CC235 (n = 2), previously associated with MBL-producing isolates, were dominant. CC111 isolates (ST111/229; serotype O12; blaVIM-2) included clonally related isolates identified in Skåne County, Sweden (n = 6), and two isolates associated with importation from Greece and Denmark. In all CC111 isolates, blaVIM-2 was located in integron In59.2 or In59 variants. The two CC235 isolates (ST235/ST230; serotype O11; blaVIM-4) were imported from Greece and Cyprus, were possibly clonally related, and carried blaVIM-4 in two different integron structures. Three isolates imported from Ghana (ST233; serotype O6; blaVIM-2), Tunisia (ST654; serotype O11; blaVIM-2), and Thailand (ST260; serotype O6; blaIMP-14) were clonally unrelated. ST233 was part of a new CC (CC233) that included other MBL-producing isolates, while ST654 could also be part of a new CC associated with MBL producers. In the isolates imported from Ghana and Tunisia, blaVIM-2 was part of unusual integron structures lacking the 3′ conserved segment and associated with transposons. The blaVIM gene was found to be located on the chromosome in all isolates. Known risk factors for acquisition of MBL were reported for all patients except one. The findings suggest that both import of successful international clones and local clonal expansion contribute to the emergence of MBL-producing P. aeruginosa in Scandinavia.

ThermotolerantCampylobacter with no or weak catalase activity isolated from dogs

ThermotolerantCampylobacter strains isolated from dog feces were characterized by phenotypical tests, DNA base composition, and DNA-DNA-hybridization. Out of 98 strains, 63 were catalase negative or weakly reacting (CNW); they were found in diarrheic as well as in healthy dogs. The CNW strains were all nalidixic-acid sensitive, hippurate negative, and grew at 42°C but not at 25°C. Seven strains were further investigated. They were sensitive to 2,3,5-triphenyl-tetrazolium chloride, reduced nitrate, and produced H2S in the lead acetate test but not in triple-sugar-iron agar. The mol% G+C for five CNW isolates ranged from 35.2–35.8, which is higher than reported for any thermotolerantCampylobacter species. The strains also formed a well-delimitated DNA homology group with 80% or more intragroup relatedness and about 40% related toC. coli andC. jejuni.

Extended-spectrum beta-lactamase-producing Escherichia coli in patients with travellers' diarrhoea.

Abstract The identification of patients carrying extended-spectrum beta-lactamase (ESBL)-producing bacteria is important, since these patients are at risk of receiving inappropriate empirical therapy if they become infected. The purpose of this study was to investigate the occurrence of ESBL-producing bacteria in patients with travellers’ diarrhoea. Patients with travellers’ diarrhoea (N = 242) having delivered stool samples for the diagnosis of Salmonella, Shigella, Yersinia or Campylobacter, were also examined for ESBL-producing Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis. The overall prevalence of faecal carriage of ESBL-producing bacteria was 24% (58/242). Of the patients who had travelled in Europe, 3% (2/63) were found to be ESBL carriers in comparison to 36% (50/138) of those who had travelled outside Europe. ESBL-producing E. coli was especially common among patients returning from India (11/14), Egypt (19/38; 50%) and Thailand (8/38; 22%). In total, 90% of the genes of the ESBL-positive samples were of CTX-M type. The CTX-M-1 group dominated, followed by the CTX-M-9 group. The repetitive sequence-based PCR fingerprint pattern showed that there was no similarity between the ESBL strains found. Patients who have travelled outside Europe are at high risk of being colonized with ESBL-producing Enterobacteriaceae, and, if infected, are also at risk of receiving inappropriate empirical antibiotic therapy.

The throat : An important site for MRSA colonization

In order to evaluate the value of bacterial cultures taken from the throat, 266 patients with MRSA were retrospectively assessed. At the time when MRSA was first detected in the patient, the most frequent sites positive for MRSA were a skin lesion (110 patients, 41%), the anterior nares (109 patients, 41%), and the throat (102 patients, 38%). In 26%, 17%, and 17% of the patients, a skin lesion, the anterior nares, and the throat, respectively, were the only site where MRSA was seen. In 123 patients cultured for MRSA because of a close contact with an already known MRSA patient, 65 patients (53%) were positive for MRSA in their throat and in 40 patients (33%), throat was the only sample site with MRSA at the time when the patient was found to be MRSA positive. 146 of the 266 patients (55%) were colonized with MRSA in the throat any time throughout the period they were MRSA positive. We conclude that throat is an important reservoir for MRSA and that samples taken from the throat should be included in screening patients for MRSA.

Activity of three disinfectants and acidified nitrite against Clostridium difficile spores.

OBJECTIVE To identify environmentally safe, rapidly acting agents for killing spores of Clostridium difficile in the hospital environment. DESIGN Three classic disinfectants (2% glutaraldehyde, 1.6% peracetyl ions, and 70% isopropanol) and acidified nitrite were compared for activity against C. difficile spores. Four strains of C. difficile belonging to different serogroups were tested using a dilution-neutralization method according to preliminary European Standard prEN 14347. For peracetyl ions and acidified nitrite, the subjective cleaning effect and the sporicidal activity was also tested in the presence of organic load. RESULTS Peracetyl ions were highly sporicidal and yielded a minimum 4 log10 reduction of germinating spores already at short exposure times, independent of organic load conditions. Isopropanol 70% showed low or no inactivation at all exposure times, whereas glutaraldehyde and acidified nitrite each resulted in an increasing inactivation factor (IF) over time, from an IF greater than 1.4 at 5 minutes of exposure time to greater than 4.1 at 30 minutes. Soiling conditions did not influence the effect of acidified nitrite. There was no difference in the IF among the 4 strains tested for any of the investigated agents. Acidified nitrite demonstrated a good subjective cleaning effect and peracetyl ions demonstrated a satisfactory effect. CONCLUSIONS Cidal activity was shown against C. difficile spores by glutaraldehyde, peracetyl ions, and acidified nitrite. As acidified nitrite and peracetyl ions are considered to be environmentally safe chemicals, these agents seem well suited for the disinfection of C. difficile spores in the hospital environment.

Prevalence of faecal ESBL carriage in the community and in a hospital setting in a county of Southern Sweden.

The aim of this study was to investigate the prevalence of extended-spectrum beta-lactamase (ESBL)-producing bacteria in patients at various hospital wards and in a group of relatively healthy volunteers, in order to obtain greater knowledge on how common these bacterial strains are in hospital settings and in the general community. Participants (n = 427) were enrolled at a University Hospital and at Primary Health Care Units (PHCUs) in Sweden in 2008 and 2010. The participants provided rectal swabs, which were tested for the occurrence of ESBL-producing bacteria. Positive samples were analysed with polymerase chain reaction (PCR) methods for bacterial strain typing and ESBL phylogroups. In 2008, the prevalence was 2.1% (2/96) in PHCU subjects and 1.8% (2/113) in hospital patients. In 2010, the prevalence was 3.0% (3/100) in PHCU subjects and 6.8% (8/118) in hospital patients. The dominating phylogroups were CTX-M-1 and CTX-M-9. All ESBL-positive isolates were Escherichia coli. We found a higher prevalence of ESBL faecal carriage than expected, both in the hospital setting and in the PHCU group.

Antimicrobial susceotibilirv of bacterial isolates in South Sweden including a 13-year follow-up study of some respiratory tract pathogens

The antibiotic susceptibility of consecutive isolates of the upper respiratory tract pathogens Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae, Branhamella catarrhalis, and Staphylococcus aureus, (100 strains of each species collected each year during March through April 1985, 1988 and 1992) to penicillin V, amoxycillin, cefaclor, cefuroxime, doxycycline, erythromycin, and co‐trimoxazole was investigated by MIC determination on PDM and PDM II agar. The MICs of the upper respiratory isolates from 1992 supplemented with 100 isolates each of Escherichia coli, Klebsiella spp., Enterobacter cloacae, Proteus mirabilis and Staphylococcus saprophytics collected during 1992 were determined against the above antibiotics plus cefadroxil, cefpodoxime, roxithromycin, ciprofloxacin, ofloxacin, and BAY Y 3118. Beta‐lactamase production was found in 10% of H. influenzae and 80–90% of S. aureus and B. catarrhalis in 1992. Among H. influenzae isolates, non‐beta‐lactamase‐induced resistance to all beta‐lactam antibiotics was first detected in 1988 and amounted to 3% of isolates in 1992. Decreased susceptibility of S. preumoniae to penicillin (>0.12 mg/1), co‐trimoxazole 32 mg/1, doxycycline (2 ml/1) and erythromycin (1 mg/1) was detected in 11%, 7%, and 8%, respectively, in 1992, which is significantly higher than in previous years at the same laboratory. Decreased susceptibility of S. pyogenes to doxycycline and erythromycin was detected in 11% and 9% in 1992. The two most recently developed antibiotics, cefpodoxime and BAY Y 3118, showed high antibacterial activity. The study emphasizes the need to screen for resistance mechanisms such as beta‐lactamase production and lowered penicillin affinity.

Antibiotic resistance of coagulase-negative staphylococci in an orthopaedic department

Coagulase-negative staphylococci (CNS) were cultured from the anterior nares of surgeons, theatre and ward staff, and from patients before and 2 weeks after a total hip replacement. The CNS found in ward staff were more resistant to antibiotics than those in surgeons and theatre staff. Methicillin resistance of CNS in patients increased from 4 to 31% following surgery. Gentamicin-resistant CNS were only found postoperatively, in 20% of patients, in most of whom gentamicin-loaded acrylic bone cement was used.

Antimicrobial susceptibilities of Listeria monocytogenes strains isolated from 1958 to 1982 in Sweden.

Antibiotic susceptibility was studied in 175 clinical isolates of Listeria monocytogenes. There were no major changes in the susceptibility of strains between 1958 and 1982. Benzylpenicillin and ampicillin had MICs for 90% of the strains (MIC90) of 0.5 micrograms/ml. Gentamicin also had good activity against L. monocytogenes, with an MIC90 of 1.0 microgram/ml. All the new beta-lactamase-stable cephalosporins tested had relatively poor activity against L. monocytogenes. Of the bacteriostatic antibiotics, trimethoprim had by far the lowest MIC90 (0.06 microgram/ml), and in combination with sulfamethoxazole (co-trimoxazole), it had an MIC90 of 0.5 microgram/ml. Both erythromycin and doxycycline had low MIC90s (0.25 microgram/ml).

Duration of colonization with extended-spectrum beta-lactamase-producing Escherichia coli in patients with travellers' diarrhoea.

Abstract Background: Resistant Enterobacteriaceae have become a worldwide epidemic during the last decade and are a great threat to health care worldwide. International travel is a major risk factor for becoming colonized with extended-spectrum beta-lactamase (ESBL)-producing bacteria. Data on the persistence of colonization with ESBL-producing bacteria in the faecal flora are limited.Methods: A prospective cohort study was performed between October 2007 and October 2010. Fifty-eight patients with faecal carriage of ESBL-producing Escherichia coli from a previous study of patients with travellers’ diarrhoea were included.Results: Forty-one of the patients had a complete follow-up. Ten of these patients (24%) carried ESBL-producing E. coli at the first follow-up point (3–8 months), of whom 4 had a new ESBL strain. At the 3-y follow-up, 4 patients carried ESBL (10%), of whom 1 had 2 new ESBL strains.Conclusions: The long duration of ESBL carriage is worrisome. These carriers may be an important source of the spread of ESBLs in the population and this has implications for the clinical management of patients.