SULM – Schweizerische Union für Labormedizin | Union Suisse de Médecine de Laboratoire | Swiss Union of Laboratory Medicine

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V DONÀ1, S KASRAIAN1, R ZBINDEN2, B SAVIC3, F IMERI3, H FURRER4, N LOW5, A ENDIMIANI1

1Institute for Infectious Diseases, University of Bern, Bern, Switzerland, 2Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland, 3Laborgemeinschaft 1, Zurich, Switzerland, 4Department of Infectious Diseases, Bern University Hospital, University of Bern, Bern, Switzerland, 5Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland

Background: Antimicrobial resistance in Neisseria gonorrhoeae is a major public health concern, requiring continuous surveillance to identify emerging resistance and monitor susceptibility trends.

Methods: Overall, 270 N. gonorrhoeae isolates collected between 1989 and 2015 (of which: 1989-91, n=57; 1999-2003, n=71; and 2011-2015, n=99) in Bern (n=86) and Zurich (n=184) were included in our study. Antimicrobial susceptibility tests for cefixime, ceftriaxone, ciprofloxacin, azithromycin and spectinomycin were assessed using the Etest method on GC agar to obtain MIC values. Results were interpreted according to the EUCAST 2015 criteria. Sequence type (ST) was obtained from NG multi-antigen sequence typing (NG-MAST) for 105 (38.9%) representative isolates (of which: 1989-91, n=12; 2001-2005, n=32; and 2011-2015, n=61).

Results: The following MIC50/90 (µg/ml) and % of susceptible isolates were recorded: cefixime (1989-1991: ≤0.016/0.023, 100%; 1999-2003: ≤0.016/,≤0.016, 100%; 2011-2015: ≤0.016/0.094, 96%), ceftriaxone (1989-1991: ≤0.016/≤0.016, 100%; 1999-2003: ≤0.016/0.023, 100%; 2011-2015: ≤0.016/0.032, 100%), ciprofloxacin (1989-1991: ≤0.016/≤0.016, 98%; 1999-2003: ≤0.016/4, 79%; 2011-2015: ≤0.016/≥32, 53%), and azithromycin (1989-1991: 0.125/0.38, 67%; 1999-2003: 0.19/0.38, 69%; 2011-2015: 0.19/0.38, 75%). All N. gonorrhoeae isolates were fully susceptible to spectinomycin. The most common STs in each period were: 1989-91 (ST10856, 3/12); 1999-2003 (ST8672, 3/32); 2011-2015 (ST2992, 8/61; ST1407, 3/61).

Conclusions: In Switzerland, MIC creep for extended-spectrum cephalosporins is occurring (4/99, 4.0% cefixime resistant isolates in 2011-2015). Ciprofloxacin resistance rose from 2% (1989-1991) to 47% (2011-2015) over the study period; the highest prevalence (89%) was in 2012. Around 30% of isolates in all periods were non-susceptible to azithromycin. The presence of international hyperepidemic clones (ST2992 and ST1407) was observed. Our results are consistent with those globally observed.

This study was funded by the SwissTransMed (Rapid Diagnosis of Antibiotic Resistance in Gonorrhoea, RaDAR-Go).

C HIRZEL1, L HIRZBERGER1, H FURRER1, A ENDIMIANI2

1Department of Infectious Diseases, Bern University Hospital, University of Bern, Bern, Switzerland, 2Institute for Infectious Diseases, University of Bern, Bern, Switzerland

Introduction: A. urinae may cause severe infections (bacteremia and endocarditis) associated with high mortality. However, data on bactericidal and synergistic activity for clinically implemented antibiotics is scarce.

Methods: We performed time-kill (TK) analyses on 2 clinical isolates (AU1 and AU2) and ATCC700306 for penicillin (PG), ceftriaxone (CRO), gentamicin (GEN), daptomycin (DAP) and their combinations. TK experiments were performed in TH broth (supplemented with 50 µg/ml calcium for experiments with DAP). All experiments were performed at least 3 times at antibiotic concentrations of 0.5x, 1x, 2x, and 4x the MICs. Using the EUCAST criteria for viridans streptococci AU1 and AU2 were CRO-resistant (MICs, 2 µg/ml). ATCC was GEN high-level resistant (MIC, 512 µg/ml), whereas all strains were PG- and DAP-susceptible (MICs <0.125 and ≤1 µg/ml, respectively). CFU/ml count was determined at 0, 2, 4, 6, 8, 24, 30, and 48 hrs. Bactericidal activity was defined as a ≥3-log10 decrease in CFU/ml compared to the initial inoculum at 8 and 24 hrs. Synergism was defined as a ≥2-log10 decrease in CFU/ml at 8 and 24 hrs comparing the antimicrobial combination to the most active single antimicrobial drug.

Results: PG or CRO alone were not bactericidal for all strains, whereas DAP exhibited bactericidal activity at all MICs for AU2 and ATCC. The combination of PG or CRO with GEN was bactericidal for AU1 and AU2 at concentrations ≥1x MICs. Bactericidal synergism was detected for PG or CRO combined with GEN in the 2 clinical isolates. PG plus CRO showed non-bactericidal synergism for ATCC. DAP with GEN was synergistic at 1x MICs for AU1, whereas the killing activity of DAP was too pronounced to detect potential synergism in AU2.

Discussion: We demonstrated that the combination of PG or CRO with GEN is synergistic and bactericidal. Moreover, our data suggests that DAP may represent a potential bactericidal treatment alternative against A. urinae. This finding could be important for the treatment of patients with a β-lactam allergy or renal insufficiency.

This work was supported by grant 84800508 2014-15 from Bern University Hospital and University of Bern.

F. OECHSLIN1, P. PICCARDI1, M. GIDDEY1, S. MANCINI1, J. GABARD2, P. MOREILLON1, J.M. ENTENZA1, G. RESCH1, Y-A. QUE3

1Dept. of Fundamental Microbiology, University of Lausanne, Switzerland, 2Pherecydes Pharma, Romainville, France, 3Dept. of Intensive Care Medicine, Bern University Hospital, Switzerland

The continuing development of antibiotic resistance stresses the need for alternative treatment. Infective endocarditis due to P. aeruginosa is an archetype of highly lethal valve infection in human. Therefore we used in vitro and in vivo models of P. aeruginosa experimental endocarditis (fibrin clots and rats with catheter-induced aortic vegetations, respectively) to study the efficacy of an anti-pseudomonas phage cocktail and ciprofloxacin administered alone or in combination.
In fibrin clots, phage therapy decreased bacterial density by 6 log10 CFU/g in 6h. Bacterial regrowth due to phage resistance was observed after 24h, but was prevented by addition of ciprofloxacin (2x MIC). In rats, phage therapy alone decreased vegetation bacterial density by 2.5 log10 CFU/g after 6h (P<0.001), compared to 2.2 log10 CFU/g with ciprofloxacin (P<0.05). Moreover, combining phages with ciprofloxacin appeared highly synergistic with a >6 log10 CFU/g decrease in 6h, and successful treatment in 64% (7/11) of the animals.
Phage-induced killing correlated with in situ phage multiplication - as also confirmed by histology and transmission electron microscopy examination of the vegetations - and cytokines production compared to antibiotherapy alone. Importantly, no phage-resistant mutants were detected in vivo, which was most likely due to altered fitness. Indeed, two phage-resistant clones isolated in vitro were 50-70% less infective in rats with experimental endocarditis (P<0.01 versus parent strain). This infectivity decrease was either due to a 362 kb deletion encompassing the galU gene, resulting in impaired LPS synthesis, or a 15 bp deletion in the pilT gene resulting in impaired motility.
In conclusion, phage therapy significantly reduced P. aeruginosa experimental endocarditis and was highly synergistic with ciprofloxacin. Phage-resistant mutants selected in vitro resulted in impaired infectivity, due to reduced in vivo fitness. Phage therapy alone or combined with antibiotics represents a promising alternative in the treatment of P. aeruginosa infections and merits further consideration.
R. LIENHARD1, L. VON ALLMEN2, L. BERTAIOLA-MONNERAT3, A. DUMOULIN4, M.L. TRITTEN1, H.H. SIEGRIST1

1ADMED Microbiology, and Laboratory, National Reference Centre for Tick-borne Diseases (NRZK), La Chaus-de-Fonds, Switzerland, 2ADMED Microbiology, La Chaux-de-Fonds, Switzerland, 3Laboratory of Microbiology, Hôpital Cantonal, Fribourg, Switzerland. , 4Institut Central des Hôpitaux, Hôpital du Valais, Sion, Switzerland

Purpose. Cytokine CXCL13 was quantified in CSF to evaluate its diagnostic potential for neuroborreliosis. Material and Method. One hundred and sixty-two CSF samples were quantified for cytokine CXCL13 on the CXCL 13 ELISA (Euroimmun, Lübeck, Germany). A selection of 55 patients presenting neuroborreliosis with production of specific intrathecal antibodies (SIA) was used to test sensitivity. The determination of SIA in IgG and IgM was made using the IDEIA Lyme Neuroborreliosis test (Oxoid, Basel Switzerland). Specificity was tested on 77 CSF samples of patients presenting central nervous system disorder with known aetiology. A further 30 CSF samples coming from suspected neuroborreliosis with a negative SIA on our test, but a positive SIA determined in the primary laboratory were analysed. The recently defined cut-off value of 250 pg/ml was used. Results and Discussion. We obtained a sensitivity for CXCL13 of 85.5% and a specificity of 94.8%. In the group with suspected neuroborreliosis, 10 (33.3%) CSF were positive. CXCL13 chemokine secretion is not stimulated by any specific Borrelia burgdorferi s.l. antigen. This unspecific marker showed, however, a very highly specific answer for acute neuroborreliosis. Furthermore most unspecific reactions can be easily identified. Sensitivity was rather low, it showed a better correlation with IgM SIA than IgG SIA. A delay of antibiotic therapy is essential to consider testing CXCL13 as its level drops quickly after the first dose. This frequently unavailable information might be a reason for lower sensitivity. Conclusion. Quantitative CXCL13 in CSF should be implemented in neuroborreliosis diagnosis as SIA determination harbours some pitfalls and PCR sensitivity is not satisfactory.
V. POST1, L.G. HARRIS2, M. MORGENSTERN3, R.G. RICHARDS1, T.F. MORIARTY1

1AO Research Institute, AO Foundation, Davos Switzerland, 2University of Swansea, Swansea, United Kingdom, 3BGU Murnau, Murnau Germany

Staphylococci are common opportunistic pathogens colonizing the human population. The data available to date on nasal colonization in surgeons has been limited. A prospective study was undertaken in late 2013. The aim was to identify the prevalence of staphylococci (S. aureus/methicillin-resistant S. aureus (MRSA) and coagulase-negative staphylococci (CoNS/MRCoNS)) in an international cohort of surgeons. Nasal swabs and basic demographic data were collected from participants at an international educational event, on an anonymous and voluntary basis. MRSA isolates were subjected to agr-, spa- and MLST typing, and the presence of 22 virulence factors was screened for by PCR. Additionally, biofilm-forming ability, haemolytic activity, staphyloxanthin production and antibiotic resistance were determined for these MRSA isolates. The genome of a rifampicin resistant MRSA was sequenced, due to the importance of this antibiotic in patients served by orthopedic surgeons. Amongst the 1,166 human surgeons, the average overall S. aureus nasal colonization rate was 28% and MRSA rate 2% while the MRSA rate for veterinary surgeons was 5%. MRCoNS nasal carriage rate was 21%. The 26 MRSA displayed no remarkable virulence gene pattern and 35% of the isolates carried at least one of the Panton-Valentine leukocidin lukFS-PV, the exfoliative toxin eta or the toxic shock syndrome tst genes. All isolates were resistant to multiple antibiotics. Resistance to rifampicin was due to 3 mutations in the rpoB gene. Half of the isolates belonged to well-described clonal lineages, ST1, ST5, ST8, ST45 and ST59 that are associated with severe infections and increased patient mortality. Two of the 3 veterinarian MRSA belonged to epidemic livestock-associated MRSA clonal lineages ST398 and ST8 associated with high transmission potential between animals and humans. In conclusions, surgeons are colonized by S. aureus and MRSA at broadly equivalent rates to the general population. Twenty-six surgeons were colonized with multiply antibiotic resistant MRSA and belonged to clonal lineages with high transmission potential and causing increased infection severity.

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