gms | German Medical Science

18th Symposium on Infections in the Immunocompromised Host

International Immunocompromised Host Society

15. to 17.06.2014, Berlin

Effects of Human Polymorphonuclear Neutrophils (HPNs) Alone or in Combination with Four Antipseudomonal Antibiotics against Pseudomonas aeruginosa Biofilms

Meeting Abstract

  • A. Chatzimoschou - 3rd Dept of Pediatrics, Hippokration University Hospital, Thessaloniki, Greece
  • M. Simitsopoulou - Greece
  • T.J. Walsch - Greece
  • E. Roilides - Greece

18th Symposium on Infections in the Immunocompromised Host. Berlin, 15.-17.06.2014. Düsseldorf: German Medical Science GMS Publishing House; 2014. Doc14ichs42

doi: 10.3205/14ichs42, urn:nbn:de:0183-14ichs423

Veröffentlicht: 3. Juni 2014

© 2014 Chatzimoschou et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Objectives: PA is implicated in an estimated 10–20% of all hospital-acquired infections and immunocompromised patients are susceptible to those infections. Cystic fibrosis (CF) airway bacteria are rarely eradicated by antibiotics and host immune defences due to their ability to form biofilms (BFs). Our aim was to examine the in vitro activity of four antibiotics (Amikacin (AMK), Ceftazidime (CEF), Ciprofloxacin (CIP) and Colistin (CST)) alone and in combination with PMNs against PA BF in comparison to their activities against their planktonic cells (PL) counterparts.

Methods: Eight CF clinical isolates of PA, either susceptible to AMK (AMKS), CEF (CEFS), CIP (CIPS), CST (CSTS) or resistant to AMK (AMKR), CEF (CEFR), CIP (CIPR), CST (CSTR) were used. All isolates were grown by incubation in cation-adjusted Mueller-Hinton broth in 96-well flatbottomed plastic plates under constant shaking for 48h at 37oC in order to form BFs. PMNs from healthy donors at an effector-to-target (E:T) ratio of 1:20 or 2:20 were incubated further for 24h alone or in combination with 2, 8 or 32mg/l of AMK, CEF, CIP or CST. Percent damage of BF or PL was assessed by XTT assay. Synergy was concluded when the observed bacterial damage was significantly higher to the expected sum of damages; whereas, antagonism was defined when the observed bacterial damage was significantly lower to the expected sum of damages. ANOVA (n=6) with Dunnett's test was performed.

Results: For all resistant isolates (RI), PMN-induced bacterial damage against BF and PL was E:T dependent, however no statistically significant differences were observed for sensitive isolates (SI). Damage induced by PMNs did not significantly differ between BF and PL for RI while statistically significant differences were observed for SI. Simultaneous treatment of PA BF and PL cells of AMK-R or AMK-S isolates with AMK (2, 8 or 32 mg/l) and PMNs (1:20 or 2:20) resulted in additive or synergististic results. However, when BF and PL of CEF-R and CEF-S isolates were treated with PMNs at the above E:T ratios additive results were observed only to the PL cells of CEF-R and some conditions of CEF-S. In the case of BF, antagonistic interactions were observed when PMNs of 1:20 were combined with 2 and 32mg/l of CEF. For CEF-S BF no interactions were concluded. A few additive interactions were also concluded for the PL of CIP-S isolate. In the case of BF for both CIP isolates only a few additive results were observed. No significant collaboration was noted between CST and PMN on PL damage for both isolates for all conditions. However, additive effects were noted when PMN were combined with 1 or 4 mg/l CST for BF of CSTR. Synergistic effects were noted when PMNs were combined with 4 mg/l CST for BF of CSTS. When PMN combined with CST (1 mg/l) additive effects were observed on BF of CSTS isolate.

Conclusions: PA BFs are more resistant than PL to the activities of PMNs, of AAs alone and to the combinations of PMNs with the 4 AAs. Synergy or additivity is exhibited between PMNs and AMK for both BF and PL for RI and SI. Additive results were observed between PMNs and CEF for PL cells of both isolates while antagonism is exhibited between PMNs and CEF for both isolates. Most of the PMN and CST combinations tested exhibit additive or synergistic effects on BFs of PA. Even high concentrations of AAs alone or in combination with PMNs do not achieve eradication of PA, suggesting a possible mechanism of PA persistence in the respiratory tract of CF patients.

Keywords: Pseudomonas, biofilms, neutrophils, cystic fibrosis, immunocompromised