Searching Criteria

Searching criteria

Only PubMed indexed papers from 1990 to August 2014 were included. The keywords used for the web search were: A. baumannii AND bacteremia, pneumonia, ventilator-associated pneumonia, ventilator-associated tracheobronchitis, meningitis, ventriculitis, carbapenem, sulbactam, colistin, polymyxins, tigecycline, fosfomycin, colistin-glycopeptide combination, colistin-rifampicin combination, outbreak, endemic, epidemic, transmission, control, clone, PFGE, MLST, sequence types. Moreover, we searched for: carbapenem, sulbactam, colistin, polymyxins, tigecycline, fosfomycin AND pharmacokinetics, pharmacodynamic, nebulized, central nervous system, intrathecal, intraventricular. The references of the eligible studies were hand-searched in order to identify additional potentially appropriate studies. The search for articles was limited to papers published in English, Spanish, and French. Meeting abstracts were excluded.

Transmission of Acinetobacter

A. baumannii is commonly acquired through cross-transmission because of its propensity to survive in the hospital environment and persistently contaminate fomites[1]. Admission to a room previously occupied by a patient colonized with A. baumannii increases the risk for the subsequent patient admitted to the room to become colonized or infected by the same pathogen[2],[3].

Colonized patients act also as reservoirs. Colonization with A. baumannii has been shown to precede infection, with patients colonized at different sites (eg, skin, oropharynx, rectum). It has been shown that colonization with genetically identical strains of A. baumannii precedes bacteremia in 85% of the patients[4].

Hands of hospital personnel and visitors play an important role in the spread of A. baumannii during outbreaks or in endemic settings[5],[6],[7]. It seems likely that the infected or colonized patient forms the primary reservoir of infection, with such patients shedding extremely large numbers of A. baumannii cells into their surrounding environment where this pathogen may survive for long periods.

Gloves and gowns can be contaminated with A. baumannii7, even much more often than other MDR pathogens in the course of routine patient-care activities. Pulsed-field gel electrophoresis determined that 91% of healthcare worker isolates were related to an environmental or patient isolate[8].

Airborne transmission of A. baumannii has also been documented. A. baumannii has been recovered in the air of patient rooms and the airborne isolates were clonally related to the clinical isolates cultured from patients[9] even though this is not the main mechanism of spread7,[10].

Recommendations for genotyping

The most common methods used for genotyping of A. baumannii include pulsed-field gel electrophoresis (PFGE)[11],[12],[13],[14],[15], amplified fragment length polymorphism (AFLP) analysis[16], multiple locus variable-number tandem repeat analysis (MLVA)[17],[18], multilocus sequence typing (MLST)[19],[20],[21] or single locus sequence typing[22], other PCR-based and sequence-based methods[23],[24],[25], [26],[27], and whole-genome sequencing (WGS) analysis[28],[29].

PGFE, AFLP and MLVA represent DNA-based fingerprinting methods. Molecular typing by PFGE analysis of ApaI-digested genomic DNA is a well-standardized method for A. baumannii and has been widely used to study clonal outbreaks and local epidemiology[30],[31],[32]. It is considered a gold standard for molecular strain characterization at the local level, however its interlaboratory comparability is questioned when international comparisons are attempted. AFLP has gained importance as a possible reference method for the identification of international clones I-III16. MLVA is a high-resolution typing method, suitable for studies of the local epidemiology17,18. Both AFLP and MLVA are more demanding and expensive compared to PGFE; furthermore, their methodology may differ significantly among centers thus producing non-comparable results.

On the other hand, PCR and sequence based methods are suitable for strain phylogeny studies and large-scale epidemiologic studies and have been widely adopted for years. Methods used include repetitive extragenic palindromic PCR (rep-PCR) analysis, single locus amplification and sequence-based typing, trilocus sequence-based typing (3LST) and multiplex PCRs designed to selectively amplify multiple alleles belonging to different sequence groups[33], [34].

MLST is considered the gold standard method to investigate the population structure and global epidemiology of bacteria. However there are still issues to be resolved, relating to the number of housekeeping genes that are required for a robust characterization of a population. Two MLST databases are available for Acinetobacter (distinguishing A. baumannii and non-baumannii Acinetobacter species), namely the Oxford scheme at PubMLST ( that has been used for A. baumannii and A. nosocomialis and the Pasteur scheme ( recherche/genopole/PF8/mlst/Abaumannii.html) for various Acinetobacter spp. The number of characterized strains is different between these two databases; furthermore, lineages identified by these databases are not identical, indicating the need for international harmonization. WGS methods are able to elucidate the evolutionary pathways of emerging antibiotic-resistance in A. baumannii isolates recovered from a single patient, a single institution or a wider epidemiologic setting28,[35],[36]. There are no large-scale studies comparing the different genotyping methods, although most of the current publications use more than one methodology for genotyping. Reproducibility and comparability have to be considered, in order to select the most suitable methods to be used as international epidemiological methods for strain typing.

Recommendations

We recommend that genotyping of A. baumannii should be performed in the following situations: in the occurrence of an outbreak, in endemicsituations or when a new resistant phenotype of A. baumannii is introduced (BIII).

We recommend the dissemination of the results to the personnel of the implicated wards/hospitals along with interpretation and association with (additional) infection control measures (AIII).

No firm recommendation could be actually issued about the best method to be used or whether locally applied methods should be used or a reference laboratory is preferred (BIII).

Networking and international collaboration for comparative large scale studies are clearly needed (AIII).

Table 1 of ESM. Mechanisms of antimicrobial resistance in A. baumannii

* Mechanisms of resistance associated with chromosomal mutations, either related to point mutations or insertion of IS elements.

** Mechanisms of resistance associated with the acquisition of resistant genes located in mobile genetic elements, either plasmids, tansposons and integrons.

Table 2 of ESM.Strength of recommendation and quality of evidence

Table 3 of ESM. Terms and definitions used in this document

MDR denotes Multi-drug resistant

XDR denotes Extreme drug resistant

PDR denotes Pandrug resitant

[1] Jawad A, Seifert H, Snelling AM, Heritage J, Hawkey PM. Survival of Acinetobacter baumannii on dry surfaces: comparison of outbreak and sporadic isolates. J Clin Microbiol. 1998 ; 36: 1938-41

[2] Weber DJ, Rutala WA, Miller MB, et al. Role of hospital surfaces in the transmission of emerging healthcare-associated pathogens: norovirus, Clostridium difficile, and Acinetobacter species. Am J Infect Control 2010; 38:S25–S33

[3] Nseir S, Blazejewski C, Lubret R, et al. Risk of acquiring multidrug-resistant Gram-negative bacilli from prior room occupants in the intensive care unit. Clin Microbiol Infect 2011; 17:1201–1208.

[4] Thom KA, Hsiao WW, Harris AD, Stine OC, Rasko DA, Johnson JK. Patients with Acinetobacter baumannii bloodstream infections are colonized in the gastrointestinal tract with identical strains. Am J Infect Control 2010; 38: 751-3.

[5] Barbolla RE, Centrón D, Maimone S, Rospide F, Salgueira C, Altclas J, Catalano M. Molecular epidemiology of Acinetobacter baumannii spread in an adult intensive care unit under an endemic setting. Am J Infect Control 2008; 36: 444-52.

[6] Markogiannakis A, Fildisis G, Tsiplakou S, Ikonomidis A, Koutsoukou A, Pournaras S, Manolis EN, Baltopoulos G, Tsakris A. Cross-transmission of multidrug-resistant Acinetobacter baumannii clonal strains causing episodes of sepsis in a trauma intensive care unit. Infect Control Hosp Epidemiol. 2008; 29: 410-7.

[7] Morgan DJ, Liang SY, Smith CL, Johnson JK, Harris AD, Furuno JP, Thom KA, Snyder GM, Day HR, Perencevich EN. Frequent multidrug-resistant Acinetobacter baumannii contamination of gloves, gowns, and hands of healthcare workers. Infect Control Hosp Epidemiol 2010; 31: 716-21.

[8] Morgan DJ, Rogawski E, Thom KA, Johnson JK, Perencevich EN, Shardell M, Leekha S, Harris AD. Transfer of multidrug-resistant bacteria to healthcare workers' gloves and gowns after patient contact increases with environmental contamination. Crit Care Med. 2012; 40: 1045-51.

[9] Munoz-Price LS, Fajardo-Aquino Y, Arheart KL, Cleary T, DePascale D, Pizano L, Namias N, Rivera JI, O'Hara JA, Doi Y. Aerosolization of Acinetobacter baumannii in a trauma ICU*. Crit Care Med. 2013; 41: 1915-8.

[10] Landelle C, Legrand P, Lesprit P, Cizeau F, Ducellier D, Gouot C, Bréhaut P, Soing-Altrach S, Girou E, Brun-Buisson C. Protracted outbreak of multidrug-resistant Acinetobacter baumannii after intercontinental transfer of colonized patients. Infect Control Hosp Epidemiol 2013 ; 34: 119-24.

[11] Seifert H, Dolzani L, Bressan R, van der Reijden T, van Strijen B, Stefanik D, et al. Standardization and interlaboratory reproducibility assessment of pulsed-field gel electrophoresis-generated fingerprints of Acinetobacter baumannii. J Clin Microbiol 2005;43:4328–35.

[12] Giannouli M, Tomasone F, Agodi A, Vahaboglu H, Daoud Z, Triassi M, et al. Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii strains in intensive care units of multiple Mediterranean hospitals. J Antimicrob Chemother 2009;63:828–30

[13] Pournaras S, Markogiannakis A, Ikonomidis A, Kondyli L, Berthimouti K, Maniatis AN, et al. Outbreak of multiple clones of imipenem-resistant Acinetobacter baumannii isolates expressing OXA-58 carbapenemase in an intensive care unit. J Antimicrob Chemother 2006;57:557–61.

[14] Valenzuela JK, Thomas L, Partridge SR, van der Reijden T, Dijkshoorn L, Iredell J. Horizontal gene transfer in a polyclonal outbreak of carbapenem-resistant Acinetobacter baumannii. J Clin Microbiol 2007;45:453–60.

[15] Zarrilli R, Vitale D, Di Popolo A, Bagattini M, Daoud Z, Khan AU, et al. A plasmid-borne blaOXA-58 gene confers imipenem resistance to Acinetobacter baumannii isolates from a Lebanese hospital. Antimicrob Agents Chemother 2008;52:4115–20.

[16] Dijkshoorn L, Aucken H, Gerner-Smidt P, Janssen P, Kaufmann ME, Garaizar J, et al. Comparison of outbreak and nonoutbreak Acinetobacter baumannii strains by genotypic and phenotypic methods. J Clin Microbiol 1996;34:1519–25.

[17] Pourcel C, Minandri F, Hauck Y, D’Arezzo S, Imperi F, Vergnaud G, et al. Identification of variable-number tandem-repeat (VNTR) sequences in Acinetobacter baumannii and interlaboratory validation of an optimized multiple-locus VNTR analysis typing scheme. J Clin Microbiol 2011;49:539–48.

[18] Minandri F, D’Arezzo S, Antunes LC, Pourcel C, Principe L, Petrosillo N, et al. Evidence of diversity among epidemiologically related carbapenemase producing Acinetobacter baumannii strains belonging to international clonal lineage II. J Clin Microbiol 2012;50:590–7.

[19] Bartual SG, Seifert H, Hippler C, Luzon MA, Wisplinghoff H, Rodrìguez-Valera F. Development of a multilocus sequence typing scheme for characterization of clinical isolates of Acinetobacter baumannii. J Clin Microbiol 2005;43:4382–90.

[20] Hamouda A, Evans BA, Towner KJ, Amyes SG. Characterization of epidemiologically unrelated Acinetobacter baumannii isolates from four continents by use of multilocus sequence typing, pulsed-field gel electrophoresis, and sequence-based typing of blaOXA-51-like genes. J Clin Microbiol 2010; 48:2476–83.

[21] Di Popolo A, Giannouli M, Triassi M, Brisse S, Zarrilli R. Molecular epidemiology of multidrug-resistant Acinetobacter baumannii strains in four Mediterranean countries with a multilocus sequence typing scheme. Clin Microbiol Infect 2011;17:197–201.

[22] Pournaras S, Gogou V, Giannouli M, Dimitroulia E, Dafopoulou K, Tsakris A, Zarrilli R Single locus sequence-based typing of blaOXA-51-like gene for rapid classification of Acinetobacter baumannii clinical isolates to international clones. J Clin Microbiol. 2014; 52: 1653-7.

[23] Ecker JA, Massire C, Hall TA, Ranken R, Pennella TT, Agasino Ivy C, et al.Identification of Acinetobacter species and genotyping of Acinetobacter baumannii by multilocus PCR and mass spectrometry. J Clin Microbiol 2006;44: 2921–32.

[24] Zander E, Nemec A, Seifert H, Higgins PG. Association between b- lactamase-encoding blaOXA-51 variants and DiversiLab rep-PCR-based typing of Acinetobacter baumannii Isolates. J Clin Microbiol 2012;50:1900–4.

[25] Turton JF, Gabriel SN, Valderrey C, Kaufmann ME, Pitt TL. Use of sequence based typing and multiplex PCR to identify clonal lineages of outbreak strains of Acinetobacter baumannii. Clin Microbiol Infect 2007;13:807–15.

[26] Giannouli M, Cuccurullo S, Crivaro V, Di Popolo A, Bernardo M, Tomasone F, et al. Molecular epidemiology of multidrug-resistant Acinetobacter baumannii in a tertiary care hospital in Naples, Italy, shows the emergence of a novel epidemic clone. J Clin Microbiol 2010;48:1223–30.

[27] Decker BK, Perez F, Hujer AM, Hujer KM, Hall GS, Jacobs MR, Gebreyes WA, Zoll ST, Massire C, Eshoo MW, Ecker DJ, Rather PN, Bonomo RA. Longitudinal analysis of the temporal evolution of Acinetobacter baumannii strains in Ohio, USA, by using rapid automated typing methods. PLoS One. 2012;7:e33443.

[28] Adams MD, Chan ER, Molyneaux ND, Bonomo RA. Genomewide analysis of divergence of antibiotic resistance determinants in closely related isolates of Acinetobacter baumannii. Antimicrob Agents Chemother 2010;54:3569–77.

[29] Snitkin ES, Zelazny AM, Montero CI, Stock F, Mijares L, NISC Comparative Sequence Program, et al. Genome-wide recombination drives diversification of epidemic strains of Acinetobacter baumannii. Proc Natl Acad Sci USA 2011; 108:13758–63.

[30]Seifert H, Dolzani L, Bressan R, van der Reijden T, van Strijen B, Stefanik D, et al. Standardization and interlaboratory reproducibility assessment of pulsed-field gel electrophoresis-generated fingerprints of Acinetobacter baumannii. J Clin Microbiol 2005;43:4328–35.

[31] Giannouli M, Tomasone F, Agodi A, Vahaboglu H, Daoud Z, Triassi M, et al. Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii strains in intensive care units of multiple Mediterranean hospitals. J Antimicrob Chemother 2009;63:828–30

[32] Pournaras S, Markogiannakis A, Ikonomidis A, Kondyli L, Berthimouti K, Maniatis AN, et al. Outbreak of multiple clones of imipenem-resistant Acinetobacter baumannii isolates expressing OXA-58 carbapenemase in an intensive care unit. J Antimicrob Chemother 2006;57:557–61.

[33] Ecker JA, Massire C, Hall TA, Ranken R, Pennella TT, Agasino Ivy C, et al. Identification of Acinetobacter species and genotyping of Acinetobacter baumannii by multilocus PCR and mass spectrometry. J Clin Microbiol 2006 ; 44: 2921–32.

[34]Turton JF, Gabriel SN, Valderrey C, Kaufmann ME, Pitt TL. Use of sequence based typing and multiplex PCR to identify clonal lineages of outbreak strains of Acinetobacter baumannii. Clin Microbiol Infect 2007;13:807–15.

[35] Hornsey M, Loman N, Warheam DW, Ellington MJ, Pallen MJ, Turton JF, et al. Whole-genome comparison of two Acinetobacter baumannii isolates from a single patient, where resistance developed during tigecycline therapy. J Antimicrob Chemother 2011;66:1499–503.

[36] Ansaldi F, Canepa P, Bassetti M, Zancolli M, Molinari MP, Talamini A, Ginocchio F, Durando P, Mussap M, Orengo G, Viscoli C, Icardi G. Sequential outbreaks of multidrug-resistant Acinetobacter baumannii in intensive care units of a tertiary referral hospital in Italy: combined molecular approach for epidemiological investigation. J Hosp Infect. 2011; 79: 134-40.