Molecular characterization of carbapenem-resistant Acinetobacter species in an Irish university hospital: predominance of Acinetobacter genomic species 3

Abstract

A 30 month prospective study of Acinetobacter species encountered in the Central Pathology Laboratory of St James's Hospital, Dublin, Ireland, was conducted to investigate the prevalence and molecular epidemiology of carbapenem resistance in such isolates. Acinetobacter genomic species 3 (AG3) was found to be the predominant Acinetobacter species (45/114, 39 %) in our institution. A total of 11 % of all Acinetobacter species (12/114) and 22 % of AG3 isolates (10/ 45) were carbapenem resistant. Carbapenem resistance was mediated by Ambler class D blactamase OXA-23 in all 12 isolates, with insertion sequence ISAba1 found upstream of bla OXA-23 . ISAba1 was also found upstream of bla ADC-25 , which encodes the enzyme AmpC, in an Acinetobacter baumannii isolate, and upstream of the aminoglycoside-acetyltransferaseencoding gene aacC2 in three AG3 isolates. Inter-species plasmidic transfer was most likely involved in the emergence and spread of bla OXA-23 among the Acinetobacter isolates within our institution. The emergence of carbapenem resistance was associated not only with prior carbapenem use but also with the use of other antimicrobial agents, most notably b-lactam/blactamase-inhibitor combinations. The study demonstrated the emerging trend of carbapenem resistance in the wider context of the Acinetobacter genus, and reiterated the paramount importance of the prudent use of antimicrobial agents, stringent infection control measures and resistance surveillance of pathogens.

TheAcinetobacter baumanniigroup:a systemic review

“…In most regions, the Acinetobactor baumannii group was the most frequently isolated genospecies. But in Ireland[11] and Germany[16], Acinetobacter genospecies 3 was found to be the most predominant genospecies. In addition, the proportions of Acinetobacter baumannii and Acinetobacter genospecies 3 were approximately equal in the Netherland,[17] and Acinetobacter genospecies 13TU was the most prevalent genospecies in Norwegian blood cultures.…”

Molecular Characterization of β-Lactamase Genes and Their Genetic Structures inAcinetobacterGenospecies 3 Isolates in Taiwan

“…Mobile genetic elements, including insertion sequences (IS) and integrons, may contribute to ␤-lactamase overproduction and dissemination (26, 31). Several carbapenemases (IMP-1, IMP-4, VIM-2, OXA-23, and OXA-58) and versatile AmpC cephalosporinases (ADC-12 to ADC-23) have been found in AG3 (2,3,12,20,22,36) but with few studies on their genetic support to elucidate possible transmission mechanisms.Nineteen AG3 clinical isolates were collected from three hospitals in Taiwan from 1999 to 2007 and were identified using the API 32GN kit (bioMerieux, Marcy-l'Etoile, France) and recA and rpoB sequencing (15,16). Sixteen distinct pulsotypes were identified among the isolates, and each blood isolate displayed a different pulsotype, indicating nonclonal relatedness.…”

“…It was reported to be the most frequently isolated Acinetobacter species in Hong Kong, Sweden, and Ireland (3, 4, 32). Carbapenem-resistant or multidrug-resistant (MDR) AG3 has been found globally in the past decade (3,12,18,20,36).In Acinetobacter spp., ␤-lactamases are the most common contributors to resistance to extended-spectrum cephalosporins and carbapenems, including extended-spectrum ␤-lactamases (ESBL), metallo-␤-lactamases (MBL), carbapenem-hydrolyzing class D ␤-lactamases (CHDL), and Acinetobacter-derived cephalosporinases (ADC) (24, 27). Mobile genetic elements, including insertion sequences (IS) and integrons, may contribute to ␤-lactamase overproduction and dissemination (26, 31).…”

Clinical Features of Infections and Colonization by Acinetobacter Genospecies 3

“…However, since molecular tools are not usually available for routine clinical practice, other Acinetobacter species with similar phenotypes are usually misidentified as A. baumannii. When the prevalence of these genospecies is assessed with genetic tools, many authors identify Acinetobacter genospecies 3 as the most commonly isolated species after A. baumannii or even the most frequently isolated (2,13). Nonetheless, despite its remarkable prevalence, clinical data regarding infections produced by Acinetobacter genospecies 3 are scarce (8,9).…”

“…Paired categorical and continuous variables were compared using 2 or Fisher's exact test and the Mann-Whitney U test, respectively. Significance was set at a P value of Ͻ0.05.…”