Molecular epidemiology of Acinetobacter baumannii in different hospitals in Tripoli, Lebanon using bla OXA-51-like sequence based typing
Our study provided a global view of molecular epidemiology of A. baumannii isolates from hospitals in Tripoli, Lebanon. Tripoli is a city that hosts a large
number of refugees and wounded Syrians, which may explain the high number of wound specimens in our collection. Although,
A. baumannii is an opportunistic nosocomial pathogen, it is increasingly reported from infections
occurring outside hospitals, particularly skin and soft-tissue infections and pneumonia
25]. A. baumannii has also been a well-documented pathogen associated with wound infections in USA
troops from the Iraq and Afghanistan wars 26], 27]. The typology of these situations raised questions about their origins and the potential
involvement of an environmental reservoir 25]. The origin of infections from Syrian patients was ambiguous. Although it was likely
that nosocomial infections occurred, a number of infections were present at the time
of admission of the patients in Lebanese hospitals 24]. These infections may have been acquired from environmental sources at the time of
injury, during the patient stay in Syrian hospitals, or during a direct evacuation
from the theatre of operations to Lebanon. Unfortunately, data concerning the date
of injury, the length of hospitalisation, and the conditions of care and treatment
in Syrian hospitals are lacking.
Approximately 60Â % of our isolates showed a carbapenem resistance phenotype. The production
of OXA-23 was the major carbapenem resistance mechanism, with an upstream insertion
of ISAba1, thus supporting international data about the worldwide emergence of this carbapenemase
28]–30]. Alarmingly, 5 NDM-1 producing isolates have been detected from 4 Syrian patients
24] and one from a Lebanese patient.
blaOXA-51-like is an intrinsic oxacillinase gene naturally occurring in A. baumannii, and more than 95 variants have been identified to date 31]. However, the occasional detection of blaOXA-51 in Acinetobacter nosocomialis and Acinetobacter genomic species “close to 13TU†limit its use as a single identification method.
Therefore, it is always combined with others techniques 32], 33]. Genetic diversity of blaOXA-5 gene has been explored and found to be very interesting for identifying epidemic
clones 16], 18], 19], 34], 35]. Thus, the full gene sequencing has been proposed as a single typing method for A. baumannii. As being simple and rapid, we have initially screened here the epidemiological belonging
of our isolates to the previous identified clonal lineages by blaOXA-51-like SBT. We have then randomly selected isolates from each of the representative blaOXA-51-like sequences for MLST analysis. In our study, blaOXA-51-like gene sequencing correctly assigned all isolates to their corresponding clonal complexes.
Here, the blaOXA-66 gene variant, which is associated with ST2 (belonging to CC2) 16], 19], 35], 36], was predominant and found in 63 % of the A. baumannii isolates. The isolates carrying the blaOXA-66 gene variant have been identified in samples obtained from the different hospitals
in Tripoli. These findings are consistent with those observed worldwide since CC2
was reported in more than 34 countries in Europe, Asia, Africa, Australia, USA, and
South America 36]. Eighty percent of our carbapenem resistant isolates belonged to this clone and OXA-23
was the only carbapenem resistance mechanism found. The high level of antimicrobial
resistance may represent one of the main causes for its propensity and its successful
predominance in hospitals throughout the world 10], 36]. The blaOXA-69 gene variant was the second gene mostly found in our collection. This gene was commonly
associated with ST1 (belonging to CC1) but interestingly, we found two blaOXA-69 isolates belonging to the new sequence type ST460 (SLV of ST1). Both isolates were
isolated from wounded Syrian patients. The blaOXA-94 was another blaOXA-51-like gene variant found in our study, it was associated with clonal complex CC85 (named
as CC6 in the study of Pournaras et al. 19]). CC85 is currently formed by ST6, ST85, ST464, and ST528. In our study blaOXA-51-like SBT revealed the same sequence blaOXA-94 variant in the two identified sequences ST6 and ST85. We have recently detected ST464
in chicken and we found blaOXA- 94 as a blaOXA-51 variant 37]. Our 4 NDM-1 producing Syrian isolates belonged to ST85. Indeed, this ST has also
been responsible for an outbreak in France. It is usually imported from North Africa
38], 39] and seems to be an emerging clone.
blaOXA-64 is a blaOXA-51-like variant associated with CC25 19]. ST25 (the founder of CC25) was also an emerging clone reported in Europe, Asia,
Africa and USA 36], 40], and from pets in Reunion Island, a French territory located in Western Indian Ocean
41].
Different carbapenemases have been identified in this clone, as OXA-23, OXA-24 and
OXA-58 36]. Otherwise, NDM-1 producing ST25 was also detected in Germany and Kenya 41]–43]. Within our four identified isolates belonging to ST25, one isolate was a NDM-1 producing
isolate recovered from a urine sample of an 80-year-old Lebanese patient suffering
from amyloidosis and anaemia at Nini hospital, Tripoli, Lebanon. Finally, compared
to carbapenem resistant isolates belonging to successful emerging clones, most of
susceptible isolates were very diverse, belonging to different sequence types (Table 1).