الفهرس 
Global epidemiology of Acinetobacter baumanniiOnly 14 pages are availabe for public view
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Abstract
During the last decades, Acinetobacter baumannii becomes a global
problem that threatens many health care settings. Acinetobacter baumannii is
characterized by its extraordinary ability to persist in the environment.
Moreover, it has a magnificent ability to acquire and express multiple
resistance mechanisms against major antibiotic classes. There is no unique
bacterial metabolic test that can differentiate it from other non-lactose
fermenter Gram-negative bacteria; furthermore, the pathogenicity of
Acinetobacter species is not the same. Acinetobacter baumannii strains are the
most frequently involved in severe infections.
In the present study, a total of 1365 samples including 1223 clinical
and 142 environmental samples were collected from Tanta University
teaching hospitals during the period from April 2014 to July 2017. Out of these
samples, 77 different Acinetobacter baumannii isolates, including 69 clinical
and 8 environmental isolates, were recovered with 5.6% incidence of
detection. The identification of these tested isolates was performed using
microscopic, cultural as well as standard biochemical tests. Furthermore, the
polymerase chain reaction (PCR) detection of the blaOXA-51-like carbapenemase
gene was performed. It was found that the majority of A. baumannii isolates
(39/69, 56.5%) were recovered from respiratory tract infection cases. This was
followed by burn infections or bacteremia (7/69, 10.1%), urinary tract
infections (6/69, 8.7%) and wound infections (5/69, 7.2%).
Abstract
Simplex conventional PCR technique was applied to all tested isolates
for detection of the genes encoding the adhesive virulence factors; fimH and
csgA genes. These two genes were detected in 21 (27.3%) and19 (24.7%) of
isolates, respectively. Out of these isolates, 5 (6.5%) isolates carried both fimH
and csgA while the remaining (42, 54.5%) isolates carried none of these two
genes.
All the studied 77 A. baumannii isolates were tested for susceptibility
to each of sixteen different antimicrobial agents by Kirby-Bauer disc diffusion
method. High frequency of resistance for A. baumannii isolates was observed
to piperacillin (100%) followed by ciprofloxacin (93.5%), ceftriaxone and
cefotaxime (89.6%), while the low rate of resistance was noticed to imipenem
(45.4%), tobramycin (29.9%) and tetracycline (26%). Colistin showed the
highest activity where all tested isolates were sensitive to this drug.
The resistance of Gram-negative bacteria to antimicrobials is most
probably due to the production of deactivating enzymes, which are
chromosomally encoded or most often plasmid-mediated, active antibiotic
efflux, restricted outer membrane permeability or combination of these
resistance strategies. In this study, it was found that 67 out of 77 (87%) A.
baumannii isolates produced β-lactamase enzymes. Out of these 67 β-
lactamase-producing A. baumannii isolates, 53 (79.1%) and 35 (52.2%)
isolates were AmpC and carbapenemases producers, respectively. Moreover,
it was observed that blaOXA-23-like was more prevalent than blaOXA-58-like in our
tested 35 carbapenemases-producing isolates with the incidence of 68.6% and
17.1%, respectively.
Other possible resistance mechanisms including efflux and outer
membrane permeability were also studied. Efflux mechanism was detected in
Abstract
95% of our tested A. baumannii isolates that were resistant to at least a member
of studied antibiotics including aminoglycosides, quinolones, tetracyclines,
and β-lactams especially imipenem. Different protein bands of molecular
weights 19, 22, 25, 29, 33, 36, 40, 47, and 50 kDa were either detected,
overproduced or even lost in the electropherograms of the tested A. baumannii
isolates. Some of these changes were used to explain the antimicrobial
resistance of our A. baumannii isolates. Protein with a molecular weight of
about 40 kDa, was a major protein as it was detected in all the tested isolates.