الفهرس 
TitleOnly 14 pages are availabe for public view
 |  | from | 124 |  |  |
| | | from | 124 | | |
Abstract
Pseudomonas aeruginosa is one of the leading nosocomial pathogens worldwide. Nosocomial Infections caused by this organism are often hard to treat because of both the intrinsic resistance of the species and its remarkable ability to acquire further resistance mechanisms to multiple groups of antimicrobial agents (including β-lactams, aminoglycosides and fluoroquinolones). Worryingly, these mechanisms are often present simultaneously, thereby conferring multiresistant phenotypes.
Aminoglycosides are a vital component of antipseudomonal chemotherapy implicated in the treatment of a variety of infections, particularly pulmonary infections in cystic fibrosis (CF) patients.
Bacterial resistance against aminoglycosides is mediated by three distinct classes of mechanisms: decrease of intracellular drug concentration, target site modification and enzymatic drug modification. Enzymatic modification is the most common type of aminoglycoside resistance. Over 50 different enzymes have been identified. Enzymatic modification results in high-level resistance.
The aim of this work was to determine the aminoglycosides resistance pattern in P. aeruginosa obtained from clinical samples and to identify the genetic determinates responsible for aminoglycosides resistance.
A total of 42 non lactose fermenter, oxidase positive isolates were included in this study. All strains were isolated from patients admitted to Medical Research Institute Hospital. Different types of specimen included: Sputum, Broncho-alveolar lavage (BAL), Endotracheal tubes (ETT), swab from infected wounds, urine and blood.
The 42 strains were tested for growth at 42°C and inoculated on TSI agar. They showed K\no change reaction on TSI agar, and grew at 42° C except two strains showed a weak growth. 62% of them produced pyocyanin pigment; the strains that showed weak growth at 42° C did not produce the pigment.
The 42 strains were tested by MALDI TOF MS, 40 strains were identified to the species level as P. aeruginosa, the two strains which showed weak growth at 42°C were identified as Pseudomonas resinovorans and Stenotrophomonas maltophilia.
31(74%) of the 42 strains had a score value higher than 2 , allowing genus and species identification. 30 (71.5 %) of them were diagnosed as P. aeruginosa and only 1 (2.5%) was diagnosed as Stenotrophomonas maltophilia . On the other hand, 11 (26%) strain had lower scores ranging from (1.7 to 2).
50% of the Pseudomonas strains were isolated from wounds followed by 28% from urinary tract infection and 22% from respiratory tract infection. Out of the 40 P. aeruginosa isolates included in the current study 33 (83%) isolates were MDR.
Among the 40 P. aeruginosa isolates, resistance to aminoglycosides was higher for kanamycin (100%), followed by neomycin (98%) and netilmicin (92%). On the other hand resistance to amikacin was lower (80%) followed by gentamicin and tobramycin (90%).it was found that, (80%) of P. aeruginosa strains were resistant to all tested aminoglycosides. While, 10% showed the same pattern of resistance except for amikacin sensitivity.
Different Acetylation enzymes (aac(6’)-Ia ,aac(6’)-IIa-Ib, aac(3)-IIa ) genes were detected among P. aeruginosa strains, their prevalence ranged from 38% to 80%. Phosphorylation enzyme (aph(3’)-VI) gene was detected in 63% of P.aeruginosa strains. Adenylation enzymes (ant(2”)-Ia, ant(4’)-IIa) were detected in 38% & 53% of Pseudomonas aeruginosa strains respectively. Target modification enzyme gene (rmtD) was detected in 40% of P. aeruginosa strains. Aminoglycosides modifying enzymes and the target modification enzymes were present in different patterns, with more than one enzyme per strain, rendered impossible to match aminoglycoside resistance pattern with aminoglycoside resistance genes.
In conclusion
MALDI-TOF MS is a convenient method for identification of P. aeruginosa.
High level of antibiotic resistance including multidrug resistance isolates was detected among P. aeruginosa isolated from clinical samples.
High level of aminoglycoside antibiotic resistance was detected among P. aeruginosa isolates.
Among the forty P. aeruginosa strains, resistance to amikacin was lower (80%) compared to gentamicin and tobramycin.
AME genes were detected in the following order, aac(3)-IIa , aph(3’)-VI, aac(6’)-IIa-Ib, ant(4’)-IIa, ant(2”)-Ia and aac(6’)-Ia.
16S rRNA methylase was detected in 40% of the isolates.
Aminoglycoside resistance pattern could not be linked to resistance genes.