الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 222 |  |  |
| | | from | 222 | | |
Abstract
Acinetobacter isolates are challenging pathogens responsible for serious nosocomial
infections. They can survive in the clinical environment with great resistance to
disinfectants, antibiotics, moist and dry conditions as; they can use different metabolic
sources and have the ability to form biofilms
The aim of this work was to investigate the spread of Acinetobacter spp isolated
from clinical and hospital environmental samples from departments and ICUs of
Menoufia University Hospitals, determine the susceptibility patterns and the
resistance phenotypes of Acinetobacter isolates. Also, the study aimed to detect of
class B (metallo β-lactamases) and class D (oxacillinase) carbapenemases among
Acinetobacter isolates and to detect the prevalence of class I integrons among
Acinetobacter isolates and the correlation between its carriage and resistance pattern.
This study was performed in Medical Microbiology and Immunology
Department, Faculty of medicine, Menoufia University during the period from
December 2014 to December 2016. Clinical samples (n=402), hospital
environmental samples (958) and samples from staff members hands (n=200) were
collected and processed according to standard microbiological methods.
Acinetobacter species identification was done by using Vitek -2 system.
Antimicrobial susceptibility testing for Acinetobacter isolates was performed
by disk diffusion method for piperacillin, ampicillin/sulbactam,
piperacillin/tazobactam, ceftazidime, cefotaxime, ceftriaxone, cefepime, doripenem,
meropenem, imipenem, amikacin, gentamicin, tobramycin, tetracycline,
Summary
169
doxycycline, ciprofloxacin, levofloxacin, gatifloxacin, trimethoprimsulfamethoxazole,
tigecycline and colistin. Minimal inhibitory concentration (MIC)
of imipenem and colistin was determined by agar dilution method and results were
interpreted according to CLSI.
Imipenem non susceptible Acinetobacter isolates were further tested
phenotypically for MβLs production by imipenem/EDTA combined disk test and for
oxacillinases production by determining imipenem MIC by agar dilution method
before and after addition of 200 mM sodium chloride in the testing medium.
Multiplex PCR assay was performed for detection of class 1 integron (IntI1),
class B carbapenemase genes (bla IMP1 and blaVIM2), class D carbapenemase gene
(bla oxa 23) and aminoglycosides resistance gene (aac(6)lb) using specific primers
for the corresponding genes.
A total of 52 Acinetobacter isolates were obtained from different clinical
samples. Acinetobacter infections were more common among males (63.5%),
patients aged from 35 to 60 years (36.5%), who stayed in hospitals for more than 7
days (88.5%), admitted to ICUs (51.9%), used antibiotic (90.4%), exposed to
invasive procedures (71.2%) and had associated co-morbidities (73.1%).
About 51.9% (27/52) of clinical and 82.8% (24/29) of hospital environmental
Acinetobacter spp were isolated from ICUs. The highest rate of clinical
Acinetobacter isolation was from respiratory secertions (48.05%) and the highest
rate of hospital environmental Acinetobacter isolation was from suction catheters
(20.7%)
Regarding Vitek 2 results, A. baumannii was the predominant Acinetobacter
species isolated from clinical (78.9%) and environmental (89.65%) samples.
Summary
170
Antimicrobial susceptibility tests using disk diffusion method revealed that
clinical Acinetobacter isolates were highly resistant to ceftriaxone, cefotaxime
(92.3% for each), ampicillin –sulbactam, cefipime (90.4% for each), pipercillin,
ceftazidime (88.5% for each), pipercillin- tazobactam (84.6%), and tobramycin
(80%). The resistance rate to imipenem, meropenem, doripenem, and amikacin was
observed in 65.4%, 63.5%, 57.7% and 75% of isolates respectively. On the other
hand 55.8%, 59.6% and 78.8%of the clinical Acinetobacter isolates were susceptible
to tigecycline, doxycycline and colistin respectively. Also, environmental
Acinetobacter isolates were highly resistant to pipercillin, ampicillin –sulbactam,
ceftazidime, cefipime (89.7% for each), ceftriaxone, cefotaxime, ciprofloxacin
(86.2% for each), pipercillin- tazobactam and tobramycin (82.8% for each).
Resistance to imipenem, meropenem, doripenem, and amikacin was observed in
68.1%, 58.2%, 58.2% and 69% of isolates respectively. On the other hand 58.6%,
72.4% and 82.8% of the environmental Acinetobacter isolates were susceptible to
tigecycline, doxycycline and colistin respectively.
Statistical analysis revealed no statistically significant difference between disk
diffusion and MIC agar dilution methods in detection of imipenem susceptibility but
revealed a statistically significant difference between the two methods regarding
colistin susceptibility.
About 86.4%, 58% and 2.5% of all Acinetobacter isolates were MDR, XDR and
PDR respectively
About 43/53 (81.1%) of all imipenem non susceptible (INS) Acinetobacter
isolates were MβLs producers by CDT and 47/53 (88.7%) were oxacillinases
producers by detection of 4 fold decrease in imipenem MIC after addition of 200
mM sodium chloride to the testing medium by agar dilution method.
Summary
171
About 79.2% (42/53) of INS Acinetobacter carried IntI1gene while bla
VIM2, bla Oxa 23 and aac(6)lb were detected in 8/53 (15.1% for each) of
isolates. About 9/65 (13.8%) of amikacin non-susceptible Acinetobacter isolates
(clinical and environmental) had aac(6)lb gene. On the other hand all
Acinetobacter isolates (imipenem susceptible and non-susceptible) did not have
bla IMP1.
Infections with positive IntI1 Acinetobacter isolates were more common
among males (65.6%), patients at age group (35-60years) (40.6%), who stayed
in hospital for more than 7 days (96.9%), admitted to ICUs (65.6%), used
chemotherapeutic agents (96.9%) exposed to invasive procedures (87.5%) and
had associated co-morbidities (93.8%). Integron positive Acinetobacter isolates
were associated with increase resistance to antibiotic compared with integron
negative isolates.
All clinical and hospital environmental Acinetobacter isolates that were
resistant to piperacillin, ampicillin /sulbactam, piperacillin/tazobactam,
ceftriaxone, ceftazidime, cefepime, cefotaxime, trimethoprimsulfamethoxazole,
gentamicin, and tobramycin carried intI1 gene. Also, clinical
isolates that were resistant to ciprofloxacin (93.8%), gatifloxacin (93.6%),
tetracyclines, levofloxacin (90.6% for each), doripenem, meropenem and
imipenem (84.4% for each) carried intI1 gene. Hospital environmental
Acinetobacter isolates resistant to ciprofloxacin (100%), Gatifloxacin (94.1%),
tetracyclines (82.4%), amikacin, levofloxacin, doripenem, meropenem and
imipenem (88.2% for each) carried intI1 gene also.
Considering PCR as the gold standard molecular confirmatory test, the
sensitivity, specificity, PPV, NPV and accuracy of imipenem-EDTA combined
Summary
172
disk test were 100%, 51.06%, 17.86%, 100% and 55.8% respectively for
clinical Acinetobacter isolates and 100%, 53.8%, 20%, 100% and 58.62%
respectively for environmental Acinetobacter isolates in relation to PCR results.
In this study the sensitivity, specificity, PPV, NPV and accuracy of MIC agar
dilution with sodium chloride test were 100%, 41.3% 18.18%, 100% and 48.08%
respectively for clinical Acinetobacter isolates and 100%, 50% 18.755, 100% and
55.17% respectively for environmental Acinetobacter isolates in relation to PCR
In this study the sensitivity, specificity, PPV, NPV and accuracy of amikacin disk
diffusion method were 75%, 27.27% 15.79%, 85.7% and 36% respectively for
clinical Acinetobacter isolates and 100%, 34.62%, 15%, 100% and 41.38%
respectively for environmental Acinetobacter isolates in relation to PCR results.
Also, 2/8 (25%) of amikacin susceptible clinical Acinetobacter isolates had
aac(6)lb gene.