الفهرس 
Description of staphylococciOnly 14 pages are availabe for public view
 |  | from | 233 |  |  |
| | | from | 233 | | |
Abstract
S.aureus and CoNS are major cause of nosocomial infections and human diseases. MRSA and MRCoNS infections are important cause of
morbidity and mortality in large hospitals, but also are increasingly acquired in
the community.
The goal of the present work was to evaluate the magnitude of MRSA,
MRCoNS, VRSA and VRCoNS infections in Menoufia University Hospitals
as well as in the community associated isolates and to investigate their
susceptibility patterns. Also, Screening of methicillin and vancomycin resistant
staphylococci by phenotypic and genotypic methods. We aimed also to study
the biofilm forming capacity among studied staphylococcal isolates by
phenotypic methods and to detect genes assosciated with biofilm formation.
Also, to analyse the association between biofilm forming capacity and
multidrug resistance in staphylococci.
This study comprised two groups. The 1st group included 250 inpatients
(136 males and 114 females) from different wards and ICUs units of Menoufia
University Hospitals having different nosocomial infections. Their ages ranged
from 3 days to 77 years old (mean±SD; 30.45±10.32 years old). Different
samples were collected from group I patients (one specimen from each patient).
Group II included 90 community healthy persons (37 males and 53females).
Their ages ranged from 15-60 years (mean±SD; 35.43±12.53 years old).
Samples were collected from their noses.
Isolation and identification of organisms were done according to the
standard microbiological methods.S. aureus was the most common organism isolated from clinical
specimens (27.8%) followed by Klebsiella spp. (27.3 %) and CoNS (21.2 %).
The most frequent isolate from community carriers were S. aureus (47.7 %)
followed by CoNS (37.5 %).
Antibiotic susceptibility testing by disk diffusion method revealed higher
rates of resistance among S.aureus and CoNS C.Is. compared to commensal
isolates.
S. aureus isolates were highly resistant to penicillin ampicillin,
amoxicillin-clavulonic acid (94% for each), oxacillin (82.4%),
trimethoprim/sulfamethoxazole (88.2%), cefoxitin (82.4%), cefotriaxone
(79.4%), ciprofloxacin (70.6%), teicoplanin (67.6%), rifampicin (67.6%),
tetracycline (66.2%) and chloramphinicol (63.2%). On the other hand, the
sensitivity to linezolid was 98.5%.
CoNS C.Is. were highly resistant to penicillin (92.6 %), ampicillin (90.4
%), amoxicillin/clavulanate (84.6 %)}, ciprofloxacin (88.5 %), oxacillin and
cefoxitin (78.8 %), cefotriaxone (75 %), chloramphinicol (71.2 %), tetracycline
(67.3 %) and rifampicin (63.5 %). Moderately resistant to teicoplanin (46.2 %)
and trimethoprim/sulfamethoxazole (55.8 %), on the other hand, the sensitivity
to linezolid was 100 %.
Commensal S.aureus and CoNS showed lower rate of resistance when
compared to C.Is. They were 100% sensitive to vancomycin, teicoplanin,
ceftriaxone, and ciprofloxacin.
Identification of resistance pattern of MRSA and MRCoNS isolates was
achieved by cefoxitin disc diffusion method and confirmed by PCR
determination of mecA gene. For S. aureus isolates, PCR study detected 52
positive MecA isolates (92.2 %) out of 56 methicillin-resistant isolates detected
by cefoxitin disc diffusion method. The sensitivity of cefoxitin disc diffusion method was 100 %, specificity was 75 % and diagnostic accuracy was 94 %.
For CoNS, PCR study detected 40 positive MecA isolates (97.6 %) out of 41
methicillin-resistant isolates detected by disc diffusion method. The sensitivity
of cefoxitin disc diffusion method was 100 %, specificity was 92 % and
diagnostic accuracy was 98 %.
The rate of MRSA infection (82.4%) and MRCoNS (78.8%) was higher
in C.Is. than commensals MRSA (21.4%) and MRCoNS (9.1%).
Detection of S.aureus and CoNS isolates intermediate and resistant to
vancomycin was achieved by vancomycin screen agar method and confirmed
by MIC. About 68 % of S. aureus C.Is. were VISA/VRSA and 46.1 % of CoNS
C.Is. were VICoNS /VRCoNS by vancomycin screen agar, and by MIC
determination, 26.5 % of S. aureus C.Is. were VRSA and 19.2 % of CoNS C.Is.
were VRCoNS.
Comparing the results of MIC and PCR, for S. aureus isolates, PCR study
detected 7 positive VanA isolates (38.9 %) out of 18 vancomycin resistant
isolates detected by MIC. The sensitivity of MIC method was 100 %,
specificity was 52 % and diagnostic accuracy was 63 %. For CoNS, PCR study
detected 5 positive VanA isolates (50 %) out of 10 vancomycin resistant
isolates detected by MIC. The sensitivity of MIC method was 100 %,
specificity was 85% and diagnostic accuracy was 87 %.
Vancomycin rsistance was detected only in S.aureus (26.5%) and in CoNS
(19.2%) C.Is., while commensal S.aureus and CoNS did not show resistance to
vancomycin.
Detection of biofilm formation was carried out by Congo red agar (CRA),
modified Congo red agar (MCRA) and microtitre plate adherence (MTP)
methods. The percent of S. aureus C.Is. showing biofilm by CRA, MCRA and
by MTP tests were 41.2 %, 42.6 % and 45.6 %, respectively. The percent of S. aureus commensals showing biofilm by CRA, MCRA and by MTP tests were
7.1 % for each of the three test results. Among studied CoNS C.Is, detection of
biofilm-formation by CRA, MCRA and MTP test were 55.8 %, 61.5 % and
76.9 %, respectively. While among studied CoNS commensals, detection of
biofilm-formation by CRA, MCRA and MTP test were 27.3 % for each of the
three tests. There was statistically significant difference between ability to form
biofilm in clinical and commensal strains regarding the three methods.
Confirmation of biofilm formation by detection of icaAD genes was done
by PCR, IcaA gene alone was not detected in any isolate, while icaD gene
alone was detected in 13.2 % of S. aureus C.Is., 4.8 % of S. aureus
commensals, 21.2 % of CoNS C.Is and 27.3 % of CoNS commensals. Both
icaA and icaD genes were detected in 25.1 % of S. aureus C.Is and in 42.3 % of
CoNS C.Is. The percent of total numbers of strains contained genes were 38.2
% S. aureus C.Is, 4.8 % S. aureus commensals, 63.5 % CoNS C.Is and 27.3 %
of CoNS commensals.
Comparing the results of the phenotypic methods for detection of biofilm
production and genotypic detection of ica genes, in S.aureus C.Is. PCR study
detected 21 +ve icaD (75 %) out of 28 biofilm producing isolates detected by
CRA method, The sensitivity of CRA method was 81 %, specificity was 83 %
and diagnostic accuracy was 82 %. PCR study detected 21 +ve icaD (72.4 %)
out of 29 biofilm producing isolates detected by MCRA method, the sensitivity,
specificity and diagnostic accuracy of MCRA method was 81 % for each. Also
PCR study detected 26 +ve icaD (83.9 %) out of 31 biofilm producing isolates
detected by MTP method, the sensitivity of MTP was 100 %, specificity was 88
% and diagnostic accuracy was 93 %. Regarding CoNS C.Is. PCR study
detected 27 +ve icaD (93.1 %) out of 29 biofilm producing isolates detected by
CRA method, the sensitivity of CRA method was 82 %, specificity was 89 % and diagnostic accuracy was 85 %. PCR study detected 27 +ve icaD (84.4 %)
out of 32 biofilm producing isolates detected by MCRA method, the sensitivity
of MCRA method was 82 %, specificity was 74 % and diagnostic accuracy was
79 %. PCR study detected 33 +ve icaD (82.5%) out of 40 biofilm producing
isolates detected by MTP method, the sensitivity of MTP was 100 %,
specificity was 63 % and diagnostic accuracy was 87 %.
The present study showed that combination of CRA and MTP results
gave a better prediction of biofilm formation.
The present study showed that there is strong association between
methicillin and vancomycin resistance and the ability to form biofilm. About
55.4 % of MRSA C.Is. were biofilm producers with high statistically
significant difference when compared with MSSA, also 33.3 % of commensal
MRSA were biofilm producers. Regarding MRCoNS C.Is, 97.6 % were biofilm
producers with high statistically significant difference when compared with
MSCoNS, while all commensal MRCoNS were biofilm producers. All
vancomycin resistant CoNS strains were biofilm producers with high
statistically significant difference when compared with VSCoNS, while 77.8 %
of VRSA were biofilm producers with statistically significant difference when
compared with VSSA.
Regarding different departments of our hospital, patients from ICU,
pediatric, internal medicine and orthopedic surgery departments showed higher
percentage of S.aureus than other departments with statistically significant
difference. MRSA were significantly isolated from all departments. Patients
from ICU, pediatric and orthopedic surgery departments showed higher
percentage of VRSA than other departments with statistically significant
difference. Patients from ICU, internal medicine and urology departments
showed higher percentage of biofilm forming strains than other departments with statistically significant difference.
Patients from ICU, pediatric and orthopedic surgery departments showed
higher percentage of CoNS with statistically significant difference. MRCoNS,
were significantly isolated from all departments except burn unit. Patients from
pediatric and burn unit departments showed the highest percentage of VR
CoNS with statistically significant difference. Biofilm forming CoNS strains
were highly disseminated in all departments except pediatric department with
statistically significant difference.
Staphylococus aureus, MRSA, VRSA, CoNS, MRCoNS and VRCoNS
infections were more commonly found in old age patients ( >50 years).
History of antibiotic treatment, invasive interventions were the most common
risk factors associated with S.aureus, MRSA, VRSA, CoNS, MRCoNS and
VRCoNS infections.