الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
200 isolates were identified from 220 clinical samples collected
from Benha university hospital to isolate any growth of Staphylococcus
aureus.
The age of the patients ranged from 3 days to 55 years with the mean
age 27.5years.
The sex of the patients under the study was 65 female and 155 male.
These samples were cultured on (blood agar, Mac-Conkey and
mannitol salt agar).
The 200 isolates were collected from pus (128), ear discharge (2),
urine (43) and blood (27) .
• It was shown that the prevalence of gram positive cocci was 41.5%
(83 Gram+ve cocci out of 200 isolates).
• The prevalence of Staphylococcus aureus isolates was 28% (56
S.aureus isolates out of 200 isolates).
• The prevalence of other gram positive cocci was 13.5% (27 out of
200 isolates), 25 of them were coagulase negative staphylococci
and 2 were streptococci.
• The prevalence of gram negative bacilli was 58.5% (117 out of
200).
Identification of MRS A was done b the followin methods:
Detection of mec A gene(the gold standard method) was done by
real time PCR(22 S.aureus strains were MRSA and 34 S.aureus were
MSSA).
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Phenotypic identification was done and compared with real time PCR
and it was found that:
• Disk diffusion method :
By oxacillin lug, the sensitivity of this method was 90.9% and
specificity was 94.1%.
By oxacillin 5ug, the sensitivity of this method was 90.1% and
specificity was 76.5%.
By cefoxitin 30 ug, the sensitivity of this method was 100% and
specificity was 94.1%,
• E-test MIC strips with oxacillin, the sensitivity of this method
was 90.9% and specificity was 94.1%.
• The PBP2a latex agglutination test, the sensitivity of this
method was 100% and specificity was 100%.
It is found that real time PCR and latex agglutination test did not
detect two border line resistance S.aureus (their MIC was 4-8ug/ml) as
they did not have mec A gene and also lack PBP2a (the product of the
gene).These BORSA strains was detected by all used disk diffusion
methods and E-test.
from our results, it is declared that if compared with real -time PCR
only latex agglutination test is able rapidly and reliably to detect
methicillin resistance in S.aureus as it yielded the best sensitivity and
specificity.
The time taken by latex agglutination test for detection of MRSA from
isolated S.aureus colonies was 20 min. The PBP2a latex agglutination
assay is less complicated than PCR for mec A and has been shown to be
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more sensitive than other phenotypic methods, such as the use of
oxacillin disk diffusion method and oxacillin E-test strips.
However, cefoxitin 30ug disk diffusion test yielded the sensitivity
of latex agglutination test (lOO% for both of them) but its specificity was
lower than latex and it can be used as screening test as it gave no false
negative results, however it is not a conclusive test as it detects 2
hyperproducers of B-lactamases as MRSA and it is also time consuming
test.
Oxacillin E-test strips yielded the same sensitivity and specificity of
the oxacillin 1ug disk diffusion method.
In conclusion, the new molecular assay (real time PCR) was found
to be rapid and robust. Because it is a largely automated assay, less
hands-on work is needed, consumes shorter time than conventional PCR
and it can be used for direct detection ofMRSA from non sterile clinical
specimen, however, it is not yet available in the majority of routine
diagnostic laboratories because of their elevated technical requirements.
In absence of real time PCR, latex agglutination test is the best method
for MRSA detection from isolated colonies.
Both real time PCR and latex agglutination test avoid. missing of
cryptic MRSA strains which should be treated with vancomcin and other
antimicrobials against MRSA. Also avoid unnecessary use of
vancomycin to B-Iactamase hyper producers (BORSA) strains which
could be treated with B-Iactam -B-Iactamase inhibitor compounds.