Comparative study between methicillin resistant staphylococcus aureus (MRSA)‎ agr + isolates and MRSA agr-isolates

العناوين الأخرى

دراسة مقارنة بين عزلات المكورات العنقودية الذهبية المقاومة للمثيسلين الحاوية على agr و غير الحاوية على agr

مقدم أطروحة جامعية

al-Dhahabi, Ali Makki Hamad

مشرف أطروحة جامعية

al-Mathkhuri, Harith Jabbar Fahd

أعضاء اللجنة

Audah, Jamilah G.
Khilkhal, Intisar N.

الجامعة

جامعة بغداد

الكلية

كلية العلوم

القسم الأكاديمي

قسم علوم الحياة

دولة الجامعة

العراق

الدرجة العلمية

ماجستير

تاريخ الدرجة العلمية

2013

الملخص الإنجليزي

The study has begun on August 2011 until June 2012, in which 250 nasal swabs were collected from healthcare workers (HCWs) and admitted patients at Al- Kahdamia Teaching Hospital and Al-Numan Hospital at Baghdad.

All isolates have been diagnosed depending on microscopical and biochemical tests and confirmed by MASTASTAPH-Latex kit and Api Staph System.

It was found that 100% of the 250 isolates were belong to Staphylococcus spp., 42.2% were diagnosed as coagulase-positive staphylococci (COPS).

The study of antibiotic susceptibility test to 11 different antibiotics showed that Staphylococcus aureus was 100% resistant to penicillin G whereas for cefoxitin (alternative to methicillin) resistance was 94.3%.

There were a variable resistance percentage for the rest of antibiotics: trimethoprim/sulfamethoxazole (50%), erythromycin (38%), tetracycline (34.9%), gentamicin (28.5%), ciprofloxacin (29.2%) and vancomycin (3.8%), whereas they showed high sensitivity to rifampin (96.2%), clarithromycin (78%) and clindamycin (73.3%).

Real-time PCR was used to detect mecA gene in eight S.

aureus, the results were in accordance of that obtained by cefoxitin disc diffusion test that used for investigating MRSA.

The results showed that the overall prevalence of agr defective (agr-) among S.

aureus isolates was eight (7.5%).

It is markedly noticeable that all these agrisolates were found only in HCWs, seven MRSA and one MSSA.

The study showed that there is a significant relationship (P <0.05) between the intermediate resistance to vancomycin and agr system in which that all agrisolates were VISA.

The study of some virulence factors revealed that agr system controls the production of DNase, protease, lipase and urease as all agr+ isolates showed capability to produce these enzymes whereas its counterpart agr– couldn't.

The results of DNase test were confirmed for eight S.

aureus by real-time PCR assay for the detection of the nuc gene and it came similarly to DNase agar test.

b On the other hand the study of protein profile by SDS-Gel electrophoresis showed that agr + isolates produce many exoproteins that are not produced by agr - strains.

The biofilm-forming ability of S.

aureus was evaluated via two methods: first, for all isolates (106 isolates) by microtiter plates and the result revealed that 2% of the tested isolates were highly-strong producers while 22% of isolates were strong producers, 45% were mild producers and 31% were weak.

It should be noted that all agr- isolates distributed among strong producers group (6 of 8 isolates) and highly strong group (2 of 8 isolates) and agr- isolates were gave the highest productivity for biofilm among isolates S.

aureus.

Second, four isolates of MRSA, two agr+ (S1٦ and S1۹) and two agr - (S42 and S47), were tested for their ability to adhere on different material (1 cm2); urinary catheter, polystyrene, glass and stainless steel.

The study showed that both agr - (S42 and S47) have shown to express stronger biofilm amount than agr+ (S1٦ and S1۹), while urinary catheter and polystyrene had higher adhesive properties of bacteria than glass, while steel didn’t show any adhesive properties.

Inhibition of biofilm formation by the extracellular protein of agr+ isolates (extracted from S16) were studied on two agr - isolates (S42 and S47).

The results revealed that there is a significant decreased (p˂ 0.05) of biofilm production from۱.235 to ۰.٤30 for S42 isolate and 0.931 to 0.395 for S47 isolate.

This study showed a novel type of motile behavior exhibited by S.

aureus migrate over surfaces, an effect governed by agr locus, as all agr + isolates had the ability to spread on soft agar, while all isolates of agr - isolates (MRSA or MSSA) didn’t have the ability to spread on soft agar.

However all S.

aureus isolates has failed to spread on BHI agar.

Three of agr+ isolates (S29, S30 and S75) showed small-colony variants (SCVs) which exhibit distinctive phenotypic characteristics on agar, such as very small-sized colonies and markedly lacked of hemolysin production, these subpopulation is considered as agr mutant arising from their agr+ ancestors as they c lost each of their hemolytic activity on blood agar and inability to spread on soft agar.

Histopathological changes in murine skin showed that agr+ isolates caused ulceration, congestion, inflammatory cells infiltration, hemorrhage and hyperplasia of epidermis; while agr- isolates have a slight effect on the murine skin represented by infiltration of inflammatory cells with a large quantity of colonies developing on the skin tissue.

These results confirmed the association of agr+ isolates with high virulence and pathogenicity.

التخصصات الرئيسية

الأحياء

عدد الصفحات

152

قائمة المحتويات

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-597811