Blood culture metho ds CtilConventional versus Automation * Blood is a circulating tissue which Transfer O2 and nutrients to the cells caries immune system cells and proteins and deliver Co2 and metabolic wastes to excretory organs. * Blood is sterile and circulate in a closed system and nowadays is used as a part by medical treatmen in Transfusion and can be infected by different germs. Bacteremia , fungemia , viremia parasitemia refers The presence of bacteria , fungi , viruses and parasites in circulaion Bacteremia maybe silent (()psubclinical) and the patient may not be aware of the preson of microbes in his circulation Septicemia (sepsis) is a clinical syndrome characterized by fever , chills , hyhperventil ati on prosttiteration , (blood poisioning) , etc….. Sepsis results when circulating bacteria are abundant , can escape the immune system , and produce toxins . cytokines produced by inflammatory cells accelerlate the condition . The sequllae of the sepsis may be multiple organ dysfunction , DIC , and death. Sepsis although Traditionally associated with Gram Negative btibacteria ,EtEntero bac ter iaceae ( endotoxin) , but nowadays , Gram positive bacteria assaccharohyltic , non fermenters , and anaerobes can also produce sepsis syndrome. *Bacteremia may be Transient during tooth (dental) manipulation , severe dental Brushing and bowel movement . In this state the bacteria are cleared by Reticuloendothelial (RE) and no or mild symptoms. *In patients with congenital anomally of heart valves , Some times this Type of bacteremia may produce Endocarditis. Intermittent bacteremia occurs when there is a locous of infection in extltravascular and bdbody spaces such as Abscesses , empyema , pertonitis , cellulitis Continous bacteremia occur when the infection is intravascular infection of the endocardium and endothelial lining of arteries , anurysem , indwelling Cannulas. Conditions which may be related to sepsis . • Colonization of exteranl nares with staph aureus . Contamination of wounds with MRSE , MRSA in hospitalized patients and immunoCompromised. • *clostridium septicum in patient with neoplastic disease like colon carcinomas. • *Strepto coccus bovis – in patients with endocarditis , and colonic carcinomas. sepsisOccurred by clostridium perfrinngens can cause massive hemolysis with high morta lity. Conventional blood culture , Also is yet the most popular tttest in a sepsis work up , btbut have many disadvantages . Such as: No enough nutrient medium Longgy time by incubation 10-30days to detect growth number of bottles- 2 to 6 and long incubation peroid Bactericidal effect by serum and immune cells , can inhibit growth of invading organism. Automated Blood culture:
Advantages: Rapid and accurate Diagnosis of Bacteremia Rappgid Growing of fastidious or ganism Causing septicemia short turn around time of detection of bacteremia and septicemia Low volume of Blood for each bottle from 0.5ml in neonate to 5ml in adult. Much lower cost of bottles in comprasion of similar systems. Continue:
Much more user friendly than other systems
Capable of Growing anaerobic bacteria
Suit a ble for cult uri ng of bod y flu ids (csf -jitjoint ) Definitions: AST performing (old name antibiogram) is the second most critical test in clinical microbiology . In conventional method (()Disk diffusion) the pattern of sensitivity and resistivity is qualitative Here the lab needs at least (18-24 hours) for Doing Antibiogram. Continue: By this system also there are many Controversye both in test performing and interpretations. for some antibiotics disk diffusion doesn`t become standardized according to CLSI pp(rotocols. (vancomycin etc…) Also there are many differences between th e sens it ivity pattern pharmacodynamics of the drug , site of infections etc… In order to over come these parameters one solution is to determine the minimum concentration of t he drug (MIC) and in some cases like endocarditis (()ABE,SBE) The minium lethal bactericidal concenteratim should be determined. Performing MIC, MBC is trouble and need experience , time , dilutions , and also the ppgure state of each drug. In DL Blood culture: o The medium contains resin beads. The beads can lyse WBC s and release bacteria within them to improve detection rate. o The medium contains agents which neutralize A wide variety of antibiotics, shortens time by detection. o The beads also woldn’t interference with microscopic examination while systems containing activated carbon dosen’t do this Also activated carbon may have inhibitory effects on some bacterial growth. 9 In bottles one made of multi-layer polymeric fiber. They are lightweight and brokeable so much more safe and avoid biohazard esplashes. 9 Vaccum blood sampling improve safety and less contamination 9 The system enhances the growth of micro bes (even fastidi ous ones) and fungi 9 The growth of bacteria are detectable even with < = 100 cfu organism 9 Growth of majority of bacteria are evident even between 15-21 and for some fast grower even 7- 10 hours. 9 Like other systems in DL blood culture system bottles are adapted for growth of aerobic, anaerobic and bottles for neoate and infants 9 In comprasion with other system the cast per bottle is very low 9 And usually one bblottle suffiffiicient for each patient to R/o bacteremia. The bottles in the system are agitated in every ten minutes and any positive signs are alarmed by audio, door lightflash and screen flash Technical sepecifications. The bacterial growth is identified by colorimetry and AST by turbidometry ¾ Fully automated sampling device can be equipped so as to reduce work load prevent errors in sampling and guarantee biological safety . ¾ percise and reliable microbes identification at species and subsepecies. ¾ the system support the growth of enterobibacteria… nonfermenters, Gram pos iiitive cocci , vibrionaceae and even fungi (yeast) ¾ continue: ¾ DL 96 is able to screen ESBL s organisms , fungi drug sensitivity with at least 5 antifungal drugs ¾ DL96 ID/AST system has been programmed accordi ng to CLSI regulations ¾ Every antibdbiotic provide 8 llflevels of concentration in test card ¾ The system is percise , rapid and cost effective, both for patient care and lab budget. Informations: • In automated blood culture the principle is according to libration of Co2 molecules during bacterial metabolism. • The change in the PH of the medium is sensed by a flourscent tag in the bottle in BD system , and by scattered light in Bact/Alert system In Trek Esp system a mixture of gases such as O2 consumption and H2, Co2 libration is detect by the sensors.
In the DL Blood culture system the principle of detection is according to colorimetry. change in the color of the bottle and carbonate sensor.