Effect of Blood Agar from Different Animal Blood on Growth Rates and Morphology of Common Pathogenic Bacteria

Abstract

Sheep and horse blood are the most commonly used blood for the isolation of microorganisms from human tissue and fluids. However, in many developing countries such as Nigeria, expired human blood from blood banks is still used despite the risk of exposure to HIV and other blood-borne infections, because it is easy to obtain. Blood agar made from blood of rams (similar to sheep), cows, chickens and goats, which are very common in Nigeria, were therefore evaluated. The isolation rates, colony size and morphology as well as haemolytic characteristics of common hospital pathogens such as Pseudomonas aeruginosa, Klebsiella pneumonae, Staphylococcus aureus, and Streptococcus spp, were tested on blood agar prepared from the different animal blood types. All reactions were observed at 24 hrs and 48 hrs respectively. Good growth was achieved by all isolates on rabbit, sheep and chicken blood agar though the best growth was achieved on ram blood agar but there was no significant variation in their morphology. There were differences in their abilities to distinguish haemolytic patterns. Beta Haemolytic Streptococci remained the same on all the blood agar, but the haemolysis of Staphylococci aureus and Pseudomonas aeruginosa varied on different media while haemolysis was least consistent on chicken and cow blood agar. Ram blood agar gave the best reactions in terms of good growth rates of organisms, good morphological characterization as well as good haemolytic reactions. Besides, it is easily available and large quantities of blood can be obtained. Despite the good qualities of ram blood agar observed in this study, however, there is a need for it to be tested further for its ability to support more fastidious organisms.

Human, cattle and goat blood as substitutes for sheep blood in blood-supplemented culture media

“…1,12 All four types of blood agar gave β-haemolysis for group A and B streptococci and α-haemolysis for pneumococci. However, β and α-haemolysis were minimal and difficult to observe on HBA.…”

“…Robert Koch (1843Koch ( -1910) is considered as the father of artificial culture media. 1 Agar media supplemented with 5% blood are widely used in laboratories for routine isolation, identification and antibiotic susceptibility testing (ABST) of bacterial pathogens. 1,2 Some fastidious bacteria such as Neisseria and Haemophilus species require "X" factor (Haemin) and "V" factor (Nicotinamide adenine dinucleotide -NAD) which are found in blood cells.…”

“…4 Defibrinated sheep blood is largely preferred because it prevents growth of some nonpathogenic commensals (eg: Haemophilus haemolyticus) due to growth inhibitors and also gives the best haemolytic patterns. 1 Horse blood has also been recommended and is used in some countries. 4 However, in many developing countries, including Sri Lanka, sheep and horse blood are difficult to obtain due to unavailability of these animal sources.…”

“…2,6 Human blood is not generally recommended for enrichment of agar media because of poor bacterial isolation rates and inability to demonstrate proper organism characteristics. 1,2,6 Presence of antibodies, antibiotics and various inhibitory components in human blood can account for this. 2 The haemoglobin level of animals such as sheep and cattle are around 8-16 mg/dl 7 in comparison with the haemoglobin level of human red cell concentrate (20 mg/dl).…”

Usefulness Of Microbial Cytotoxins In The Diagnosis Of Selected Bacterial Infections

“…Wzbogacone krwią podłoże agarowe stanowi jedną z najpowszechniej używanych pożywek namnażających do hodowli bakterii chorobotwórczych. Określe nie morfologii wzrostu kolonii oraz typu hemolizy pozwalają na wstępną identyfikację patogennych drobnoustrojów lub ukierunkowanie diagnostyki na określone grupy drobnoustrojów [11]. Procedura testu CAMP polega na posiewie, w linii prostej na podłożu agarowym z 5% dodatkiem odwłóknionej krwi owczej, szczepu wzorcowego S. aureus oraz prostopadłym dosianiu do niego badanych paciorkowców (Ryc.…”