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RELEVANCE OF BLOOD CULTURE TO THE DIAGNOSIS AND TREATMENT OF SEPTICEMIA

ABSTRACT

A study of septicaemia was conducted in Enugu metropolis with a view to determine the relevance of blood culture to the diagnosis and treatment of this disease. The subjects comprised of  three hundred and fifty (350) children and adults of both sexes aged between one day to 70 years having clinical features suggestive of septicaemia, who were on admission at University Of Nigeria Teaching Hospitals (UNTH), Enugu.  Their blood specimens were seeded into thioglycolateand glucose broths and incubated at 37 °C for 7 days. Subcultures were performed after 1, 2, 3, 4 and 7 days respectively. Growth (positivity) in the broths was assessed using conventional diagnostic methods namely macroscopy(visualization), Gram filming (microscopy) and culture. The bacterial isolates harvested were subjected to in-vitroantibiotic susceptibility tests using the disc diffusion method. Etiology was established in 104 out of 350 subjects indicating an incidence of 29.7%. This difference in prevalence among different age groups was statistically significant(P < 0.01). The males (59/350, 16.86%) appeared to be more susceptible to septicaemia than the females (45/350, 12.9%) in all the age groups. This variation had no statistical significance (P > 0.01). Monomicrobialsepticaemia had ahigher prevalence (91.3%) than polymicrobialsepticaemia (8.65%). Staphylococcus aureusand Escherichia coliconstituted 33.3%. Most of the offensive microbes were facultative anaerobes (93.3%) while very few were strict aerobes (7.69%) and strict anaerobes (1.92%). The isolated anaerobes were Peptostreptococcussp. (1%) and Bacteroidesfragilis(1%). The in vitro susceptibility of the bacterial isolates to antibiotics indicated 78.9-92.9% sensitivity to vancomycin, zinnat, peflacin and fortum. However, they were 60 – 90% resistant to penicillin, ampicillin, tetracycline and septrin. This study confirmed the diverse nature of bacterial etiologies of septicaemia in Enugu metropolis; the need for the use ofthioglycolate broths, first subcultures on or before 24 h instead of starting off for after 48 h of incubation, complementary application of macroscopy, Gram filming and culture including antibiotic susceptibility test as an integral part of diagnosis and treatment of septicaemia is hereby advocated, most especially in the developing countries of the world.

CHAPTER ONE

INTRODUCTION

Blood is normally sterile in healthy individuals. It is the main transport mechanism connecting all different parts of the body. As it serves as a transport system for oxygen, food materials, waste products and others round the body, it can also carry microbes (Eugene et al., 1998).   However, it has no normal flora and the presence of microorganism in it indicates failure of the defence mechanisms to maintain its sterility. In many cases such a failure is transitory and of no clinical importance but in others, it is serious and life threatening. Lymphoid tissue is an important part of the defence system acting as a filter to intercept potentially invasive pathogens as well as being the headquarter of the lymphocytes on which immunity is heavily dependent. This filter system is however liable to clinically significant infections by intercepted pathogen and it is also the primary target for some factors of infection (Douglas  et al., 1981). The involvement of blood, lymphatic system and heart in many infections give us the knowledge of the presence of bacteria in the blood. Various authors have reported bacteraemia immediately after incision of an abscess, tonsillectomy and tooth extraction (Fischer et al., 1941; Murry et al., 1941). Robert et al. (1997) described bacteraemia as a  transitory disease in which bacteria present in the blood  are usually eliminated from the vascular system by the  reticulo endothelial system with no harmful effect, but in host with reduced immunity, septicaemia results.

The term septicaemia is often used in describing severebacteraemic  infections or a condition in which the blood  serves as a site of bacteria multiplication as well as a means of transfer of the infectious agent from one site to  the other. The clinical picture frequently present in septicaemia is that of septic shock which is recognized by a severe febrile episode with chills, fever, malaise, tachycardia mental confusion, hyperventilation and toxicity, a hypotension (drop in blood pressure) and prostration  which results when circulating bacteria multiply at a rate  that exceeds their removal by phagocytes. Complications include disseminated intravascular coagulation (DIC) and acute renal failure (Shanson, 1999).

The mortality rate varies between 15 and 35%,  depending on the age, the underlying condition and the  treatment given (Shamson, 1998). Prompt recognition of septicaemia and immediate treatment based on the knowledge of the likely causative organism is essential.  Septicemias which are of bacterial origin are caused by myriads of bacteria varying from one locality to another. Many studies on septicaemia in Nigeria have been on neonates and childhood and also retrospective (Dawodu et al., 1980) and there is therefore paucity of information on prospective study on septiceamia in different strata of society in Nigeria.

1.1     BLOOD CULTURE

Thisis a culture of blood microbiologically that is employed for the detection of diseases which are spreading through the bloodstream. One of such disease is septicemia. This culture of blood is possible because the bloodstream is usually a sterile environment and it is carried out through a laboratory test which will check for bacteria or other microorganisms in a blood sample. Most cultures check for bacteria. A culture may be done using a sample of blood, tissue, stool, urine, or other fluid from the body. When signs or symptoms of a systemic infection is noticed in a patient, results from a blood culture can verify that an infection is present, and they can identify the type (or types) of microorganism that is responsible for the infection. A good example is when blood tests identifies the causative organisms in neonatal epiglottitis, sepsis, severe pneumonia, puerperal fever and fever of unknown origin (FUO). However, negative growths do not exclude infection. The usual risks of venipuncture and the occurrence of false positive results approximately 3%+ of the time, can lead to inappropriate treatment (Madeo et al., 2003).

1.2   SEPTICAEMIA

Septicaemia is often referred to as either blood poisoning, bacteremia or sepsis, although it could be argued that each of the terms are not entirely accurate, but are often used interchangeably by scientists (Al-Khafaji et al., 2010). Sepsis is not just limited to the blood and can affect the whole body, including the organs. Septicaemia (another name for blood poisoning) refers to a bacterial infection of the blood, whereas sepsis can also be caused by viral or fungal infections. Septicaemia also known as Sepsis is a condition that arises when the body’s response to infection injures its own tissues and organs (Deutschman and Tracey, 2014).Common signs and symptoms include fever, increased heart rate, increased breathing rate, and confusion. (CDC, 2014). There may also be symptoms related to a specific infection, such as a cough with pneumonia, or painful urination with a kidney infection. In the very young, old, and people with a weakened immune system, there may be no symptoms of a specific infection and the body temperature may be low or normal rather than high(Martí-Carvajal et al., 2012). Severe sepsis is sepsis causing poor organ function or insufficient blood flow. Insufficient blood flow may be evident by low blood pressure, high blood lactate, or low urine output. Septic shock is low blood pressure due to sepsis that does not improve after reasonable amounts of intravenous fluids are given (Dellinger et al., 2013).

Sepsis is caused by an immune response triggered by an infection (Jui, 2011; Deutschman and Tracey, 2014).  The infection is most commonly bacterial, but it can also be from fungi, viruses, or parasites (Jui, 2011) Common locations for the primary infection include: lungs, brain, urinary tract, skin, andabdominal organs. Risk factors include young or old age, a weakened immune system from conditions such as cancer or diabetes, and major trauma or burns (CDC, 2014). Diagnosis is based on meeting at least two systemic inflammatory response syndrome (SIRS) criteria due to a presumed infection. Blood cultures are recommended preferably before antibiotics are started; however, infection of the blood is not required for the diagnosis (Jui, 2011). Medical imaging should be done to look for the possible location of infection (Patel and Balk, 2012).  Other potential causes of similar signs and symptoms include: anaphylaxis, adrenal insufficiency, low blood volume, heart failure, andpulmonary embolism among others (Jui, 2011).

1.3     OBJECTIVES OF THE RESEARCH

This objectives of this research are to;

Determine the relevance of blood culture to the diagnosis and treatment of septicaemia.

Compare the occurrence of Gram positive and Gram negative bacteria in the subjects with culture – proven septicaemia.

Determine which gender(male or female) is more prone to septicaemia.

1.4    JUSTIFICATION

It is important to ensure that bloodstream infections are diagnosed accurately and that infecting pathogens, their antimicrobial susceptibilities, and the possible primary sources of infection are evaluated thoroughly, to enable optimal targeted antimicrobial therapy.Blood cultures and their microbiological analysis are highly essential and important for the diagnosis and treatment of septicaemia (sepsis).Blood culture is important for early diagnosis and treatment of patients with septicaemia as survival depends on early detection and administration of adequate empirical antimicrobial therapy.

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