The term bacteraemia refers to the transient presence of organisms in the blood (generally without causing symptoms) as a result of local infection or penetrating injury. The term septicaemia, on the other hand, is usually reserved for when bacteria or fungi are actually multiplying in the blood, usually with the production of severe systemic symptoms such as fever and hypotension. Pyaemia describes the serious situation when, in a septicaemia, organisms and neutrophil polymorphs embolize to many sites in the body causing abscesses, notably in the lungs, liver and brain. Septicaemia has an extremely high mortality and demands immediate attention. Septic shock is discussed on p. 713.
The term primary septicaemia is used to describe the situation when the focus of infection is not apparent. Such patients are generally elderly, undernourished or suffering from chronic disease, particularly alcoholic cirrhosis and diabetes. The common sites of infection and infective agents responsible for secondary septicaemia are shown in Tables 1.3 and 1.4. Pneumococcus and Haemophilus influenzae are common causes of septicaemia in children, whereas in neonates Gram-negative rods and group B streptococci are the most likely aetiological agents. Neisseria gonorrhoeae is a common cause of septicaemia in young adults, but it is usually mild without serious effects intravenous drug abusers frequently suffer bacteraemia and septicaemia often caused by Staph. aureus, Pseudomonas and erratia.
Fever, rigors and hypotension are the cardinal features of severe septicaemia. However, the illness may be preceded by less specific symptoms such as headache, lethargy, apprehension and subtle changes in conscious level. Other clinical features and their pathogenesis are shown in Table 1.5.
Septicaemia is almost always treated initially on the basis of a clinical diagnosis after appropriate specimens have been sent to the laboratory. Probable origins of infection and likely pathogens must be sought on the basis of a careful history and examination. The type of infection
will clearly differ in hospitalized and otherwise previously healthy adults (see Tables 1.3 and 1.4). Body fluids or other specimens (blood, urine, CSF, tissue or abscess aspirates) should be submitted to full microbiological examination. Imaging investigations such as ultrasonography and CT scan may be required. Catheters or cannulae, which might be sources of infection, should be removed and sent for culture.
Management of septic shock is discussed on p. 720. Antibiotic therapy should be commenced immediately. If the organism and its antibiotic sensitivities are unknown, a combination of drugs should be chosen to cover the likely pathogens. If there is an obvious site of skin sepsis, drugs such as flucloxacillin (1 g 6-hourly i.v.) plus benzylpenicillin (to cover f3-haemolytic streptococci) should be used. In severe sepsis with osteomyelitis or endocarditis, an aminoglycoside to cover Staph. aureus should be used. If bowel sepsis is suspected, then a broaderspectrum drug of the cephalosporin group (e.g. cefuroxime/cefotaxime/ceftazidime) would be advisable. In the absence of any helpful clinical guidelines, a combination of a penicillin drug that is active against Pseudomonas such as piperacillin (200-300 mg kg-l daily) with an aminoglycoside such as gentamicin (3-5 mg kg-l daily in divided doses every 8 hours) should be given. Metronidazole (1 g every 8 hours by rectum) is often added to provide additional cover against anaerobic organisms. Steroids should not be used for the treatment of septicaemia or septicaemic shock.