DIAGNOSIS OF SEPTICEMIA

Causative organisms:

(Mention those bacteria that you are well-conversant with)

Gram negative cocci – meningococci, gonococci, hemophilus
Gram negative bacilli – Salmonella typhi, EIEC, almost all causes of UTI, Infective endocarditis (including HACEK organisms), meningitis.
Gram positive organisms (rare) – Streptococcus, Staphylococcus, Pneumococcus, almost all organisms that cause osteomyelitis and pneumonia.

Material for diagnosis:

Venous blood – 3 samples at 0, 30 and 90 min intervals from admission
Urine
CSF (if features of meningeal irritation are present)
Swab from suspected skin lesion


Steps of diagnosis:
Exams and Tests

Physical examination may show:

Low blood pressure
Low body temperature or fever
Signs of associated disease (such as meningitis, epiglottitis, pneumonia, or cellulitis)

Tests that can confirm infection include:
Blood culture
Urine culture
CSF culture
Culture of any suspect skin lesion
CBC
Platelet count
Clotting studies
PT
PTT
Fibrinogen levels
Blood gases

BLOOD CULTURE
A minimum of 10 ml of blood is taken through venipuncture and injected into two or more "blood bottles" with specific media for aerobic and anaerobic organisms.
Care needs to be taken that the bottles are not contaminated with bacteria from staff members or other patients. To that end, the patient's skin is rubbed or sprayed with denaturated alcohol and betadine applied to the sampling site. Sterile gloves should be used to minimize contamination.
To maximise the diagnostic yield of blood cultures multiple sets of cultures (each set consisting of aerobic & anaerobic vials filled with 3-10 mL) may be ordered by medical staff.
Set 1= L. antecubital fossa at 0 minutes
Set 2= R. antecubital fossa at 30 minutes
Set 3= L. or R. antecubital fossa at 90 minutes
Ordering multiple sets of cultures increases the probability of discovering a pathogenic organism in the blood and reduces the probability of having a positive culture due to skin contaminants.
After inoculating the culture vials on the hospital floor, they are sent to the microbiology lab clinical pathology department. Here the cultures are entered into a blood culture machine, which keeps the samples at body temperature. The blood culture instrument reports positive blood cultures (cultures with bacteria present, thus indicating the patient is "septic") by monitoring carbon dioxide levels produced by bacteria in the vials via fluorescence detected by a light emitting diode (LED). Most cultures are monitored for 5-days, after which, if the vials are negative, they are removed.
If a vial is positive, a microbiologist will perform a Gram Stain on the blood for a rapid, general ID of the bacteria, which they will report to the attending physician of the septic patient. The blood is also subcultured or "Subed" onto agar plates to isolate the pathogenic organism for culture and suceptability testing, which takes up to 3 days time. This culture & sensitivity (C&S) process IDs the species of bacteria. Antibiotic sensitivities are then assessed on the isolate to inform clinicians on appropriate antibiotics for treatment.
Some guidelines for infective endocarditis recommend taking up to 6 sets of blood for culture (around 60 ml).

URINE EXAMINATION:
(Summarize the Laboratory diagnosis for UTI)
CSF EXAMINATION:
(Summarize the Laboratory diagnosis of Meningitis)

ROUTINE EXAMINATIONS
CBC - may show neutrophilia (enteric fever may show neutropenia)
Platelet count - may decrease following DIC
Clotting studies
PT - may rise following DIC r hepatocellular failure
PTT - may rise in DIC
Fibrinogen levels – may be low in DIC
FDP – may rise in DIC
Blood gases – may be abnormal in respiratory failure (raised pCO2 and low pO2)

CONCLUSION:
Based on the above investigations we can reach a diagnosis of septicemia.