Source of Infection

Introduction

Usually a thorough review of systems on history is enough to identify the likely source of infection (the screening questions on the left side column is generally adequate)
Confirmatory microbiological testing does not need to proceed to make the decision to commence antibiotics if the source is clear or if the patient is unwell (consult a nationally or locally accepted standard such as Australian Therapeutic Guidelines)
In cases of uncertainty and if the patient is unwell it is reasonable to provide empirical cover to both Gram Positive and Gram Negative organisms e.g. Flucloxacillin and Gentamicin
Where source is unclear and patient is well, a period of observation for more localising symptoms to develop is reasonable
A basic screen of urinalysis and CXR is reasonable in a moderately unwell patient. Blood cultures are indicated if there is evidence of septicaemia
It is more reliable and accurate to culture fluid from the site of infection e.g. abscesses, urine, effusions, collections then attempt to identify the organism by blood culture

HISTORY	EXAMINATION	INVESTIGATION	FOCI
Dysuria, Frequency, Nocturia Flank pain Recent bladder instrumentation/IDC	Suprapubic/Flank tenderness	Urinalysis – leucocytes, nitrates, blood MSU	UTI
Cough/Sputum Dyspnea Chest pain	Tachypnea Decreased oxygenation Focal chest findings	CXR abnormalities	LRTI
Headache Photophobia Recent respiratory infection	Neck stiffness Altered concious state Seizures (esp. encephalitis) Focal signs (if abscess)	CT brain Lumbar puncture	CNS infections
Positional headache Facial pain Purulent rhinorrhea Post-nasal drip Maxillary dental pain	Sinus tenderness	Sinus xrays	Sinusitis
Otalgia Ear discharge	Red, bulging drum		Otitis media
Non-specific GI symptoms Nausea, vomiting, diarrhea or constipation Dysuria (adherent inflammatory mass to bladder)	Localised abdominal tenderness with peritonism	Abdominal U/S Abdominal CT	Intrabdominal infection
Perianal pain, swelling or discharge	Rectal tenderness	Rectal swab	Perianal infection
Pelvic pain PV discharge Dyspareunia Tampon use Recent gynae instrumentation STD risk factors	Cervical excitation Adnexal tenderness/mass	Vaginal swab	Gynaecological infection
Open sores/rashes Recent skin trauma/surgical trauma	Skin inflammation (remember to examine entire lower limb, back and sacrum)		Cellulitis
Bone/Joint pain	Bone tenderness Decreased ROM Joint swelling/tenderness	Joint aspirate	Osteomyelitis Septic arthritis Septic bursitis

	New murmurs Splinter haemorrhages	Echocardiogram	Endocarditis
	Purpuric Rash		Meningococcal Sepsis