ID: Sepsis, fever and serious bacterial infections

• Sepsis and fever: Recognising Sepsis | Managing Sepsis and Septic Shock | Empirical Antibiotics by Source | Approach to the Febrile Patient | Pyrexia of Unknown Origin
• Nervous system: Bacterial Meningitis | Encephalitis | Brain and Spinal Epidural Abscess
• Blood and heart: Staphylococcus aureus Bacteraemia | Infective Endocarditis
• Bone, joint and soft tissue: Septic Arthritis | Osteomyelitis and Discitis | Prosthetic Joint Infection | Diabetic Foot Infection | Necrotising Soft Tissue Infection | Toxic Shock Syndrome
• Gut, toxins and animals: Infectious Diarrhoea and Food Poisoning | Tetanus, Botulism and Diphtheria | Lyme Disease and Other Zoonoses | Bites
• Revision: Infections at a Glance | Spot the Diagnosis | Exam-style Scenarios | Key Points | Guidelines and Further Reading

🚨 Sepsis, fever and serious bacterial infections — page 2 of the Infectious Diseases chapter. Sepsis kills when recognition or antibiotics are delayed, and many serious infections (meningitis, necrotising fasciitis, septic arthritis, spinal abscess) cause permanent harm within hours. The principles are the same every time: recognise early, take cultures, give the right antibiotics fast, support the circulation and control the source. Pneumonia, UTI and cellulitis are covered in their own chapters; antibiotic details are on page 1.
Your four questions for every patient: Is this sepsis, and how sick is the patient (NEWS2, lactate, organ dysfunction)? Where is the source? What organisms are likely, and which antibiotic covers them? Does the source need draining, removing or cutting out?

Recognising Sepsis

• Sepsis — life-threatening organ dysfunction caused by a dysregulated response to infection (Sepsis-3).
• Septic shock — sepsis needing vasopressors to keep mean arterial pressure at 65 mmHg or more, with lactate over 2 mmol/L despite adequate fluid — mortality around 40%.
• Think "could this be sepsis?" in anyone with an infection who looks unwell or has abnormal observations — especially if they are confused, breathless, mottled or not passing urine.
• NEWS2 (adults in the UK) — respiratory rate, oxygen saturation, oxygen use, systolic BP, heart rate, consciousness (new confusion counts) and temperature:
  • Score 7 or more (or 5–6 with high concern) — high risk: immediate senior review; antibiotics within 1 hour if infection is suspected.
  • Score 5–6 — urgent review (within 1 hour); antibiotics within about 3 hours if infection is likely, sooner if deteriorating.
  • A score of 3 in any single parameter needs urgent review.
• Red flags — new confusion, systolic BP 90 mmHg or less, heart rate over 130, respiratory rate 25 or more, new oxygen need, no urine for 18 hours (or under 0.5 mL/kg/hour), mottled or ashen skin, non-blanching rash, lactate 2 or more.
• High-risk groups — very old or very young, frail, recent surgery or chemotherapy (neutropenic sepsis — antibiotics within 1 hour), immunosuppressed, no spleen, pregnant or recently pregnant, people who inject drugs, people with lines or devices.
• Signs can be hidden — older people may have no fever; beta-blockers mask tachycardia; steroids mask fever and pain; hypothermia is a poor sign.
• Children — use age-appropriate scores and the NICE traffic-light system (see the Paediatric Infections chapter).

Managing Sepsis and Septic Shock

• The first hour — "Sepsis Six" (UK Sepsis Trust):
  • Give oxygen to target saturations (94–98%, or 88–92% if at risk of hypercapnia).
  • Take blood cultures (and other samples from the likely source).
  • Give IV antibiotics (local empirical guidelines; check allergies).
  • Give IV fluids — 500 mL crystalloid bolus over 15 minutes if hypotensive or lactate over 2, reassess, repeat (often up to about 30 mL/kg), watching for overload.
  • Measure lactate (and FBC, U&E, LFTs, CRP, clotting, glucose, blood gas).
  • Measure urine output (catheter in severe sepsis).
• Escalate early — senior review, outreach or critical care if not responding to fluids, lactate stays high, or organ failure progresses; agree a treatment escalation plan and resuscitation status.
• Septic shock:
  • Noradrenaline to keep mean arterial pressure at 65 mmHg or more (ideally via a central line; peripheral for short periods in some units).
  • Hydrocortisone (e.g. 200 mg a day) if shock persists despite vasopressors.
  • Ventilation, kidney replacement therapy, glucose control, VTE prophylaxis in ITU.
• Source control — within hours where possible: drain abscesses and empyema, decompress an obstructed infected kidney or bile duct, remove infected lines, debride necrotic tissue, repair perforations.
• Review antibiotics at 48–72 hours with culture results — narrow, switch to oral or stop (Start Smart — Then Focus).
• Hold nephrotoxic and hypotensive drugs (ACE inhibitors, diuretics, NSAIDs, metformin) during acute illness.
• After sepsis — many survivors have weakness, fatigue, poor sleep, anxiety, memory problems; arrange follow-up and rehabilitation.

⚠️ Safety Pearl: Every hour of delay in antibiotics in septic shock increases mortality. Don't wait for results, imaging or a lumbar puncture — take blood cultures and give antibiotics, then investigate.

Empirical Antibiotics by Source

Approach to the Febrile Patient

• Fever — temperature 38°C or more; may be absent in older, immunosuppressed or very sick people.
• History:
  • Localising symptoms — cough, dysuria, abdominal pain, headache and neck stiffness, joint pain, skin changes, wounds, diarrhoea.
  • Travel (in the last year — malaria up to a year or more for some species), contacts (household illness, TB, outbreaks), animals and occupation (farmers, vets, sewer workers), food (undercooked meat, unpasteurised dairy), water (freshwater swimming), insect and tick bites.
  • Sexual history and injecting drug use (HIV, hepatitis, endocarditis, skin and bone infections).
  • Devices and procedures — lines, catheters, prosthetic valves and joints, pacemakers, recent surgery, dental work.
  • Immune status — chemotherapy, steroids, biologics, HIV, splenectomy, diabetes.
  • Drugs — new drugs (drug fever), antipsychotics (NMS), serotonergic drugs, recreational drugs (MDMA, cocaine).
  • Vaccination history.
• Examination — full examination including skin (rashes, wounds, injection sites), mouth and teeth, lymph nodes, heart murmurs, chest, abdomen (liver, spleen, tenderness), joints and spine, lines and catheters, perineum and pressure areas, eyes (conjunctival suffusion in leptospirosis, Roth spots), neck stiffness.
• Non-infective causes of fever — drugs, VTE (PE), cancer (lymphoma, kidney, liver), autoimmune and inflammatory disease (vasculitis, Still's disease), transfusion reactions, thyroid storm, gout, pancreatitis, after surgery or MI, heat stroke, NMS and serotonin syndrome, alcohol withdrawal.
• Rash and fever — non-blanching rash (meningococcal disease — emergency), viral exanthems (measles, chickenpox), drug reactions (DRESS, SJS), toxic shock (erythroderma), endocarditis (petechiae, Janeway lesions), secondary syphilis (palms and soles), rickettsial infection (eschar after travel), Lyme disease (erythema migrans).

Pyrexia of Unknown Origin

• Definition — fever over 38.3°C on several occasions for at least 3 weeks, without a diagnosis after basic investigations (outpatient or inpatient). Subgroups — healthcare-associated, neutropenic and HIV-associated PUO have different causes.
• Main groups of causes:
  • Infection — TB (especially extrapulmonary), abscesses (abdominal, pelvic, dental), endocarditis (culture-negative), osteomyelitis, CMV, EBV, HIV, brucellosis, Q fever, typhoid, malaria, leishmaniasis.
  • Cancer — lymphoma, leukaemia, kidney cell carcinoma, liver tumours or metastases.
  • Inflammatory — giant cell arteritis and polymyalgia (older people), adult-onset Still's disease (young adults — very high ferritin, salmon-pink rash, sore throat, arthralgia), SLE, vasculitis, sarcoidosis, IBD.
  • Miscellaneous — drug fever, recurrent PE, thyroiditis, factitious fever, periodic fever syndromes (familial Mediterranean fever), haemophagocytic lymphohistiocytosis (HLH — very high ferritin, cytopenias, organomegaly — serious).
• Approach — repeated careful history and examination; stop non-essential drugs; FBC and film, ESR and CRP, LFTs, U&E, LDH, ferritin, CK, urinalysis and culture, several blood cultures, HIV test, serology guided by exposures, autoantibodies (ANA, ANCA, rheumatoid factor), chest X-ray; then CT chest, abdomen and pelvis; PET-CT; echocardiography; biopsy of anything abnormal (lymph node, liver, bone marrow, temporal artery).
• Avoid "blind" antibiotics and steroids in a stable patient — they hide the diagnosis (e.g. culture-negative endocarditis, partially treated TB, lymphoma masked by steroids).

Bacterial Meningitis

• Likely organisms by age:
  • Newborns — group B streptococcus, E. coli, Listeria.
  • Children and young adults — Neisseria meningitidis, Streptococcus pneumoniae (Hib now rare due to vaccination).
  • Older adults (over about 60) — pneumococcus, Listeria.
  • Immunosuppressed, pregnant, alcohol excess — add Listeria; consider Cryptococcus and TB.
  • After neurosurgery or with shunts — staphylococci, Gram-negatives.
• Features — headache, fever, neck stiffness, photophobia, vomiting, reduced consciousness or confusion, seizures, focal signs; non-blanching petechial or purpuric rash in meningococcal disease (may start as a blanching rash). The classic triad (fever, neck stiffness, altered mental state) is often incomplete; Kernig's and Brudzinski's signs are insensitive.
• Meningococcal septicaemia — can kill within hours with little sign of meningitis: fever, cold hands and feet, leg pain, mottled skin, rash, tachycardia, shock.
• Immediate management:
  • Community — if meningococcal disease is suspected, give IM or IV benzylpenicillin (adults 1.2 g) without delaying transfer.
  • Hospital — ABC, blood cultures, then IV ceftriaxone 2 g every 12 hours within 1 hour; add IV amoxicillin 2 g every 4 hours if Listeria is possible (over 60, immunosuppressed, pregnant, alcohol excess); add vancomycin (± rifampicin) if penicillin-resistant pneumococcus is possible (recent travel to areas of high resistance).
  • Dexamethasone (adults — 10 mg IV every 6 hours for 4 days) with or just before the first antibiotic dose in suspected bacterial meningitis — reduces hearing loss and death in pneumococcal meningitis; stop if another cause is found; not for meningococcal septicaemia without meningitis.
• Lumbar puncture — as soon as safe (ideally within 1 hour) without delaying antibiotics; CT first only if there are signs of raised intracranial pressure or a mass (focal signs, papilloedema, new seizures, GCS 12 or less, severe immunosuppression). Don't do an LP in shock, a rapidly spreading rash, coagulopathy or local skin infection.
• CSF in bacterial meningitis — high neutrophils, high protein, low glucose (under 60% of blood glucose), Gram stain and culture, PCR (meningococcus, pneumococcus); blood meningococcal PCR (EDTA) also helps.
• Public health — notify on suspicion; droplet precautions for the first 24 hours of antibiotics; UKHSA arranges prophylaxis for close contacts (single-dose ciprofloxacin, usually for household contacts in the previous 7 days) and vaccination when appropriate.
• Complications — hearing loss (audiology follow-up for all), seizures, hydrocephalus, SIADH, cerebral oedema, stroke, limb loss and skin necrosis (meningococcal), DIC.
• Viral meningitis (enterovirus, HSV-2, VZV) — milder, lymphocytic CSF with normal glucose; supportive; check HIV.

Encephalitis

• Encephalitis — inflammation of the brain tissue: fever, headache, confusion, behaviour change, reduced consciousness, seizures, focal signs (dysphasia, hemiparesis).
• Causes:
  • Herpes simplex virus (HSV-1) — the commonest treatable cause in the UK; temporal lobes (memory problems, olfactory hallucinations, behaviour change).
  • VZV (often with immunosuppression or rash), enteroviruses, EBV, CMV (immunosuppression), HIV, measles.
  • Travel-related — Japanese encephalitis, tick-borne encephalitis, West Nile virus, rabies.
  • Autoimmune — anti-NMDA receptor encephalitis (young women — psychiatric symptoms, seizures, abnormal movements, autonomic instability; look for ovarian teratoma), LGI1 (older adults — faciobrachial dystonic seizures, low sodium, memory loss); paraneoplastic encephalitis.
• Investigations — LP (lymphocytes, raised protein, normal glucose; HSV and VZV PCR — may be negative in the first 48 hours, repeat if suspicion remains), MRI (temporal lobe changes in HSV), EEG (non-convulsive seizures), HIV test, autoimmune antibodies (serum and CSF).
• Treatment — IV aciclovir 10 mg/kg every 8 hours (adjusted for kidney function) started immediately on suspicion — don't wait for CT, LP or PCR; usually 14–21 days for confirmed HSV encephalitis; hydrate well; treat seizures; immunotherapy (steroids, IVIG, plasma exchange, rituximab) for autoimmune encephalitis.
• Prognosis — HSV encephalitis untreated has high mortality; survivors often have memory, behaviour and epilepsy problems — rehabilitation.

Brain and Spinal Epidural Abscess

• Brain abscess:
  • Sources — spread from teeth, sinuses and ears; blood spread from endocarditis, lung abscess, right-to-left heart shunts (congenital heart disease, pulmonary AVMs); trauma or neurosurgery; Toxoplasma and Nocardia in immunosuppression.
  • Features — headache (most), fever (only about half), focal signs, seizures, raised pressure.
  • Ring-enhancing lesion on contrast CT or MRI (differential — tumour, toxoplasmosis, TB).
  • Treatment — neurosurgical aspiration or excision (diagnosis and treatment), ceftriaxone plus metronidazole (empirical), usually 6 weeks or more; find the source (dental, ENT, echo).
• Spinal epidural abscess — an emergency:
  • Risk factors — injecting drug use, diabetes, recent spinal procedures or epidurals, bacteraemia (S. aureus), immunosuppression.
  • Classic progression — back pain → nerve root pain → weakness, numbness and sphincter problems; fever is often absent; CRP and ESR raised.
  • Urgent whole-spine MRI; blood cultures; neurosurgical decompression if there is any neurological deficit; long antibiotic course (S. aureus most common).
• Subdural empyema — complicates sinusitis or otitis; rapid deterioration; neurosurgical emergency.

Staphylococcus aureus Bacteraemia

• S. aureus in the blood is always significant — mortality around 20–30%; it seeds heart valves, bones, joints, spine, kidneys and prosthetic material.
• Common sources — IV cannulas and central lines, skin and soft tissue infections, injecting drug use, surgical wounds, bone and joint infections, pneumonia (after influenza), dialysis lines; sometimes no source is found (consider endocarditis).
• Management bundle (infection specialist review for all):
  • IV flucloxacillin (MSSA) or vancomycin, teicoplanin or daptomycin (MRSA or true penicillin allergy).
  • Remove the source — take out lines and cannulas; drain collections.
  • Repeat blood cultures every 48–72 hours until negative.
  • Echocardiogram — TTE for all; TOE if high risk (prosthetic valve, device, injecting drug use, persistent bacteraemia, embolic signs).
  • Look for metastatic infection — back pain (discitis, epidural abscess), joint pain, new murmurs.
• Duration — at least 14 days IV from the first negative culture for uncomplicated infection (removable source removed, no prosthetic material, fever and bacteraemia settling within 72 hours, no endocarditis or deep infection); 4–6 weeks if complicated (endocarditis, osteomyelitis, persistent bacteraemia). Some selected patients can switch to oral therapy under specialist advice.
• Prevention — daily cannula review (remove if not needed; VIP score), aseptic line care, MRSA screening and decolonisation.

Infective Endocarditis

• Covered in detail in the Pericardial Disease and Endocarditis chapter; key infectious points:
• Organisms:
  • S. aureus — the commonest; acute, destructive; injecting drug use (often tricuspid valve — septic lung emboli).
  • Viridans streptococci — subacute; dental source.
  • Enterococci — older people; GI or urinary source.
  • Streptococcus gallolyticus (S. bovis) — linked to colorectal cancer — arrange a colonoscopy.
  • Coagulase-negative staphylococci — prosthetic valves and devices.
  • Culture-negative — prior antibiotics, HACEK organisms, Coxiella (Q fever), Bartonella, Brucella, fungi.
• Suspect it with fever plus a new murmur, embolic events (stroke, splinter haemorrhages, Janeway lesions), immunological signs (Osler's nodes, Roth spots, glomerulonephritis), or S. aureus or streptococcal bacteraemia without a clear source.
• Diagnosis (modified Duke criteria) — typical organisms in separate blood cultures plus echocardiographic evidence (vegetation, abscess, new valve leak) are the major criteria; take three sets of blood cultures from separate sites before antibiotics in stable patients.
• Treatment — prolonged IV bactericidal antibiotics (4–6 weeks) guided by the endocarditis team; surgery for heart failure, uncontrolled infection (abscess, persistent bacteraemia), large vegetations with emboli, prosthetic valve and fungal infection.
• Prophylaxis — antibiotic prophylaxis is not routinely recommended for dental procedures in the UK (NICE); emphasise good dental hygiene and prompt treatment of infections in at-risk people.

Septic Arthritis

• An emergency — bacteria destroy cartilage within days; mortality is significant in older people.
• Features — a hot, swollen, painful joint with markedly reduced movement (often the knee, then hip, shoulder, wrist, ankle); fever may be absent.
• Risk factors — older age, rheumatoid arthritis and other joint disease, prosthetic joints, diabetes, immunosuppression, recent joint injection or surgery, skin infection, injecting drug use.
• Organisms — S. aureus (most), streptococci; Neisseria gonorrhoeae in sexually active young adults (migratory joint pains, tenosynovitis, scattered pustules); Gram-negatives in older people and injecting drug users; Salmonella in sickle cell disease.
• Investigations — aspirate the joint before antibiotics (unless septic and aspiration is delayed): cell count (often very high neutrophils), Gram stain, culture, crystals (gout and pseudogout can coexist with infection — crystals don't exclude sepsis); blood cultures; CRP, ESR; X-ray; gonococcal PCR (urethral, cervical, throat, rectal) if relevant.
• Treatment:
  • Empirical IV flucloxacillin (clindamycin or vancomycin if allergic; vancomycin if MRSA risk); ceftriaxone for gonococcal or Gram-negative infection; adjust to cultures.
  • Joint washout — repeated aspiration or arthroscopic or open washout (orthopaedics).
  • Duration — usually around 4–6 weeks in total (IV then oral).
  • Prosthetic joint — urgent orthopaedic referral (see Prosthetic Joint Infection).
• Differential — gout, pseudogout, reactive arthritis, haemarthrosis, trauma, inflammatory arthritis flare.

Osteomyelitis and Discitis

• How bone gets infected:
  • Blood spread — children (ends of long bones), adults (vertebrae and discs), people who inject drugs, sickle cell disease (Salmonella and S. aureus).
  • Spread from nearby infection — diabetic foot ulcers, pressure sores, after fracture surgery or open fractures, dental infection (jaw).
• Features — bone pain, tenderness, fever (often absent in chronic disease), overlying redness, sinus tracts (chronic); vertebral osteomyelitis and discitis — persistent back pain, often worse at night, with raised CRP and ESR; may cause epidural abscess and cord compression.
• Organisms — S. aureus (most), streptococci, Gram-negatives (older, urinary source, injecting), TB (spinal — Pott's disease), Brucella (travel, unpasteurised dairy), Salmonella (sickle cell).
• Investigations — blood cultures (often positive in vertebral infection), MRI (most sensitive; X-ray changes take 2 weeks or more), bone biopsy for culture and histology before antibiotics if the patient is stable (essential to target long treatment); echocardiogram if S. aureus or streptococcal bacteraemia.
• Treatment — usually 6 weeks or more; oral antibiotics with good bone penetration can be as effective as IV after an initial period (OVIVA trial) — specialist decision; surgery to remove dead bone (sequestrum), drain abscesses or stabilise the spine.
• Monitoring — CRP trend, clinical response, repeat imaging if not improving.

Prosthetic Joint Infection

• Timing:
  • Early (within about 3 months of surgery) — S. aureus, Gram-negatives; wound problems, fever, pain.
  • Delayed (3 months to 2 years) — low-grade organisms such as coagulase-negative staphylococci and Cutibacterium; persistent pain, loosening.
  • Late — blood spread from a distant infection (e.g. S. aureus bacteraemia, dental infection) to a previously good joint.
• Features — pain, swelling, wound discharge; a sinus tract communicating with the prosthesis confirms infection.
• Bacteria form a biofilm on the implant — antibiotics alone rarely cure it.
• Don't start antibiotics in a stable patient before the orthopaedic team has taken samples (aspiration or multiple tissue samples at surgery) — unless the patient is septic.
• Surgery — DAIR (debridement, antibiotics and implant retention) for early infection with a stable implant; one- or two-stage revision for chronic infection; long antibiotic courses; rifampicin is added for staphylococcal biofilm (never alone; check interactions).

Diabetic Foot Infection

• Why it happens — neuropathy (unnoticed injuries), poor blood supply, high glucose impairing immunity, foot deformity.
• Severity (NICE NG19):
  • Mild — local infection with redness under 2 cm around an ulcer.
  • Moderate — redness over 2 cm or deeper infection (abscess, osteomyelitis, septic arthritis, fasciitis).
  • Severe — with signs of sepsis.
• Assess — depth (probe to bone suggests osteomyelitis), pus, gas, smell, foot pulses and ischaemia (ABPI may be falsely high — calcified arteries; toe pressures), X-ray (gas, bone changes), MRI if osteomyelitis suspected; deep tissue or bone samples rather than superficial swabs.
• Treatment — mild: oral flucloxacillin (clarithromycin, erythromycin or doxycycline if allergic); moderate to severe: broader cover (e.g. co-amoxiclav, or piperacillin–tazobactam ± vancomycin if severe or MRSA) per local guidance; urgent multidisciplinary foot team referral; surgical drainage and debridement; offloading; vascular assessment (revascularisation); glucose control.
• Emergencies — limb-threatening ischaemia, gangrene, deep abscess, gas in tissues, sepsis → same-day surgical or vascular review.
• Charcot foot — hot, swollen, red foot without much pain in neuropathy (may mimic infection) — offload urgently.

Necrotising Soft Tissue Infection

• Necrotising fasciitis — rapidly spreading infection along the fascia that kills tissue; mortality around 20–30% even with treatment.
  • Type 1 (polymicrobial — anaerobes and coliforms) — diabetes, older people, after surgery; Fournier's gangrene (perineum and genitals).
  • Type 2 — group A streptococcus (± S. aureus) — can affect healthy people, often after minor trauma, chickenpox, or injecting.
• Warning signs:
  • Pain out of proportion to the visible signs (early — skin may look almost normal).
  • Rapid spread (mark the edge — check hourly), tense oedema beyond the redness, blisters (bullae), dusky or purple skin, crepitus, skin numbness (late — nerves destroyed), skin necrosis.
  • Systemic toxicity — tachycardia, hypotension, confusion, AKI, raised CK and lactate.
• Management — urgent surgical exploration and debridement (the definitive diagnostic test — "grey, dishwater" fluid, fascia separating easily); repeated debridement; don't delay for imaging (CT can show gas but a normal scan doesn't exclude it); broad-spectrum antibiotics plus clindamycin (toxin suppression) ± MRSA cover; resuscitation and critical care; IVIG may be considered in streptococcal toxic shock.
• Gas gangrene (Clostridium perfringens) — after traumatic or surgical wounds; severe pain, crepitus, bronze skin, rapid toxicity — surgery, high-dose penicillin plus clindamycin.
• Public health — invasive group A strep is notifiable; UKHSA may advise prophylaxis for close household contacts.

Toxic Shock Syndrome

• Cause — bacterial "superantigen" toxins switch on huge numbers of T cells → cytokine storm.
• Staphylococcal TSS — tampons and menstrual cups, nasal packing, wounds, burns, post-partum; blood cultures often negative.
• Streptococcal TSS — with invasive group A strep infection (necrotising fasciitis, pneumonia, puerperal sepsis); blood cultures usually positive; higher mortality.
• Features — high fever, low blood pressure, diffuse red rash (like sunburn — erythroderma), peeling of the palms and soles 1–2 weeks later, vomiting and diarrhoea, muscle pain, confusion, multi-organ failure (kidney, liver, low platelets).
• Treatment — remove the source (tampon, packing; drain or debride), aggressive resuscitation and critical care, anti-staphylococcal or anti-streptococcal antibiotic plus clindamycin (or linezolid), IVIG in severe streptococcal TSS.

Infectious Diarrhoea and Food Poisoning

• Management — oral rehydration; most cases settle without antibiotics; temporarily stop drugs that worsen dehydration (diuretics, ACE inhibitors, metformin, SGLT2 inhibitors).
• Send stool samples if bloody, severe or prolonged (over 7 days), after travel, in outbreaks, hospitalised or immunosuppressed patients, food handlers, or when C. difficile is possible.
• Avoid antimotility drugs (loperamide) in bloody diarrhoea or fever.
• Exclusion — stay off work or school until 48 hours after symptoms stop (longer for some organisms and risk groups — food handlers, healthcare workers, young children).
• Notify suspected food poisoning and infectious bloody diarrhoea. C. difficile is covered on the hospital infection page; travellers' diarrhoea and typhoid on the tropical page.

Tetanus, Botulism and Diphtheria

• Tetanus (Clostridium tetani spores in soil):
  • Through wounds (including minor ones, burns, and injecting drug use — "skin popping"); the toxin blocks inhibitory nerve signals.
  • Features — lockjaw (trismus), fixed smile (risus sardonicus), neck and back stiffness (opisthotonus), painful spasms triggered by noise or touch, autonomic instability; consciousness preserved.
  • Treatment — human tetanus immunoglobulin, wound debridement, metronidazole, benzodiazepines and muscle relaxants, ITU (ventilation, magnesium); then vaccinate (infection doesn't give immunity).
  • Prevention — vaccination (5 doses in total in the UK schedule); for tetanus-prone wounds (soil contamination, puncture, devitalised tissue, compound fractures, burns), give a vaccine booster if not up to date and immunoglobulin for high-risk wounds in incompletely vaccinated people (UKHSA Green Book).
• Botulism (Clostridium botulinum toxin blocks acetylcholine release):
  • Forms — wound botulism (injecting heroin), foodborne (home-preserved foods), infant (honey).
  • Features — descending symmetrical paralysis starting with cranial nerves (double vision, ptosis, slurred speech, swallowing difficulty), fixed dilated pupils, dry mouth, constipation, urinary retention; no sensory loss, no fever, alert.
  • Treatment — antitoxin urgently (via UKHSA — don't wait for confirmation), monitor FVC and ventilate if needed, wound debridement and antibiotics (wound botulism); notify.
• Diphtheria (Corynebacterium diphtheriae — rare in the UK because of vaccination):
  • Grey, adherent pseudomembrane on the tonsils and throat, swollen "bull neck", airway obstruction; toxin causes myocarditis and neuropathy; skin (cutaneous) diphtheria in travellers and migrants.
  • Treatment — diphtheria antitoxin, penicillin or a macrolide, airway management, cardiac monitoring; isolate; notify; contact tracing and prophylaxis.

Lyme Disease and Other Zoonoses

• Tick bites — remove the tick promptly with fine-tipped tweezers or a tick removal tool, close to the skin; no routine antibiotic prophylaxis in the UK; watch for a rash for 30 days.
• Lyme serology — may be negative in the first 4 weeks; test again if negative but suspicion remains; don't test or treat for vague symptoms without a clinical picture.
• Toxoplasmosis is covered on the Viral, Fungal and Parasitic Infections page; rabies on the Tropical and Travel Medicine page.

Bites

• Dog, cat and human bites — clean thoroughly, assess depth and involvement of tendons, joints and bone (X-ray for possible fractures or tooth fragments); surgical review for hand wounds, deep wounds and those near joints.
• Antibiotics (NICE NG184):
  • Prophylaxis (3 days of co-amoxiclav) for cat bites that break the skin, human bites that break the skin, and dog bites with deep or high-risk features (hands, feet, face, genitals, near joints or prosthetics, crush injuries), and for people at high risk (diabetes, immunosuppression, asplenia, cirrhosis).
  • Treatment of infected bites — co-amoxiclav (doxycycline plus metronidazole if penicillin-allergic) — Pasteurella (cats and dogs — rapid onset), Eikenella (human bites), streptococci, staphylococci, anaerobes.
  • Capnocytophaga from dog bites can cause overwhelming sepsis in people without a spleen.
• Tetanus — check vaccination status; bites are tetanus-prone wounds.
• Blood-borne viruses after human bites that draw blood — assess hepatitis B, hepatitis C and HIV risk.
• Rabies — any mammal bite or scratch abroad in a rabies-risk country, or a bat bite or scratch in the UK, needs urgent rabies risk assessment (UKHSA) — wound washing, vaccination ± immunoglobulin.

Infections at a Glance