ID: Hospital infection, the immunocompromised host, vaccination and public health

🏥 Hospital infection, the immunocompromised host, vaccination and public health -page 6 (the last page) of the Infectious Diseases chapter. Many infections are caused by healthcare -catheters, lines, antibiotics, surgery and shared wards -and many are preventable. A growing number of patients are immunosuppressed by cancer treatment, transplant drugs, steroids and biologics, and they get different infections that progress faster. Vaccination and public health action protect everyone else.
Your four questions for every patient: Did the infection come from healthcare, and could it have been prevented (devices, antibiotics, hygiene)? Is the patient immunosuppressed -and in what way (neutrophils, antibodies, T cells, spleen, complement)? What screening, prophylaxis and vaccines do they need? Do contacts, staff or the ward need protecting?

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Healthcare-Associated Infection

• Healthcare-associated infections (HCAIs) -affect a significant proportion of hospital inpatients at any time; they prolong stays, drive resistance and kill.
• The commonest -pneumonia (including aspiration), urinary infections (mostly catheter-related), surgical site infections, bloodstream infections (lines and cannulas), C. difficile, norovirus and other GI infections.
• Key causes -invasive devices, surgery, antibiotics (C. difficile and resistance), immunosuppression, frailty, and spread between patients on hands and equipment.
• Prevention (see Infection Prevention and Control on page 1):
  • Hand hygiene at the five moments; bare below the elbows.
  • Device stewardship -only insert lines and catheters when needed, use aseptic technique, review daily, remove as soon as possible.
  • Antimicrobial stewardship -Start Smart -Then Focus.
  • Screening and isolation (MRSA, CPE), environmental cleaning, care bundles (central lines, ventilators, surgical sites), staff vaccination.
• Mandatory surveillance in England -MRSA, MSSA, E. coli, Klebsiella and Pseudomonas bloodstream infections, C. difficile infection, and surgical site infections after some operations; serious cases get a post-infection review.

Clostridioides difficile Infection

• C. difficile -a spore-forming anaerobic bacterium; toxins (A and B) damage the colon. Spores survive on surfaces for months and are not killed by alcohol gel.
• Risk factors -antibiotics (especially clindamycin, cephalosporins, co-amoxiclav and quinolones; any antibiotic can cause it), age over 65, hospital or care home stay, PPIs, immunosuppression, IBD, recent bowel surgery, tube feeding.
• Features -diarrhoea (Bristol type 5–7), abdominal pain and cramps, fever, raised white count; severe disease can cause ileus without diarrhoea, toxic megacolon (distension, tenderness), perforation, AKI and death.
• Testing -only test unformed stool when there is no other clear cause (e.g. laxatives); two-step test:
  • GDH or PCR (shows the organism is present) then toxin test.
  • Toxin positive -C. difficile infection; GDH or PCR positive but toxin negative -possible carriage (isolate; treat only if clinically likely).
  • Don't repeat a positive test within 28 days or test for "clearance".
• Signs of severe infection -white count over 15 × 10⁹/L, creatinine rising over 50% above baseline, temperature over 38.5°C, signs of severe colitis (abdominal signs, distension, imaging); life-threatening -hypotension, ileus, toxic megacolon, perforation.
• Management (NICE NG199):
  • Isolate in a side room with its own toilet; gloves and aprons; soap and water hand washing; chlorine-based cleaning.
  • Stop the causing antibiotic if possible (or switch to a lower-risk one) and review PPIs and laxatives; avoid antimotility drugs.
  • Fluids and electrolytes; daily review of stool chart, abdomen, white count and creatinine.
  • First episode -oral vancomycin 125 mg four times daily for 10 days; fidaxomicin 200 mg twice daily for 10 days if vancomycin fails.
  • Life-threatening -oral vancomycin 500 mg four times daily (plus IV metronidazole), urgent surgical and specialist review (colectomy may be needed); vancomycin by NG tube or rectally in ileus.
  • Recurrence (about 1 in 5) -fidaxomicin; faecal microbiota transplant after two or more recurrences.
• Prevention -antibiotic stewardship (fewer broad-spectrum drugs, shorter courses), stop unnecessary PPIs, rapid isolation and testing, environmental cleaning.

MRSA

• Meticillin-resistant Staphylococcus aureus -resistant to flucloxacillin and most other beta-lactams; colonises the nose, skin, wounds and throat.
• Screening -targeted screening of higher-risk patients (e.g. before elective surgery, admissions to ICU, renal and other high-risk units, previous MRSA) according to local policy (nose, groin, wounds, catheter urine).
• Decolonisation -nasal mupirocin (or alternative) and chlorhexidine body wash for 5 days, especially before surgery; repeat screening.
• Infection control -contact precautions (side room where possible), hand hygiene, dedicated equipment.
• Treatment of MRSA infection -vancomycin or teicoplanin (serious infections), linezolid or daptomycin (alternatives), doxycycline or co-trimoxazole (milder skin and soft tissue infections, by sensitivity); rifampicin or fusidic acid only in combination.
• Community-associated MRSA (often PVL-producing S. aureus) -recurrent boils, abscesses and occasionally severe necrotising pneumonia in otherwise healthy young people; drain abscesses, decolonise the household.
• MRSA bacteraemia -managed as S. aureus bacteraemia (see page 2); a post-infection review looks for lessons (lines, screening, decolonisation).

Resistant Gram-Negatives -ESBL and CPE

• ESBL-producing Enterobacterales (E. coli, Klebsiella) -common, including in the community; carriage in the gut is often silent:
  • Infections -UTI, pyelonephritis, biliary and abdominal sepsis, pneumonia.
  • Treatment -serious infections usually need a carbapenem (meropenem or ertapenem); alternatives by sensitivity (piperacillin–tazobactam sometimes, temocillin, aminoglycosides); oral options for UTI -nitrofurantoin, fosfomycin, pivmecillinam.
  • Flag on records so future empirical antibiotics are chosen wisely.
• Carbapenemase-producing Enterobacterales (CPE) -resistant to carbapenems and often almost everything else:
  • Screen (rectal swab) patients who in the last 12 months were in hospital abroad, in UK hospitals with CPE problems, or were previously positive; isolate until results are known (local policy).
  • Strict contact precautions; inform IPC; treatment needs specialist advice (e.g. ceftazidime–avibactam, colistin, combination therapy).
• Other resistant organisms -Pseudomonas and Acinetobacter (ICU, burns, ventilators), VRE (haematology, renal, ICU), Candida auris.
• Colonisation is not infection -don't treat a positive screening swab; do use the information to choose antibiotics if the patient becomes septic.

Hospital-Acquired Pneumonia

• Hospital-acquired pneumonia (HAP) -pneumonia starting 48 hours or more after admission; ventilator-associated pneumonia (VAP) -after 48 hours of mechanical ventilation.
• Organisms -early (under about 5 days) often community organisms; later or after recent antibiotics -Gram-negatives (including Pseudomonas, Klebsiella, ESBL), S. aureus (including MRSA).
• Diagnosis -new chest X-ray changes plus fever, purulent sputum, rising oxygen needs or white count; send sputum (or ETT aspirate in VAP) and blood cultures; consider other causes (PE, heart failure, atelectasis, aspiration pneumonitis).
• Treatment (NICE NG139; local guidelines) -non-severe and lower risk of resistance: oral options (e.g. co-amoxiclav, doxycycline); severe or higher risk of resistance: IV broad-spectrum (e.g. piperacillin–tazobactam) ± MRSA cover; review at 48–72 hours; usually 5–7 days in total.
• Aspiration -chemical pneumonitis after aspiration often settles without antibiotics; aspiration pneumonia is treated like HAP (routine anaerobic cover isn't usually needed).
• Prevention -head of bed raised, oral care, swallow assessment after stroke, early mobilisation, avoiding unnecessary sedation, minimising ventilation (sedation holds, VAP bundles), pneumococcal and influenza vaccination.

Catheter-Associated Urinary Infection

• The biggest risk is having a catheter -risk rises each day; most catheter urine becomes colonised (bacteriuria) within weeks.
• Only use catheters when needed -urinary retention, accurate output monitoring in critical illness, some surgery, end-of-life comfort; not for convenience or incontinence alone; daily review and early removal (nurse-led removal protocols).
• Don't dipstick catheter urine and don't treat asymptomatic bacteriuria -treat only symptoms (fever, rigors, loin pain, new confusion with no other cause, suprapubic pain, haematuria).
• Management (NICE NG113):
  • Consider removing the catheter, or change it if it has been in for more than 7 days, before starting antibiotics -and send a urine sample from the new catheter.
  • Antibiotics per local guidance and previous cultures (e.g. nitrofurantoin or trimethoprim for lower symptoms if suitable; IV options if systemically unwell); usually 7 days.
• Prevention -aseptic insertion, closed drainage, bag below the bladder, regular emptying with clean technique, catheter passport, trial without catheter.

Line Infections

• Peripheral cannulas -phlebitis and S. aureus bacteraemia; check every shift (VIP score); remove at the first sign of phlebitis and when no longer needed; avoid "just in case" cannulas.
• Central venous catheters, PICCs, ports and dialysis lines -central line-associated bloodstream infection (CLABSI):
  • Features -fever, rigors (especially during or after flushing the line), redness or pus at the exit site or along the tunnel, sepsis without another source.
  • Paired blood cultures (line and peripheral) -line cultures that become positive more than 2 hours before peripheral ones suggest the line is the source.
  • Organisms -coagulase-negative staphylococci, S. aureus, Gram-negatives (including Pseudomonas), enterococci, Candida.
• Remove the line if there is S. aureus, Pseudomonas, Candida or mycobacteria, tunnel or pocket infection, severe sepsis, persistent bacteraemia after 72 hours, endocarditis or septic thrombosis; line salvage (antibiotics plus antibiotic "lock" solution) may be tried for some CoNS infections in patients with few alternatives (e.g. long-term parenteral nutrition).
• Prevention -insertion bundles (hand hygiene, full barrier precautions, 2% chlorhexidine skin preparation, best site), aseptic non-touch technique for every access, chlorhexidine dressings, daily review of need.

Norovirus and Ward Outbreaks

• Norovirus ("winter vomiting bug") -the commonest cause of ward closures; incubation 12–48 hours; sudden vomiting (often projectile) and diarrhoea for 1–3 days; very infectious (aerosols from vomiting, contaminated surfaces); immunity is short-lived.
• Vulnerable patients -older and frail people (dehydration, AKI, falls), the immunosuppressed (prolonged infection).
• Control:
  • Isolate or cohort affected patients; close bays to admissions; inform the IPC team.
  • Soap and water for hands (alcohol gel is less effective); gloves, aprons and fluid-resistant masks when cleaning up vomit.
  • Enhanced cleaning with chlorine-based products; restrict visitors and staff movement between areas.
  • Staff stay off work until 48 hours symptom-free.
  • Send stool samples (PCR) from early cases to confirm.
• Other ward outbreaks -C. difficile, influenza, COVID-19, CPE, VRE, scabies, invasive group A strep (maternity, burns); recognising clusters early is key.

Neutropenic Sepsis

• Definition -neutrophil count 0.5 × 10⁹/L or less with a temperature over 38°C or other signs or symptoms of sepsis (NICE CG151); most often 7–14 days after chemotherapy.
• Signs may be subtle -little pus or inflammation without neutrophils; steroids mask fever; some patients present feeling "unwell" or cold and shivery.
• Immediate management:
  • Treat as an emergency -IV piperacillin–tazobactam within 1 hour of arrival (local alternative if penicillin-allergic), without waiting for the blood count if chemotherapy was recent.
  • Blood cultures (peripheral and from each line lumen), FBC, U&E, LFTs, CRP, lactate, urine, chest X-ray if respiratory symptoms; examine mouth, skin, line sites, chest, perineum (no rectal examination).
  • Don't routinely add an aminoglycoside or glycopeptide; add vancomycin for suspected line infection, MRSA, severe sepsis or skin infection.
• After 48–72 hours -tailor to cultures; low-risk patients (e.g. by MASCC score) may switch to oral antibiotics or go home with close follow-up.
• Persistent fever for 4–7 days despite antibiotics -look for fungal infection (CT chest, galactomannan) and consider empirical antifungal therapy.
• Prevention -patient education (the chemotherapy alert card and 24-hour helpline), G-CSF and antibacterial or antifungal prophylaxis in high-risk regimens.

⚠️ Safety Pearl: A patient who has had chemotherapy and is unwell with a fever has neutropenic sepsis until proven otherwise. Antibiotics go in within 1 hour -before the blood count comes back.

Infections After Transplantation

Time after solid organ transplant	Typical infections
First month	Hospital and surgical infections -wound infections, line and catheter infections, pneumonia, C. difficile, resistant bacteria, infections from the donor; HSV reactivation
1–6 months (peak immunosuppression)	Opportunistic infections -CMV, Pneumocystis, EBV, BK virus (kidney transplant nephropathy), Listeria, Toxoplasma (heart), Nocardia, Aspergillus and other fungi, TB reactivation, hepatitis B reactivation
Over 6 months	Mostly community infections (pneumonia, UTI, influenza) -more severe; late CMV; post-transplant lymphoproliferative disorder (EBV); chronic viral infections; skin cancers

• Prophylaxis -co-trimoxazole (PCP), valganciclovir or monitoring for CMV, antifungals in some, vaccines before transplant.
• Stem cell transplant -prolonged neutropenia (bacterial and fungal infections), then T-cell deficiency (CMV, adenovirus, PCP), graft-versus-host disease and its treatment (steroids) adding further risk; haemorrhagic cystitis (BK virus, adenovirus).
• Drug interactions -tacrolimus, ciclosporin, sirolimus and everolimus levels are raised by macrolides and azoles and lowered by rifampicin (see the Renal Anatomy, Physiology and Pharmacology chapter) -always check before prescribing.
• Fever in a transplant patient -may also be rejection, drug reaction or PTLD; involve the transplant team early; signs of infection may be muted.
• Live vaccines are contraindicated after transplant.

Biologics, Steroids and Other Immunosuppressants

Treatment	Main infection risks
Corticosteroids (higher doses, longer courses)	Bacterial infections, PCP (especially with other immunosuppressants), TB reactivation, fungal infections, Strongyloides hyperinfection, shingles; fever and signs masked
Anti-TNF drugs (infliximab, adalimumab, etanercept)	TB reactivation (often extrapulmonary), serious bacterial infections, Listeria, histoplasmosis and other endemic fungi, hepatitis B reactivation
Rituximab and other anti-CD20 drugs	Hepatitis B reactivation, low antibodies (recurrent chest infections), PCP, PML, poor vaccine responses
JAK inhibitors (tofacitinib, baricitinib, upadacitinib)	Shingles, serious infections, TB
Complement inhibitors (eculizumab, ravulizumab)	Meningococcal infection -vaccination (ACWY and B) and often antibiotic prophylaxis essential
Natalizumab	PML (JC virus)
Alemtuzumab, fludarabine, cladribine	Profound lymphopenia -CMV, PCP, herpes viruses, Listeria; irradiated blood (purine analogues)
Methotrexate, azathioprine, mycophenolate	Bacterial and viral infections, shingles, PCP (in combination)
Chemotherapy	Neutropenic sepsis, mucositis, fungal infections

• Screen before starting biologics and strong immunosuppression:
  • TB -history, chest X-ray, IGRA; treat latent TB first (usually at least 1 month before the biologic, per specialist advice).
  • Hepatitis B (HBsAg, anti-HBc), hepatitis C, HIV.
  • VZV immunity (vaccinate if non-immune and there is time).
  • Strongyloides serology in people from endemic areas.
• PCP prophylaxis (co-trimoxazole) -considered for people on high-dose steroids for long periods, especially combined with other immunosuppressants, and for many chemotherapy and transplant regimens.
• Vaccinate before immunosuppression where possible -pneumococcal, influenza, COVID-19, shingles (non-live), hepatitis B; give live vaccines (e.g. MMR, varicella) at least 4 weeks before starting; no live vaccines during treatment.
• Babies exposed to biologics in late pregnancy (e.g. infliximab) -avoid live vaccines (e.g. rotavirus, BCG) in the first months (specialist advice).

Primary Immunodeficiency

• Suspect immunodeficiency with infections that are SPUR -Serious, Persistent, Unusual (opportunistic organisms or sites) or Recurrent -or with failure to thrive, family history, or autoimmunity with infections. Secondary causes (drugs, HIV, CLL, myeloma, nephrotic syndrome, protein loss, malnutrition) are far more common -check them first.

Type	Examples	Infection pattern and clues
Antibody (B-cell)	Common variable immunodeficiency (adults), X-linked agammaglobulinaemia (boys), selective IgA deficiency	Recurrent sinus and chest infections with encapsulated bacteria, bronchiectasis, Giardia; CVID -autoimmunity, granulomas, lymphoma; IgA deficiency -often no symptoms, false-negative coeliac tTG-IgA, reactions to blood products
T-cell and combined	Severe combined immunodeficiency (SCID), DiGeorge syndrome (22q11 deletion)	Infants -failure to thrive, chronic diarrhoea, thrush, PCP, severe viral infections, reactions to live vaccines; DiGeorge -low calcium, heart defects, facial features
Phagocyte	Chronic granulomatous disease	Abscesses (skin, liver, lung, lymph nodes) with S. aureus, Aspergillus, Burkholderia, Nocardia; granulomas
Complement	Late components (C5–C9) deficiency; early components (C1–C4)	Recurrent Neisseria (meningococcal) infections -test complement after a second episode or unusual serogroups; early component defects -lupus-like disease

• First tests -FBC and film, immunoglobulins (IgG, IgA, IgM), specific antibody responses to vaccines (tetanus, pneumococcal), lymphocyte subsets, complement (CH50, AH50), HIV test; refer to clinical immunology.
• Treatment -prophylactic antibiotics, immunoglobulin replacement (IV or subcutaneous) for antibody deficiency, avoid live vaccines in significant immunodeficiency, stem cell transplant or gene therapy for SCID and some others.
• Hereditary angioedema (C1 inhibitor deficiency) -recurrent swelling without urticaria, abdominal attacks; not an infection problem but a complement disorder (see the Urticaria and Blistering chapter).

How Vaccines Work and Who Shouldn't Have Them

• Vaccines train the immune system to recognise an organism or toxin so it can respond fast on exposure; herd immunity protects people who can't be vaccinated when enough others are.
• Types:
  • Live attenuated -MMR, varicella, rotavirus, nasal flu (children), BCG, yellow fever, oral typhoid -strong immunity but can cause disease in the immunosuppressed.
  • Inactivated, subunit, toxoid, conjugate -e.g. tetanus, diphtheria, pertussis, polio (injected), Hib, pneumococcal, meningococcal, hepatitis A and B, HPV, injectable flu, shingles (Shingrix), RSV.
  • mRNA and viral vector vaccines -COVID-19.
• Contraindications:
  • Anaphylaxis to a previous dose or a vaccine component (rare).
  • Live vaccines -significant immunosuppression (chemotherapy, transplant, high-dose steroids -e.g. prednisolone 20 mg or more daily for 2 weeks or longer, biologics, advanced HIV) and pregnancy.
• Not contraindications -mild illness without fever, egg allergy (MMR and most flu vaccines can be given -check the Green Book), prematurity (vaccinate by chronological age), breastfeeding, a family history of reactions, stable neurological conditions, being on antibiotics.
• Common side effects -sore arm, mild fever, irritability; MMR can cause a mild rash or fever 7–10 days later. Fainting after injection is common in teenagers.
• Vaccine hesitancy -listen, acknowledge concerns, give clear information (MMR is not linked to autism), and keep the conversation open.

The UK Vaccination Programme

Age	Vaccines (simplified -the schedule has been updated in 2025–26; check the current Green Book)
8, 12 and 16 weeks	6-in-1 (diphtheria, tetanus, pertussis, polio, Hib, hepatitis B); MenB; rotavirus (oral, live -8 and 12 weeks only); pneumococcal (PCV)
1 year	MMR (first dose), pneumococcal booster, MenB booster
18 months	Booster doses and the second MMR-containing dose (moved earlier, with chickenpox vaccine added as MMRV, under recent changes)
3 years 4 months	4-in-1 pre-school booster (diphtheria, tetanus, pertussis, polio)
2–17 years	Annual nasal flu vaccine (live)
12–13 years	HPV (boys and girls -single dose for most)
14 years	3-in-1 teenage booster (tetanus, diphtheria, polio); MenACWY
Pregnancy	Pertussis (from 16 weeks, ideally by 32 weeks), influenza (any stage, in season), RSV (from 28 weeks), COVID-19 as advised
Older adults	Influenza yearly (65 and over), pneumococcal (65), shingles (Shingrix -from 65, catch-up up to 80), RSV (75 and over, with catch-up), COVID-19 boosters as advised

• Catch-up -check vaccination history for migrants, people who missed doses, and adults (MMR at any age if unvaccinated).
• Pertussis vaccine in pregnancy protects babies in the first weeks of life, before their own vaccines work.

Vaccines for Special Groups

• No spleen or splenic dysfunction (including sickle cell disease) -pneumococcal, Hib/MenC, MenACWY, MenB, annual influenza, COVID-19; lifelong antibiotic advice and stand-by antibiotics (see the Haematology Anatomy, Physiology and Pharmacology chapter).
• Immunosuppression -inactivated vaccines (pneumococcal, influenza, COVID-19, Shingrix, hepatitis B as indicated); give before treatment starts where possible; avoid live vaccines; household contacts should be vaccinated (including against flu and varicella) to protect them.
• Chronic disease -heart, lung, kidney, liver disease and diabetes -influenza, pneumococcal, COVID-19; hepatitis A and B for chronic liver disease; hepatitis B for CKD and dialysis.
• Healthcare workers -hepatitis B (check antibody response), MMR (two doses or proof of immunity), varicella (if non-immune), annual influenza, COVID-19, BCG for some at-risk roles, pertussis for those working with newborns in some settings.
• Men who have sex with men -hepatitis A and B, HPV (up to age 45), mpox (if at higher risk), MenB in some outbreaks.
• People who inject drugs -hepatitis A and B, tetanus.
• Travellers -see the Tropical and Travel Medicine page.
• Contacts of TB -BCG for unvaccinated infants and children at higher risk (BCG is offered to babies in high-incidence areas or with a parent or grandparent from a high-incidence country).

Contacts and Prophylaxis

Infection	Contact action (usually arranged with UKHSA health protection teams)
Meningococcal disease	Single-dose ciprofloxacin for close contacts (household and kissing contacts in the 7 days before illness); vaccination if the serogroup is vaccine-preventable; healthcare workers only after direct exposure to respiratory secretions without a mask
Tuberculosis	Screen household and close contacts (symptoms, IGRA, chest X-ray); treat latent TB (e.g. 3 months of rifampicin plus isoniazid, or 6 months of isoniazid); BCG for some unvaccinated children
Measles	MMR within 3 days for susceptible contacts; human normal immunoglobulin within 6 days for susceptible pregnant women, immunosuppressed people and infants
Chickenpox	Aciclovir or valaciclovir on days 7–14 after exposure for susceptible pregnant women and immunosuppressed people; VZIG for exposed neonates
Pertussis (whooping cough)	Macrolide (azithromycin or clarithromycin) for the case within 21 days of cough onset; prophylaxis for close contacts if a vulnerable person is in the household (young infants, pregnant women near term) or contacts work with them; vaccination
Invasive group A strep	UKHSA may advise antibiotics for close household contacts (especially in clusters or high-risk contacts); advise contacts to seek help for symptoms
Hepatitis A	Vaccine within 14 days (± immunoglobulin for some)
Hepatitis B	Vaccine ± HBIG for sexual and household contacts and after exposures
Influenza	Antiviral prophylaxis for at-risk contacts in outbreaks (e.g. care homes)
Diphtheria	Swabs, antibiotics and vaccination for close contacts
HIV	PEP within 72 hours; partner notification
Rabies	Wound washing, vaccine ± immunoglobulin (urgent risk assessment)
Scabies	Treat the whole household and close contacts at the same time

Managing Outbreaks

• An outbreak -two or more linked cases of the same infection, or more cases than expected in a place or time (e.g. on a ward, in a care home, school or restaurant).
• Steps:
  • Recognise it -clusters of diarrhoea, respiratory illness, resistant organisms or unusual infections.
  • Confirm the diagnosis -appropriate samples; agree a case definition.
  • Control spread -isolation or cohorting, closing bays or wards to admissions, enhanced cleaning, hand hygiene, PPE, staff exclusion, visitor restrictions.
  • Inform -the infection prevention and control team, microbiology, and UKHSA (and notify where required).
  • Find the source -food, water, equipment, a colonised person, a contaminated environment (whole genome sequencing helps link cases).
  • Communicate with staff, patients and families; record actions; declare the outbreak over (usually after two incubation periods without new cases); learn lessons.
• Community outbreaks -schools and nurseries (exclusion advice), care homes (vaccination, antiviral prophylaxis for influenza), food premises (environmental health), prisons and hostels (TB, hepatitis).
• The doctor's duties -notify suspected notifiable diseases, report clusters, follow advice, and protect colleagues (vaccination, staying off work when infectious).

Prevention at a Glance

Situation	What to do
C. difficile	Isolate, soap and water, stop the causing antibiotic and PPI, oral vancomycin 125 mg four times daily for 10 days
MRSA carriage	Contact precautions; decolonise (mupirocin and chlorhexidine) before surgery
Previous hospital stay abroad	CPE screen and isolate pending results
Urinary catheter	Only if needed; review daily; don't dipstick; change before treating CAUTI
Central line	Insertion bundle, ANTT, remove when not needed; remove for S. aureus or Candida
Norovirus	Close bay, soap and water, chlorine cleaning, staff off until 48 hours symptom-free
Chemotherapy with fever	Piperacillin–tazobactam within 1 hour
Before biologics or rituximab	TB (IGRA), hepatitis B and C, HIV, VZV, Strongyloides; vaccinate first
Long-term high-dose steroids plus another immunosuppressant	Consider co-trimoxazole PCP prophylaxis, bone protection, steroid card
Complement inhibitor	Meningococcal ACWY and B vaccines ± antibiotic prophylaxis
Asplenia	Pneumococcal, Hib/MenC, MenACWY, MenB, influenza; penicillin V; stand-by antibiotics
Pregnancy	Pertussis, influenza, RSV vaccines; no live vaccines
Meningococcal case	Ciprofloxacin for close contacts; notify

Spot the Diagnosis

Clue	Diagnosis
Diarrhoea on day 6 of co-amoxiclav in an 82-year-old on omeprazole	C. difficile infection
Abdominal distension, no diarrhoea, WCC 30 in known C. difficile	Ileus or toxic megacolon -life-threatening
GDH positive, toxin negative, formed stool	Carriage -don't treat
Third episode of C. difficile in 6 months	Consider faecal microbiota transplant
Recurrent boils in a family; PVL-positive S. aureus	Community-associated MRSA -decolonise household
Rectal swab positive for OXA-48 in a patient treated in hospital abroad	CPE carriage -isolate
Rigors during flushing of a Hickman line	Line infection
Line culture positive 3 hours before peripheral culture	Catheter-related bloodstream infection
Positive catheter urine dipstick in a well, confused-at-baseline patient	Asymptomatic bacteriuria -don't treat
Sudden projectile vomiting in 6 patients and 2 nurses on one ward	Norovirus outbreak
Fever 38.6°C 10 days after chemotherapy	Neutropenic sepsis -antibiotics within 1 hour
Fever for 6 days despite antibiotics in prolonged neutropenia	Consider invasive fungal infection
Kidney transplant 3 months ago, rising creatinine, BK virus in blood	BK virus nephropathy
Fever, low white count and colitis 2 months after a liver transplant	CMV disease
Disseminated TB 6 months after starting infliximab	Anti-TNF TB reactivation (screening missed or failed)
Jaundice and very high ALT after rituximab in an anti-HBc-positive patient	Hepatitis B reactivation
Meningococcal sepsis in a patient on eculizumab	Complement inhibitor -needed vaccination and prophylaxis
Shingles in a patient on a JAK inhibitor	JAK inhibitor-associated zoster
Recurrent pneumonia and sinusitis, low IgG and IgA, bronchiectasis	Common variable immunodeficiency
Second episode of meningococcal disease in a young adult	Late complement deficiency -test
Liver abscesses and Aspergillus pneumonia in a boy	Chronic granulomatous disease
Infant with thrush, chronic diarrhoea, PCP and no lymphocytes	SCID
Anaphylaxis to a blood transfusion with undetectable IgA	Selective IgA deficiency
Can a child with egg allergy have MMR?	Yes
Patient on prednisolone 40 mg for 3 weeks asks about yellow fever vaccine	Live vaccine -contraindicated

Exam-style Scenarios

1. An 81-year-old woman on day 8 of co-amoxiclav for pneumonia has 7 episodes of watery diarrhoea a day. She takes lansoprazole. WCC 19 × 10⁹/L, creatinine 160 (baseline 90). Stool C. difficile toxin is positive.
Answer: Severe C. difficile infection.

• Isolate (side room with own toilet), soap and water, chlorine cleaning; stop co-amoxiclav if possible and stop lansoprazole; IV fluids.
• Oral vancomycin 125 mg four times daily for 10 days; daily review of stools, abdomen, WCC, creatinine and lactate.
• Urgent surgical review if distension, ileus, peritonism or worsening (toxic megacolon); escalate to life-threatening treatment if needed; review her pneumonia treatment with microbiology.

2. A 47-year-old woman 9 days after chemotherapy for breast cancer phones the chemotherapy helpline with shivering and a temperature of 38.3°C. She arrives in the emergency department 40 minutes later.
Answer: Suspected neutropenic sepsis.

• Assess quickly; blood cultures (peripheral and from her port), then IV piperacillin–tazobactam within 1 hour of arrival -don't wait for the blood count.
• FBC, U&E, LFTs, CRP, lactate, urine, chest X-ray if indicated; examine the port, mouth, skin and perineum (no rectal examination).
• Review at 48–72 hours with results; consider oral step-down if low risk and improving.

3. A 55-year-old man with a kidney transplant 3 months ago presents with breathlessness, a dry cough and fever. Oxygen saturation is 88% on air and falls further on walking. He stopped co-trimoxazole prophylaxis a month ago because of a rash.
Answer: Probable Pneumocystis pneumonia (also consider CMV).

• Oxygen; induced sputum or bronchoscopy for PCP PCR; CMV PCR; blood cultures; CT chest.
• Treat PCP with an alternative to co-trimoxazole if the rash was severe (specialist advice -e.g. other regimens), plus steroids if hypoxic.
• Check tacrolimus levels and interactions with any new drugs; involve the transplant team.

4. A 42-year-old woman with rheumatoid arthritis is about to start adalimumab. Her IGRA is positive; chest X-ray is normal and she has no symptoms. She was born in India.
Answer: Latent TB infection before anti-TNF therapy.

• Exclude active TB; start latent TB treatment (e.g. 3 months of rifampicin plus isoniazid -check interactions; or 6 months of isoniazid with pyridoxine) and usually start the biologic after at least a month (specialist advice).
• Also test hepatitis B and C, HIV, VZV immunity and Strongyloides serology.
• Vaccinate before starting -pneumococcal, influenza, COVID-19, Shingrix; no live vaccines on treatment.

5. A 34-year-old man has had 4 pneumonias in 3 years, chronic sinusitis and recently Giardia. CT chest shows bronchiectasis. IgG is 2.1 g/L and IgA undetectable; IgM is low. He takes no immunosuppressants and HIV is negative.
Answer: Probable common variable immunodeficiency.

• Refer to clinical immunology -confirm with specific antibody responses and lymphocyte subsets; exclude secondary causes (protein loss, lymphoma, drugs).
• Immunoglobulin replacement (IV or subcutaneous), airway clearance for bronchiectasis, prompt antibiotics for infections.
• Avoid live vaccines; watch for autoimmunity, granulomatous disease and lymphoma.

Key Points

• Hand hygiene, device removal and antibiotic stewardship prevent most healthcare-associated infections.
• C. difficile -the "4 Cs" (clindamycin, cephalosporins, co-amoxiclav, ciprofloxacin) plus PPIs; alcohol gel doesn't kill spores.
• C. difficile -oral vancomycin first-line; fidaxomicin for failure or recurrence; FMT after two recurrences; ileus can occur without diarrhoea.
• Colonisation (MRSA, ESBL, CPE) is not infection -but it guides antibiotic choice.
• Screen for CPE after hospital care abroad.
• Don't dipstick catheter urine; change long-term catheters before treating CAUTI.
• Remove infected lines with S. aureus, Pseudomonas or Candida.
• Norovirus -close bays, soap and water, staff off until 48 hours symptom-free.
• Neutropenic sepsis -piperacillin–tazobactam within 1 hour; don't wait for the count.
• After transplant: first month -surgical; 1–6 months -CMV, PCP, opportunistic; later -community infections and PTLD.
• Before biologics -screen for TB, hepatitis B and C, HIV, VZV and Strongyloides; vaccinate first.
• Rituximab -hepatitis B reactivation; complement inhibitors -meningococcus; JAK inhibitors -shingles.
• SPUR infections suggest immunodeficiency -but secondary causes are commoner.
• Recurrent Neisseria infection -test complement.
• No live vaccines in pregnancy or significant immunosuppression; egg allergy is not a contraindication to MMR.
• Pertussis, influenza and RSV vaccines in pregnancy protect the baby.
• Ciprofloxacin for meningococcal contacts; MMR within 3 days or immunoglobulin within 6 days for measles contacts.
• Report outbreaks and notifiable diseases promptly.

Guidelines and Further Reading

• NICE NG199: Clostridioides difficile infection -antimicrobial prescribing
• UKHSA: Updated guidance on the management and treatment of C. difficile infection
• National Infection Prevention and Control Manual for England; NICE QS61 (infection prevention and control)
• UKHSA: Framework of actions to contain carbapenemase-producing Enterobacterales
• NICE NG139: Pneumonia (hospital-acquired) -antimicrobial prescribing
• NICE NG113: Urinary tract infection (catheter-associated) -antimicrobial prescribing
• NICE CG151: Neutropenic sepsis
• NICE NG33: Tuberculosis (including screening before anti-TNF treatment)
• UKHSA Green Book: Immunisation against infectious disease (schedule, immunosuppression, asplenia, healthcare workers)
• UK Primary Immunodeficiency Network (UKPIN) resources
• UKHSA: Guidance for public health management of meningococcal disease, pertussis, measles and invasive group A strep
• BNF -for current doses