Specific infections and causative organisms

OVERVIEW

• key infections, organisms and suggested treatments
• antibiotic selection varies by geographic location and institution – consult local guidelines and sensitivity patterns

ABDOMINAL SEPSIS

• includes: acute peritonitis, appendicitis, cholangitis, cholecystitis, diverticulitis, PID
• Empiric Treatment – Cefuroxime + Metronidazole OR Tazocin

ANIMAL CONTACT

• Chlamydophila psittaci (birds -> pneumonia)
  – Erythromycin (macrolides) or Moxifloxacin (quinolones)
• Coxiella burnetii (Q fever) – pregnant animals and hides -> pneumonia + endocarditis)
  – Doxycycline or Chloramphenicol
• Burcella suis (feral pigs)
  – Doxycycline + Rifampicin/Gentamicin
• Burcella abortis (stock animals)
  – Doxycycline + Rifampicin/Gentamicin
• Leptospirosis (rats)
  – Doxycycline or Benzylpenicillin
• Toxoplasma gondii (cats)
  — Pyrimethamine
• Hydatid disease = Echinococcus granulosus (dog faeces)
  – surgical resection + albendazole
• Cysticercosis (infected meat esp pork)
• Bacillus antracis (wool)
  – penicillin, doxycycline or ciprofloxacin
• Bartonella henselae – (cat scratch disease)
  – doxycycline, macrolides, cotrimoxazole, ciprofloxacin, gentamycin
• Cryptosporidiosis (domestic and wild animals)
  – no specific treatment

BITES/PUNCH INJURIES

Empiric Antibiotics

• Prophylaxis – Amoxycillin + Clavulanate OR Doxycycline + Metronidazole
• Established Infection – Amoxycillin Clavulanate OR Cefazolin + Metronidazole

Organisms:

• Staph. aureus
• Streptococcus
• Anaerobes (including Clostridium tetani)
• Eikenella corrodens (human)
• Pasteurella (cats and dogs)
• Capnocytophagia canimorsus (cats and dogs)
• Bartonella henselae (cat scratch)
• Lyssa virus (bats)

Tetanus Immunisation!

CELLULITIS

Empiric Antibiotics

• Flucloxacillin OR Cephazolin

DIARRHOEA

Primary

Empiric antibiotics

• only indicated in the really sick -> ciprofloxacin or norfloxacin

Organisms

• Shigella species
• Salmonella species
• Campylobacter species
• Yersina enterocolitica
• Enterohaemorrhagic Escherchia coli (EHEC)
• Entamobeba histolytica

Antibiotic-induced

Empiric antibiotics

• Metronidazole

ENCEPHALITIS

Empiric Treatment – Acyclovir (HSV) or Ganciclovir (CMV)

• HSV
• CMV
• EBV
• HSV – type 6
• Arboviruses
• Coxsackie viruses
• Enteroviruses
• Echoviruses
• Adenoviruses
• Influenzae viruses
• Hepatitis A virus
• Murray Valley encephalitis
• Hendra viruses (equine morbillivirus)
• Japanese encephalitis
• HIV
• Toxoplasma gondii
• Plasmodium falciparum
• Rickettsieae
• Borrelia burgdorferi
• CJD
• Rubella
• Measels

ENDOCARDITIS

Empiric Antibiotics

Native valves

• Flucloxacillin OR Cephazolin +/- Gentamicin

Prostetic valves or Hospital Acquired

• Flucloxaillin OR Vancomycin + Rifampicin + Gentamicin

Organisms

• Staphylococci (aureus, lugdenensis)
• Streptococci (viridans, sanguis)
• Enterococci
• Oral gram negative bacilli – (HACEK group: Haemophilus (parainfluenaze, aphrophilus), Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae)
• Coxiella burnetii
• Legionella
• Bartonella
• Pseudomonas aeruginosa
• Neisseria gonorrhoea
• Corynebacterium diptheriae
• Fungi – Candida and Aspergillus

MENINGITIS

Dexamethasone

• 0.15mg/kg IV with first antibiotic

Empiric Antibiotics

• Ceftriaxone + Vancomycin

Organisms

• Streptococcus pneumoniae
• Niesseria meningitides
• Haemophilus influenzae
• Listeria monocytogenes (age extremes)
• Steptococcus agalactaie (neonates)
• Escherichia coli (neonates)
• Staph + Gram-negative bacilli (skull trauma or neurosurgery)
• Mycobacterium tuberculosis
• Cryptococcus neformans (immunosuppressed)
• Leptospira interrogans
• Burcella
• Borrelia bugdoferi
• Treponema pallidum
• Viruses – Enteroviruses, Abroviruses, Coxsackie viruses

MYONECROSIS (gas gangrene)

Empiric Treatment

• Surgical Debridement -> Benzylpenicillin or Metronidazole

Organisms

• Clostridium perfringens or Clostridium septicum

NECK INFECTIONS

Empiric antibiotics

• Pencillin + Clindamycin + Gentamicin OR Third generation Cephalosporin + Metronidazole

Types

• Ludwig angina – sublingual/submaxillary space infection
• Retropharyngeal and parapharyngeal space infections
• Lemierre syndrome – retrotonsillar infection with the anaerobe Fusobacterium necrophorium which enters the jugular vein and disseminates

Organisms

• – mixed oral flora (gram positive, negative and anaerobes)
  – S. pyogenes
  – S. viridans
  – S. pneumoniae
  – S. aureus
  – Fusobacterium nucleastum
  – Bacteroides oralis
  – Spirochaeta
  – Peptostreptococcs
  – Neisseria spp
  – Pseudomonas
  – E.coli
  – H. influenzae

NECROTISING FASCIITIS

Empiric Treatment

• Surgical Debridement
• Meropenem + Clindamycin
• New antibiotic guidelines: flucloxacillin + clindamycin

Organisms

• – Gram positive infection – Group A Streptococci, Staph aureus
  – Mixed infection – Gram negative enteric bacilli, Vibrio, Anaerobes

OSTEOMYELITIS/SEPTIC ARTHRITIS (single, native joint)

Empiric Treatment

• Flucloxacillin OR Cephalzolin

PELVIC INFLAMMATORY DISEASE

Empiric Antibiotics

• Ceftriaxone + Azithromycin +/- Metronidazole

Organisms

• usually polymicrobial
• can be sexually acquired or non-sexually acquired

• Chlamyophilia trachomatis
• Neisseria gonorrhoea
• Mycoplasma hominis
• Ureaplasma urealyticum
• Actinomyces (if IUD in situ)

PNEUMONIA

COMMUNITY ACQUIRED PNEUMONIA

Empiric Antibiotics – Cefuroxime + Erythromycin (NZ)

• Streptococcus pneumoniae
• Haemophilus influenzae (underlying COPD)
• Mycoplasma pneumoniae
• Chlamydia pneumoniae
• Legionella

HOSPITAL ACQUIRED PNEUMONIA

Empiric Antibiotics

• Cefuroxime +/- Piperacillin-Tazobactam (if not responding)

Organisms

• Aerobic gram negative bacilli (ESCAPM)
• MRSA
• Enterobacter (multi-drug resistant)
• Pseudomonas aeruginosa (multi-drug resistant)
• Acinetobacter
• Stentrophomonas maltophilia
• Fungi – Aspergillus
• Viral – influenza, RSV

POST-TRAUMATIC WOUND INFECTIONS

Mild to Moderate (skin injury only, no soiling or presenting within 4 hours)

• Flucloxacillin

Severe (wound soiling, tissue damage, devitalised tissue, perforated viscus)

• surgery, Amoxicillin + Clavulanate +/- Gentamicin

PROSTHETIC JOINT INFECTIONS

Empiric Treatment

• consult ID early (Vancomycin)

SEPSIS

COMMUNITIY ACQUIRED SEPSIS

• no obvious source
• immunocompetent adult

Empiric antibiotics

• Ceftriaxone

HOSPITAL ACQUIRED SEPSIS

• no obvious source
• immunocompetent adult
• Staph aureus = commonest pathogen

Empiric Treatment:

• Piperacillin + Tazobactam 4.5g Q 8hrly OR Flucloxacillin + Gentamicin
• Vancomycin (if suspected MRSA)
• Meropenem (if suspected ESBL)

CHILDREN

Meningitis NOT excluded

• Empiric Treatment
  < 6 months – amoxicillin + cefotaxime + vancomycin Empiric Treatment
  > 6 months – flucloxacillin + cefotaxime OR ceftriaxone + vancomycin

Meningitis excluded

• Empiric Treatment
  < 4 months – amoxicillin + gentamicin Empiric Treatment
  > 4 months – flucloxacillin + cefotaxime OR ceftriaxone

THE IMMUNOSUPPRESSED

IMPAIRED IMMUNOGLOBULIN PRODUCTION (B-cell mediated)

• including post-splenectomy
• nephrotic syndrome
• myeloma
• CLL
• immunosuppressive therapy
• AIDS
• at risk of encapsulated bacterial infection

Empiric Treatment –

• Streptococcus pneumoniae and pyogenes
• Enterococcus species
• Neisseria meningitidis and gonorrhoea
• Haemophilus influenzae
• Salmonella species
• Escherichia coli
• Pseudomonas aeruginosa
• Capnocytopaga canimorsus
• Bacteroides species
• Plasmodium species + other parasites

IMPAIRED CELL-MEDIATED IMMUNITY (T-cell mediated)

• AIDS
• immunosuppressive therapy

Empiric Treatment –

• Pneumocystis jiroveci
• Cryptococcus neoformans
• Toxoplasma gondii
• CMV
• HSV
• VZV
• Fungi – Candida albicans
• Mycobacterium tuberculosis and avium
• Legionella species
• Nocardia species
• Streptococcus pneumoniae
• Strongyloides stercoralis

IMPAIRED NEUTROPHIL NUMBER AND/OR FUNCTION

• neutropenia = < 0.5 or expected decline to less than 0.5
• post-chemotherapy
• post-transplantation
• chronic granulomatous disease

Empiric Antibiotics

• Piperacillin-Tazobactam 4.5g Q8hrly (add Vancomycin for MRSA, add Meropenem for ESBL)

Organisms

• Gram negative bacilli
• Staphylococcus aureus
• Streptococcus viridans
• Fungi – Candida, Aspergillus, Mucormycosis (add voriconazole or amphortericin B)

TOXIC SHOCK MEDIATED EXFOLIATING SYNDROMES

Empiric Treatment

• Antibiotics (see below) – Clindamycin (? helps stop toxin production)
• Immunoglobulin with Streptococcus (0.4-2g/kg for 2 doses)

Staphylococcal scaled skin syndrome (Staph aureus)

• Flucloxacillin OR Cephazolin

Streptococcal toxic shock syndrome (Group A Streptococcus)

• Benzylpenicillin OR Cephazolin

URINARY TRACT INFECTIONS

• uncomplicated = adult, female, no urological defect
• complicated = all others
• anyone 15-29 years with urethral symptoms -> send first past urine for Chlamydia

UNCOMPLICATED

Empiric antibiotics

• Trimethoprim OR Nitrofurantoin

COMPLICATED

Empiric antibiotics

• Cefaclor OR Nitrofurantoin (pregnancy)

COMMUNITY PYELONEPHRITIS

Empiric antibiotics

• Gentamicin OR Cefuroxime

ACUTE PROSTATITIS

Empiric antibiotics – Cefuroxime then Ciprofloxacin

ESBL (E coli or Klebsiella)

Cystitis

• empiric antibiotics – Nitrofurantoin or Amoxycillin-Clavulanate

Pyelonephritis

• empiric antibiotics – Ertapenem 1g Q12hrly

WATERBORNE AGENTS

• Aeromonas species (fresh water)
• Shewanella putrifaciens (salt water) –
• Vibrio species (warm salt water) – third generation cephalosporin or tetracycline (doxycycline)
• Pseudomonas aeruginosa (spa baths) – piperacillin-tazobactam, tircarcillin-clavulanate, ceftazidime, cefepime, imipenem, meropenem
• Legionella species (water tanks) – macrolides (erythromycin)