01Approach to the Critical Patient/attcp45

Sepsis and hemodynamic threats

›Sepsis recognition

›High fever with hemodynamic instability

›SBP < 90 mmHg

›MAP < 65 mmHg

›Tachycardia with signs of poor perfusion

›Lactate >= 2 mmol/l

›Altered mental status

›Broad-spectrum antibiotics within 1 hour of sepsis recognition

›Blood cultures before antibiotics when feasible

›Class I recommendation

›Endocarditis complication alert

›New cardiac murmur with fever after rodent exposure

›Echocardiography urgently

›Infectious disease consult

›Embolic phenomena

›Splenic infarct or renal infarct

›CT abdomen/pelvis if suspected

Airway and monitoring

›Monitoring bundle

›Continuous cardiac monitoring

›Myocarditis risk

›Arrhythmia risk

›Continuous pulse oximetry

›Target SpO2 >= 94%

›Serial blood pressure monitoring

›Vasopressor initiation if persistent hypotension despite fluids

›Escalation triggers

02History/hx70

Exposure and timeline

›Rodent exposure

›Rat or rodent bite or scratch within 3 weeks

›Pet rats, wild rats, mice, gerbils, hamsters

›Laboratory animal handlers

›Indirect exposure

›Handling rat feces, urine, or saliva without gloves

›Rodent-infested living conditions

›Ingestion exposure

›Contaminated food or water in rodent-infested environment

›Haverhill fever variant presentation

›Incubation and symptom timeline

›Typical incubation 2 to 10 days after exposure

›Range extends to 3 weeks

›Bite wound often healed by symptom onset

›Abrupt onset of fever and rigors

›Myalgias and headache

›Vomiting and nausea

Classic symptom triad

›Fever

›High fever often > 39 degrees C

›Relapsing or periodic pattern

›Rigors

›Triad incomplete in over half of cases

›Absence of rash does not exclude diagnosis

›Absence of arthritis does not exclude diagnosis

›Rash

›Erythematous maculopapular rash on extremities

03Physical Exam/exam60

Vitals and general appearance

›Stability assessment

›Temperature

›High fever often > 39 degrees C

›Hypothermia in severe sepsis

›Heart rate

›Tachycardia as early sign

›Bradycardia if myocarditis

›Blood pressure

›SBP < 90 mmHg in septic shock

›MAP < 65 mmHg target threshold

›General appearance

›Toxic appearance in severe cases

›Diaphoresis and flushing

Skin and wound exam

›Rash characteristics

›Distribution

›Dorsum of hands and feet

›Palms and soles

›Extremities predominantly

›Morphology

›Erythematous macules and papules

›Hemorrhagic pustules

›Petechiae or purpuric lesions in severe cases

›Differentiate from meningococcemia when purpuric

›Rapid clinical deterioration in meningococcemia

›Non-blanching purpura requires immediate assessment

›Bite wound site

04Differential Diagnosis/ddx58

Immediate life threats

›Cannot miss diagnoses

›Meningococcemia

›ICD-10 A39.2

›Petechial or purpuric rash with rapid deterioration

›Immediate empiric coverage required

›Septic shock from other source

›ICD-10 A41.9

›Requires broad empiric coverage until source identified

›Infective endocarditis

›ICD-10 I33.0

›Duke criteria application

›TEE if high suspicion with negative TTE

Fever rash and arthritis mimics

›Disseminated gonococcal infection

›ICD-10 A54.49

›Sexually active patients

›Tenosynovitis and pustular rash on extremities

›Positive cervical or urethral cultures

›Rocky Mountain spotted fever

›ICD-10 A77.0

›Tick exposure history

›Centripetal rash spread from extremities

›Doxycycline empiric treatment if suspected

›Lyme disease

›ICD-10 A69.20

›Erythema migrans rash

›Tick exposure in endemic area

05Laboratory Tests/lt55

Blood cultures and organism-specific testing

›Blood cultures

›Essential before starting antibiotics

›Notify lab to hold cultures for extended incubation

›S. moniliformis is fastidious and requires enriched media

›Media requirements

›Enriched with serum, ascitic fluid, 5% blood, or yeast extract

›Incubate up to 7 to 14 days

›Antibiotics render cultures negative rapidly

›Cultures before treatment is critical

›Molecular diagnostics

›16S rRNA PCR gene sequencing

›From blood, joint fluid, or bite-site crust

›Highly valuable when cultures are negative or antibiotics already started

›Bite-site crust can yield DNA weeks after exposure

›Metagenomic next-generation sequencing

›Emerging diagnostic tool

›Identified S. moniliformis genome within 72 hours with negative blood cultures

Core laboratory panel

›Inflammatory and infection markers

›Complete blood count

›Leukocytosis with left shift

›Anemia in prolonged or severe cases

›CRP and ESR

›Elevated in active infection

›Trend useful for treatment response

›Procalcitonin

›Bacterial infection support

06Diagnostic Tests/dt54

Scoring Systems

›Diagnostic scoring

›No validated clinical decision rule specific to rat bite fever

›Diagnosis relies on clinical triad plus exposure history

›Classic triad present in fewer than 50% of cases

›Duke criteria for endocarditis

›Applied when endocarditis is suspected complication

›S. moniliformis endocarditis reported with Duke criteria application

›Sepsis criteria

›SOFA score for organ dysfunction assessment

›qSOFA as bedside screening tool

MRI

›MRI indications in rat bite fever

›Osteomyelitis or discitis suspected

›Back pain with neurologic deficits

›MRI spine with contrast

›More sensitive than plain radiographs for early osteomyelitis

›CNS involvement suspected

›MRI brain with contrast for meningitis or abscess

›Gadolinium enhancement patterns

›Joint complications

›MRI of affected joint if destructive arthritis suspected

›Assess for osteomyelitis adjacent to septic joint

CT

›CT indications in rat bite fever

›Endocarditis with embolic complications

›CT abdomen and pelvis for splenic or renal infarcts

›CT chest for septic pulmonary emboli

07Disposition/dispo39

Admission indications

›Hospitalization criteria

›All confirmed or suspected cases requiring IV antibiotics

›Inability to take oral medications

›Sepsis or hemodynamic instability

›Endocarditis concern

›Admit for IV penicillin G 4 to 6 weeks

›Cardiac surgery consultation if valve destruction

›CNS involvement

›Meningitis requires prolonged IV antibiotics

›ICU level care if altered mental status

›Immunocompromised patients

›Lower threshold for admission

›Prolonged or complicated course anticipated

ICU criteria

›Critical care indications

›Septic shock

›Vasopressor requirement

›Lactate > 2 mmol/l despite resuscitation

›Endocarditis with hemodynamic instability

›Acute severe valvular regurgitation

›Heart failure from valve destruction

›Meningitis with neurologic compromise

›GCS <= 13

›Seizures

Discharge criteria and follow-up

›Discharge criteria for uncomplicated presentations

›Reliable oral intake

08Treatment/t74

First-line antibiotic therapy

›IV penicillin G for moderate to severe disease

›Standard dosing

›12 to 20 million units per day IV divided every 4 hours

›Duration 3 to 4 weeks for uncomplicated disease

›Endocarditis dosing

›4 weeks minimum duration

›Infectious disease guidance for valve involvement

›Pediatric dosing

›150,000 to 250,000 units per kg per day IV divided every 4 hours

›Duration based on severity

Step-down oral therapy

›Oral penicillin V step-down

›After clinical improvement on IV penicillin

›To complete 7 to 14 days total for uncomplicated cases

›500 mg PO every 6 hours in adults

›Amoxicillin alternative oral step-down

›500 mg PO every 8 hours

›Well tolerated for outpatient completion

›Duration targets by severity

›Uncomplicated rat bite fever

›7 to 14 days total course

›Minimum 7 days after fever resolution

›Endocarditis

›4 to 6 weeks IV penicillin G

›Surgical valve repair or replacement if indicated

›Meningitis or osteomyelitis

›4 to 6 weeks depending on response

09Special Populations/sp48

Pregnancy

›Pregnancy considerations

›Antibiotic safety

›Penicillin G is safe in all trimesters

›Amoxicillin safe as oral step-down

›Doxycycline contraindicated in pregnancy

›Infection risk

›S. moniliformis bacteremia can cause placental infection

›Risk of miscarriage, preterm labor, stillbirth reported

›Imaging guidance

›Echocardiography preferred over CT when possible

›MRI without gadolinium preferred for CNS assessment

›CT when benefit clearly outweighs risk

›Fetal monitoring

›When fetal viability reached

›Obstetrics consultation for co-management

Geriatric

›Older adult considerations

›Atypical presentation

›Rash may be absent or subtle

›Arthritis may be attributed to pre-existing joint disease

›Diagnosis delayed more often in older patients

›Endocarditis risk

›Pre-existing valvular disease increases risk

›Aortic stenosis and mitral regurgitation common in older adults

›Lower threshold for echocardiography

›Antibiotic dosing adjustments

›Renal function often reduced

10Background/b79

Epidemiology

›Incidence and distribution

›Rare but underdiagnosed condition

›Exact incidence unknown due to underreporting

›Estimated hundreds of cases annually in the US

›Geographic distribution of causative organisms

›Streptobacillus moniliformis predominant in Americas, Europe, Australia

›Spirillum minus predominant in Asia (sodoku)

›Demographic patterns

›Children most commonly affected, > 50% of reported cases

›Pet rodent ownership increasing incidence in urban settings

›Laboratory animal workers and pet store employees at risk

›Mortality and morbidity

›Untreated mortality 7 to 13%

›Death from septic shock, endocarditis, or meningitis

›Early diagnosis and treatment dramatically improves outcomes

›Morbidity

›Endocarditis occurs in subset of cases, especially with valvular disease

›Arthritis may persist if treatment delayed

Pathophysiology

›Causative organisms

›Streptobacillus moniliformis

›Gram-negative pleomorphic rod

›Fastidious, requires enriched media for culture

›Normal oral flora of rats and other rodents

›Spirillum minus

›Gram-negative spiral organism

›Darkfield microscopy or Giemsa stain for identification

›Causes sodoku variant in Asia

›Transmission and inoculation

›Direct inoculation via bite or scratch

›Rat normal oral flora enters tissue

›Local wound often heals before systemic illness

›Haverhill fever variant

›Ingestion of contaminated food or water

›Outbreaks in rodent-infested settings described

›GI symptoms more prominent

›Indirect contact

›Fomites, rodent excreta without direct bite

›Disease mechanism

›Bacteremia after local inoculation

›Organism spreads hematogenously

›Tropism for joints and cardiac valves

›Joint involvement

›Immune-mediated synovitis predominant mechanism

›Migratory pattern due to ongoing bacteremic seeding

›Endocarditis mechanism

›Pre-existing valve damage as nidus

›Vegetation formation on damaged endothelium

›Embolic complications from vegetations

Therapeutic Considerations

›Antibiotic principles

›Penicillin G remains drug of choice

›Highly susceptible organism

›IV route for moderate to severe disease

›Oral penicillin or amoxicillin for uncomplicated step-down

›Duration guided by clinical syndrome

›Uncomplicated cases 7 to 14 days

›Endocarditis 4 to 6 weeks

›Osteomyelitis or meningitis 4 to 6 weeks

›Culture and susceptibility testing

›Perform susceptibility when possible given fastidious growth

›No standardized breakpoints for S. moniliformis

›Diagnostic strategy

›Awareness of exposure history critical

›Exposure history is primary diagnostic trigger

›Classic triad absent in majority of cases

›Extended culture incubation

›Standard incubation protocols miss diagnosis

›Must communicate suspicion to microbiology laboratory

›Molecular testing as complement

›16S rRNA PCR valuable when cultures negative

›Metagenomic sequencing emerging option

›Prevention

›Wound management after rodent bite

›Thorough washing immediately

›Tetanus prophylaxis

›Prophylactic antibiotics considered in immunocompromised or high-risk hosts

›Rodent exposure reduction counseling

›Gloves when handling rodents

›Avoiding bare-hand contact with feces or urine

›Household rodent control measures

11Patient Discharge Instructions/pdi30

copy discharge instructions

›Rat bite fever home care instructions

›Take all prescribed antibiotics exactly as directed until the full course is complete

›Do not stop early even if feeling better

›Take with food if stomach upset occurs

›Rest and stay well hydrated

›Drink plenty of fluids daily

›Wound care if bite site present

›Keep clean and dry

›Watch for increasing redness or discharge

›Warning signs requiring immediate return to emergency department

›High fever returning or worsening after starting antibiotics

›New rash or worsening of existing rash

›Severe joint swelling or inability to move a joint

›Difficulty breathing or chest pain

›Racing or irregular heartbeat

›Severe headache or stiff neck

›Confusion or difficulty waking up

›Weakness or numbness

›Follow-up instructions

›See your doctor within 2 to 3 days of discharge

›Blood culture results may become available

›Antibiotic adjustment may be needed

›Complete all follow-up appointments as scheduled

›Report any new symptoms promptly

›Prevention after discharge

›Wear gloves when handling pet rodents

›Wash hands thoroughly after contact

12References/r21

Guidelines and key sources

›Primary references

›Centers for Disease Control and Prevention rat bite fever guidance

›Clinical diagnosis and management recommendations

›Hagelskjaer LH et al. systematic review of rat bite fever

›Clinical features and outcomes in reported cases

›Elliott SP. Rat bite fever and Streptobacillus moniliformis

›Clinical Microbiology Reviews 2007

›Comprehensive organism and disease review

›Case series and reports

›Endocarditis case series

›Valve involvement patterns and outcomes

›Duke criteria application to S. moniliformis endocarditis

›Molecular diagnostics in rat bite fever

›16S rRNA PCR and metagenomic sequencing case reports

›Culture-negative diagnosis facilitated by molecular methods

›Diagnostic coding

›ICD-10 A25.1 Streptobacillosis

›Rat bite fever due to S. moniliformis

›ICD-10 A25.0 Sodoku

›Rat bite fever due to Spirillum minus

›SNOMED CT rat bite fever disorder

Evidence & Review

Evidence & Review