Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (85 page)

Gram stain; eg, carbapenem or (3rd-gen ceph + amp + [clinda or metronidazole])

• Type II: PCN + clinda. If ↑ risk of CA-MRSA, + vanco. If concern for strep, IVIG.

Prognosis

• Generally fatal if untreated; reported mortality 20–50%

CLOSTRIDIAL MYONECROSIS (GAS GANGRENE)

Definition

• Life-threatening, fulminant clostridial infection of skeletal muscle •
Wound contamination
w/ clostridial spores after
trauma
(penetrating or crush injury) • Most commonly
C. perfringens
;
C. septicum
assoc w/ cancer (GI, heme), even w/o trauma
Clinical manifestations

• Incubation period 6 h to 2–3 d • Sense of heaviness/pain, often at site of trauma; rapid worsening; marked systemic toxicity • Bronze skin discoloration, tense bullae, serosanguineous or dark fluid and necrotic areas •
Crepitus
present but not prominent (gas is in muscle), may be obscured by edema
Diagnostic studies

• Gram stain:
lg
,
Gram
bacilli w/ blunt ends
(can be Gram-variable)
, few polys • Bacteremia in ~15%

• Plain radiographs: gas dissecting into muscle
Treatment

•
Surgical exploration with débridement
, fasciotomies and amputation if necessary •
Antibiotics
: high-dose
penicillin G
24 MU IV divided q2–3h +
clinda
900 mg IV q8h

OSTEOMYELITIS

Infection of bone due to hematogenous seeding or direct spread from contiguous focus
Microbiology
(
NEJM
1997;336:999;
Lancet
2004;364:369)

•
Hematogenous
:
S. aureus
; mycobacterial infection of vertebral body = Pott’s disease •
Contiguous focus
(may be acute or chronic)

open fracture, orthopedic surgery, etc.:
S. aureus
and
S. epi

skin breakdown + vasc. insuffic. (eg, diabetic foot):
polymicrobial
(aerobic + anaerobic GPC & GNR)

Clinical manifestations

• Surrounding soft-tissue compromise ± fistula to superficial skin • ± Fever, malaise and night sweats (more common in hematogenous than contiguous) • Vertebral osteomyelitis (seen in Pts >50 y): unremitting, focal back pain, usually fever (
NEJM
2010;362:1022)
Diagnostic studies
(
JAMA
2008;299:806)

• Identification of the causative organism is key •
Culture from tissue
(surgical sampling/needle bx),
not
swabs of ulcers or fistulae drainage • High suspicion in diabetic foot (see above) if can probe ulcer to bone or ulcer >2 cm
²

•
Blood cultures
(more often
with acute hematogenous osteomyelitis) •
ESR
>70 greatly increases likelihood of osteo (
JAMA
2008;299:806) • Imaging

Plain radiographs: normal early in disease; lytic lesions seen after 2–6 wk

MRI
: can detect very early changes (overall Se 90%, Sp 82%;
Archives
2007;167:125)

CT: can demonstrate periosteal reaction and cortical and medullary destruction

CT & MRI very Se but ↓ Sp; false
if contig focus w/ periosteal reaction, Charcot Ds

Radionuclide imaging: very Se but non-Sp (false
if soft tissue inflammation)

Treatment

•
Antibiotics
(based on cx data) × 4–8 wk •
Surgery
should be considered for any of the following: acute osteo that fails to respond to medical Rx, chronic osteo, complications of pyogenic vertebral osteo (eg, early signs of cord compression, spinal instability, epidural abscess) or infected prosthesis

EPIDURAL ABSCESS

Etiology

• Hematogenous spread (
²
/
₃
): skin infection, soft tissue (dental abscess) or endocarditis • Direct extension (
¹
/
₃
): vertebral osteo, sacral ulcer, spinal anesthesia or surgery, LP

• Risk factors: diabetes, renal failure, alcoholism, IVDU, immunosupp.

•
S. aureus
most common pathogen, increasing incidence of MRSA
Clinical manifestations

•
Back pain
(unremitting including midline) + often
fever
± nerve root or cord signs
Diagnostic studies

•
MRI
• Aspiration of abscess fluid for Gram stain & cx or operative Gram stain & cx • Blood cx (frequently
)
Treatment

•
Antibiotics ± surgery
(decompressive laminectomy and débridement) for failure to improve on medical Rx or early s/s of cord compression (w/ vertebral osteo and epidural abscess, may see paraplegia 48–72 h after first signs)

INFECTIONS OF THE NERVOUS SYSTEM

ACUTE BACTERIAL MENINGITIS

Definition

• Bacterial infection of the subarachnoid space

Clinical manifestations
(
NEJM
2006;354:44;
Lancet
2012;380:1684)

•
Fever
(77%),
headache
(87%),
stiff neck
(31%),
photosensitivity
, Δ
MS
(69%) (defined as GCS <14),
seizures
(5%); 2 of 4 (fever, HA, stiff neck, Δ MS) present in 95%

• Presentation may be
atypical
(eg, lethargy w/o fever) in elderly and immunosupp.

Physical exam

•
Nuchal rigidity
(Se 31%),
Kernig’s sign
(Pt supine, hip flexed at 90°, knee flexed at 90°;
if passive extension of knee results in resistance),
Brudzinski’s sign
(Pt supine and limbs supine;
if passive neck flexion → involuntary hip and/or knee flexion)