temporary/semipermanent catheters. Alternately, in patients with prosthetic devices, i.e.,
artificial joints, heart valves, plastic shunts, etc, CoNS bacteremias are often the only indication
of device-associated infection (10). The treatment of CoNS CVC infections is CVC removal
(1,10). The device related CVC CoNS infections are subacute/chronic and are not usually a
diagnostic or therapeutic problem in the critical care setting.
If the isolate from continuous/high culture positivity blood cultures is subsequently
identified asS. aureus, the clinician should look for a source, i.e., osteomyelitis, abscess, CVC or
device-associated infection, or ABE. If not readily apparent from the past medical history,
physician examination, and routine laboratory tests, the abscesses may be detected by imaging
studies, i.e., CT/MRI or gallium/indium scans. ABE may be ruled out by transthoracic
echocardiography (TTE) or transesophageal echocardiography (TEE). Patients with vegeta-
tions without bacteremia, i.e., marantic endocarditis, do not have ABE, and patients with
positive blood cultures without a vegetation have bacteremia without ABE (10,12,25).
MSSA/MRSA CVC Infections.CVC-associated infections may be diagnosed by removing the
catheter and sending the CVC tip for semiquantitative culture. If the removed CVC tip grows
15 colonies of the same organism, i.e., MSSA/MRSA from a peripherally drawn blood
culture, then the diagnosis of CVC line infection is confirmed. Patients with positive CVC tip
cultures without bacteremia have CVC colonization, but not CVC infection. Those with
positive blood cultures and negative removed catheter tip cultures have bacteremia but not IV
line infection. The preferred therapy of CVC infections is catheter removal since prolonged
high-level bacteremia may result in metastatic seeding through other organs or may result in
ABE (1,11,25,26).
In general, without hematogenous seeding/contiguous spread MSSA/MRSA do not
cause CNS infections (1,21). The important exceptions are CNS shunt-related infections
secondary to ventriculo-atrial (VA) or VP shunts or secondary to implant-associated infection
materials, i.e., plate/mesh or ventriculostomy drainage tubes. MSSA/MRSA acute purulent
meningitis is a recognized complication of ABE. MSSA/MRSA rarely, if ever, is associated
with oral infections. Excluding dental implant infections, neither biliary infections nor UTIs are
caused by MSSA/MRSA.S. saprophyticusis the only staphylococcal uropathogen that occurs as
community-acquired cystitis in young females and does not cause pyelonephritis/urosepsis
and is not an issue in critical care (1,21).
Renal MSSA/MRSA abscesses may complicate renal surgery or may occur as a result of
contagious/hematogenous spread. Staphylococcal renal abscesses are cortical in contrast to
medullary abscesses that are due to, in the main, aerobic GNBs (1,21).
MSSA/MRSA may cause septic arthritis, either by hematogenous spread or by direct
inoculation into the joint during aspiration/steroid injections. MSSA/MRSA is the most
common cause of acute osteomyelitis, but is also a common pathogen in chronic osteomyelitis
particularly in patients with diabetes mellitus/peripheral vascular disease (1,21,25).
Besides culture of blood, infected materials or purulent materials, serious systemic
MSSA/MRSA infections may be indirectly diagnosed by demonstrating an elevation in
teichoic acid antibody (TAAb) titers. TAAb titers1:4 indicate a deep-seated underlying
infection, i.e., osteomyelitis, abscess, or ABE. All patients with these infections do not have
positive TAAb titers and a negative TAAb titer does not rule out a deep-seated/systemic
MSSA/MRSA infection. TAAb titers are unhelpful in diagnosing CoNS infections. TAAb titers
are particularly helpful in determining the duration of therapy in CVC line infections in
determining the duration of therapy. Patients with MSSA/MRSA bacteremia due to CVC
catheters should have a TAAb titer drawn at two weeks. If the titer is negative, two weeks of
anti-MSSA/MRSA therapy is sufficient. However, patients with MSSA/MRSA bacteremia due
to a CVC catheter and an elevated TAAb titer at two weeks should be treated as if they have
ABE for four weeks after CVC removal (Table 4) (1,10,11,26,27).
Staphylococci rarely, if ever, cause pneumonia in normal hosts. IVDAs with tricuspid
valve ABE have septic pulmonary emboli that may mimic pneumonia. Even diabetics who are
frequently colonized with MSSA/MRSA are not predisposed to developS. aureusCAP (28).
CA-MSSA/MRSA pneumonia occurs virtually only in patients with influenza pneumonia
(27,29–35). MSSA/MRSA rarely, if ever, causes NP/VAP (1,27).S. aureusCAP complicating
504 Cunha