approach to infectious diseases

8/16/2019 Approach to Infectious Diseases

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Approach to Infectious DiseasesIn addition to the frequent lack of fever, infections in older adults may be associated

with a nonspecific decline in baseline functional status such as increased confusion,

falling, and anorexia. For some seniors, exacerbations of underlying illness (eg, atrialfibrillation) may be the predominant feature of infection.

Fever of unknown origin Fever of unknown origin (F!") is a classic medicalsyndrome defined as temperature #$%.$&' (&F) for at least three weeks andundiagnosed after one week of medical evaluation. *he differential diagnosis of F!"in older patients differs from that in younger adults

+oughly a third of older patients with F!" have treatable infections (eg, intra-abdominal abscess, bacterial endocarditis, tuberculosis, perinephric abscess, or occult osteomyelitis) ndocarditis and tuberculosis are more common in older

adults than in younger patients.

+/iant cell arteritis (/'0, also known as temporal arteritis) and polymyalgiarheumatica (12) account for 3 percent of all F!" in the older population .*he evaluation of F!" in patients age #4 years should include arheumatological evaluation including early temporal artery biopsy, particularly ifthe erythrocyte sedimentation rate or liver en5ymes are elevated

+0lthough earlier references suggested malignancy, particularly lymphoma, wasa more common cause of F!" in older adults, more recent series suggest

malignant disease as a cause of F!" occurs with similar frequency in old andyoung adults, perhaps due to the ability to establish a diagnosis by moreaggressiveimaging6'* scanning before patients reach F!" definitions. In bothyoung and older adults, non-7odgkin8s lymphoma accounts for the ma9ority ofcases due to malignancy.

Infective endocarditis

*he diagnosis of I is often more difficult in older patients. Fever, leukocytosis,

embolic events, splenomegaly, skin lesions ("sler nodes, :aneway lesions), and

con9unctival hemorrhages are less common with advanced age. ;alvular vegetations

are also less common, while intracardiac abscesses and paravalvular complications

are relatively more common in older than younger adults< these locali5ed infection

sites may not be detected by transthoracic echocardiography (TTE). *hus, a

lower threshold to perform transesophageal echocardiography (TEE) may be

indicated in older patients



Fever is the most common symptom of I (up to 3 percent of patients)< it is oftenassociated with chills, anorexia, and weight loss. "ther common symptoms of Iinclude malaise, headache, myalgias, arthralgias, night sweats, abdominal pain,dyspnea, cough, and pleuritic pain =>?. 1atients with I associated with dentalinfection may report tooth pain or related symptoms.

Cardiac murmurs are observed in approimately !" percent of patients.#upportive signs include splenomegaly and cutaneous manifestations such aspetechiae or splinter hemorrhages. 1etechiae are observed in @ to > percent ofpatients< they may be present on the skin (usually on the extremities) or on mucousmembranes such as the palate or con9unctivae . Aplinter hemorrhages consist ofnonblanching, linear reddish-brown lesions under the nail bed 'linical manifestationsreflecting complications of I may be present at the time of initialpresentation and6or may develop subsequently, as discussed below. Bhen present,such findings warrant independent diagnostic evaluation, concurrent with evaluation

for I.

elatively uncommon clinical manifestations that are highly suggestive of I includeC

+ Janeway lesions – Nontender erythematous macules on the palms and

soles

+"sler nodes D *ender subcutaneous violaceous nodules mostly on the pads ofthe fingers and toes, which may also occur on the thenar and hypothenareminences (picture >)

+oth spots D xudative, edematous hemorrhagic lesions of the retina with palecenters

Infective endocarditis (IE) refers to infection of the endocardial surface ofthe heart$ it usually refers to infection of one or more heart valves orinfection of an intracardiac device. isk factors for I include cardiac factors(history of prior I, presence of a prosthetic valve or cardiac device, or history of valvular or congenital heart disease) and noncardiac factors (intravenous druguse, indwelling intravenous catheter, immunosuppression, or a recent dental orsurgical procedure).

+*he clinical manifestations of I are highly variable< I may present as anacute, rapidly progressive infection or as a subacute or chronic disease withlow-grade fever and nonspecific symptoms. Fever is the most commonsymptom of I (up to 3 percent of cases)< it is often associated with chills,anorexia, and weight loss. "ther symptoms of I include malaise, headache,myalgias, arthralgias, night sweats, abdominal pain, dyspnea, cough, andpleuritic pain. 'ardiac murmurs are observed in approximately %E percent ofpatients. Aupportive signs include cutaneous manifestations such as petechiae

or splinter hemorrhages

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+I is associated with a broad array of systemic complications< these includecardiac and neurologic complications, septic emboli, metastatic infection, andsystemic immune reactions. 'linical manifestations reflecting these

complications may be present at the time of initial presentation and6or maydevelop subsequently. 'linical manifestations of a complication of I warrantindependent diagnostic evaluation, concurrent with evaluation for I.

+*he diagnosis of I should be suspected in patients with fever (with or withoutbacteremia) in the setting of relevant cardiac and noncardiac risk factors. *hediagnosis is established based on clinical manifestations, blood cultures (orother microbiologic data), and echocardiography.

+%t least three sets of blood cultures should be obtained from separate

venipuncture sites prior to initiation of antibiotic therapy. For patients whoare clinically stable& antimicrobial therapy may be deferred while awaitingthe results of blood cultures and other diagnostic tests. For patients withsigns of clinical instability& initiation of empiric antimicrobial therapy (afterthree blood cultures have been obtained) is appropriate.

+*ypical microorganisms consistent with I include Staphylococcus aureus&viridans streptococci& Streptococcus gallolyticus (formerly S. bovis),70' (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella)organisms, or community-acquired enterococci

+'ulture-negative I should be suspected in patients with negative bloodcultures and persistent fever with one or more clinical findings consistent withinfective endocarditis (eg, stroke or other manifestations of emboli). 'ulture-negative I should also be suspected in patients with vegetation onechocardiogram and no clear microbiologic diagnosis.)

+chocardiography should be performed in patients with suspected I. Ingeneral& transthoracic echocardiography (TTE) is the first diagnostic testfor patients with suspected IE. Transesophageal echocardiography (TEE)has higher sensitivity than TTE and is better for detection of cardiaccomplications such as abscess& leaflet perforation& and pseudoaneurysm.In some circumstances& it is reasonable to forgo TTE and proceed to TEE.

+0dditional evaluation for patients with suspected I includeselectrocardiography, chest radiography, other radiographic imaging tailored toclinical manifestations, and dental evaluation.



OSTEOMYELITIS

• "steomyelitis occurs either as a result of hematogenous seeding,contiguous spread of infection to bone from ad9acent soft tissues and 9oints, or direct inoculation of infection into the bone as a result of traumaor surgery. 7ematogenous osteomyelitis is usually monomicrobial, whileosteomyelitis due to contiguous spread or direct inoculation is usuallypolymicrobial.

+Staphylococcus aureus, coagulase-negative staphylococci, and aerobic gram-negative bacilli are the most common organisms< other pathogens includingstreptococci, enterococci, anaerobes, fungi, and mycobacteria have also beenimplicated

+0cute osteomyelitis typically presents with gradual onset of pain over severaldays. Gocal findings (tenderness, warmth, erythema, and swelling) and systemicsymptoms (fever, rigors) may also be present. 'hronic osteomyelitis tends tooccur in the setting of previous osteomyelitis and presents with recurrent pain,erythema, or swelling, sometimes in association with a draining sinus tract.



+2ost cases of diabetic foot osteomyelitis occur in the setting of ulcers thatdevelop in the absence of exposed bone. If a diabetic foot ulcer is larger than' ' cm or bone is palpable& osteomyelitis is so likely that additionalnoninvasive evaluation may not be needed. ositive results of a probetobone test are sufficient for diagnosis of osteomyelitis.

+*he reference standard for diagnosis of osteomyelitis is isolation of bacteriafrom a bone biopsy sample obtained via sterile technique, together withhistologic findings of inflammation and osteonecrosis. Hone biopsy may not beneeded for patients with radiologic studies consistent with osteomyelitis in thesetting of positive blood cultures. 'ultures obtained from sinus tract drainageare not reliable

• *pen biopsy is preferable over needle biopsy$ bone samples should

be obtained at the time of surgical debridement if performed.

1ercutaneous needle biopsy is an alternative to open biopsy< ideally, itshould be performed via intact tissues and under radiographic guidanceto optimi5e yield. +one biopsy should be obtained prior to treatmentwith antimicrobial therapy whenever possible.

+Treatment of osteomyelitis often re,uires both surgical debridement of

necrotic material and antimicrobial therapy for eradication of infection. *he

optimal duration of antibiotic therapy is not certain< we suggest continuing parenteral

antimicrobial therapy at least six weeks from the last debridement

In stable patients, antibiotics may be held pending establishment

of microbiologic diagnosis or obtaining cultures from bone

debridement or biopsy. Total duration of antibiotic therapy (IV

and step-down oral) is four to eight weeks.

• -adiographs are of limited sensitivity and specificity in the

detection of acute osteomyelitis. Hone findings such as osteolysis andperiosteal new bone formation may not be evident until to > daysfollowing onset of infection. -adiographs are particularly useful for

demonstrating findings of chronic osteomyelitis< these may includecortical erosion, periosteal reaction, mixed bony lucency and sclerosis,and sequestra.

+agnetic resonance imaging (-I) is the best modality for obtainingdetailed anatomic delineation of the etent of bone marrow and soft tissueinflammation. It is especially useful for evaluation of osteomyelitis in the foot(particularly in the setting of diabetes) and in the vertebrae (given its excellentdepiction of the spinal cord and associated structures).



SEPTIC ARTHRITIS

+Aeptic arthritis due to bacterial infection is often a destructive form of acutearthritis. In most cases, bacterial arthritis arises from hematogenous spread tothe 9oint. Hacterial arthritis can also arise as a result of a bite or other trauma,direct inoculation of bacteria during 9oint surgery, or, in rare cases, followingextension of preexisting bony infection through the cortex into the 9oint space.

+Hacteremia is more likely to locali5e in a 9oint with preexisting arthritis,particularly if associated with synovitis. 1atients with rheumatoid arthritis appear

to be especially prone to bacterial arthritis< the risk may also be increased ingout, pseudogout, osteoarthritis, and 'harcot arthropathy.

+2any pathogens are capable of causing bacterial arthritis. "rganisms suchas S. aureus and streptococci have a higher propensity to cause 9oint infectionsthan gram-negative bacilli, which typically cause infections following trauma or inpatients with severe underlying immunosuppression. +1atients with bacterialarthritis usually present acutely with a single swollen and painful 9oint (ie,monoarticular arthritis). *he knee is involved in more than E percent of cases<wrists, ankles, and hips are also commonly affected.

+The definitive diagnostic test is identification of bacteria in the synovialfluid. In the setting of suspected 9oint infection, synovial fluid aspiration shouldbe performed (prior to administration of antibiotics)< fluid should be sent for/ram stain and culture, leukocyte count with differential, and assessment forcrystals

+Treatment of acute bacterial arthritis consists of antibiotic therapy and /oint drainage. *he initial choice of antibiotics for treatment of septic arthritis isbased on the /ram stain. *he initial regimen should be tailored to culture andsusceptibility results when available. *he typical duration of therapy is three tofour weeks.



If the initial 0ram stain of the synovial fluid shows grampositive cocci& wesuggest treatment with vancomycin. If the initial 0ram stain of thesynovial fluid shows gramnegative bacilli& we suggest treatment with athirdgeneration cephalosporin

+If the initial 0ram stain is negative and the patient is immunocompetent&we suggest treatment with vancomycin(0rade 'C). If the initial 0ram stainis negative and the patient is immunocompromised& we suggest treatmentwith vancomycin plus a thirdgeneration cephalosporin (0rade 'C).

+In general, we recommend 9oint drainage in the setting of septic arthritis

(0rade 1+), as this condition represents a closed abscess collection. "ptionsfor drainage include needle aspiration (single or multiple), arthroscopic drainage,or arthrotomy (open surgical drainage). (Aee :oint drainage above.)

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