Infections in Patients With Diabetes

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Infections in Patients With Diabetes

Disclosures

http://www.medscape.com/viewarticle/510525

August 19, 2005

Zarbock

Infections in Patients With Diabetes

JoAnn Deasy, PA-C, MPH, a practitioner with the California Emergency

Physicians at San Mateo General Hospital, presented the session

on " Infections in Patients With Diabetes " at the American Academy of

Physician Assistants' annual conference in June 2005. Deasy is also

a faculty member with the Pace University Physician Assistant

Program and Touro University California Physician Assistant Program.

Deasy cited statistics indicating that about 18.2 million Americans

(6.3% of the population) have diabetes, although 5.2 million don't

know they have it.[1] Patients with diabetes are predisposed to

infections. One study compared all people with diabetes mellitus

(DM) in Ontario, Canada, on April 1, 1999 to matched non-DM controls.

[2] Study investigators calculated the risk ratios of having an

infectious disease and of death due to infectious disease. Nearly

half (46%) of all people with diabetes had at least 1

hospitalization or outpatient visit for infections compared with 38%

of controls without diabetes. The risk ratio for diabetic vs

nondiabetic persons was 1.21. The risk ratio for infectious disease-

related hospitalization was up to 2.17, and was 1.92 for death

attributable to infection.

Many individual infections are more common in people with diabetes,

Deasy remarked, including pneumonia caused by certain organisms;

pyelonephritis; soft tissue infections, including the " diabetic

foot " ; necrotizing fasciitis; and mucocutaneous Candida infections.

Others occur almost exclusively in diabetics: invasive (malignant)

otitis externa, rhinocerebral mucormycosis, and emphysematous

infections (cholecystitis and pyelonephritis). Some infections

result in increased severity when they occur in diabetic patients

and are associated with increased complications. Data from a study

by Bertoni and colleagues[3] suggest that diabetic adults are at

greater risk for infection-related mortality, and that excess risk

may be mediated by cardiovascular disease (CVD). The study authors

found that when diabetes was combined with CVD, the relative

mortality risk was 3.0 (1.8-5.0), while diabetic patients without

CVD had a risk of 1.0 (0.5-2.2).

Infections also cause considerable morbidity and mortality in

patients with diabetes. They may precipitate metabolic derangements

and, conversely, the metabolic derangements of diabetes may

facilitate infection.[4] Several immune function factors are related

to this increased risk, Deasy said. First, neutrophil function is

depressed, affecting adherence to endothelium, chemotaxis, and

phagocytosis. The antioxidant systems involved in bacteriocidal

activity may be compromised, and cell-mediated immunity is probably

depressed. These impairments are exacerbated by hyperglycemia and

acidemia but are reversed substantially, if not entirely, by

normalization of pH and blood glucose levels.[4,5]

Head and Neck Infections

Two head and neck infections that are associated with high rates of

morbidity and mortality -- invasive (malignant) otitis media and

rhinocerebral mucormycosis, are seen almost exclusively in diabetic

patients.

Invasive ( " malignant " ) otitis media is an uncommon but potentially

life-threatening infection, almost always due to Pseudomonas

aeruginosa. It slowly invades from the external canal into adjacent

soft tissues, mastoid, and temporal bone and eventually spreads

across the base of the skull. Of note, invasive otitis media occurs

primarily in elderly diabetic patients whose diabetes is under

control. Patients report a history of weeks to months of severe

pain, otorrhea, and hearing loss. Intense cellulitis is combined

with edema of the ear canal. Deasy made clear that cellulitis is

often misdiagnosed as chronic otitis media, an entity that is rarely

painful. Laboratory studies generally reveal a normal white blood

cell count but a high erythrocyte sedimentation rate. CT and MRI

studies are essential for defining the extent of bone and soft-

tissue involvement. CT shows bony destruction of the skull base in

advanced cases. Surgical debridement is an essential part of

therapy. Intravenous antipseudomonal antibiotics, such as

quinolones, should be started at once.[6]

Rhinocerebral mucormycosis is a life-threatening fungal infection,

most often due to Rhizopus, Absidia, and Mucor species.[7] Patients

present with facial or ocular pain and nasal stuffiness; generalized

malaise and fever may also be present, although they may appear

nontoxic. Intranasal black eschars or necrotic turbinates may be

found. Deasy emphasized that these sites should be biopsied and

frozen tissue sections should be examined by a pathologist.

Treatment consists of surgical debridement of the involved sinuses

and prolonged intravenous therapy with amphotericin B. Untreated,

this entity is universally fatal; if recognized early, there is a

20% survival rate.[7]

Pulmonary Infections

Overall, any respiratory infection in diabetic patients is

associated with increased mortality. Diabetic persons are 4 times

more likely to die from pneumonia or influenza than are nondiabetic

persons.[8]

Specific infections, such as those caused by Staphylococcus aureus

and gram-negative organisms, are more frequent in diabetes.

According to one study, up to 30% of diabetics are nasal carriers of

S aureus as compared with 11% of healthy individuals. On the basis

of their high nasal carriage rate, diabetic persons are thought to

be at an increased risk for S aureus pneumonia.

More common organisms, such as Streptococcus pneumoniae, Legionella,

and influenza are associated with increased morbidity and mortality.

[9] Antiviral agents are recommended treatment in the setting of

influenza. Diabetic persons have a normal response to vaccines.

Because of diabetic patients' increased susceptibility to

complications, routine immunization against pneumococcus and

influenza is recommended for all patients.[5]

Genitourinary Infections

Deasy said that asymptomatic bacteriuria, defined as > 105 CFU per

milliliter of urine, is 3 times more common among diabetic than

nondiabetic women. However, there is no difference in the

development of symptomatic urinary tract infection (UTI), time to

onset of symptoms, pyelonephritis, or need for hospitalization.[10]

Consequently, diabetes is not an indication for screening for or

treating asymptomatic bacteriuria.

The symptoms and signs of cystitis in the diabetic patient are the

same as for nondiabetic patients. However, because of the high

incidence of unsuspected upper tract UTI in diabetic persons, the

recommendation is to consider 7- to 14-day treatment with

antibiotics.[11] In addition, owing to the incomplete bladder

emptying associated with cystitis in conjunction with the high

glucose concentrations in the urine, Candida albicans may also be

seen.

Emphysematous cystitis is a rare complication characterized by the

presence of gas in the bladder wall and presents with gross

hematuria, pneumaturia, and chronic abdominal pain. It often

responds to intravenous antibiotic therapy.

Bilateral pyelonephritis is twice as common in patients with

diabetes and predisposes to a more severe infection of the upper

urinary tract. Emphysematous pyelonephritis is almost exclusively an

infection of diabetics and carries a grave prognosis.[11] A flank

mass, which can be accompanied by crepitus, is present in 60% of

cases. The diagnosis is established by identifying gas in renal

tissue, which is well demonstrated by CT. Treatment includes rapid

supportive measures and intravenous antibiotics. The overall

mortality is 30%; nephrectomy is the treatment of choice in most

patients.

Abdominal Infections

Although cholecystitis is probably no more common in patients with

diabetes than in the general population, severe fulminating

infection, especially with gas-forming organisms (enteric gram-

negative rods and anaerobes) is more common.[4] The early clinical

manifestations are similar to those of acute cholecystitis, with

gallstones present in only 50% of patients. Crepitus on abdominal

exam may be present but clinical signs of peritonitis may be absent.

Deasy noted that even with cholecystectomy and broad-spectrum

antibiotics, this virulent infection is associated with gangrene and

perforation and has a 15% mortality.

Skin and Soft Tissue Infection

Diabetic patients appear to have skin infections more often than

their nondiabetic counterparts. Sensory neuropathy, atherosclerotic

vascular disease, and hyperglycemia all predispose diabetic patients

to skin and soft-tissue infections. Blood glucose levels > 250 mg/dL

significantly increase a patient's risk for soft-tissue infection.

[4] Other risk factors for the development of cellulitis include a

past history of cellulitis, edema, peripheral vascular disease,

tinea, and dry skin. The predominant organisms are group A

streptococcus (GAS) and S aureus.

Of great concern to the general public but especially to people with

chronic diseases, such as diabetes, Deasy remarked, is the increase

in community-associated methicillin-resistant S aureus (CA-MRSA). A

recent report in The New England Journal of Medicine[12] evaluated

CA-MRSA in 3 communities and found that 77% of skin or soft tissue

infections were methicillin-resistant. The underlying conditions in

patients 18 years or older in this study were smoking (35%),

previous skin infection (21%), and diabetes (19%).

Outpatient antibiotic treatment of cellulitis for GAS and

methicillin-susceptible Staphylococcus aureus (MSSA) includes

dicloxacillin or cephalexin (Keflex). However, because these do not

cover CA-MRSA, doxycycline or trimethoprim-sulfamethoxazole is

necessary. One way to evaluate treatment efficacy is to draw a line

surrounding the area of cellulitis and observe, over time, whether

the infection is spreading or receding.

Necrotizing fasciitis is a deep-seated, life-threatening infection

of subcutaneous tissue with progressive destruction of fascia, fat,

and muscle. The infection risk increases in diabetes, alcoholism,

and intravenous-drug users (IVDU). Ninety percent of cases are

caused by anaerobes and 1 or more facultative aerobes; 10% are

associated with GAS, with or without S aureus. Deasy emphasized that

clinical features include pain out of proportion to skin findings

and anesthesia of overlying skin. There is violaceous discoloration

of the skin that evolves into vesicles and bullae; crepitus is seen

in half of cases. Soft tissue gas is seen on radiograph or CT.

Immediate aggressive surgical debridement is necessary as are broad-

spectrum intravenous antibiotics.

A recent article described necrotizing fasciitis caused by CA-MRSA;

although current or past IVDU represented 43% of patients, 21% were

patients with diabetes.[13]

Diabetic Foot Infections. Foot infection is the most common soft

tissue infection associated with DM, with disease-related peripheral

neuropathy and peripheral vascular disease playing major roles in

this complication of diabetes. More serious complications include

osteomyelitis, amputation, and death. Infection begins after minor

trauma and may progress to cellulitis, soft tissue necrosis, and

extension into bone.

Deasy stated that exploration of the ulcer is crucial to determine

the depth of the ulcer (the palpable bone strongly suggests

osteomyelitis). It is also important to determine the presence of

sinus tracts and to obtain a culture. Involved organisms include GAS

and S aureus, as well as aerobic gram-positive cocci, gram-negative

rods, and anaerobes.

Outpatient management of foot ulcers begins with debridement of the

necrotic tissue and administration of antibiotics including

dicloxacillin, cephalexin, augmentin, and clindamycin (for CA-MRSA).

In moderate-to-severe cellulitis that places the limb at risk, the

patient should be hospitalized for broad-spectrum antibiotic therapy

and surgical intervention.

Prevention of foot ulcers involves a multidisciplinary team

approach. Daily foot care should be included in patient education,

and proper foot care habits, such as protective footwear and

pressure reduction, should be reinforced at every office visit. As

in most diabetes-related infections, glycemic control plays an

important role.

Deasy concluded that vigilant measures should be instituted to

prevent infection in diabetic patients. She further emphasized that

when infections do occur, evolving resistance patterns must be

considered.

References

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