Patients with diabetes are at an increased overall risk of infections, which is associated with increased morbidity and mortality. Some common infections that are seen in patients with diabetes are discussed in this article.

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Diabetes and infections

The patient with diabetes should be counselled about the common infection exclusively seen in patients with uncontrolled diabetes. Innate immunity disturbances have been associated with infections. Some uncommon but life-threatening infections occur almost exclusively in people with diabetes. Examples include the rhinocerebral form of mucormycosis, malignant otitis externa, Fournier gangrene and emphysematous forms of cystitis, pyelonephritis, and cholecystitis. The prevalence of viral infections such as Hepatitis C virus infection is high in patients with diabetes as compared to other forms of chronic liver disease and those without liver disease.

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Pathophysiology

Impaired phagocytosis by neutrophils, macrophages and monocytes, impaired neutrophil chemotaxis, and impaired innate cell-mediated immunity appears to be the most important systemic disturbances of the immune system. Multiple disturbances in innate immunity have a role in the pathogenesis of the increased prevalence of infections in people with diabetes.

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Infections involving the head and neck

Malignant otitis externa: Invasive infection of the external auditory canal and skull base that typically arises in elderly patients with diabetes. More than 91% of cases are caused by pseudomonas aeruoginosa, followed by aspergillus or other fungal infections. Systemic antipseudomonal antibiotics like quinolones have a good cure rate, prolonged treatment of 6-8 weeks is recommended. Patients usually are afebrile, with purulent discharge, severe otalgia and hearing impairment. Hallmark is the finding of granulation tissue usually at the junction of the cartilaginous and osseous portions of the canal. For infection caused by fungal infection treatment includes surgical debridement along with antifungals like voriconazole, posaconazole and amphotericin B.

Mucormycosis: This infection is essentially confined to immunocompromised individuals, caused by fungi of the rhizopus and mucore species. Disseminated forms along with rhino cerebral, pulmonary, gastrointestinal, and cutaneous forms are seen, rhino cerebral being the most lethal in patients with diabetes. Treatment mainly consists of surgical debridement, along with prolonged I/V therapy with amphotericin B or other antifungals.

Endophthalmitis: People with diabetes are prone to secondary Endophthalmitis due to metastatic complications of septicemia. In such cases, the most likely pathogens are E coli and Klebsiella. The treatment consists of broad-spectrum antibiotic.

Periodontal disease: Periodontal disease is very common in people with diabetes, particularly in patients with poorly controlled diabetes. Tooth abscesses and episodes of bacteremia also become more likely.

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Respiratory tract infection and tuberculosis

People with diabetes are approximately three times more likely to develop tuberculosis when compared to non-diabetic patients which also increases the risk of treatment failure. The association of TB with diabetes is attributed to impaired innate immunity as well as reduced adaptive T-helper type 1 response. Like other infections, Tuberculosis can also result in the deterioration of glycemic control and complicate the management of diabetes in such patients. To avoid oral diabetic drug interaction with tuberculosis drugs, some national treatment guidelines strongly recommend the use of insulin therapy in patients as there is no drug interaction seen with insulin.

Patients with diabetes are more prone to community-acquired pneumonia usually caused by Staphylococcus aureus. Annual vaccination is recommended for diabetic patients, especially the elderly.

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Infections of the urinary tract

Urinary tract infection: It’s very common in patients with diabetes. Asymptomatic bacteriuria also occurs in high frequency, upper UTI is five times more common in diabetic patients with bilateral involvement. Diabetes has been associated with the increased risk of complications of UTI, serious or unusual forms of infection and the need for prolonged hospitalisation. Diabetic autonomic neuropathy is an important predisposing factor for UTI along with age, duration of diabetes and degree of control of diabetes.

Pseudomonas aueroginosa should be suspected in patients with h/o recent hospitalisation. A poor response to appropriate antibiotic therapy should raise suspicion of the presence of complications like renal papillary necrosis and peripheric abscess.

Renal papillary necrosis: It is 5 times more common in diabetic patients with colicky pain in the flanks, fever, pyuria and chills. Suspicion in patients with persistent fever, and flank pain despite antibiotic cover should raise suspicion of pyelonephritis.

Renal abscesses: These can be either renal carbuncles (caused by Staph aureus) or corticomedullary abscesses (caused by E coli and proteus). This is due to reflux, obstruction or due to instrumentation. Symptoms reported are flank pain, fever with chills and severe abdominal pain.

Treatment consists of antibiotic coverage as per culture sensitivity and a prolonged duration of antibiotics (7- 14 days) is required to resolve the infection. Fungal UTIs should be treated with bladder irrigation with amphotericin, a single IV dose of amphotericin or oral fluconazole. For renal abscesses drainage along with antibiotic cover should be considered.

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Intrabdominal infections

Emphysematous cholecystitis: It is a rare variant of acute cholecystitis caused by ischemia of the gall bladder wall and infection with gas-producing organisms. It is strongly associated with patients with diabetes. Clostridium perfringens, E coli and Bacillus fragilis are frequently encountered organisms. The presentation is like cholecystitis, Murphy sign might be absent in patients with underlying diabetic neuropathy. Emergency surgery is needed due to the high incidence of gangrene and perforation.

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Skin and soft tissue infections

Skin infections are again commonly seen in patients with diabetes, particularly in association with poor glycemic control. Sensory neuropathy, atherosclerotic vascular disease and hyperglycemia predispose people with diabetes to skin and soft tissue infections. Staphylococcus aureus is the most common organism causing skin infections in patients. Balanitis and vulval candidiasis are common presenting features of diabetes.

Necrotising fasciitis: It is a deep-seated life-threatening infection of subcutaneous tissue, followed by the destruction of fascia, fat and muscle.

Fournier gangrene: It is a form of necrotising fasciitis which involves the perineum. Due to compromised immunity, diabetic patients are more prone to such infections. Polymicrobial infection is most commonly observed, with streptococcus and Enterobacteriaceae being the most commonly isolated. Timely diagnosis with broad-spectrum antibiotics with aggressive surgical debridement and fasciotomy is the mainstay of treatment.

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Infected diabetic foot

One of the common infections seen in diabetic OPD is related to peripheral neuropathy and peripheral vascular disease associated with diabetes. Serious complications include osteomyelitis and amputation. Infection often begins with minor trauma followed by cellulitis, soft tissue necrosis and ultimately reaching bone causing osteomyelitis. The organisms commonly involved are group A streptococcus and S. aureus as well as gram-positive cocci and gram-negative rods and anaerobes.

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Principles of treatment, prevention and general care

Education regarding good glycemic control is the foremost thing that should be counselled to the patients and general steps to maintain health and nutrition are all important measures aimed at minimising risk. Careful attention to foot care is particularly emphasised for all patients. The choice of antibiotic therapy should be followed the same general principles as for any individual without diabetes. The use of empirical broad-spectrum antibiotics is generally recommended until the microbiological results are available. In treating UTIs longer courses of antibiotic therapy may be appropriate.

Antiviral agents are recommended in the setting of influenza, and a more aggressive treatment approach may be appropriate even when the presentation is relatively late. The importance of appropriate referral to surgical or other specialist colleagues should be practised by the treating physician.

There is no contraindication for currently available vaccines just on the basis of diabetes alone. Because of increased susceptibility to complications, routine immunisation against pneumococcus and influenza is recommended, particularly for older people with diabetes or for those with additional co-morbidity such as chronic respiratory disease. Hepatitis B vaccination is also important although some populations may require additional or booster doses over and above standard recommended regimens.

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Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

About the author of this article: Dr Hitesh Saraogi is a diabetologist and physician at Dhanvantari Hospital, Raj Nagar Extension, Ghaziabad.