Approximately 30% of the human population is colonised by this commensal bacteria. This article addresses the most prevalent presentation and management of staph infections.

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Since the 1990s, two significant changes in S. aureus epidemiology have occurred: an epidemic of community-associated skin and soft tissue infections (primarily driven by certain methicillin-resistant S. aureus [MRSA] strains) and a rise in the frequency of healthcare-associated infections (especially infective endocarditis and prosthetic device infections).

Staphylococcus aureus is a serious pathogen for both communities and hospital-acquired illnesses. S. aureus resistant to methicillin was identified shortly after its release in October 1960. In India, the prevalence of MRSA among S. aureus isolates varies from 40 to 70 per cent, with variations reported in hospital and community settings.

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What's a staph infection and how does it spread?

Staph bacterium is carried on the skin by around 1 in every 4 persons. Unless they enter the body via a cut, Staph bacteria seldom cause damage. When this occurs, the bacteria may create an infection on the skin, resulting in an open sore, or infection of one of the body's systems. These systemic infections may be serious and even lethal.

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Different types of staph infection

Staph bacterias are capable of causing a wide range of infections, including:

• Skin infections, which lead to open sores
• Bacteremia and sepsis
• Infection of the bone (Osteomyelitis)
• Endocarditis
• Food poisoning
• Pneumonia
• Toxic shock syndrome (TSS) etc

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How does the infection spread?

Although many individuals carry staph germs on their skin or in their noses, not everyone will acquire a staph infection. Infection only happens when staph bacteria enter the skin or body through a cut, scrape, or contaminated food. Staph bacteria may be transmitted by skin-to-skin contact with an infected individual. Therefore, adopting excellent cleanliness is the greatest method to prevent a staph infection. In settings where people gather, such as public pools, schools, gyms, and residential facilities, proper cleanliness standards are crucial.

Clinical presentations

Depending on the kind of infection, the symptoms of a staph infection may include:

1. Infections of the skin may cause painful or swollen lumps or sores. They may include pus or other fluids, and a crust may develop. Cellulitis may cause discoloured and heated skin.
2. Osteomyelitis may cause discomfort, swelling, heat, and discolouration at the site of infection of the bone. They may also induce fever and chills.
3. Endocarditis is an infection of the endocardium of the heart. It produces flu-like symptoms, including fever, tiredness, chills, arrhythmia, and shortness of breath.
4. Food poisoning causes nausea, vomiting, diarrhoea, fever, and probable dehydration.
5. Pneumonia with a high fever, cough, chills, chest discomfort, and shortness of breath.
6. Toxic Shock Syndrome (TSS) causes hypotension, high temperature, vomiting, diarrhoea, and disorientation. Occasionally, a sunburn-like rash may also emerge.

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Management

Basic approach

The clinical presentation determines the therapeutic strategy for skin and soft tissue infections:

1. Patients with nonpurulent infections (i.e., cellulitis or erysipelas in the absence of abscess or purulent discharge) should be treated with empiric antibiotics.
2. Patients with drainable abscesses should undergo incision and drainage. In addition, antibiotic treatment is necessary if clinical conditions are met.
3. Patients with purulent cellulitis (i.e., cellulitis accompanied by purulent discharge in the absence of a drainable abscess) should be treated with antibiotics.

Treatment of underlying problems (such as oedema or underlying cutaneous abnormalities) is also part of management. Elevation aids oedema and inflammatory drainage. The skin should be properly moisturized to prevent dryness and cracking.

NSAID usage in cellulitis; some experts believe these medicines might disguise signs and symptoms of inflammation in individuals with necrotizing soft tissue infection, leading to delayed identification. While some evidence suggests that NSAIDs may speed up the healing process in people with cellulitis.

Oral vs parenteral treatment: Patients with mild infections may be treated orally. In the following cases, parenteral antibiotics are indicated:

1. Systemic indications of toxicity (e.g., temperature more than 100.5 degrees Fahrenheit (38 degrees Celsius), hypotension, or persistent tachycardia).
2. The rapid development of erythema.
3. Clinical progression after 48 hours of oral antibiotic treatment Inability to tolerate oral medication.
4. The proximity of the lesion to an implanted medical device (eg, prosthetic joint or vascular graft)
5. Individual clinical conditions, such as the severity of clinical presentation and comorbidities of the patient, should guide the decision to commence parenteral treatment.

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Pragmatic clinical strategy

Cellulitis 

1. Nonpurulent cellulitis (cellulitis without purulent discharge or exudate and no accompanying abscess) should be treated with empiric antibiotics for beta-hemolytic streptococci and methicillin-susceptible Staphylococcus aureus (MSSA) infection.
2. Cefazolin for intravenous treatment and cephalexin for oral therapy are common choices. After the commencement of antibiotic medication, erythema may become more intense.
3. This may be the result of the elimination of microorganisms that produce particles that exacerbate local inflammation and should not be confused with therapeutic failure.
4. Patients with cellulitis normally have symptomatic improvement within 24 to 48 hours after initiating antimicrobial treatment; however, noticeable improvement of clinical symptoms may take up to 72 hours in more severe instances.
5. After this period, persistent erythema and/or systemic symptoms should warrant examination of resistant infections or alternate diagnosis. In such instances, culture data should be carefully evaluated, radiographic assessment for deeper infection should be pursued, and it is feasible to expand antibiotic coverage to include gram-negative bacilli awaiting more diagnostic results.
6. The length of treatment should be tailored to the clinical response. Patients with simple cellulitis whose infection has improved within five to six days may discontinue treatment. In the presence of severe illness, sluggish response to medication, or immunosuppression, antibiotic therapy may be prolonged for up to 14 days.

Purulent infection: Purulent infection describes the presence of a drainable abscess or cellulitis with purulent discharge (in the absence of a drainable abscess). An infection including purulence (whether the process originated as an abscess [with secondary cellulitis] or as cellulitis [with secondary purulence]) may be caused by S. aureus, which should be noted in the selection of empiric antimicrobial treatment.

Drainable abscess present: Incision and drainage should be performed on patients with drainable abscesses. An oral antibiotic with action against MRSA and beta-hemolytic Streptococcus should be delivered one hour before the surgery to those at risk for endocarditis.

Role of antibiotic therapy: Antibiotics are favoured for individuals undergoing incision and drainage of a skin abscess. Particularly, antibiotic therapies are recommended for individuals with any of the following conditions :

• Multiple lesions
• Single abscess more than 2 cm
• Extensive surrounding cellulitis
• Comorbidities and associated immunosuppression
• Systemic signs of toxicity (eg, fever >100.5°F/38°C, hypotension, or sustained tachycardia)
• Inadequate clinical response to incision and drainage alone
• Presence of an indwelling medical device (such as a prosthetic joint, vascular graft, or pacemaker)
• High risk for adverse outcomes with endocarditis (these include a history of infective endocarditis, presence of prosthetic valve or prosthetic perivalvular material, unrepaired congenital heart defect, or valvular dysfunction in a transplanted heart)
• High risk for transmission of S. aureus to others (such as athletes or military personnel)

However, as many abscesses may be effectively treated with incision and drainage alone, professional opinion differs, and it is permissible to forego antibiotic treatment in otherwise healthy individuals with tiny abscesses (e.g., 2 cm in diameter) and none of the aforementioned risk factors. In individuals with numerous antibiotic sensitivities or intolerances, an antibiotic-sparing strategy may be especially persuasive.

Purulent cellulitis (no drainable abscess) 

Antibiotics should be administered to patients with cellulitis coupled with purulent discharge (in the absence of a drainable abscess). For all patients with a purulent illness, the strategy for empiric antibiotic selection is the same:

1. Patients with drainable abscess and relevant clinical criteria.
2. Patients with cellulitis and associated purulent drainage, in the absence of a drainable abscess.

At the start of antibiotic medication, it is beneficial to record the physical findings at baseline. A baseline digital picture should be captured for progress monitoring.

Pathogens to cover: In the absence of culture findings, patients with purulent infections should be treated with empiric treatment for MRSA infection.

Choosing an antibiotic agent: 

1. Clindamycin, TMP-SMX, and tetracyclines (doxycycline or minocycline) are all options for empiric oral treatment of purulent infection ( with action against MRSA).
2. The therapeutic effectiveness of clindamycin and TMP-SMX for the treatment of simple skin infections is equivalent. For oral coverage against MRSA, TMP-SMX, doxycycline, or minocycline are commonly preferred; clindamycin is used less often because of its increased risk of Clostridioides difficile infection.
3. Oxazolidinones (linezolid or tedizolid), delafloxacin, and omadacycline are further anti-MRSA medicines; they should be kept for situations in which none of the other regimens described may be used.
4. Optional parenteral treatments for MRSA include vancomycin and daptomycin.

Duration of therapy: 

1. The optimal length of therapy for the treatment of skin and soft tissue infections depends on the clinical presentation and should be guided by the clinical response.
2. After 24 to 48 hours, patients with mild infections requiring outpatient treatment with oral antibiotics should be reevaluated to determine clinical response. Patients with MRSA who respond to oral medication are normally treated for 5 days; however, in cases of severe infection, sluggish response to therapy, or immunosuppression, the time may be extended to 14 days.
3. Lack of response may be related to infection with the resistant organism(s), insufficient adherence, or the existence of a more severe illness than previously thought.
4. Patients with infections requiring parenteral treatment (without bacteremia or involvement beyond soft tissue) are routinely treated for 5 to 14 days. Once there are indications of clinical improvement and no evidence of systemic toxicity, parenteral antibiotics may be switched to oral antibiotics.
5. For patients with a radiographically identified abscess, follow-up imaging may be beneficial for evaluating therapeutic response.

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Treatment of MRSA infections in India:

The management of Staphylococcus and MRSA infections in India is illuminated by a recently published study.

General comments

1. MRSA prevalence in India may vary between 32% and 80% of the S. aureus population.
2. The treatment of MRSA bacteremia involves immediate source management (such as removal of involved vascular catheters and/or drainage of purulent collection, if present) and a quick beginning of effective antibiotic medication.
3. Vancomycin or teicoplanin are the recommended treatments for MRSA.
4. Teicoplanin may be substituted for vancomycin when nephrotoxicity is a concern.
5. Daptomycin is another effective treatment for invasive MRSA infections.
6. As an alternate treatment for MRSA, telavancin, ceftaroline, and linezolid may be utilised.

Skin and soft tissue infections

1. The percentage of Staphylococcal SSTIs caused by MRSA varies widely, ranging from 7 per cent to 70 per cent.
2. All critically sick SSTI patients should get empiric MRSA coverage. It should also be explored in patients with recurrent non-critical SSTI who did not respond to earlier treatment and for whom acceptable cultures were sent.
3. Clinical and epidemiologic criteria alone are insufficient to predict the probability of MRSA infection.
4. In uncomplicated cutaneous abscesses or furuncles, incision and drainage are preferred over the use of antibiotics.
5. Vancomycin or teicoplanin should be the first-line treatment for MRSA in complex SSTIs.
6. Daptomycin/ceftaroline are further choices for empirical treatment.
7. The definitive treatment relies on the susceptibility of the isolate and may include clindamycin and cotrimoxazole, among others.
8. One week is the optimal period of therapy for SSTIs without complications.
9. Two to three weeks is the optimal period of therapy for complicated SSTIs.

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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.

The author is a practising super specialist from New Delhi.