Community Acquired MRSA From PedsCases

In this post, I link to and excerpt from PedsCasesCommunity Acquired MRSA,
by Jordanna Roesler Oct 30, 2021.

All that follows is from the above resource.

This podcast presents an overview of community acquired methicillin-resistant Staphylococcus aureus (MRSA). This episode will discuss its common clinical presentations, describe common treatment options, identify risk factors and highlight the importance of antimicrobial resistance and stewardship. This podcast was developed by Jordanna Roesler, a medical student at the University of British Columbia, under the guidance of  Dr. Wingfield Rehmus, a pediatric dermatologist at BC Children’s Hospital and the University of British Columbia, Dr. Jennifer Tam, a pediatric infectious disease specialist at BC Children’s Hospital and the University of British Columbia, and Dr. Laura Sauvé, a pediatric infectious disease specialist at BC Children’s Hospital and the University of British Columbia, and the chair of the CPS Infectious Diseases committee.

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In this podcast, we will discuss community acquired methicillin-resistant Staphylococcus aureus skin infections, an emerging issue in the pediatric population.


You are a third-year medical student at a busy pediatric
clinic and your preceptor asks you to see Rachel, a 12-year-old girl brought in by her mother.

Rachel’s mother is concerned about a purulent lesion on Rachel’s right lower limb, which she says looks like a “spider bite”. Upon further questioning, Rachel’s mother tells you that their family had just come back from a picnic when she noticed the
mark on Rachel’s right lower leg. Rachel’s mother is very worried that Rachel may have been bitten by a spider and about the possibility of an infection. Rachel describes her lesion as red, very painful, and “icky”.

You recall that sometimes lesions caused by antibiotic resistant Staph. aureus are misdiagnosed as spider bites (Dominguez, 2004). Let’s discuss the clinical presentation and differential diagnosis for Staph. aureus infections so we can work through Rachel’s case.

Clinical Presentation and Differential Diagnosis:

Recall that Staph. aureus are gram-positive, aerobic bacteria that are cocci-shaped and arranged in clusters. While skin and soft tissue infections are more common, Staph. aureus can also cause more serious illnesses such as pneumonia, bacteremia, and osteomyelitis (Robinson and Salvadori, 2011). Today we will focus on the various clinical presentations of skin and soft tissue infections caused by Staph. aureus.

Staph. aureus is a common cause of many skin and soft tissue infections, and both methicillin-susceptible Staph. aureus (or, MSSA) and methicillin-resistant Staph. aureus (MRSA) should be considered when a child presents with a skin and soft tissue infection (Robinson and Salvadori, 2011).

The spectrum of presentation is wide, ranging from asymptomatic skin and soft tissue infections, to life-threatening invasive infection. Typically, community acquired MRSA
presents as a skin and soft tissue infection.


If your history and physical exam has allowed you to diagnose a specific type of skin infection, a diagnostic sample should be sent if possible.

If incision and drainage is done, a sample should be sent to the microbiology lab to identifythe bacteria and susceptibility profile.

It is optimal to send a sample of purulence to the lab, as a swab
alone has a lower yield than aspirated purulence. If you can’t aspirate purulence, then you can swab the skin; however, keep in mind that a swab of intact skin is unlikely to be helpful.

A gram stain and culture with susceptibility testing is the only way that MRSA can be distinguished from methicillin- susceptible Staph. aureus (also known as MSSA) and A gram stain and culture with susceptibility testing is the only way that MRSA can bedistinguished from methicillin-susceptible Staph. aureus (also known as MSSA) and other viral or bacterial causes (Heilpern, 2007). The results of the culture will also guide
your treatment choices (Miller et al., 2007).


Let’s return to our case. You decide to swab the purulent aspect of the abscess and send it for cultures. You then incise and drain the abscess.

Your preceptor mentions that if Rachel had been systemically ill then more investigations, like a blood culture, may have been completed. You discuss that other reasons for ordering a blood culture include immunodeficiency and neutropenia. Otherwise, children with uncomplicated skin and soft tissue infections generally do not require blood cultures (Trenchs et al., 2015)

You ask Rachel’s mom to follow up with the clinic if there isn’t any improvement within 48 hours or if Rachel becomes systemically ill. You also remind Rachel and her mom to not share any personal items such as towels and sports equipment.

Later, the culture returns positive for gram positive cocci in clusters and susceptibility testing confirms the diagnosis of community acquired MRSA.

Antimicrobial Resistance:

Community acquired MRSA is resistant to all beta-lactam antibiotics, therefore cephalosporins, such as cephalexin, and penicillins, including cloxacillin, should not be used (Irvine, 2012).

The choice of non-beta-lactam antibiotic depends on the local
antibiogram and susceptibility patterns. Some more specific antibiotic choices to consider will be described shortly. Unfortunately, resistance to many of the commonly prescribed antibiotics such as mupirocin, fluoroquinolones, tetracyclines, and clindamycin is on the rise, leading to issues of increasing antimicrobial resistance (Styers, et al., 2006). Therefore, it is important to promote antibiotic stewardship and adhere to health authority guidelines outlining the responsible use of antimicrobials to help reduce the rate and risk of increasing resistance.

Management and Treatment of CA-MRSA Skin Abscesses: (Robinson and Salvadori, 2011)

Let’s discuss the management and treatment of community acquired MRSA skin abscesses as outlined by the Canadian Pediatric Society, also known as CPS. The CPS has provided statements and a treatment table outlining the management options of community acquired MRSA skin abscesses in infants and children. While drainage of community acquired MRSA skin abscesses is usually sufficient for previously healthy children who are older than three months of age with an uncomplicated skin abscess, certain cases may require antibiotics. These cases include:

See p. 10 of the script PDF for treatment recommendations.


Antibiotics used to treat community acquired MRSA should be chosen based on the severity of infection or disease, patient factors, the route of administration, and cost in order to promote positive patient outcomes (Nemerovski and Klein, 2008).

Generally, Trimethoprim/sulfamethoxazole (TMP-SMX) is well tolerated, covering both MSSA and community acquired MRSA. Therefore, it is often used in the case of an uncomplicated abscess warranting antibiotics (Robinson and Salvadori, 2011).

TMP/SMX is generally not used in neonates due to the concern that sulfamethoxazole may displace bilirubin from albumin and lead to hyperbilirubinemia and kernicterus (Wadsworth and Suh, 1988).

Clindamycin is another option if susceptible; however, more community acquired MRSA isolates have shown to be resistant, and clindamycin may increase the risk of Clostridium difficile colitis (Robinson and Salvadori, 2011). Also, the liquid formulation is unpalatable, so it may not be well tolerated in young children that cannot swallow tablets.

Doxycycline* is another antibiotic that treats MRSA, but it is used less often in the pediatric population due to previous concerns regarding tooth discoloration, and it is only available in pill form. Linezolid is another oral antibiotic that could be used; however, it is cost-prohibitive and therefore not recommended in cases of uncomplicated skin abscesses (Robinson and Salvadori, 2011).

*Please see When can doxycycline be used in young children? from AAP News. H. Cody Meissner, M.D., FAAP, February 27, 2020.

Take Home Messages:

1. Risk factors for community acquired MRSA include frequent use of antibiotics, challenges in maintaining personal hygiene, overcrowded living conditions, sharing personal items, recent skin trauma, atopic dermatitis, and skin-skin contact. Remember though, many children with community acquired MRSA may not have any risk factors.
2. Community acquired MRSA can lead to systemic illness such as septic arthritis, pneumonia, osteomyelitis, necrotizing fasciitis, and sepsis.
3. A swab and culture are needed to definitively diagnose a lesion suspected to have been caused by community acquired MRSA.
4. Drainage alone (with no antibiotics) is preferred for community acquired MRSA skin abscesses in children older than 3 months of age without significant cellulitis. However, antibiotics may be used in addition to drainage in infants
under three months of age, and in children with underlying medical conditions, systemic symptoms, or extensive cellulitis.
5. Antimicrobial resistance is an ongoing health issue, and it is important to promote antibiotic stewardship to help reduce the rate and risk of antimicrobial resistance

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