By Al Kline DPM

 

Group A streptococcal infections are caused by the group A streptococcal bacterium.  In 2000, the Centers for Disease Control (CDC) reported 8,800 cases of severe group A streptococcal (GAS) infections, a rate of 3.1 per 100,000 people.   It is estimated that over 10 million of these infections present annually.  The streptococcal bacterium is especially tissue toxic when presenting in the leg and foot.  The bacterium is responsible for a variety of infections ranging from strep throat to TSS (toxic shock syndrome).  In the foot, it is most commonly associated with necrotizing fasciitis and secondary tinea pedis infections.  When it infects the dermis and epidermis it has commonly been called  flesh-eating disease due to its tissue destructive nature and appearance.  Cellulitis is associated with inflammation and infection of the skin structures and underlying subcutaneous tissues where abscesses can form.  Erysipelas is associated with the more superficial layers of the epidermis.  St. Anthony’s Fire,  as more commonly called in the middle ages, group A streptococcus pyogenes is the primary cause of erysipelas in the lower extremity and foot.  The NIH recently reported an increase in group A streptococcal infections presenting in children with Impetigo which has traditionally been a staphylococcal disease.  In other research by the NIAID and NIH, health experts have identified over 120 different strains of group A streptococci, which produce their own unique proteins.  This may prove to be a challenge in providing proper antibiotic treatment as newer strains immerge.   To date, penicillins and other beta lactams are the treatment of choice for group A streptococcus and no resistant strains has been reported.  As further study of the DNA protein sequences continue, new vaccines are emerging to combat this troublesome infection.  As a result of this research, the first group A streptococci vaccine clinical trial in over 30 years was conducted.  The vaccine proved effective in not only strep throat, but a host of other infections including rheumatic fever and impetigo in children. 

 

In the foot, vaccines to prevent primary and secondary group A strep pyogenes infections have not been researched.  It would be interesting to research such vaccines to prevent these infections in patients most susceptible to this destructive foot infection.  The diabetic, vascularly compromised and immunocompromised patients are the most susceptible to this type of foot infection.   Probably the most commonly seen strep infection follows secondary bacterial infection and inoculation from tinea pedis.  Acute tinea can cause blister formation and set the stage for secondary bacterial infection.  Historically, staphylococcal infections came to the forefront.  More recently, these secondary infections are attributed to streptococcal group A infections, diptheroid bacilli, e.coli and enterobacter bacilli.    This is especially true when patients present with ulcerative type lesions to the interspace and a flesh-eating appearance in-between the toes following a case of uncontrolled tinea pedis.  A case is presented to highlights such a condition.

 

Case Presentation 

A 37 year old diabetic patient presents on consultation in the emergency room.  The patient reports to pain and infection of the right foot.  According to the patient, about 3 to 4 days prior to her presentation, she began to note blisters to her toes with wheeping to the interspaces of the right foot only.  She relates to buying a second-hand pair of tennis shoes at a garage sale and wearing the shoes without socks.  Shortly, thereafter, her right foot began to swell and the erythema began to spread quite rapidly.  On clinical evaluation, she had severe ‘wheeping’ and ulcerative changes to the interspaces of the foot with frank erysipelas and cellulitis to the forefoot and dorsum of the foot.  Laboratory data reveals a serum blood sugar of 598 ug/dl that required IV insulin treatment in the emergency room.  She denied any fevers, chills, nausea or vomiting.  Her admitting temperature is 98 with a stable blood pressure.   Other pertinent laboratory data revealed a 15,000 white cell count with left shift.  The patient has no drug allergies and is presently on Depakote, Xanax, Glucophage and other medications she cannot recall.  She denies alcohol or tobacco abuse.  She was admitted  to the hospital floor with further evaluation.

 

Cultures and Treatment Protocol 

 

There was no indication for blood cultures due to her lack of fever.  She was placed on  Zosyn 3.75 gm IV q6 hours after local tissue and swab cultures were performed.  This process was very painful and the patient was placed on narcotics prior to culturing.  X-rays were ordred to rule out gas producing changes and/or possible gas gangrene/necrotizing fasciitis in the forefoot. 

An MRI was also ordered which identified cellulitis involving digits two through five.  The phalanges of those digits revealed increased enhancement.  The first proximal and distal phalanges also reveal increased enhancement.  No fluid collection is present suspicious for abscess.  The impression reveals an enhanced suspicion for osteomyelitis involving the phalanges of digits one through five.  Here, in fig. 1, there is enhancement noted to the 2nd interspace, but located more dorsally in the soft tissues.  Clinical correlation helps us to differentiate the probability of osteomyelitis.  In this patients case, there was no penetration into the interspaces or tracking abscesses.  Erosional and ulcerative changes are noted, however, the likelihood of osteomyelitis is unlikely without penetration of the joint space. 

Sagital sequencing along the long axial axis reveals some T1 enhancement imaging as the images work down from top to bottom.  Again, here in these views, there is some enhancement to the 2nd interspace region and diffuse enhancement to the interspaces more consistent with cellulitis.  The cultures results revealed GAS pyogenes with multi contaminant organisms including diptheroid bacilli, e.coli and enterbacter agglomerans group.  The group A streptococcal speciesis highly susceptible to Zosyn which is piperacillin ( a synthetic penicillin) and tazobactam (a beta lactamase inhibitor).  Zosyn is ideal for moderate to severe infections caused by piperacillin-resistant and pieracillin/tazobactam-susceptible strains.  The e.coli and enterobacter are all susceptible organisms to piperacillin/tazobactam combination.  It was questionable if the gram positive rods of diptheroid bacilli were susceptible to Zosyn, so Vancoymcin was added as a secondary IV antibiotic to combat gram positive infection.  The patient was also placed on 750mg of Griseofulvin daily during the IV antibiotic phase of treatment since fungal infection was a precursor organism.  It is recommended you give Griseofulvin 750mg in divided doses (such as 250mg TID). 

Parenteral treatments included daily washes with chlorohexidine gluconate soap, Domeboro’s soaks (Aluminum Acetate), interspace separation with 2×2 gauze, whirlpool and daily dressing changes.

 

Summary 

 

Group A streptococcal infections of the foot are common as a secondary infection to tinea pedis, especially within the interspaces of the foot.  It appears to breakages in the skin with blister formation can predispose the diabetic patient to streptococcal infections.  In this case, her susceptibility to infection was heightened due to her elevated hyperglycemia and poor diabetes control. 

Along with antibiotic treatment, antifungal treatment is recommended along with parenteral treatments including cholorohexidine gluconate washes, interspace separation, whirlpool irrigation and daily wound care and dressing changes.  Antibiotic treatment of choice for this infection is Zosyn or any penicillin antibiotic or other beta lactams approved by the FDA for treatment of streptococcal pyogenes.  Susceptibility testing is usually not required since, as with vancomycin, resistant strains have not been recognized to date. 

 

 

 

References

 

 

 Davis, L., Benbenisty, K.  Erysipelas  eMedicine Online article.   

 

 

Health Matters:  Group A Streptococcal Infections.  HIAID, NIH, Nov. 2005. 

 

 

Nucleus Medical Reference Library:  Group A Streptococcal Infections – Severe.  Online article .   

 

 

Wyeth-Zosyn.com 

 

 

© Al Kline DPM, 2006 

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