Peds ID Board ReviewGuada Lopez-Marti, MD

June 2011

Question 1

The lab reports the growth of community-associated methicillin-resistant Staphylococcus aureus (MRSA) from a culture you submitted of ear drainage from a 3-year-old child you admitted with chronic otitis externa. Nursing personnel and house staff ask what infection control measures you recommend for the child.

Of the following, in addition to standard precautions, your BEST recommendation is to:

A.institute airborne isolation for the child B.institute droplet isolation for the child C.limit the child’s visitors to parents wearing gowns and gloves D.move the child to a negative-pressure room and prohibit

visitors E.move the child to a private room and start contact isolation

Answer 1: E move the child to a private room and start contact isolation

The child described in the vignette should be placed in contact isolation and moved to a private room, if possible, because he has ear drainage due to a drug-resistant pathogen

Such actions would be reasonable for any child known to harbor a drug-resistant organism, particularly multiply-resistant ones

Neither placing him in a negative-pressure room nor adding airborne or droplet precautions is appropriate, although contact and droplet precautions are recommended for group A streptococcal skin and soft-tissue infections

There is no need to limit visitors, although anyone visiting should adhere to appropriate infection control measures

Question 2

You are evaluating a 3-day-old infant who has been feeding poorly for 1 day and developed left knee swelling 8 hours ago

She was born at term by vaginal delivery to a 20-year-old woman who had no prenatal care but reports that she had an uneventful pregnancy

Physical examination shows a lethargic, jaundiced infant whose vital signs are within normal limits for age. She has purulent discharge from both eyes and swelling around the left knee and right ankle. You obtain a Gram stain of the synovial fluid drawn from her left knee (Figure)

Figure

Cont

Of the following, the MOST appropriate antibiotic to treat this infant’s infection is:

A. ampicillin B. cefotaxime C. ceftriaxone D. gentamicin E. vancomycin

Answer 2: B cefotaxime

The neonate described in the vignette has disseminated gonococcal infection manifesting clinically as ophthalmia neonatorum and septic arthritis of the left knee and ankle.

The causative agent, Neisseria gonorrhoeae,is anonmotile, aerobic, gram-ne coccus that typically occurs in pairs (diplococci)

Gonorrhea is transmitted exclusively through vertical transmission, as in this case, or sexual contact.

Based on current susceptibility patterns of N gonorrhoeae strains, extended-spectrum cephalosporins are the drugs of choice for treatment in the United States

Ceftriaxone should be used with caution in preterm neonates and neonates who have hyperbilirubinemia, such as the infant described in the vignette

For treatment in patients with hyperbilirubinemia, cefotaxime becomes the agent of choice

Question 3

You are consulted in the neonatal intensive care unit (NICU) about treatment for late-onset sepsis in a 4-week-old infant who had been born at 25 weeks’ gestation. The neonatal fellow reports that the infant has developed shock, metabolic acidosis, and anuria. Laboratory values include a white blood cell count of 2.55x109/L with 15% bands, 10% segmented neutrophils, and 75% lymphocytes and a platelet count of 33x109/L

Of the following, the MOST appropriate empiric antimicrobial regimen for this infant is:

A. ampicillin and gentamicin B.ceftazidime and gentamicin C.vancomycin, ceftazidime, and fluconazole D.vancomycin, ceftazidime, and gentamicin E.vancomycin, rifampin, and gentamicin

Answer 3: Dvancomycin, ceftazidime, and gentamicin

Late-onset infection in a very low-birthweight (VLBW) infant in the NICU frequently is caused by gram-negative bacteria and is associated with high mortality

In one series, Pseudomonas infection accounted for 2.7% of late-onset infection in VLBW infants

Mortality rates differed significantly between gram-positive infections (11.2% died), all gram-negative infections (36.2%), and sepsis caused by Pseudomonas (74.4%)

Therefore, aminoglycosides are indicated for the infant described in the vignette, despite the worsening renal function because of the high index of suspicion of late-onset sepsis, which has a chance of being caused by P aeruginosa

P aeruginosa infection is relatively uncommon in pediatrics, with most infections occurring in hospitalized patients

P aeruginosa is an opportunistic pathogen that rarely causes disease in healthy persons

Question 4

A very low-birthweight infant, who was born 10 days ago at 29 weeks’ gestation, is receiving parenteral nutrition via a peripherally inserted central catheter. You are consulted because a blood culture obtained when he developed abdominal distention, apnea, and bradycardia becomes positive. 

Of the following, the MOST likely organism causing this infection is:

A.Candida albicans B.Escherichia coli C.Staphylococcus aureus D.Staphylococcus epidermidis E.Streptococcus agalactiae

Answer 4: DStaphylococcus epidermidis

Neonatal bloodstream infection occurring beyond 7 days of age is designated late-onset sepsis (LOS)

The most common cause of LOS, particularly in the very low-birthweight neonate, such as the infant described in the vignette, is coagulase-negative Staphylococcus (CoNS), the prototype of which is S epidermidis

The next most common causes of LOS in preterm infants are Candida albicans and S aureus. Escherichia coli and other enteric gram-negative rods, and Pseudomonas aeruginosa

Streptococcus agalactiae does cause LOS, but it is implicated more often in early-onset infection

As pathogens, CoNS almost exclusively cause health-care-associated disease in hosts who have underlying broadly defined compromise

Question 5

You are asked to evaluate a child who has refractory staphylococcal toxic shock syndrome characterized by continued oliguria and hypotension, despite fluid resuscitation, resulting in pulmonary edema. Her antibiotic therapy includes vancomycin and clindamycin. The intensivist and residents ask what additional therapeutics you suggest.

Of the following, your MOST likely recommendation is the addition of:

A.an antistaphylococcal monoclonal antibody B.dexamethasone C.immune globulin intravenous D.polyclonal antistaphylococcal capsular polysaccharide

immune globulin E.polyspecific antistaphylococcal superantigen

immunoglobulin

Answer 5: Cimmune globulin intravenous

The use of immune globulin intravenous may be considered in staphylococcal toxic shock for: 1) infection refractory to several hours of aggressive therapy, 2) an undrainable focus, or 3) persistent oliguria with pulmonary edema, as described for the child in the vignette

The data to support the use of corticosteroids for refractory toxic shock are few and contradictory

Polyclonal antistaphylococcal capsular polysaccharide immune globulin, polyspecific antistaphylococcal superantigen immune globulin, and an antistaphylococcal monoclonal antibody (tefibazumab) are in early human trials and remain promising, but as yet unproven, adjuncts to antibiotic therapy

Cont. Management of Staphylococcal Toxic Shock Syndrome  

 Fluid management to maintain adequate venous return and cardiac filling pressures to prevent end-organ damage

Anticipatory management of multisystem organ failure

Parenteral antimicrobial therapy at maximum doses

- Kill organism with bactericidal cell wall inhibitor (eg, beta-lactamase–resistant antistaphylococcal antimicrobial agent)

- Consider therapy for methicillin-resistant Staphylococcus aureus (uncommonly reported in toxic shock syndrome) in the critically ill patient (eg, vancomycin or linezolid)

 Stop enzyme, toxin, or cytokine production with protein synthesis inhibitor (eg, clindamycin or linezolid)

Immune globulin intravenous may be considered for infection refractory to several hours of aggressive therapy, or in the presence of an undrainable focus, or persistent oliguria with pulmonary edema

Question 6

A 6-month-old girl presents to your office for a follow-up visit after being evaluated 5 days ago in the local emergency center for an illness characterized by fever, vomiting, and diarrhea that began one week after they returned from a vacation visiting family in India.  In the emergency center, she was evaluated with a complete blood count, blood culture, urinalysis with urine culture, and stool culture.  

All results of these tests were normal, except for the blood and stool cultures, which grew Salmonella serotype Typhi resistant to ampicillin and trimethoprim-sulfamethoxazole, and susceptible to ceftriaxone, cefotaxime, chloramphenicol, azithromycin, and ciprofloxacin. Today her parents report her diarrhea has improved but has not resolved. Physical examination shows an alert, well-hydrated afebrile infant with a normal physical examination.

The best next step in management of this patient’s condition is to:

A.administer intravenous ceftriaxone    B.administer oral azithromycin C.administer oral ciprofloxacin D.repeat blood culture and treat only if still positive E.repeat stool culture and treat only if still positive

Answer 6: Aadminister intravenous ceftriaxone   

All infections with Salmonella Typhi should be treated, regardless of age of the patient and site of involvement, to prevent complications associated with typhoid fever. Intravenous ceftriaxone is the preferred response in this vignette on the basis of the organism’s antibacterial susceptibility pattern and the patient’s young age

Infants and young children infected with S Typhi may have less fever and appear less toxic than older children and adults, and their initial presentation may mimic a nonspecific viral syndrome, as was seen in this patient

Infection with S Typhi should be suspected in all febrile patients with abdominal signs and symptoms, especially if there is a history of recent foreign travel or exposure to other infected individuals

Classic typhoid (enteric) fever is more often seen in older children; it is a protracted bacteremic illness characterized by fever, malaise, anorexia, constipation, lethargy, headache, and abdominal pain. Abdominal distension, tenderness, and hepatosplenomegaly often are found on examination

Question 7

You are asked to consult on a 2-year-old patient who has been in the pediatric intensive care unit (PICU) for almost 3 weeks. During his hospitalization, he has had problems with decreased renal output and an elevated serum creatinine. He remains intubated and had a new-onset fever overnight. Blood and sputum specimens were sent for culture, and results are pending, although the Gram stain on the sputum sample is showing gram-negative rods. Overnight he required an increase in his ventilator settings, and his chest radiograph has a new density in the left lower lobe.

Of the following, the MOST appropriate antibiotic regimen to administer while awaiting culture results is:

A.amoxicillin-clavulanate B.ampicillin-sulbactam C.cefazolin and gentamicin D.ertapenem E.piperacillin-tazobactam

Answer 7: Epiperacillin-tazobactam

The patient described in the vignette has ventilator-associated pneumonia.

Based on the Gram stain, potential causative organisms include Pseudomonas aeruginosa, Enterobacteriaceae, such as Klebsiella and Enterobacter, and Stenotrophomonas maltophilia. Piperacillin-tazobactam provides coverage for the P aeruginosa, Enterobacteriaceae

Ampicillin-sulbactam, amoxicillin-clavulanate, and ertapenem are not effective against P aeruginosa. Given the history of decreased renal output, it would be prudent at this point to avoid the use of gentamicin, and cefazolin would not be an appropriate choice because most Enterobacteriaceae are resistant

Question 8

You are asked to evaluate a 6-year-old girl who presents with a 1-day history of a generalized, erythematous, macular rash; hypotension; and worsening respiratory distress. She had an upper respiratory tract infection 2 weeks ago. Laboratory findings include:

Peripheral white blood cell count: 4.0x109/L Hemoglobin: 10.5 g/dL Platelet count: 50x109/L Differential count: 75% segmented neutrophils, 10% band

forms, and 15% lymphocytes Creatinine: 2 mg/dL Blood urea nitrogen: 25 mg/dL Alanine aminotransferase: 400 units/L Aspartate aminotransferase: 340

units/L                                                                                      

cont

Of the following, the BEST antibiotic combination to include in the empirical therapy for this child is:

A.ceftriaxone and gentamicinB.linezolid and rifampinC.meropenem and aztreonamD.penicillin G and clindamycinE.vancomycin and gentamicin

Answer 8: D.penicillin G and clindamycin

The girl described in the vignette presents with toxic shock syndrome

Because Streptococcus pyogenes and Staphylococcus aureus toxic shock syndromes cannot be distinguished on clinical findings, empirical antimicrobial therapy should include a combination of an antistaphylococcal agent and a protein (toxin) synthesis-inhibiting antimicrobial agent such as clindamycin

None of the other antimicrobial regimens listed contains a protein (toxin) synthesis-inhibiting antimicrobial agent

After a pathogen is identified, the therapy can be modified as appropriate

Question 9

You are asked to consult on a 15-year-old pregnant girl in whom syphilis has been diagnosed. She states that she developed hives and generalized swelling when given amoxicillin for sore throat as a child.

Of the following, the MOST appropriate management option for this patient is:

A.intravenous desensitization for penicillin B.oral desensitization for penicillin C.skin testing for penicillin allergy D.therapy with ceftriaxone E.therapy with penicillin G

Answer 9: C.skin testing for penicillin allergy

Parenteral penicillin G is the only documented effective therapy for the treatment of syphilis during pregnancy

Because the girl described in the vignette has a history compatible with an immunoglobulin (Ig)E-mediated allergic response to penicillin, she should undergo skin testing for a potential penicillin allergy before initiation of antibiotic therapy. If her skin test results are negative, she can receive conventional penicillin therapy. If her skin test results are positive, she requires desensitization before drug administration

Penicillins are the most common class of antibiotics to induce severe or life-threatening immunoglobulin (IgE)-mediated allergic responses (eg, urticaria, pruritus, flushing, angioedema) or anaphylaxis (eg, hypotension, tachycardia, laryngeal edema, bronchospasm). IgE-mediated reactions are immediate (within 1 hour) and accelerated (1 to 72 hours); reactions occurring after 72 hours usually are not IgE-mediated

Cont

Of note, only 10% of individuals who have histories of penicillin allergy actually have allergic reactions when treated with penicillin

Antibody against native penicillin is directed at the beta-lactam ring. Ninety-five percent of native penicillin is metabolized into benzylpenicilloyl poly-L-lysine, called the “major determinant.” Other important penicillin allergens are referred to as “minor determinants.”

Skin testing can reliably identify persons at high risk for IgE-mediated type I reactions. Testing should include both the major and minor determinants of penicillin allergy because testing with the major determinants alone would miss 3% to 10% of minor determinant-positive patients

If the major determinant is not available for skin testing, patients should be desensitized in a monitored setting

Some experts suggest desensitization regardless of whether the skin test results are negative; others suggest gradual test dosing with oral penicillin in a monitored setting. Oral desensitization is safer and easier to perform and can be completed in 4 hours, after which parenteral penicillin can be administered

Skin testing reliably identifies IgE-mediated reactions but not other types of hypersensitivity reactions occurring more than 24 hours after drug administration.

Morbilliform rashes to penicillin are not IgE-related. Such patients have a low risk for severe reactions with re-exposure to the drug and might be able to undergo a gradual dose challenge to the drug in a monitored setting

Gell-Coombs

Classification Time of Onset Mediator Clinical Signs

Skin Testing

Indicated

 Type I  <1 hour IgE

Anaphylaxis:

urticaria,

angioedema,

wheezing,

laryngeal edema,

hypotension

 Yes

 Type II     >72 hoursIgG/IgM +

complement

Immune

cytopenias, some

organ

inflammation

 No

 Type III  >72 hours

IgG or IgM

immune

complexes

Serum sickness,

drug fever,

vasculitis, tissue

injury

 No

 Type IV  >72 hoursT cells and

cytokines

Contact

dermatitis, some

organ

inflammation

 No

Table. Immunologic Classification of Hypersensitivity ReactionsNote: Beta-lactam antibiotics can cause all four types of hypersensitivity reactions

Question 10

An 3-year-old boy is referred to your clinic for evaluation of a tuberculin skin test (TST) that has an area of induration of 11 mm. He was born in Pakistan and recently moved to the United States so his parents could train at the local university. He received Bacille Calmette-Guérin (BCG) vaccination at birth. He has been well, and there is no report of fevers, cough, chills, sweats, or weight loss. A chest radiograph appears normal. His pediatrician has concluded that he has latent tuberculosis infection (LTBI) and asks for your opinion about what to do next. 

Of the following, the MOST appropriate option for this child is to: A.administer another dose of BCG B.begin isoniazid therapy C.perform an interferon-gamma release assay D.perform human immunodeficiency virus (HIV) antibody testing E. repeat the TST

Answer 10: B.begin isoniazid therapy

After BCG vaccination, distinguishing between a positive TST result caused by Mycobacterium tuberculosis or Mycobacterium bovis infection and that caused by BCG vaccination may be difficult

The 2009 Red Book states that “generally, interpretation of TST results in BCG recipients is the same as for people who have not received BCG…when evaluating an asymptomatic child who has a positive TST result and who possibly received BCG, the result should not be attributed to BCG vaccine.” In a child who was born in a region with a high prevalence of TB, a TST result of induration of 10 mm or greater, as described for the boy in the vignette, is considered to be positive (Table)

According to Red Book recommendations, the pediatrician should conclude that the child has LTBI and should initiate a 9-month course of isoniazid therapy to prevent TB disease

Table: Definitions of +TST

Induration 5 mm or greater

Children in close contact with known or suspected contagious people with tuberculosis disease

Children suspected to have tuberculosis disease:

Findings on chest radiograph consistent with active or previous tuberculosis disease

Clinical evidence of tuberculosis diseaseb

Children receiving immunosuppressive therapyc or with immunosuppressive conditions, including human

immunodeficiency (HIV) infection

cont

Induration 10 mm or greater

Children at increased risk of disseminated tuberculosis disease:

Children younger than 4 years of age

Children with other medical conditions, including Hodgkin disease, lymphoma, diabetes

mellitus, chronic renal failure, or malnutrition (see Table 3.80, p 684)

Children with likelihood of increased exposure to tuberculosis disease:

Children born in high-prevalence regions of the world

Children frequently exposed to adults who are HIV infected, homeless, users of illicit

drugs, residents of nursing homes, incarcerated or institutionalized, or migrant farm

workers

Children who travel to high-prevalence regions of the world

cont

Induration 15 mm or greater

Children 4 years of age or older without any risk factors

 

aThese definitions apply regardless of previous bacille Calmette-Guérin (BCG) immunization (see also

Interpretation of TST Results in Previous Recipients of BCG Vaccine, p 685); erythema alone at TST site

does not indicate a positive test result. Tests should be read at 48 to 72 hours after placement.

bEvidence by physical examination or laboratory assessment that would include tuberculosis in the

working differential diagnosis (eg, meningitis).

cIncluding immunosuppressive doses of corticosteroids.

Final recommendations

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