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Guada Lopez-Marti, MD June 2011.  The lab reports the growth of community-associated methicillin- resistant Staphylococcus aureus (MRSA) from a culture.

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Presentation on theme: "Guada Lopez-Marti, MD June 2011.  The lab reports the growth of community-associated methicillin- resistant Staphylococcus aureus (MRSA) from a culture."— Presentation transcript:

1 Guada Lopez-Marti, MD June 2011

2  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

3  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

4  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

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6  Of the following, the MOST appropriate antibiotic to treat this infant’s infection is:  A. ampicillin  B. cefotaxime  C. ceftriaxone  D. gentamicin  E. vancomycin

7  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

8  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 2.55x10 9 /L with 15% bands, 10% segmented neutrophils, and 75% lymphocytes and a platelet count of 33x10 9 /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

9  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

10  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

11  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

12  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

13  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

14  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

15  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

16  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

17  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

18  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

19  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: 4.0x10 9 /L  Hemoglobin: 10.5 g/dL  Platelet count: 50x10 9 /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

20  Of the following, the BEST antibiotic combination to include in the empirical therapy for this child is:  A.ceftriaxone and gentamicin  B.linezolid and rifampin  C.meropenem and aztreonam  D.penicillin G and clindamycin  E.vancomycin and gentamicin

21  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

22  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

23  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

24  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

25 Gell-Coombs Classification Time of OnsetMediatorClinical Signs Skin Testing Indicated Type I <1 hourIgE Anaphylaxis: urticaria, angioedema, wheezing, laryngeal edema, hypotension Yes Type II >72 hours IgG/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 hours T cells and cytokines Contact dermatitis, some organ inflammation No Table. Immunologic Classification of Hypersensitivity Reactions Note: Beta-lactam antibiotics can cause all four types of hypersensitivity reactions

26  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

27  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

28 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 disease b Children receiving immunosuppressive therapy c or with immunosuppressive conditions, including human immunodeficiency (HIV) infection

29 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

30 Induration 15 mm or greater Children 4 years of age or older without any risk factors a These 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. b Evidence by physical examination or laboratory assessment that would include tuberculosis in the working differential diagnosis (eg, meningitis). c Including immunosuppressive doses of corticosteroids.

31  Med study is a great resource, use it!  Practice TONS of questions  Have confidence  You will PASS, do not worry!


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