Bacteremia in an ambulatory setting. Improved outcome in children treated with antibiotics

Management of fever without source in infants and children

Twenty percent of febrile children have fever without an apparent source of infection after history and physical examination. Of these, a small proportion may have an occult bacterial infection, including bacteremia, urinary tract infection (UTI), occult pneumonia, or, rarely, early bacterial meningitis. Febrile infants and young children have, by tradition, been arbitrarily assigned to different management strategies by age group: neonates (birth to 28 days), young infants (29 to 90 days), and older infants and young children (3 to 36 months). Infants younger than 3 months are often managed by using low-risk criteria, such as the Rochester Criteria or Philadelphia Criteria. The purpose of these criteria is to reduce the number of infants hospitalized unnecessarily and to identify infants who may be managed as outpatients by using clinical and laboratory criteria. In children with fever without source (FWS), occult UTIs occur in 3% to 4% of boys younger than 1 year and 8% to 9% of girls younger than 2 years of age. Most UTIs in boys occur in those who are uncircumcised. Occult pneumococcal bacteremia occurs in approximately 3% of children younger than 3 years with FWS with a temperature of 39.0 degrees C (102.2 degrees F) or greater and in approximately 10% of children with FWS with a temperature of 39.5 degrees C (103.1 degrees F) or greater and a WBC count of 15, 000/mm(3) or greater. The risk of a child with occult pneumococcal bacteremia later having meningitis is approximately 3%. The new conjugate pneumococcal vaccine (7 serogroups) has an efficacy of 90% for reducing invasive infections of Streptococcus pneumoniae. The widespread use of this vaccine will make the use of WBC counts and blood cultures and empiric antibiotic treatment of children with FWS who have received this vaccine obsolete.

Reevaluation of outpatients with Streptococcus pneumoniae bacteremia

BACKGROUND

The reevaluation process for outpatients recalled for Streptococcus pneumoniae bacteremia has not been standardized. Children who return ill or with new serious focal infections require admission and parenteral antibiotic therapy. Limited data exist to guide the follow-up management of those patients identified as having occult pneumococcal bacteremia.

OBJECTIVES

Characterize the outcomes of outpatients with pneumococcal bacteremia based on their evaluation at follow-up. For patients who are well-appearing without serious focal infection, propose a management scheme for reevaluation.

METHODS

Retrospective review of outpatients with pneumococcal bacteremia. Patients with immunocompromise, those identified with focal bacterial infection at the initial visit, or those admitted at the initial visit were excluded. Data were collected from the initial visit (when blood culture drawn) and follow-up visit with regard to clinical parameters, laboratory data, diagnoses, and any antibiotic treatment. Decision tree analysis was used to generate a model to predict children at high risk for persistent bacteremia (PB).

RESULTS

A total of 548 episodes of pneumococcal bacteremia were studied. Seventy-three children received no antibiotic, 239 oral antibiotic, and 236 parenteral antibiotic at the initial visit. Median age, temperature, and white blood cell (WBC) count were 13.5 months, 40.0 degrees C, and 20 400/mm(3). Forty-one patients had PB or new focal infections (15 with PB alone, 4 had focal infection and PB). Eight patients had meningitis at follow-up. Ninety-two percent returned because of notification of the positive blood culture result. A repeat blood culture was obtained in 92%, 23% had a lumbar puncture, 33% had a chest radiograph, and 12% were admitted. PB was associated with the antibiotic treatment group, elevation of temperature, and WBC count at follow-up. A simple management scheme using 2 sequential decision nodes of antibiotic treatment (none vs any) and then temperature at follow-up (>38.8 degrees C) would have predicted 16/19 patients with PB (sensitivity =.84 and specificity =.86).

CONCLUSIONS

All patients with pneumococcal bacteremia need prompt reevaluation. For well-appearing patients without new focal infection, the utility of diagnostic testing (specifically repeat blood cultures) and the need for admission may be determined by the use of antibiotics at the initial evaluation and the presence of fever at follow-up. The majority of patients can be managed as outpatients entirely. Patients who did not receive antibiotics at the initial evaluation and those treated with oral antibiotics but remain febrile are at the highest risk for persistent bacteremia.

Occult bacteremia in young febrile children

The evaluation of nontoxic-appearing, young, febrile children has been a subject of considerable debate. Of young, nontoxic-appearing children aged 3 to 36 months with temperatures of 39 degrees C or more and no clear source, approximately 2% to 3% have occult bacteremia. Of these bacteremias, approximately 90% are caused by S. pneumoniae, 5% by nontyphoidal Salmonella sp., and 1% by N. meningitidis. Most children with occult pneumococcal bacteremia improve spontaneously, but approximately 25% of untreated patients have persistent bacteremia or develop new focal infections, including 3% to 6% who develop meningitis. Occult meningococcal bacteremia, although rare, has frequent complications, including meningitis in approximately 40% and death in approximately 4%. Less is known about the natural history of untreated occult nontyphoidal Salmonella bacteremia. Empiric antibiotic treatment of children with occult bacteremia decreases the rate of complications, including meningitis. Few disagree that febrile, young children at risk for occult bacteremia require a careful clinical evaluation and close follow-up. The benefits of laboratory screening and selective empiric antibiotic treatment of febrile children at risk for occult bacteremia have to be weighed against the costs of screening tests and blood cultures, inconvenience, temporary discomfort to patients, risk for side effects of antibiotics, and the role of antibiotics in the development of bacterial resistance. Although great debate exists concerning the role of empiric antibiotics, a strategy for obtaining blood cultures and empirically administering antibiotics on the basis of an increased ANC, in addition to close clinical follow-up, may be effective in reducing the frequency and severity of uncommon but adverse sequelae. A highly effective S. pneumoniae bacterial conjugate vaccine will soon be available, which will benefit all children, and will alter the ways that clinicians evaluate fully immunized young, febrile children.

Parenteral vs oral antibiotics in the prevention of serious bacterial infections in children with Streptococcus pneumoniae occult bacteremia: a meta-analysis

OBJECTIVE

To determine whether parenteral antibiotics are superior to oral antibiotics in preventing serious bacterial infections in children with Streptococcus pneumoniae occult bacteremia.

METHODS

Using the MEDLINE database, the English language literature was searched for all publications concerning bacteremia, fever, or Streptococcus pneumoniae from 1966 to January 1, 1997. All nonduplicative studies with a series of children with S. pneumoniae occult bacteremia having both orally treated and parenterally treated groups were reviewed. Children were excluded from individual studies if at the time of their initial evaluation they were immunocompromised, had a serious bacterial infection, underwent a lumbar puncture, or did not receive antibiotics.

RESULTS

Only 4 studies met study criteria. From these studies, 511 total cases of S. pneumoniae occult bacteremia were identified. Ten of 290 (3.4%) in the oral group and 5 of 221 (2.3%) in the parenteral antibiotic group developed serious bacterial infections (pooled p-value = 0.467, pooled OR = 1.48; 95% CI, 0.5-4.3). Two patients in the oral group (0.7%) and 2 patients in the parenteral group (0.9%) developed meningitis (pooled p-value = 0.699, pooled OR = 0.67; 95% CI, 0.1-5.1).

CONCLUSION

The rates of serious bacterial infections and meningitis did not differ between children who were treated with oral and parenteral antibiotics. The extremely low rate of complications observed in both groups suggests no clinically significant difference between therapies. A study with >7,500 bacteremic children (or >300,000 febrile children) would be needed to have 80% power to prove parenteral antibiotics are superior to oral antibiotics in preventing serious bacterial infections.

Predictors of occult pneumococcal bacteremia in young febrile children

STUDY OBJECTIVE

Occult pneumococcal bacteremia (OPB) occurs in 2.5% to 3% of highly febrile children 3 to 36 months of age, and 10% to 25% of untreated patients with OPB experience complications, including 3% to 6% in whom meningitis develops. The purpose of this study was to identify predictors of OPB among a large cohort of young, febrile children treated as outpatients using multivariable statistical methods.

METHODS

We derived and validated a logistic regression model for the prediction of OPB. We evaluated 6,579 outpatients 3 to 36 months of age with temperatures of 39 degrees C or higher who previously had been enrolled in a study of young febrile patients at risk of OPB in the emergency departments of 10 hospitals in the United States between 1987 and 1991; 164 patients (2.5%) had OPB. We randomly selected two thirds of this population for the derivation of the model and one third for validation. In the derivation set, we analyzed the univariate relationships of six variables with OPB: age, temperature, clinical score, WBC count, absolute neutrophil count (ANC), and absolute band count (ABC). All six variables were then entered into a logistic regression equation and those retaining statistical significance were considered to have an independent association with OPB.

RESULTS

Patients with OPB were younger, more frequently ill-appearing, and had higher temperatures, WBC, ANC, and ABC than patients without bacteremia. Only three variables, however, retained statistically significant associations with OPB in the multivariate analysis: ANC (Adjusted odds ratio [OR] 1.15 for each 1,000 cells/mm3 increase, 95% confidence interval [CI] 1.06, 1.25), temperature (adjusted OR 1.77 for each 1 degree C increase, 95% CI 1.21, 2.58), and age younger than 2 years (adjusted OR 2.43 versus patients 2 to 3 years old, 95% CI interval 1.11, 5.34). In the derivation set, 8.1% of patients with ANCs greater than or equal to 10,000 cell/mm3 had OPB (95% CI 6.3, 10.1%) versus .8% of patients with ANCs less than 10,000 cells/mm3 (95% CI .5, 1.2%). When tested on the validation set, the model performed similarly.

CONCLUSION

Independent predictors of OPB in children 3 to 36 months of age with temperatures of 39 degrees C or higher treated as outpatients include ANC, temperature, and age younger than 2 years. These predictors may be used to develop clinical strategies to limit laboratory testing and antibiotic administration to those children at greatest risk of OPB.

Controlled comparison of bioMérieux VITAL and BACTEC NR-660 systems for detection of bacteremia and fungemia in pediatric patients

The bioMérieux VITAL automated blood culture system measures a decrease in fluorescence to detect the presence of microorganisms in blood. To assess the performance of VITAL with AER aerobic medium versus that of the nonradiometric BACTEC NR-660 PEDS PLUS medium for the detection of sepsis in children, a total of 12,146 blood specimens were collected at three university medical centers and inoculated into AER and PEDS PLUS bottles that were weighed before and after filling. The sample volumes were considered adequate in 6,276 bottle pairs. The total yield of isolates was 629, of which 489 (78%) were judged to be the cause of true infections. Staphylococci (P < 0.001) and yeasts (P < 0.05) were detected more often in PEDS PLUS bottles, as were all microorganisms combined (P < 0.001). The improved detection in the PEDS PLUS medium was most marked for patients on antimicrobial therapy (P < 0.001), but remained statistically significant even for patients not on therapy (P < 0.025). There were 431 episodes of sepsis, including 407 considered adequate for analysis. Of the 363 unimicrobial episodes, 278 were detected by both bottles, 64 were detected by PEDS PLUS bottles only, and 21 were detected by AER bottles only (P < 0.01). No false-negative cultures were detected by terminal subculture of the PEDS PLUS bottles when the companion AER bottle was positive. However, there were 14 false-negative cultures (7 yeasts, 5 staphylococci, 1 Enterococcus faecalis, and 1 Enterobacter sp.) on terminal subculture of the AER bottles when the companion PEDS PLUS bottle was positive. When both systems were positive, the VITAL system detected bacteria earlier than did the BACTEC system by a mean of 1.6 h. Also, false-positive signals were less common with the VITAL system. We conclude that the VITAL system with AER medium must be modified to improve the detection of clinically important staphylococci and yeasts if it is to perform comparably to the BACTEC NR-660 nonradiometric system with PEDS PLUS medium for a pediatric population.

Do oral antibiotics prevent meningitis and serious bacterial infections in children with Streptococcus pneumoniae occult bacteremia? A meta-analysis

OBJECTIVE

To determine whether oral antibiotics prevent meningitis and serious bacterial infections in children with Streptococcus pneumoniae occult bacteremia.

DATA SOURCES

Using the Medline database, the English-language literature was searched for all publications concerning bacteremia, fever, or S pneumoniae from 1966 to April 1996.

STUDY SELECTION

All studies that included a series of children with S pneumoniae occult bacteremia containing orally treated and untreated groups. Children were excluded from individual studies if they were immunocompromised, had a serious bacterial infection, underwent a lumbar puncture, or received parenteral antibiotics.

DATA EXTRACTION

Three authors independently reviewed each article to determine the number of eligible children and the outcome of children meeting entry criteria.

DATA SYNTHESIS

Eleven of 21 studies were excluded, leaving 10 evaluable studies with 656 total cases of S pneumoniae occult bacteremia identified. Patients who received oral antibiotics had fewer serious bacterial infections than untreated patients (3.3% vs 9.7%; pooled odds ratio, 0.35; 95% confidence interval, 0.17 to 0.73). Meningitis developed in 3 (0.8%) of 399 children in the oral antibiotic group and 7 (2.7%) of 257 untreated children (pooled odds ratio, 0.51; 95% confidence interval, 0.12 to 2.09).

CONCLUSION

Although oral antibiotics modestly decreased the risk of serious bacterial infections in children with S pneumoniae occult bacteremia, there was insufficient evidence to conclude that oral antibiotics prevent meningitis. Published recommendations that oral antibiotics be administered to prevent serious bacterial infections in children with possible S pneumoniae occult bacteremia should be reevaluated in light of the lower risk of sequelae from S pneumoniae occult bacteremia and newer data concerning side effects from treatment.

Factors associated with increased risk in inappropriate empiric antibiotic treatment of childhood bacteraemia

To identify bacteraemic children who are at increased risk of inappropriate empiric antibiotic therapy, we performed univariate and multivariate analyses of prospectively-studied bacteraemic episodes. Appropriateness of therapy was defined according to the in vitro susceptibility of the isolate. Inappropriate empiric therapy was found in 38% of 516 bacteraemic episodes and was associated with higher mortality. The rate of inappropriate treatment was lower in neonates and infants (28% and 33%, respectively) but higher in children 1- to 5-years old (51%, P = 0.0029). The rate was dependent on the source of bacteraemia (range, 18%-70%, P = 0.0092), underlying conditions (range, 26%-53%, P = 0.0001), the specific paediatric section in which the child was hospitalized (range, 24%-70%, P = 0.0002), and the causative micro-organism (range, 15%-75%, P < 0.0001). Four clinical variables that independently and significantly affected the rate of inappropriate antibiotic treatment were identified by multivariate stepwise logistic regression analysis (odds ratios in parentheses): hospital-acquired bacteraemia (2.3), age of 1- to 5-years (2.1), cytotoxic therapy (1.8) and presence of central i.v. line (1.6).

CONCLUSION

We defined bacteraemic children who are at risk of inappropriate empiric antibiotic therapy. Special efforts are needed to improve their treatment and consequently their outcome.

Invasive pneumococcal disease among infected and uninfected children of mothers with human immunodeficiency virus infection

OBJECTIVE

To describe the incidence and clinical presentation of invasive pneumococcal disease in a cohort of children infected with human immunodeficiency virus (HIV) who were prospectively followed from birth, in comparison with uninfected children born to HIV-infected mothers and control children.

DESIGN

Prospective follow-up of a cohort recruited at birth and born to mothers with known HIV status. The person-years analysis method used the occurrence of invasive pneumococcal disease as the end point.

SETTING

Hospital-based clinic specializing in care of HIV-at-risk and HIV-infected children in Baltimore, Md.

PARTICIPANTS

Forty-one vertically HIV-infected children, 128 uninfected children born to HIV-infected mothers, and 71 control children born to mothers with negative findings for HIV but with HIV risk factors.

RESULTS

Among HIV-infected children, 10 episodes of invasive pneumococcal disease occurred during the first 36 months of life compared with 4 episodes among uninfected children and 1 episode among control subjects. The relative risk for HIV-infected children versus the combined uninfected and control groups was 12.6 with a 95% confidence interval (5.4, 28.8) and a p value for difference between groups of < 0.001. The incidence rate per 100 child-years of observation during the first 36 months of life was 11.3 for HIV-infected, 1.1 for uninfected, and 0.5 for control children. Clinical and laboratory variables were not useful in identifying HIV-infected children at risk for pneumococcal disease.

CONCLUSION

Practical strategies to prevent pneumococcal disease among HIV-infected children need to be developed.

Intramuscular versus oral antibiotic therapy for the prevention of meningitis and other bacterial sequelae in young, febrile children at risk for occult bacteremia

Because studies of the treatment of children with occult bacteremia have yielded conflicting results, we compared ceftriaxone with amoxicillin for therapy. Inclusion criteria were age 3 to 36 months, temperature > or = 39 degrees C, an acute febrile illness with no focal findings or with otitis media (6/10 centers), and culture of blood. Subjects were randomly assigned to receive either ceftriaxone, 50 mg/kg intramuscularly, or amoxicillin, 20 mg/kg/dose orally for six doses. Of 6733 patients enrolled, 195 had bacteremia and 192 were evaluable: 164 Streptococcus pneumoniae, 9 Haemophilus influenzae type b, 7 Salmonella, 2 Neisseria meningitidis, and 10 other. After treatment, three patients receiving amoxicillin had the same organism isolated from their blood (two H. influenzae type b, one Salmonella) and two from the spinal fluid (two H. influenzae type b), compared with none given ceftriaxone. Probable or definite infections occurred in three children treated with ceftriaxone and six given amoxicillin (adjusted odds ratio 0.43, 95% confidence interval 0.08 to 1.82, p = 0.31). The five children with definite bacterial infections (three meningitis, one pneumonia, one sepsis) received amoxicillin (adjusted odds ratio 0.00, 95% confidence interval 0.00 to 0.52, p = 0.02). Fever persisted less often with ceftriaxone (adjusted odds ratio 0.52, 95% confidence interval 0.28 to 0.94, p = 0.04). Although the difference in total infections was not significant, ceftriaxone eradicated bacteremia, prevented significantly more definite focal bacterial complications, and was associated with less persistent fever.

Occult bacteremia in the 3-month-old to 3-year-old age group

Occult bacteremia precedes many serious infections in children. The vast majority of patients with occult bacteremia have an elevated temperature (> or = 39 degrees C), but fever is an extraordinarily common presenting complaint in the 3- to 36-month-old age group, which is at highest risk for S pneumoniae, H influenzae type b, and N meningitidis bacteremia. On examination, most patients with bacteremia will have no findings that distinguish them from nonbacteremic children. A white blood cell count of > 15,000/microL in a child with fever will identify about two thirds of children with occult bacteremia. Blood culture remains the most definitive test. It is important to establish a rational strategy to identify and treat these children before significant sequelae occur.

Management of infants and children 3 to 36 months of age with fever without source

The evidence and guidelines presented in this article are meant to assist clinicians who manage children with FWS. However, physicians may choose to individualize therapy based on unique clinical circumstances or to adopt a variation of these guidelines based on a different interpretation of the evidence concerning these issues. No guidelines can eliminate all risk nor confine antibiotic treatment only to children likely to have occult bacteremia. The optimal management strategy reduces risk to a minimum at a reasonable cost and can be used in most practice settings.