Patients with occult bacteremia do not have clinical evidence
other than fever (a systemic response to infection). First
described in the 1960s in young febrile children with unsuspected
pneumococcal infection, bacteremia is defined as the presence of
bacteria in the bloodstream of a febrile child who was previously
healthy; the child does not clinically appear to be ill and has no
apparent focus of infection.
Slide 3
Occult bacteremia has been defined as bacteremia not associated
with clinical evidence of sepsis (shock or purpura) or toxic
appearance, underlying significant chronic medical conditions, or
clear foci of infection (other than acute otitis media) upon
examination in a patient who is discharged and sent home after an
outpatient evaluation
Slide 4
Often, the only manifestation of occult bacteremia is fever or
a minor infection (eg, otitis media, upper respiratory tract
infection). Therefore, in a busy clinic or emergency department,
infants and young children with occult bacteremia are difficult to
distinguish from others in the waiting-room.
Slide 5
Much of the pathophysiology of occult bacteremia is not fully
understood. The presumed mechanism begins with bacterial
colonization of the respiratory passages or other mucosal surface;
bacteria may egress into the bloodstream of some children because
of host-specific and organism-specific factors. Once viable
bacteria have gained access to the bloodstream, they may be
spontaneously cleared, they may establish a focal infection, or the
infection may progress to septicemia; the possible sequelae of
septicemia include shock, disseminated intravascular coagulation,
multiple organ failure, and death.
Slide 6
A child's immune system helps determine which bacteria gain
initial access to the bloodstream, whether bacteremia spontaneously
resolves or progresses to serious bacterial illness, and whether
cytokines are produced to mount a fever response. The risk of
life-threatening bacterial disease is greatest in young infants
when their immune system is least mature; they have poor
immunoglobulin G (IgG) antibody response to encapsulated bacteria
and decreased opsonin activity, macrophage function, and neutrophil
activity.
Slide 7
Clearly, some children are more susceptible to bacterial
infection, which may initially be uncomplicated bacteremia but
could rapidly lead to more serious complications. Immunosuppression
due to neoplastic disease or its treatment or defects in antibody
responses or neutrophil responses predispose certain children to
invasive infection. Bacteremia should be considered, with a low
threshold for evaluation and treatment, in patients with impaired
immunity or invasive medical devices such as indwelling central
venous lines.
Slide 8
Temperature, pulse, respiratory rate, and blood pressure can be
very useful in raising clinical suspicion for sepsis or pneumonia
and for establishing the risk for occult bacteremia. Studies have
also suggested that pulse oximetry should be used routinely as a
fifth vital sign. In younger infants, poor perfusion as judged by a
capillary-refill time of less than 2 seconds is a more sensitive
measure of cardiovascular status than pulse or blood pressure in
the early phase of sepsis.
Slide 9
In studies of occult bacteremia, children were not excluded
based on specific vital sign parameters; in very young infants, the
presence of a serious bacterial infection may not significantly
correlate with differences in pulse, respiratory rate, or blood
pressure. However, tachycardia, tachypnea, or hypotension in a
febrile or hypothermic infant are signs of sepsis and warrant a
complete evaluation.
Slide 10
Causes: Causes of occult bacteremia vary depending on the age
of the infant or child. Very young infants most commonly acquire
infections from the mother during childbirth. As a patient's age
increases, a gradual shift occurs toward community-acquired
infections.
Slide 11
Occult bacteremia due to S. pneumoniae, H. influenzae tybe B,
N. meningitidis and Salmonella spp occures in approximatly 4% of
relatively well appearing children S. pneumoniae account for 85% of
cases of occult bacteremia, with H. influenzae tybe B, N.
meningitidis and Salmonella spp accounting for the remaining
postive cultures
Slide 12
The incidence of H. influenza type B infections of all types
has decreased dramatically in the regions where the conjugate H.
influenza type B vaccine is administered to infants
Slide 13
Older infants and children are at risk for bacteremia due to
colonization of the nasopharynx or community-acquired organisms.
Hib conjugate vaccine has decreased the prevalence of invasive Hib
disease by 90% or more in industrialized countries. With the
disappearance of Hib as a cause of occult bacteremia in children,
the relative frequency of S Pneumoniae increased in some medical
centers to more than 90%. Since the introduction and widespread use
of the pneumococcal vaccines, the rate of vaccine-specific strains
has dropped considerably, leading to significant changes in the
patterns of causative organisms in more recent studies.
Slide 14
Risk Factors of Occult bacteremia: 1. Temprature exceeding 39 C
2. total WBC count greater than 15.000/L or an elevated absolute
neutrophil count, band count, ESR, CRP 3. approximately 30% of
febrile children 3- 36 months of age have no localized signs of
infection
Slide 15
Elements of the history that indicate an increased risk for
occult bacteremia in infants and children after the neonatal period
include the following: Age, (3- 36 months)which determines the
cutoff used to define fever Febrile temperature ( 3 mo and
temperature >38C [100.4F], 3-36 mo and temperature 39-39.5C
[102.2- 103.1F]) Current antibiotic use Previous hospitalizations
Chronic or underlying illness Immunodeficiency (eg,
hypogammaglobulinemia, sickle cell anemia, human immunodeficiency
virus [HIV], malnutrition, asplenia)
Slide 16
C-reactive protein (CRP) is an acute phase reactant released by
the liver following inflammation or tissue damage. Observational
studies that have evaluated CRP as a screening tool for occult
bacterial infection report a wide range of sensitivity and
specificity that vary by cutoff levels used to identify infants and
children with serious bacterial infection (SBI). In addition, CRP
concentrations generally do not increase until 12 hours after the
onset of fever and can rise in both viral and bacterial
infections.
Slide 17
- Without therapy occult Bacteremia may resolve spontaneously
without sequelae, may persist, or may lead to localized infection,
such as meningitis, pneumonia, cellulitis, or septic arthritis -
The pattern of sequelae may be related to both host factors &
the offending organism - In some children the occcult bacteremia
may represent the early signs of serious localized infection rather
than transient disease state
Slide 18
Empiric antibiotics: How well do they work? The first step in
the treatment of children with occult bacteremia is to use a
combination of age, temperature, and screening laboratory test
results to determine the risk for serious bacterial infection or
occult bacteremia. Low-risk children are generally monitored as
outpatients. Children who do not fit low-risk criteria are treated
with empiric antibiotics either as inpatients or as
outpatients.
Slide 19
Numerous studies have compared the effectiveness of oral
antibiotics and parenteral antibiotics in reducing complications of
occult bacteremia. Many of these studies were conducted before
widespread use of the conjugate Hib vaccine. Parenteral antibiotics
were generally found to be significantly more effective than oral
treatment or no treatment in reducing the sequelae of occult
bacteremia, most importantly meningitis.
Slide 20
Complication No Antibiotic Therapy, % Oral Antibiotic Therapy,
% Intramuscular/Intr avenous Antibiotic Therapy, % Persistent
bacteremia 18- 213.8 - 50- 5 New focal infection135 6.65- 7.7
Meningitis9- 104.5 8.20.3 1 Occult Bacteremia - Relationship
Between Outpatient Antibiotic Use and Complications
Slide 21
Treatment: Practice Giudelines published in 1993 recommended
that infants 3- 36 months of age who have temprature less than 39 C
and who dont appear toxic, can be observed as an outpatients
without performing diagnostic tests or administering antimicrobial
agents.
Slide 22
for non toxic appearing infants with rectal temperature of 39C
or greater 2 options are suggested 1. Obtain a blood culture and
give empirical antibiotic (Ceftriaxone 50 mg/ Kg) once dialy 2.
Obtain CBC and if WBC > 15.000or more /L, obtain blood C&S
and give empirical antibiotic therapy
Slide 23
Third option, not offered in this giudelines is to observe
selected infants as an outpatients without antibiotics after blood
culture has been obtained, the family should be instructed to
return to the clinic within 24 hrs if the fever persist or
immediately if the child condition deteriorate
Slide 24
Further Inpatient Care, Hospitalization: Neonates younger than
1 month: Most guidelines recommend hospitalization, with or without
antibiotic therapy, for all febrile infants younger than 1 month
pending culture results.
Slide 25
Infants aged 1-3 months: Most guidelines recommend
hospitalization for infants in this age group who do not meet
low-risk criteria (ie, they are ill-appearing, appear toxic, are
hypotensive, or were not previously healthy or they have a focal
infection, high-risk petechiae, UTI, or WBC count per HPF of 15).
Infants who need supportive care such as oxygen and intravenous
fluids should also be treated as inpatients, as well as those who
cannot be treated as outpatients because of caregiver,
transportation, communication, or other logistics. Outpatients
whose blood or CSF cultures are positive for known bacterial
pathogens should be readmitted for intravenous antibiotic
therapy.
Slide 26
Children aged 3-36 months: Infants and young children in this
age group should be hospitalized if sepsis is a concern because of
toxic appearance, unstable vital signs, or high-risk petechiae upon
examination. They may also be admitted if they cannot be treated as
outpatients because of caregiver, transportation, communication, or
other logistics. Many infants and young children in this age group
are initially treated as outpatients. They may need to be admitted
if a blood culture is positive for known pathogens, depending on
the clinical status of the patient and the specific organism
grown
Slide 27
Prognosis: Most episodes of occult bacteremia spontaneously
resolve, and serious sequelae are increasingly uncommon. However,
serious bacterial infections occur, including pneumonia, septic
arthritis, osteomyelitis, cellulitis, meningitis, and sepsis; death
may result. Evaluation, treatment, and follow-up of febrile infants
and young children at risk for occult bacteremia significantly
decrease the risk for serious bacterial infections and
sequelae.
Slide 28
Complication: Occult bacteremia results in morbidity and
mortality due to focal infections that arise following the initial
bloodstream infection. Most episodes of occult bacteremia
spontaneously resolve, and serious sequelae are increasingly
uncommon. However, serious bacterial infections occur, including
pneumonia, septic arthritis, osteomyelitis, cellulitis, meningitis,
and sepsis; death may result. Of all focal infections that develop
because of pneumococcal bacteremia, pneumococcal meningitis carries
the highest risk for significant morbidity and mortality, including
a 25-30% risk of neurologic sequelae such as deafness, mental
retardation, seizures, and paralysis.
Slide 29
Escherichia coli bacteraemia in a pediatric emergency service
(1995-2010) authors reported an increase in relative incidence of
E. coli bacteraemia in recent years. E. coli has been the third
most frequently isolated bacteria in blood cultures at our
emergency service between 1995 and 2009. Aim: To analyze trends,
clinical, laboratory and microbiological data of E. coli
bacteraemia in a level 3 pediatric hospital, in the last 16 years.
Conclusions: We did not see an increase of community-acquired E.
coli bacteraemia over the last 16 years in our hospital. Infections
occurred mainly in the neonatal period and first three months of
life and the most frequent diagnosis was acute pyelonephritis.
Leukocytosis is not always present, particularly in the neonatal
period. A quarter of the E. coli was resistant to ampicillin. The
outcome was favorable in most children and one died of sepsis. Acta
Med Port. Acta Med Port. 2011 Dec;24 Suppl 2:207-12. Epub 2011 Dec
31.
Slide 30
Occult pneumococcal bacteremia: a review. Occult bacteremia is
primarily caused by Streptococcus pneumoniae and has been an
intense clinical controversy in pediatric emergency medicine, with
passionate opinions rendered from inside and outside the field.
Vaccine development and widespread immunization have rapidly
affected the changing epidemiology of this disease. There is a
growing consensus that the reduction in incidence of occult
bacteremia and the significant problem of antibiotic resistance are
tipping the balance in favor of no testing and no treatment for
well-appearing febrile children between 6 and 36 months of age who
are immunized with Haemophilus influenzae B vaccination and PCV-7
(pneumococcal conjugate vaccine). This review of occult
pneumococcal bacteremia will not only elaborate on current
knowledge and clinical practice, but will also provide historical
context to this fascinating phenomenon. Pediatr Emerg Care. Pediatr
Emerg Care. 2010 Jun;26(6):448-54; quiz 455-7.
Slide 31
Reduced use of occult bacteremia blood screens by emergency
medicine physicians using immunization registry for children
presenting with fever without a source. OBJECTIVES: This study
examined whether utilization of the Florida State Health Online
Tracking System (SHOTS) immunization registry to determine
Haemophilus influenzae type B and heptavalent pneumococcal
conjugate (PCV7) vaccine status impacts the protocolized decision
to perform a screening blood draw for occult bacteremia (OB) in
young children. METHODS: A convenience sample of children 6 to 24
months of age presenting to the pediatric emergency department with
fever of greater than 39C without a source was enrolled. Physicians
were trained to use the SHOTS immunization registry and reviewed
the emergency department's fever protocol. A "preregistry" workup
plan was documented for each patient based on clinical history,
immunization status before accessing SHOTS, and physical
examination. A "postregistry" workup plan was then documented based
on the SHOTS record. Demographic and registry data were
recorded.
Slide 32
RESULTS: Preregistry workup plans indicated OB screening blood
draws for 100% (n = 91; 95% confidence interval [CI], 96-100) of
patients with unconfirmed immunization status. Of those 91
children, 58% (n = 53; 95% CI, 55-61) were documented in SHOTS as
having received their primary conjugate vaccine series at ages 2,
4, and 6 months. Registry access reduced the percentage of
screening blood draws from 100% (n = 91) to 42% (n = 38; 95% CI,
37-53; P < 0.001). CONCLUSIONS: The state immunization registry
is an adjunctive tool to caregiver recall, which can be used by
emergency medicine practitioners to confirm completion of the
primary conjugate vaccine series before making the decision to
perform blood screens for OB in children aged 6 to 24 months who
present with fever without a source. Pediatr Emerg Care. 2012
Jul;28(7):640-5.