Bacterial Infections Flashcards
What is the definition of colonization?
presence of bacteria on a body surface (ex: skin, mouth, intestines, airways, etc), but the presence of bacteria does not cause disease in a person
What is the definition of infection/sepsis?
result of bacteria causing an illness, the s/s of infx depend on where the infx is
What is the definition of septicemia?
a serious, life threatening problem caused by a bacterial organism in the blood
What is the incidence of bacterial infections in the newborn?
1-8:1000 live births
What is the mortality rate for neonatal bacterial infx?
as high as 40% for preterm infant (early onset)
The significant mortality of neonatal sepsis necessitates what action by the provider?
early detection and treatment of sepsis to optimize the prognosis
What are common risk factors for neonatal bacterial infx?
PPROM, PROM >18h, PTL, chorioamnionitis, recent maternal infx, maternal fever in the perinatal period, maternal GU tract infx (including UTI and STD), perinatal asphyxia and invasive procedures
What is chorioamnionitis?
dx made by constellation of clinical symptoms including: maternal temp >100.4, maternal HR >100bpm, fetal HR >160bpm, uterine fundal tenderness, foul smelling amniotic or vaginal discharge, purulent appearing amniotic fluid
How does perinatal asphyxia increase an infant’s risk for bacterial infx?
increased especially with PROM >18h, during asphyxial event, baby may gasp and deeply inhale infected amniotic fluid
What invasive procedures increase an infant’s risk for bacterial infx?
procedures prior to del that interfere with the integrity of the amniotic cavity- CVS, amnio; or during delivery- fetal scalp electrode, vacuum assistance; or after delivery- PIV insertion, central lines, intubation
What is Gram staining?
the first step in identifying an organism, allows for differentiations of bacteria into 1 of 2 categories; G+ appear purple/blue (retain the stain) and G- appear pink
What are some common seen Gram positive bacterial organisms in the NICU population?
coagulase-negative staphylococcus, staphylocccus aureus, listeria monocytogenes, streptococcus pneumoniae and group A streptococcus
What are some common seen Gram negative bacterial organisms in the NICU population?
neisseria meningitdies, haemophilus influenza, klebsiella pneumoniae, pseudomonoas aeruginosa, acinetobacter species, citrobacter species, enterobacter species, serratia marcescens and proteus species
What is early onset sepsis?
within the first 72 h of life; can begin in utero as resul of swallowing or inhaling infected amniotic fluid; usually present within the first 24-48h
What is late onset sepsis?
after the first 72h of life
What are commonly presenting signs of bacterial infx in neonates?
respiratory distress, temperature instability, feeding intolerance, cardiovascular signs, abnormal neurologic status and abnormal skin findings * many of these signs may also be present with other concurrent illnesses
What clinical presentation of the respiratory system would indicate bacterial infx?
tachypnes, G/F/R, apeana, cyanosis, development/increased supplemental O2 requirement, respiratory support
What clinical presentation of temperature would indicate bacterial infx?
more commonly hypothermia, could be hyperthermia; temperature lability
What clinical presentation of feeding intolerance would indicate bacterial infx?
increased gastric residuals, poor feeding patterns, vomiting
What clinical presentation of the cardiovascular system would indicate bacterial infx?
tachycardia, bradycardia, mottling, hypotension, pale or grey skin color
What clinical presentation of the neuro system would indicate bacterial infx?
irritable, lethargy, sleepiness, sz and hypotonia
What clinical presentation of the integumentary system would indicate bacterial infx?
omphalitis, blisters on the skin, swelling or redness of the soft tissue, cellulitis, necrotic skin lesions
What is a WBC?
fx to protect the body from infx; produced in the bone marrow along with RBCs and platelets
What are the 5 different types of WBCs?
Neutrophils, eosinophils, basophils, lymphocytes and monocytes
What are neutrophils primarily responsible for?
killing and digesting bacteria
What are mature neutrophils called?
segmented neutrophils- segs (has a segmented nucleus), polymorphonuclear (PMNs), neuts, polys
What are immature neutrophils called?
bands, juveniles and stabs
How does a neutrophil mature?
in the bone marrow from a myeloblast into a segmented neutrophil
What comprises the neutrophil storage pool?
in the bone marrow the metamylocytes, bands and segmented neutrophils
How does the neutrophil storage pool of a neonate differ from an adult?
significantly smaller per kg of body weight
Under normal circumstances (no active infx), how do neutrophils fx?
mature neutrophils are released from the storage pool into the blood stream, where they circulate for 6-8h, then migrate in the tissue where they live for ~ 24h.
How do neutrophils fx in the context of an active infx?
immature neutrophils-bands, are also released from the bone marrow to the blood stream as the body attempts to maximize the # of circulating neutrophils
What is meant by a “left shift”?
appearance of immature neutrophils in the blood
What is neutrophil chemotaxis?
when released, neutrophils will then migrate to the site of infx in response to bacterial toxins. this movement toward the site is immature, especially in a preterm infant
How is a CBC with diff and plt count helpful in evaluating the presence of a bacterial infx?
first line SCREENING tool to detect sepsis; the peripheral CBC is accurate, simple and sensitive as a method of screening for potential infx. a babe with sepsis may have a normal CBC & CRP in early phase of illness
With the onset of bacterial infection, when can the first change in a CBC & CRP be detected?
the onset of time bw the first ∆ in CBC and the onset of infx may be 4-6h; the onset of time bw the first ∆ in CRP and the onset of infx may be 8-12h
How should an infant be cared for in the latent period of a bacterial infx?
during the latent period, the neonate is infected and needs abx but has a normal CBC & CRP. never withhold abx on the basis of a normal C&C
What is a blood culture?
an adequate amount of blood is plead in the culture bottle to detect the presence of bacteria in the blood
What can factors can potentially alter the results of a BCX?
without adequate blood volume there is a risk of a false negative cx, if MOB had abx prior to del- cx may not grow out bc of maternal and therefore, fetal treatment
How is a glucose level helpful in evaluating the presence of a bacterial infx?
hypoglycemia can p/w sepsis
How is a CRP helpful in evaluating the presence of a bacterial infx?
CRP is a protein produced by the liver during states of inflammation, infx, trauma or tissue necrosis; an acute phase reactant
When are CRP levels generally elevated?
bacterial infx, meningitis, respiratory illness, s/p surgery, bruising, immunizations, VD>CSX, even after vacuum or forceps delivery; generally elevates 4-8h post inflammatory response events; remains elevated during ongoing inflammation, declines when inciting event resolves
How should a CRP be interpreted?
CRP does not cross the placenta, so results are not MOB’s. normal value is <1; not always elevated, so decision to tx should not be made solely on CRP; non specific and multifactorial; trends are more important than single values
What laboratory evaluations should be considered when ruling out a bacterial infx?
CBC, BCX, glucose, CRP, blood gas, CSF, electrolytes, iCalcium, renal fx test, liver fx test and magnesium levels
How are electrolytes helpful in evaluating the presence of a bacterial infx?
evaluating Na & K levels, metabolic acidosis; magnesium- especially if MOB got mag in delivery
How is a bacterial infx directly diagnosed?
through the cx of a normally sterile fluid (ex: CSF, blood, urine)
How is a bacterial infx indirectly diagnosed?
CBC, acute phase reactants (CRP, ESR)
How is a CBC evaluated?
number of WBCs, ANC, immature to total ratio and plt count
At what level is a patient considered neutropenic?
ANC <1350
Why is neutropenia significant?
strong indicator of infx
Why is an ANC significant?
tells you the total number of neutrophils available to fight infx
Why is the immature to total ratio (I:T) significant?
tells you what percentage of the circulating neutrophils are immature
What is the normal range of RBCs?
5.1-5.8
What is the normal range of WBCs?
5-30
What is the normal range of HCT?
52-58%
What is the normal range of platelets?
150-400
What is the normal range of bands?
9% (not abnormal to have some bands)
What is the normal range of segs?
52%
What is the normal range of lymphocytes?
31%
What is the normal range of monocytes?
5.8%
How does maternal hypertension affect a neonate’s ANC?
MOB with HTN may have a decreased ANC compared to MOB without HTN
How is ANC calculated?
ANC= (% segs + % immature [bands, metas, myelos]) x WBC
What is the normal course of the WBC and neutrophi count post delivery?
rise in the first day of life, in term infants ANC peaks about 8h post del- therefore a declining neutrophil count (rather than the expected physiologic increase) is concerning for infx
What might a low ANC indicate?
depletion of neutrophil storage pool or that the infant is not going to be able to mobilize enough neutrophils necessary to fight a bacterial infx
Why is exhaustion of the neutrophil storage pool of utmost concern?
infants who deplete their stores while fighting an infx are at the highest risk of dying from sepsis
Why is the I:T ratio significant for infants with bacterial sepsis?
this calculation tells us what proportion of the circulating neutrophils are immature
How do you calculate I:T ratio?
(all immature WBCs- bands, metas, myelos)/total number of WBCs
What does a I:T ration of >0.2 suggestive of?
sepsis
What does a I:T ration of >0.8 suggestive of?
bone marrow depletion and correlated with higher risk of death from sepsis
What factors can potential cause the clinician to misinterpret lab values as a “left shift”?
violent crying, stressful delivery, PIH or the lab not correcting for nucleated RBCs
What can induce thrombocytopenia?
bacterial, fungal and viral infx
How should a platelet count of <100k be interpreted?
abnormal, needs evaluation, examine for s/s of bleeding
How should a platelet count of <50k be interpreted?
risk of bleeding is increased, examine for s/s of bleeding
How should a platelet count of <20k be interpreted?
dangerously low, examine for s/s of bleeding, consider a plt transfusion; at risk for intracranial bleeding
How should abx therapy be tailored to treat early onset sepsis?
need coverage for G+ and G- organisms, abx asap
What kind of coverage does ampicllin provide?
G+ (liseria and GBS)
What kind of coverage does genatmicin provide?
G-; amino glycosides require therapeutic level monitoring
What abx should be considered if nephrotoxicity is a concern?
cefotaxime (claforan) instead of gent
How should abx therapy be tailored to treat late onset sepsis?
need coverage for staphylococci and G- bacilli (pseudomonas); typically gent and vanc
What is the length of time required for abx therapy for the treatment of sepsis?
depending on individuals clinical presentation, risk factors and medical history- may need a 7-14d course depending on the baby and babes response
What is the length of time required for abx therapy for the treatment of pneumonia with a negative blood cx?
5-10d
What is the length of time required for abx therapy for the treatment of a significant left shift with negative BCX?
5-7d
What is meningitis?
an inflammation of the membrane that lines the brain and the spinal column; one of the most serious dz affecting babes; etiology can be bacterial or viral
What is the incidence of meningitis?
0.4-1 per 1000 live birth
What are common risk factors for meningitis?
premature infants, male, infants with CNS defects and infants of mothers with obstetric complications
What are the most common pathogens for meningitis?
also the most common for bacteremia: GBS and E.Coli
How does meningitis commonly present?
begins with subtle signs of sepsis; additional specific signs include: tense or bulging fontanels, high-pitched cry, sz and neck retraction
What is the diagnostic study for meningitis?
culture of the CSF
What are non-diagnostic studies that might also be helpful in the evaluation of meningitis in the neonate?
CSF glucose, CSF protein and CSF cell count
What can the CSF glucose indicate in the evaluation of meningitis in the neonate?
glucose typically falls with meningitis, must be compared to serum glucose at the time of the LP
What can the CSF protein indicate in the evaluation of meningitis in the neonate?
typically increases with meningitis; if a bloody tap, the sample might skew higher with more protein
What can the CSF cell counts indicate in the evaluation of meningitis in the neonate?
typically increased WBC with meningitis
When meningitis is suspected, how should abx therapy be delivered?
tx should be initiated immediately; amp (G+ coverage), gent (G- coverage) and cefotax (G- coverage)
What is the length of time required for abx therapy for the treatment of G+ meningitis?
~ 2 weeks
What is the length of time required for abx therapy for the treatment of G- meningitis?
~ 3 weeks
When should a repeat CSF cx be collected?
2-3d after initiation of treatment to ensure effective coverage
What is the mortality rate a/w meningitis?
poor prognosis; mortality rates as high as 30-60%
What are potential outcomes for infants that survive meningitis?
50% may have serious neuro sequelae (hearing loss, communicating/non-communicating hydrocephalus, abnormal speech, mental or motor loss of varying degrees and sz activity) 20-50% of surviving infants will experience at least 1 or more
When is HSV vertical transmission more likely to occur?
severe neonatal infx and is much more likely to occur if the MOB contracts a primary episode of HSV late in gestation
What are s/s of HSV infx?
skin vesicles, poor feeding, lethargy, fever, shock, sz (if CNS involvement)
Why is a PCR now the recommendation for HSV encephalitis diagnosis?
more accurate than a CSF cx, PCR can make many copies of viral DNA so even small amounts can be detected; $$$, not approved for genital testing; results can be returned quicker
