Systemic Bacterial Infections
Sepsis – spread of organism/pathogen into bloodstream causing physiologic effects. Pathogen depends on age of child: Less than 3 months – E. coli and Group B Streptococcus most common. 3 mo to 4 yrs – nasopharyngeal flora.
Most carried in nasopharynx are covered with polysaccharide capsule, which confers some virulence, gives a poor antibody response for children under the age of 24 mo, and activates antibody and complement that are crucial for immunity to these organisms. The RES system also needs to be intact for optimal clearance of these pathogens.
Streptococcus pneumoniae (pneumococcus) – gram positive coccus, most common cause of systemic bacterial infections in children outside of neonatal age. Can cause:
Haemophilus influenzae type b (Hib) - gram negative bacteria that was a common cause of sepsis in children, frequently with fatal sequelae. A vaccine derivative of the capsule linked to a protein carrier has been extremely effective. Serious illness due to this organism has almost been eradicated in the United States.
Neisseriae meningitidis (meningococcus) – gram negative diplococcus that is a classic cause of overwhelming meningitis and often fatal sepsis. Meningococcus appears to be cleared more by intravascular lysis of organism as opposed to the RES system. Terminal complement (MAC) is particularly important for this. Treat with penicillin.
Host issues that predispose to sepsis with these bacteria:
- Occult bacteremia – child appears clinically well. Often has a focus of infection (eg. otitis media) plus high fever. Blood culture grows out pneumococcus. Child usually does well.
- Sepsis – child clinically ill with fever, hypotension and sepsis syndrome.
- Overwhelming sepsis – usually abnormal host, often poor splenic function (sickle cell) or asplenia; death common.
- Treatment: Penicillin is still the drug of choice for penicillin-sensitive strains. Third generation Cephalosporins (ceftriaxone) or vancomycin are being used for resistant strains.
- (1) Hypogammaglobulinemic patients – susceptible to encapsulated bacteria. Give IV gammaglobulin prophylaxis.
- (2) Patients deficient in the terminal complement components are particularly susceptible to meningococcal sepsis.
- (3) Patients with asplenia or poor splenic function – susceptible to pneumococcus. Give penicillin prophylaxis.
- (4) HIV positive children, for reasons unknown, are susceptible to encapsulated bacteria more than normal children.
mostly pneumococcus; much less HiB due to effective vaccine. Rarely meningococcus.
These organisms tend to cause lobar pneumonias. In small children, associated bacteremia is common, and may appear septic. Other causes of bacterial pneumonia include Staphylococcus aureus and Group A Streptococcus.
Bacterial (vs. viral) pneumonia will present with high fever, toxicity (clinical exam shows systemic illness), white count usually elevated with left shift , and Ý sedimentation rate.
Chest x-ray shows lobar infiltrate. Presence of pleural fluid and/or empyema common.
usually caused by the nasopharyngeal encapsulated organisms: pneumococcus most common since HiB almost eradicated. Meningococcus also relatively common.
Pathogenesis – Nasopharyngeal colonization Þ bacteremia in non-immune child. Preceding viral infection may enhance bacterial adherence to mucosa. Once bacteremic, if blood bacterial density exceeds a threshold, penetration to meninges occurs. Inflammation of brain and particularly small blood vessels occurs.
Morbidity/Mortality – despite availability of antibiotics, morbidity of childhood bacterial meningitis is high (3-5%). Hearing loss is the most frequent problem. Also, language delay, seizures, etc.
Therapy – use an organism-sensitive antibiotic with adequate penetration of meninges for an adequate duration. Augmentive anti-inflammatory therapy (dexamethasone – reduced hearing loss in Hib meningitis. Controversial for use in other bacterial meningitides) can also help. H. flu and meningococcus are "contagious". Rifampin usually given to close contacts to eradicate nasopharyngeal carriage.
Bone and Joint Infections
Hematogenous spread of bacteria - most common for acute osteomyelitis or septic arthritis in children. Common bacterial pathogens include Pneumococcus (0-3 years old), Hib (rare now), Staphylococcus aureus (all ages), Group A Streptococcus (3-6), and Pseudomonas (all ages).
Bacteria usually introduced from a skin infection or lesion. These bacteria often lodge in bone area of recent trauma (hematoma) and proliferate in this immunologically protected site.
Direct trauma to foot – sharp object piercing the bottom of the foot when child has sneakers on. Pseudomonas aeruginosa is inoculated into the joint and/or bone causing an infection. Not hematogenous spread.
Diagnosis – Affected joint or tissue red and warm to touch. Pain often presenting sign with decreased walking or change in gait. Swelling is the most common, followed by fever, ß mobility, erythema, and skin abnormalities.
Ý ESR, Ý WBC with left shift.
Gold standard – open or closed aspiration of affected area with Gram stain and culture of material obtained.
Therapy: Adequately drain the wound. Give an organism-sensitive antibiotic with good penetration into bone or joint. IV initially and can switch to high dose oral therapy later.
- Systemic symptoms common especially if hematogenous spread. Include fever.
Urinary Tract Infections
Starts as local infection (unlike other infections). Bacteria adhere to mucosa and ascend into bladder, occasionally reaching kidneys to cause pyelonephritis; at this point, hematogenous spread cause secondary bacteremia
Organisms – E. coli and other Gram negative rods; Enterococcus
Predisposing factors – Obstruction from any cause, vesicouteral reflux, instrumentation, uncircumcised male child.
Work-up includes imaging of kidney. Ultrasound most frequently used. UTI (lower) vs. Pyelonephritis (upper):
± fever, no systemic illness. Treatment: oral antimicrobial therapy (except neonates)
Pyelonephritis – CVA tenderness; fever; systemic illness;Ý WBC, Ý ESR, Ý CRP – evidence of inflammation, abnormal urinalysis with WBC casts. Treat with IV therapy until clinically improved.
- UTI – dysuria, abnormal urinalysis,