26.2 Bacterial diseases of the nervous system  (Page 5/20)

H. influenzae produces at least 16 different virulence factors, including LOS , which triggers inflammation, and Haemophilus adhesion and penetration factor (Hap), which aids in attachment and invasion into respiratory epithelial cells. The bacterium also has a polysaccharide capsule that helps it avoid phagocytosis, as well as factors such as IgA1 protease and P2 protein that allow it to evade antibodies secreted from mucous membranes. In addition, factors such as hemoglobin-binding protein (Hgp) and transferrin-binding protein (Tbp) acquire iron from hemoglobin and transferrin, respectively, for bacterial growth.

Preliminary diagnosis of H. influenzae infections can be made by direct PCR and a smear of CSF . Stained smears will reveal intracellular and extracellular PMNs with small, pleomorphic, gram-negative coccobacilli or filamentous forms that are characteristic of H. influenzae . Initial confirmation of this genus can be based on its fastidious growth on chocolate agar. Identification is confirmed with requirements for exogenous biochemical growth cofactors NAD and heme (by MALDI-TOF), latex agglutination, and RT-PCR.

Meningitis caused by H. influenzae is usually treated with doxycycline , fluoroquinolones , second- and third-generation cephalosporins , and carbapenems . The best means of preventing H. influenza infection is with the use of the Hib polysaccharide conjugate vaccine . It is recommended that all children receive this vaccine at 2, 4, and 6 months of age, with a final booster dose at 12 to 15 months of age. US Centers for Disease Control and Prevention, “Meningococcal Disease, Disease Trends,” 2015. Accessed September 13, 2016. http://www.cdc.gov/meningococcal/surveillance/index.html.

Neonatal meningitis

S. agalactiae , Group B streptococcus (GBS) , is an encapsulated gram-positive bacterium that is the most common cause of neonatal meningitis , a term that refers to meningitis occurring in babies up to 3 months of age. Thigpen, Michael C., Cynthia G. Whitney, Nancy E. Messonnier, Elizabeth R. Zell, Ruth Lynfield, James L. Hadler, Lee H. Harrison et al., “Bacterial Meningitis in the United States, 1998–2007,” New England Journal of Medicine 364, no. 21 (2011): 2016-25. S. agalactiae can also cause meningitis in people of all ages and can be found in the urogenital and gastrointestinal microbiota of about 10–30% of humans.

Neonatal infection occurs as either early onset or late-onset disease. Early onset disease is defined as occurring in infants up to 7 days old. The infant initially becomes infected by S. agalactiae during childbirth, when the bacteria may be transferred from the mother’s vagina. Incidence of early onset neonatal meningitis can be greatly reduced by giving intravenous antibiotics to the mother during labor.

Late-onset neonatal meningitis occurs in infants between 1 week and 3 months of age. Infants born to mothers with S. agalactiae in the urogenital tract have a higher risk of late-onset menigitis, but late-onset infections can be transmitted from sources other than the mother; often, the source of infection is unknown. Infants who are born prematurely (before 37 weeks of pregnancy) or to mothers who develop a fever also have a greater risk of contracting late-onset neonatal meningitis.