Seven-year study finds Group B strep as main cause of newborn bacterial meningitis

Autopsy: Brain surrounded by pus (the yellow-greyish coat around the brain, under the dura lifted by the forceps), the result of bacterial meningitis. A brain autopsy demonstrating signs of meningitis. The forceps (centre) are retracting the dura mater (white). Underneath the dura mater are the leptomeninges, which appear to be edematous and have multiple small hemorrhagic foci (red). (Image: Wikimedia Commons)

Group B strep remains predominant despite the recent introduction of GBS screening for women near delivery, according to the new report, led by Dr. Jean Gaschignard Hôpital Antoine-Béclère, Clamart, France. However, the situation is different for preterm infants - who are at higher risk of death, regardless of the cause of their meningitis.

Largest-ever study of newborn bacterial meningitis

Drawing on information from 60% of French paediatric wards from 2001 through 2007, the researchers identified 444 infants who were diagnosed with bacterial meningitis during the first 28 days of life. About two-thirds of cases were "late onset," occurring at least five days after birth. The remaining one-third were "early onset," occurring in the first four days (usually the first day).

GBS the most common cause

The most common cause was GBS, which accounted for nearly 60% of cases. The next most common, about 30%, was Escherichia coli (E. coli) - a type of intestinal bacteria. In early-onset meningitis, GBS was even more common, accounting for more than three-fourths of cases. Infants who had seizures were also more likely to be infected with GBS.

The exception was preterm infants, who were more likely to be infected with E. coli: 45% of cases, compared to 32% for GBS. The rate of E. coli infection was even higher, 54%, in very preterm infants.

Overall, 13% of newborns with bacterial meningitis died. For preterm infants or those who were small for gestational age, the mortality rate increased to 25%.

The cooperative study was performed by the Paediatric Infectious Diseases Group of the French Paediatric Society to gain insights into the rates, causes, treatment, and outcomes of newborn bacterial meningitis in France. Over the past decade, hospitals in France and other developed countries began giving preventive antibiotics during the last weeks of pregnancy (intrapartum antibiotic prophylaxis) to mothers colonized with GBS.

Study is the largest series of newborn bacterial meningitis cases ever published

This raised concerns that other causes of bacterial meningitis might become more common, or that meningitis caused by GBS might shift from early-onset to late-onset cases. "Nevertheless, at the dawn of the 21st century, GBS remains the dominant cause of neonatal bacterial meningitis in developed countries such as France," Dr. Gaschignard and co-authors write.

This study is the largest series of newborn bacterial meningitis cases ever published. "Despite this high number of reported cases, it is likely that the incidence of bacterial neonatal [newborn] meningitis remains underestimated," according to the authors. The 13% mortality rate is consistent with previous studies.

However, the risk of death is about twice as high in preterm infants. Because testing for GBS isn't usually performed until the thirty-fifth week of pregnancy, the "vast majority" of preterm infants aren't screened for GBS before birth. The researchers speculate that the higher rate of E. coli meningitis in premature infants might be partly related to their high rate of antibiotic intrapartum treatment - including amoxicillin, which kills GBS - before delivery

Source: The Pediatric Infectious Disease Journal