OVERVIEW
Streptococcus B is a conditionally pathogenic bacterium that colonizes the genital, intestinal, and urethral tracts of both males and females, and can be sexually transmitted. Neonates can be infected directly from their mothers or through the upstream transmission of parasitic bacteria from the maternal genital tract during labor. Group B streptococcal infections are rare in adults, predominantly in mothers, and in a few cases in immunocompromised patients, such as those with diabetes mellitus, chronic hepatic insufficiency, HIV infection, malignant neoplasms, and those receiving immunosuppressive therapy.
Etiology
Group B streptococcal infections account for about 8% of all streptococcal infections. It can be categorized into nine subtypes according to surface antigens, i.e., Ia, Ib, II, III, IV, V, VI, VII and VIII. In the blood plate can be A, B or C hemolytic reaction, hemolytic strains of streptococcal hemolysin produced by group A bacteria with O and S different, no antigenic. According to the biochemical classification, this group of bacteria is Streptococcus lactis-free.
Symptoms
It can be divided into two categories: neonatal infection and adult infection.
1. Group B streptococcal infection in pregnant women
Group B streptococci are common pathogens that cause puerperal fever, and these bacteria can cause puerperal infections regardless of the mode of delivery.Most of the puerperal infections caused by group B streptococci present as a single bacterial infection, with early onset of symptoms, high fever (>38.8 ℃), tachycardia, etc. Group B streptococci are also the main causative agent in causing bacteremia and wound infections in pregnant women, and streptococcal pneumonia can also occur, Meningitis, liver abscess and sepsis, etc. The mortality rate is high, and it has been reported that the mortality rate can reach 29%～52%.
2. Fetal and neonatal group B streptococcal infections
Intrauterine infections of group B streptococci can cause fetal death in utero, but the most common lesion is neonatal sepsis.
(1) Early-onset group B streptococcal infections usually develop within 7 days after delivery, and in 2/3 of cases, symptoms of infection appear within 6 hours after delivery. Neonatal infections are characterized by bacteriuria or sepsis (30%-40%), pneumonia (30%-40%), and meningitis (30%), with early-onset cases developing respiratory distress syndrome at birth.
(2) Late-onset infections In addition to early-onset infections, late-onset neonatal group B streptococcal infections are also a common type. Late-onset infections often begin after the first week of the postpartum period or even more than 10 days after birth. Meningitis and sepsis predominate and there is a risk of complicating the sequelae of meningitis. The most common serotype causing meningitis is group B streptococcus type III, which accounts for 90% of meningitis.
Examination
1. Urine examination
Group B streptococcus antigen in urine, with a high positive rate.
2. Bacterial culture
Bacteria positive.
3.Latex agglutination test
Used for early detection of patients.
Diagnosis
Mainly rely on bacterial culture.
Treatment
Group B streptococci are sensitive to penicillins, cephalosporins and erythromycin, but their degree of sensitivity is worse than that of group A streptococci.
The drug of choice for the treatment of neonates, infants and adults with group B streptococcal infections is penicillin, which can be given in combination with aminoglycoside antibiotics to achieve synergistic antimicrobial effect and expand the antimicrobial spectrum in the early stage of the infection when the pathogen is not yet determined; once the pathogen is clearly identified, penicillin can be used alone. However, aminoglycoside antibiotics are detrimental to the hearing of newborns, and the dosage is difficult to control, so they should be avoided as much as possible.