Selection of antimicrobial agents for treatment of neonatal sepsis

Real-time polymerase chain reaction for detecting bacterial DNA directly from blood of neonates being evaluated for sepsis

Speed is of the essence when evaluating an infant with symptoms consistent with sepsis. Because of the high morbidity and mortality associated with neonatal sepsis, infants receive multiple, broad-spectrum antibiotics before receiving finalized blood culture results. Incorporating an additional, reliable, yet rapid assay to detect bacteria directly from blood would facilitate timely diagnosis and appropriate care. To this end, we designed a real-time polymerase chain reaction (PCR) assay targeting the highly conserved 380 bases of 16S rDNA. DNA was extracted from whole-blood samples using a Qiagen column. The limit of detection for the TaqMan-based assay, using a Smartcycler instrument, was 40, 50, or 2000 colony-forming units per milliliter of blood (CFU/ml) of Escherichia coli, group B Streptococcus, and Listeria monocytogenes, respectively, when white blood cell counts were below 39,000/microl. Implementing this approach requires less than 4 hours for both sample preparation and real-time PCR compared with 1 to 2 days to detect growth in culture or 5 days to finalize no-growth culture results. There was an overall agreement between the results of culture and real-time PCR of 94.1% (80 of 85) in this study. These results suggest that molecular techniques can augment culture-based methods for diagnosing neonatal sepsis, especially in infants whose mothers have received intrapartum antibiotic prophylaxis.

Randomized trial using piperacillin versus ampicillin and amikacin for treatment of premature neonates with risk factors for sepsis

Premature infants with risk factors for early onset sepsis who were less than seven days of age were blindly randomized to receive either piperacillin and placebo (200 infants) or ampicillin and amikacin (196 infants). One of 30 treated infants developed positive blood cultures. The overall mortality in the two groups was 8.5% for piperacillin/placebo and 13.8% for ampicillin/amikacin (p = 0.11). Serum creatinine elevation above 100 mumol/l (1.131 mg/dl) during treatment was similar in the two groups. The effectiveness of piperacillin/placebo is similar to that of ampicillin/amikacin for empiric treatment of premature newborns with risk factors for early onset sepsis.

Role of circulating complement and polymorphonuclear leukocyte transfusion in treatment and outcome in critically ill neonates with sepsis

We examined the effects of early administration of polymorphonuclear leukocyte (PMN) transfusions in neonates with sepsis by prospectively randomizing 35 consecutive critically ill infants with sepsis, 21 of whom received PMN transfusions in addition to supportive care, one transfusion every 12 hours for a total of five transfusions. Each transfusion consisted of 15 mL/kg containing 0.5 to 1.0 X 10(9) PMN with less than 10% lymphocytes, and was subjected to 1500 rads. PMNs were obtained by continuous-flow centrifugation leukopheresis. Pretreatment values that did not significantly affect survival included weight, gestational age, sex, prematurity, C-reactive protein, initial hematocrit, platelet count and absolute granulocyte count (AGC less than or equal to 1500/mm3), IgM, IgG, IgA, neutrophil supply pool depletion, hypoxia, acidosis, and hypotension. Postnatal age was significantly lower in the nontransfused group than in the transfused group; 2.3 +/- 0.6 vs 6.1 +/- 2.2, (P less than 0.001). Positive blood cultures were obtained in 80% of both groups. Low circulating levels of total hemolytic complement were associated with a poor outcome and higher mortality: 56 +/- 4.0 IU in survivors vs 31 +/- 4.4 IU in nonsurvivors (P less than 0.01). Survival was significantly greater in the PMN transfused group than in the nontransfused group: 20 (95%) of 21 vs nine (64%) of 14 (P less than or equal to 0.05). No untoward effects were attributable to PMN transfusions, either during the study or on subsequent follow-up visits. These preliminary data suggest that early treatment with PMN transfusions improves survival in neonates with overwhelming sepsis. In addition, depleted or low circulating levels of complement may influence prognosis and thus future treatment strategies for neonatal sepsis.

Antimicrobial therapy of bacterial sepsis in the newborn infant

Septicemia continues to be an important cause of neonatal morbidity and mortality. The bacteria most commonly responsible are group B beta-hemolytic streptococci and Escherichia coli, but regional differences exist. Recently sepsis caused by Staphylococcus epidermidis has occurred with increasing frequency in several neonatal intensive care units. Other organisms are less commonly responsible. The choice of antibiotics for suspected sepsis is based on the possible organisms involved and their antibiotic susceptibility patterns, which vary from hospital to hospital and at different times in the same hospital. Currently recommended initial therapy consists of a penicillin and an aminoglycoside, usually ampicillin and gentamicin. The addition of vancomycin is indicated when staphylococcal septicemia is suspected. During outbreaks of neonatal sepsis caused by aminoglycoside-resistant gram-negative bacteria, the use of third-generation cephalosporins or acylaminopenicillins may be appropriate, depending on the results of susceptibility tests. Continuing efforts to develop antibiotics for the treatment of neonatal sepsis are warranted.

Meningitis: describing the community health problem

We identified all 391 cases of meningitis hospitalized in a metropolitan community (population 367,094) over a four-year period to assess incidence, morbidity, and mortality. The crude incidence rate was 27 per 100,000 person years; the incidence rate for children under 5 years of age was 174 per 100,000 person years. The case fatality rate was 3 per cent. Bacterial organisms were identified in 33 per cent of all cases, with H. influenzae most commonly observed (53 per cent). Only 16 per cent of hospitalized cases were known to the county health department.

Single-dose pharmacokinetics of aztreonam in pediatric patients

Single intravenous doses (30 mg/kg) of aztreonam, a novel monobactam antibiotic, were administered to 29 children from 2 days to 11 years old. Serum, urine, and, when possible, cerebrospinal fluid samples were analyzed by high-pressure liquid chromatography and microbiological methods. The concentration of aztreonam in serum 15 min after drug administration was approximately 100 micrograms/ml in all age groups. The elimination half-life varied inversely, and the clearance from serum varied directly, with age. Aztreonam pharmacokinetics in 2- to 12-year-olds were similar to those in adults. The concentration in urine was high and prolonged, with potentially therapeutic concentrations still present 12 to 24 h after infusion in all age groups. Penetration into cerebrospinal fluid averaged 17.3% in children with inflamed meninges. Standard clinical and laboratory measurements revealed no untoward reactions. The 30-mg/kg dose of aztreonam produced potentially therapeutic concentrations in serum, urine, and cerebrospinal fluid. A dosage schedule of every 6 to 8 h in older children and every 8 to 12 h in neonates is suggested for multiple-dose clinical trials.