Gentamicin resistance among Escherichia coli strains isolated in neonatal sepsis

Abstract

Neonatal sepsis is a significant cause of morbidity and mortality among term and preterm infants. Ampicillin and gentamicin are standard empiric therapy for early onset sepsis. Four cases of neonatal sepsis secondary to Escherichia coli (E. coli) found to be gentamicin resistant occurred within a five week period in one neonatal intensive care unit (NICU). To determine whether these cases could be tied to a single vector of transmission, and to more broadly evaluate the incidence of gentamicin resistant strains of E. coli in the neonatal population at our institution compared to other centers, we reviewed the charts of the four neonates (Infants A through D) and their mothers. The E. coli isolates were sent for Pulse Field Gel Electrophoresis (PFGE) to evaluate for genetic similarity between strains. We also reviewed all positive E. coli cultures from one NICU over a two year period. Infants A and B had genetically indistinguishable strains which matched that of urine and placental cultures of Infant B's mother. Infant C had a genetically distinct organism. Infant D, the identical twin of Infant C, did not have typing performed. Review of all cultures positive for E. coli at our institution showed a 12.9 percent incidence of gentamicin-resistance. A review of other studies showed that rates of resistance vary considerably by institution. We conclude that gentamicin-resistant E. coli is a relatively uncommon cause of neonatal sepsis, but should remain a consideration in patients who deteriorate despite initiation of empiric antibiotics.

Urinary Tract Infections in the Infant

“…Within the US, the incidence of ampicillin resistance in neonatal E. coli isolates has been reported to be as high as 75% and gentamicin resistance as high as 12%–17%. 54,55 In spite of approximately 90% resistance against ampicillin among the E. coli isolates from a neonatal ward, Taheri and colleagues 56 reported that clinical response was obtained in 50% of the patients, suggesting that that there is a discordance between in vitro and in vivo activity of these drugs. This may be because the urinary concentration of ampicillin is much higher than the plasma level since it is excreted through the kidneys which may allow it to overcome the minimum inhibitory concentration of certain pathogens.…”

Development of Gentamicin Resistance During Treatment of Escherichia coli Ventilator-Associated Pneumonia in a Neonate

“…24 Several cases of early onset neonatal sepsis from gentamicin resistant E coli have been reported in the literature. 9,23 For many of the cases, it was suspected that the resistant organism was transferred from the mother to the neonate during the perinatal period. 9,23 Factors associated with an increased risk of infection with resistant organisms in the neonate included: maternal hospitalization for more than 2 days, antenatal antibiotic exposure, prolonged rupture of membranes, prematurity, and low birth weight.…”

“…9,23 For many of the cases, it was suspected that the resistant organism was transferred from the mother to the neonate during the perinatal period. 9,23 Factors associated with an increased risk of infection with resistant organisms in the neonate included: maternal hospitalization for more than 2 days, antenatal antibiotic exposure, prolonged rupture of membranes, prematurity, and low birth weight. 9,23 At our site, we have found that neonates with early onset sepsis from gentamicin resistant gram-negative bacteria often had mothers who worked as hospital-based health care providers.…”

“…9,23 Factors associated with an increased risk of infection with resistant organisms in the neonate included: maternal hospitalization for more than 2 days, antenatal antibiotic exposure, prolonged rupture of membranes, prematurity, and low birth weight. 9,23 At our site, we have found that neonates with early onset sepsis from gentamicin resistant gram-negative bacteria often had mothers who worked as hospital-based health care providers. Cole et al found that E coli bacteremia was more likely to be diagnosed in the first week of life and more virulence factors were identified in isolates from the first 72 hours compared to after 72 hours of life.…”

Infection control and other stewardship strategies in late onset sepsis, necrotizing enterocolitis, and localized infection in the neonatal intensive care unit

“… 107 In the US, the reported incidence of ampicillin resistant neonatal E. coli strains is as high as 75%, and resistance to gentamicin is as high as 12-17%. 108 , 109 A retrospective study of 73 cases of neonatal UTIs in Iran reported over 90% resistance of E. coli strains against ampicillin. 110 Despite this, a clinical response was seen in 50% of infants, suggesting discordance between in vivo and in vitro activity, or higher urinary concentration of the drug.…”