Septicaemia with coagulase negative staphylococci in a neonatal intensive care unit. Risk factors for infection, and antimicrobial susceptibility of the bacterial strains

A quantitative analysis of Ureaplasma urealyticum and Ureaplasma parvum compared with host immune response in preterm neonates at risk of developing bronchopulmonary dysplasia

Multiplex, real-time PCR for the identification of Ureaplasma urealyticum and Ureaplasma parvum was performed on nucleic acids extracted from sequential endotracheal aspirates obtained from preterm neonates born at <29 weeks of gestation and ventilated for more than 48 h admitted to two level 3 neonatal intensive care units. Specimens were obtained shortly after birth and sequentially up until extubation. One hundred fifty-two specimens (93.8%) contained material suitable for analysis. Ureaplasma spp. were identified in 5 of 13 neonates studied. In most cases, the DNA load of the detected Ureaplasma species was low and decreased over time. In addition, changes in detectable Ureaplasma species DNA did not relate to changes in the inflammatory marker C-reactive protein (CRP) or respiratory status. All but two blood samples obtained at times of suspected sepsis were culture positive for other microorganisms; the species cultured were typically coagulase-negative staphylococci and were associated with increased levels of CRP (>10 mg/liter). This study was limited by the small number of patients examined and does not have the power to support or contradict the hypothesis that postnatal lung infection with Ureaplasma parvum is causally related to bronchopulmonary dysplasia (BPD) or adverse respiratory outcomes after preterm birth. However, in this study, increases in CRP levels were not associated with patients in whom Ureaplasma parvum was detected, in contrast to the detection of other bacterial species.

Risk factors for infection with coagulase-negative staphylococci in newborns from the neonatal unit of a brazilian university hospital

Background:

Coagulase-negative staphylococci (CoNS) are one of the most frequent causative agents of neonatal nosocomial infections, especially in premature and low-weight newborns. Risk factors for infection include extracellular polysaccharide production and consequent biofilm formation that permit adhesion to the smooth surface of catheters and other medical devices. The objective of this study was to identify CoNS strains isolated from 105 newborns admitted to the Neonatal Unit of our hospital, and to evaluate the association of biofilm production and host risk factors with the occurrence of infection.

Methods:

CoNS isolates were identified and classified as significant or contaminant based on clinical and laboratory data of the newborn medical records. Perinatal risk factors for infection, neonatal clinical evolution, and antibiotic treatment were analysed. In addition, the presence of genes (icaA, icaC and icaD) responsible for biofilm production in CoNS was investigated.

Results:

Among the 130 CoNS strains studied, 66 (50.8%) were classified as clinically significant and 64 (49.2%) as contaminant. There was no difference in the detection of biofilm-specific genes between CoNS strains isolated from newborns with (81.8%) and without infection (84.3%), although 11 (91.7%) of the 12 children whose death was related to CoNS were infected with strains that were positive for these genes. Forty-five (83.3%) of the 54 newborns infected with CoNS were premature and 33 (61.1%) had a birth weight ≤ 1,500 g. Most newborns infected with CoNS had been submitted to invasive procedures, including catheter use (85.2%), parenteral nutrition (61.1%), and mechanical ventilation (57.4%). S. epidermidis was the most frequently isolated species (81.5%) and was more related to infection (86.3%) than to contamination (76.5%).

Conclusion:

Most newborns infected with CoNS presented factors that contributed to the colonization and development of infection with these microorganisms, including a birth weight ≤ 1,500 g, catheter complications, use of a drain, and previous antibiotic treatment. The fact that most children who died of CoNS-related infection carried strains positive for biofilm-specific genes indicates the importance of this virulence factor for the outcome of staphylococcal infections.

Role of antimicrobial applications to the umbilical cord in neonates to prevent bacterial colonization and infection: a review of the evidence

In developing countries umbilical cord infections constitute a major cause of neonatal morbidity and pose significant risk for mortality, whereas outbreaks of cord infections continue to occur in developed country nurseries. Cord infections in developing countries can be prevented through increasing access to tetanus toxoid immunization during pregnancy, promoting clean cord care and reducing harmful cord applications and behaviors. Interventions introduced in both developed and developing countries to reduce exposure of the cord to infectious pathogens include clean cord cutting, hand-washing before and after handling the baby, bathing of the infant with antimicrobial agents and application of antimicrobials to the cord. Despite the importance of umbilical cord care, both traditionally and medically, there have been few randomized trials investigating the impact of different cord care regimens on rates of local or systemic infections, particularly in developing countries. This review examines available data on umbilical cord care, with a particular focus on those comparing rates of bacterial colonization and/or rates of cord infection among neonates receiving different umbilical cord care regimens. Although most investigators agree that topical antimicrobials reduce bacterial colonization of the cord, a firm relationship between colonization and infection has not been established. Further research in developed countries, including follow-up beyond hospital discharge, is required before advising on "best cord care practices." The paucity of published reports from developing countries indicates the need to investigate the impact of antimicrobial applications on cord and systemic infections in a community-based, prospective manner.

Risk factors for nosocomial sepsis in newborn intensive and intermediate care units

A multicentre prospective study was performed to estimate the incidence of hospital infections and to identify the most relevant risk factors for sepsis in a large and unselected population of high-risk newborns. The study involved 49 neonatal intensive care units and 17 neonatal intermediate care units in Italy. Newborns were followed up from admittance to the units until discharge. Data on demographics and clinical characteristics, exposure to the principal invasive procedures, and onset of infectious complications were prospectively collected. Only infections developing after 48 h from admittance to the unit were recorded. A multiple logistic regression was performed to identify which factors were independently associated with sepsis. Among the 8263 newborns included in the analysis, the incidence of infected newborns was 14.4 per 100 newborns and 0.9/100 days of stay. The incidence of infections was 19.1/100 newborns and 1.2/100 days of stay. Sepsis represented 15.4% of all infections (incidence 2.9/100 newborns and 0.2/100 days of stay). The following factors were independently associated with sepsis: umbilical catheterization, both through the vein and the artery for more than 5 days; mechanical ventilation for more than 5 days; necrotizing enterocolitis; birth weight equal to or less than 2500 g; nasogastric tube; total parenteral nutrition; and transfer from other hospitals. Umbilical catheters accounted for the highest proportion of sepsis (62%), followed by arterial catheters (31%), nasopharyngeal cannulae (26%), tracheal cannulae (20%), and nasal cannulae (20%). The population attributable risk for the other procedures was less than 10%.

CONCLUSION

This study demonstrates that in a large and unselected newborn population, several host factors and invasive procedures are independently associated with an increased risk of sepsis. After adjustment for clinical severity, intravascular catheterization and assisted ventilation were found to be responsible for a considerable proportion of observed sepsis. They should therefore be considered as priorities for interventions, aimed both at reducing unnecessary use and promoting more strict compliance with aseptic practices.

Characterization of coagulase-negative staphylococci causing nosocomial infections in preterm infants

The species spectrum, antibiotic susceptibility, and genomic profile of coagulase-negative staphylococci (CNS) isolated from infected preterm infants were compared with those obtained in CNS from nursery personnel. Staphylococcus epidermidis was the predominant species in the 66 investigated preterm infants (171 isolates), accounting for 64% of all isolates. A high proportion of Staphylococcus haemolyticus (32%) could be detected. In contrast to the results in patients, the spectrum in nursery personnel was broad and included more species of CNS. All isolates of CNS from preterm infants demonstrated a low rate of susceptibility to the beta-lactam antibiotics (2% sensitivity to penicillin and 6% sensitivity to oxacillin). Sensitivity to gentamicin (9%) was also rare. An unexpected observation was susceptibility to teicoplanin in only 70% of all CNS isolated from patients due to the high proportion of Staphylococcus haemolyticus. Analysis of the genomic profile of 33 isolates of Staphylococcus haemolyticus by pulsed-field gel electrophoresis revealed a relationship between the strains. An outbreak of one particular strain of Staphylococcus haemolyticus in the neonatal intensive care unit investigated can therefore not be excluded.

Colonization with coagulase-negative staphylococci in two neonatal units

Episodes of septicaemia due to coagulase-negative staphylococci (CNS) were more frequent in a level III than in a level II neonatal unit in Stockholm, Sweden. Colonization with CNS during the first 2 weeks of life was investigated in 10 infants from each unit. As the use of antibiotics differed between the two units, the aim was to correlate colonization and antimicrobial resistance patterns to antibiotic usage. Antimicrobial susceptibility of CNS to isoxazolylpenicillins, co-trimoxazole, erythromycin, clindamycin, chloramphenicol and gentamicin was determined. Selected isolates were typed with restriction endonuclease analysis of plasmid DNA and of genomic DNA. Infants were frequently colonized with multiple strains and species of CNS, and transmission of strains from patient to patient occurred within the unit. Qualitative and quantitative differences in antibiotic use were not correlated with colonization. The prevalence of resistant isolates, mostly of Staphylococcus haemolyticus, was higher in the level II unit with lower use of antibiotics. Staphylococcus epidermidis, which is generally more virulent, prevailed in the level III unit, where there were more severely ill children and invasive procedures were more frequently performed.

Nosocomial Staphylococcus epidermidis septicaemia among very low birth weight neonates in an intensive care unit

A cluster of cases of septicaemia caused by coagulase-negative staphylococci was observed among the infants at the Neonatal Intensive Care Unit (NICU) of the Karolinska Hospital in May 1987. The presence of a unique antibiogram among the blood culture isolates prompted an investigation to determine whether an epidemic strain existed or not, using antibiogram, biotyping and plasmid profiles as epidemiological markers. All 14 isolates with a unique antibiogram were investigated, and 22 isolates without the unique antibiogram served as controls. Of the 14 isolates, 11 were Staphylococcus epidermidis and had similar plasmid patterns. Of the 22 control isolates, 15 were S. epidermidis, and none had the special plasmid pattern nor any other recurring plasmid patterns. The use of plasmid profile analysis together with antibiograms thus identified a possible epidemic strain of S. epidermidis which may have been responsible for the upsurge of septicaemia cases at the NICU. The presence of an epidemic strain implies that hospital cross infection control could be important in preventing neonatal septicaemia caused by S. epidermidis.