To investigate the pathogen distribution with coagulase negative staphylococcus (CNS) excluded and antibiotic resistance of infants with sepsis during the first 3 months after birth.

A retrospective analysis was conducted on 968 isolates from 924 infants within 3 months of age who were admitted to the Guangzhou Women and Children′s Medical Center, Guangzhou Medical University from January 1, 2012 to December 31, 2016. The following items were analyzed, including pathogen distribution of 968 isolates from 924 infants within 3 months of age and with blood culture-confirmed sepsis, pathogen distribution of early-onset sepsis (EOS) infants and late-onset sepsis (LOS) infant, and antibiotic resistance of common Gram-negative bacilli and Gram-positive cocci. Chi-square test was taken to compare the constituent ratio of Escherichia coli, Klebsiella pneumoniae, group B streptococci (GBS), Staphylococcus aureus, and fungi isolated from blood culture-confirmed sepsis between EOS and LOS infants. The procedures followed in this study were in line with the ethical standards established by the Medical Ethics Committee of the Guangzhou Women and Children′s Medical Center, Guangzhou Medical University and were reviewed and approved by the committee.

①Among 968 isolates from 924 infants within 3 months of age, Gram-negative bacilli were predominant (593 strains, 61.3%, 593/968), followed by Gram-positive cocci (318 strains, 32.9%, 318/968), fungi (52 strains, 5.4%, 52/968), Gram-negative cocci (3 strains, 0.3%, 3/968) and Gram-positive bacilli (2 strains, 0.2%, 2/968). Escherichia coli (21.4%, 207/968) and Klebsiella pneumoniae (19.6%, 190/968) were the main pathogens of Gram-negative bacilli. And GBS (11.5%, 111/968), Staphylococcus aureus (7.7%, 75/968), Enterococcus faecalis (4.1%, 40/968) were the main pathogens of Gram-positive cocci. ②A total of 226 isolates were isolated from 197 EOS infants, of which the predominant pathogens were Escherichia coli (23.9%, 54/226), GBS (17.7%, 40/226) and Klebsiella pneumoniae (15.9%, 36/226). Besides, a total of 742 isolates were isolated from 727 LOS infants, of which the predominant pathogens were Klebsiella pneumoniae (20.8%, 154/742), Escherichia coli (20.6%, 153/742), and GBS (9.6%, 71/742). The proportion of GBS in 226 isolates from EOS infants was 17.7% (40/226), which was significantly higher than that of the LOS infants (9.6%, 71/742), and the difference was statistically significant (χ²=11.28, P=0.001), whereas the proportion of Staphylococcus aureus and fungi in EOS infants were 4.0% (9/226) and 2.7% (6/226), respectively, which both were lower than those of LOS infants 8.9% (66/742) and 6.2% (46/742), respectively, and both the differences were also statistically significant (χ²=5.85, P=0.016; χ²=4.28, P=0.039). ③ Among 593 strains of Gram-negative bacilli, Escherichia coli and Klebsiella pneumoniae showed high resistance to ampicillin (81.1% and 99.4%), while low resistance to piperacillin/tazobactam, amikacin, ertapenem, imipenem and cefepime with the rate of resistance ranged from 0 to 17.2%. ④ Among 318 strains of Gram-positive cocci, GBS, Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium were highly sensitive to vancomycin, tigecycline and linezolid and the rates of resistance all were 0. In addition, Staphylococcus aureus showed high resistance to penicillin, and the rate of resistance was 92.9%.

Gram-negative bacilli is the main pathogen among infants with sepsis up to the age of 3 months, followed by Gram-positive cocci. Selection of anti-bacterial agents for the treatment of infants with sepsis up to the age of 3 months should be highly aware of drug resistance.