To identify the common infectious organisms responsible for neonatal bacterial conjunctivitis, eye swabs or conjunctival scrapings were cultured from the 400 bacteria-positive neonatal patients. The most common Gram-positive bacteria were
Staphylococcus epidermis (
n = 89),
Staphylococcus saprophyticus (
n = 97),
Staphylococcus aureus (
n = 53),
alpha-hemolytic streptococcus (
n = 29),
beta-hemolytic streptococcus (
n = 17), and
Mycobacterium xerosis conjunctiva (
n = 13) (Table
2); while the most common Gram-negative bacteria were
Neisseria gonorrhoeae (
n = 75),
Haemophilus influenzae (
n = 14), and
Escherichia (E). coli (n = 13) (Table
3).
When the bacterial species in the Gram-positive samples were further categorized, we found
Staphylococcus epidermidis and
Staphylococcus saprophyticus accounted for 62.2% (
n = 186) of the 298 neonatal bacterial conjunctivitis cases, ranging from 15.8% to 82.4% in different years (Table
2).
Staphylococcus aureus accounted for 17.8% (
n = 53) of the cases, ranging from 5.0% to 45.0%.
Hemolytic streptococcus (
alpha- and beta-) accounted for 15.6% (
n = 46) of the cases, ranging from 5.9% to 36.8%.
Xerophthalmia bacilli accounted for 4.5% (
n = 13) of the cases, ranging from 0% to 10.5%. When the year-by-year data from those 15 years was compared, the proportion of cases involving
Staphylococcus epidermidis and
Staphylococcus saprophyticus experienced an increasing trend (increased by ~60%), whereas the proportion of cases with
Staphylococcus aureus and
Hemolytic streptococcus (
alpha- and beta-) showed a decreasing trend in most of the years (decreased by ~30% and ~20% respectively) (Fig.
1b). The linear regression equation of
Staphylococcus epidermidis and
Staphylococcus saprophyticus: y = 3.7× + 32.9, R
2 = 0.59; The linear regression equation of
Staphylococcus aureus: y = −2.6× + 38.7, R
2 = 0.67; The linear regression equation of
Hemolytic streptococcus (alpha- and beta-): y = −1.1× + 24.2, R
2 = 0.31; The linear regression equation of
Xerophthalmia bacilli was y = 0.04× + 4.1, R
2 = 0.0041). However, the proportion of cases with
Mycobacterium xerosis conjunctiva did not show a clear trend during those years.
When the Gram-negative bacteria in the samples were analyzed, we found that
Neisseria gonorrhoeae was detected in 73.4% (
n = 75) of the 102 Gram-negative neonatal bacterial conjunctivitis cases, ranging from 60.0% to 85.7% in different years (Table
3).
Haemophilus influenzae was detected in 13.7% (n=14) of the cases, ranging from 0% to 25.0%.
E. coli was detected in 12.7% (n=13) of the cases, ranging from 0% to 25.0%. Although the frequency of the Gram negative bacteria showed an increasing trend during those 15 years, the detection frequency of either
Neisseria gonorrhoeae, Haemophilus influenzae or
E. coli seemed to oscillate during the 15 years, without a clear trend identified (Fig.
1c). The linear regression equation of
Neisseria gonorrhoeae: y = −0.28× + 75.6, R
2 = 0.017; The linear regression equation of
Haemophilus influenza: y = −0.11× + 14.9, R
2 = 0.0054; The linear regression equation of
E. coli was y = 0.39× + 9.5, R
2 = 0.037).