Dacryocystitis was mostly occurred with bacterial infections [4, 5], and might damage the normal structure of lacrimal duct . In this retrospective study, we investigated the microbiologic culture results of dacryocystitis in adult and pediatric groups.
Similar to the endodontic infections, one microbiologic species could be nutrients for another one by the infections of lacrimal passage . The polymicrobial infection rate of this study was 12.43% (21/169), which was equal to that of previous studies (7%-30%) [20, 21]. The average number of microorganisms was 1.15 per culture, which was lower than that of previous studies, with an average of 1.5–2.3 microorganisms per culture [14, 16, 22–24]. The reason for this difference might be that the majority (17/21) of polymicrobial infection cases of our study were with only two microorganisms.
The female-to-male ratio of this study was 1.11, which is significantly lower than the previous results [14–16]. The reason for this difference might be that the major (105/169) included subjects of this study were pediatrics, with overall mean age of 16.6 years old, while the previous studies included more adult than pediatrics in their studies, with mean age of from 44 to 60 years old [14–16]. Apart from pediatric group, the female-to-male ratio in adult group could increase to 2.56 in this study, which was consistent with the reported values of previous studies [14–16]. Contrary to the adult group, the female-to-male ratio in pediatric group was only 0.69, indicating that there were less female patients than male patients in pediatric group. Previously, very few studies have investigated the sex ratio of dacryocystitis patients in pediatric group with relatively big sample size. Our current results indicated that the sex ratio of dacryocystitis patients in pediatric and adult groups might be different. Unlike in adult group, female patients might not be predominant in the pediatric group.
In the adult group, no acute dacryocystitis were observed, while in the pediatric group, both acute dacryocystitis and chronic dacryocystitis with NLDO were found. Previous studies have also reported that younger patients were more susceptible to acute dacryocystitis than chronic dacryocystitis with NLDO [14, 25]. The immature immune system of children might be one reason for this phenomenon .
The predominant microbiologic spectrum (46–90%) of dacryocystitis were reported to be gram positive isolates, while gram negative isolates only constitute 2.5–40% of pathogens [13–16, 26–28]. Contrary to those previous studies, our adult group study results showed that the gram positive isolates were not predominant, and gram positive and negative isolates were numerically equal in adult group (both 36 (48.65%)), indicating that gram negative isolates became more common and took more proportion in infection pathogen of dacryocystitis than before in adult group. However, in pediatric group, the results were still similar to the previous studies [13–16, 26–28], with gram positive isolates being the major organism (71(58.68%)) and gram negative isolates only taking a small proportion (32 (26.45%)).
In adult group, the leading isolates were Streptococcus pneumoniae (14.86%) and Coagulase negative staphylococci (12.16%). In pediatric group, the leading isolates were Streptococcus pneumoniae (24.79%) and Staphylococcus aureus (11.57%). Thus, we could find that, in both adult and pediatric groups, Streptococcus Pneumoniae took the leading position, followed by Staphylococcus spp.. Those findings were similar to previous reports [17, 29, 30], implying that Streptococcus pneumoniae and Staphylococcus spp. were the most common isolates in dacryocystitis. Because Streptococcus pneumonia was a normal inhabitant of nasopharynx, immunization might be necessary for the restriction of its spreads to other sites (e.g., the ocular tissue and organ) . For gram negative isolates, the most frequent isolate was Haemophilus influenza in both adult (5(6.76%)) and pediatric (7(5.78%)) groups, which was also consistent with previous reports [32, 33]. Besides that, compared with adult group, the fungus isolates were significantly more common in pediatric group (2 (2.70%) vs. 18 (14.88%), p = 0.007), implying that we should pay more attention to the anti-fungus treatment in pediatric dacryocystitis.
We divide the pediatric group into chronic dacryocystitis with NLDO and acute dacryocystitis groups, and found that the proportions of both gram positive and negative isolates were not significantly different between chronic and acute infection groups. However, the leading isolates in those two groups were distinct. For pediatric chronic dacryocystitis with NLDO, the leading isolates was Streptococcus pneumonia (28.43%), and for pediatric acute dacryocystitis, the leading isolates was Staphylococcus aureus (42.11%). Previous study has also suggested that the bacterial spectrum of acute and chronic dacryocystitis was different. The more virulent isolates (e.g., Staphylococcus aureus) might be more common by acute dacryocystitis [13, 14].
In term of sex, the isolates distribution showed no significant difference between male and female groups, with the leading isolate still to be Streptococcus pneumonia. Sex might have less influence on the microbiologic spectrum of dacryocystitis.
In this study, we used the lacrimal probe with sterile syringe at the end to collect samples from lacrimal sac. Using this noninvasive method, we could directly reach the lacrimal sac and take samples from lacrimal sac to the sterile syringe for culture. Thus, the collected samples would not expose to the conjunctival sac, avoiding the potential contamination by normal flora. Major normal flora of conjunctival sac has been confirmed to be gram positive isolates [2, 17, 34, 35]. Among them, Staphylococcus epidermidis accounts for about 57–87% of isolates, while Streptococcus spp. only occupied 6% [2, 17, 34, 35]. Meanwhile, our study showed that Streptococcus pneumoniae and Staphylococcus aureus were the most common isolates of dacryocystitis, which was different from the normal flora of conjunctival sac. Accordingly, we assume that the cultures obtained in this study was reliable, as there was a low possibility of contamination from conjunctival sac.