Materials and methods

PATIENTS

We examined 118 consecutive adult patients with LDO, who had been referred for lacrimal drainage surgery to the outpatient clinic of the Department of Ophthalmology, Turku University Central Hospital, between April 1994 and November 1995. The patients ranged in age from 22 to 89 (mean 63.5) years; 93 (79%) were women and 25 (21%) were men. Nine of the 118 patients with LDO were bilateral cases. Eighteen patients had previously had at least one acute episode of dacryocystitis, and seven of them had suffered from two to five acute episodes. Patients who had undergone lacrimal drainage surgery during the past year were excluded. Five patients had had previous external DCR performed 1–24 years earlier and one patient had undergone silicone intubation 1 year earlier. Altogether, 112 patients had not undergone previous lacrimal drainage operations. Informed consent was obtained from all the patients studied.

OPHTHALMIC EXAMINATION

We performed a routine ophthalmic examination including biomicroscopy, using Haag–Streit 900 instruments paying special attention to the presence of discharge and epiphora. The LDO was confirmed by irrigation of the lacrimal drainage system and by probing up to the nasal wall of the lacrimal sac fossa.

BACTERIAL ISOLATION

In all, 127 samples of the contents of the lacrimal sac were obtained from 118 patients; nine of the patients had cultures obtained from both sides. The collection of the samples was performed either by applying pressure over the lacrimal sac and allowing the purulent material to reflux through the lacrimal punctum, or by irrigating the lacrimal drainage system with sterile saline and collecting the sample from the refluxing material. The samples were collected with sterile cotton wool swabs, ensuring that the lid margins or the conjunctiva were not touched. None of the patients had used either antibiotic eyedrops or systemic antibiotics for at least a week before their visit to the outpatient clinic. Anaesthetic eyedrops were not used before the sample collection. The samples were cultured on the day of collection onto blood, chocolate, and fastidious anaerobic agar and incubated aerobically and anaerobically for 4 days. The anaerobic incubation took place in an anaerobic cabinet (Don Whitley, UK). The bacteriological isolates were identified with standard procedures.

STATISTICS

Fisher’s exact fourfold table test was used for comparing the distributions of the isolated micro-organisms between different clinical groups with a p value < 0.05 chosen to be statistically significant.

Results

CLINICAL FINDINGS

A total of 97 (76%) cases showed chronic dacryocystitis with purulent discharge and epiphora. These cases were divided into two subgroups according to the quality of discharge. Forty six cases showed copious purulent discharge or thick mucous discharge coming from the lacrimal sac, and 51 cases showed epiphora and minor mucopurulent discharge only.

Thirty (24%) patients complaining of epiphora did not show any clinical signs of infection of the lacrimal drainage system. In all of these, the reflux from the irrigated lacrimal sac was entirely clear tear fluid and saline. Our clinical diagnosis for these 30 cases was SSLD.

BACTERIOLOGICAL FINDINGS

The results of the aerobic and anaerobic cultures of the 118 patients with LDO are presented in Table 1. Of the 127 samples 107 (84%) yielded a positive culture. Of the 107 samples with positive culture results, 51 (48%) had mixed cultures with two to four organisms isolated. Altogether, 156 organisms were isolated. The majority of micro-organisms were Gram positive bacteria. Altogether, 108 Gram positive isolates were recovered, representing 69% of the overall 156 isolates cultured. Gram positive bacteria were found in 79 samples, accounting for 62% of all the samples. In 26 of the samples two to three different Gram positive bacteria were present. The most frequently cultured species was Staphylococcus epidermidis, which was isolated in 42 (33%) of the samples, accounting for 27% of all the isolates. Gram negative bacteria were recovered from 26 samples (20%). They represented 17% of the isolates, the most common Gram negative bacteria beingHaemophilus influenzae, which represented 4% of the isolates. Anaerobic micro-organisms were present in 20 (16%) samples. They accounted for 13% of the isolates, the most frequently isolated anaerobic bacteria being Propionibacterium sp, which represented 10% of the isolates, and 80% of all the anaerobic isolates.

Both the 30 cases carrying the clinical diagnosis of SSLD, and the 97 cases with chronic dacryocystitis, showed a preponderance of staphylococci, Gram positive rods, Propionibacterium sp, and a few other anaerobic organisms (Table 2). Not a single isolate of streptococci occurred in samples of the cases with SSLD, whereas these organisms were isolated significantly more often (20%) in samples of the cases with chronic dacryocystitis (p=0.004). Gram negative organisms were also isolated significantly more often (26%) in the cases with chronic dacryocystitis than in the cases with SSLD (p=0.004). There were significantly more cases with SSLD (33%) than cases with chronic dacryocystitis (10%) in which no micro-organism was found (p=0.005). In chronic dacryocystitis both the cases with copious purulent or mucous discharge and those with minor mucopurulent discharge showed Gram positive organisms frequently (Table 3), although these were even more frequent in the cases with minor mucopurulent discharge (p=0.03). However, about half (52%) of the samples of the cases with copious purulent or mucous discharge showed Gram negative organisms, whereas these bacteria were isolated in only one sample (2%) of the cases with minor mucopurulent discharge. This difference was statistically highly significant (p=0.000).

Discussion

During the past 50 years the microbiological flora of dacryocystitis have gradually changed. The proportion ofStreptococcus pneumoniae, which in the 1930s was the most common species cultured after to Staphylococcus epidermidis (albus),3 has decreased.579 In this study Gram positive bacteria were found in 69% of the isolates. This is in close agreement with the observation of 65% of Gram positive organisms by Coden et al.7 The most common organisms cultured in our study were Staphylococcus species, accounting for 47% of the isolates. This percentage compares fairly well with the results of Thicker and Buffam,6 Huber-Spitzy et al,5 and Coden et al 7(their percentages being 73%, 51%, and 49% respectively).Streptococcus pneumoniae represented 5% of the isolates in our study, which is higher than Huber-Spitzy et al 5 and Coden et al 7reported (their percentages being 2% and 2.3%).

Gram negative organisms represented 17% of the isolates of the total material in this study, the most frequently isolated species beingHaemophilus influenzae (4%). Previously, Huber-Spitzyet al 5 reported Gram negative organisms accounting for 26% of isolates, the most frequent species beingEscherichia coli (12%). Coden et al 7 observed Gram negative organisms in 27% of all isolates, including Pseudomonas aeruginosa in 9% andHaemophilus species in 6% of isolates.

In the cases with chronic dacryocystitis Gram negative organisms were isolated in 26% of samples in this study. Gram negative organisms occurred statistically highly significantly more frequently in cases with copious purulent or mucous discharge than in cases with minor discharge. This tallies with the practice that chronic dacryocystitis with mucous or purulent discharge is a contraindication for elective intraocular surgery. In lacrimal drainage surgery of such cases the antimicrobial prophylaxis should also cover Gram negative organisms.

In this study anaerobic bacteria were seen in 13% of the overall 156 isolates, mostly including Propionibacterium species (80% of anaerobic isolates). Previously, anaerobic bacteria have been reported to account for 7% of isolates, the most frequent anaerobic bacteria being Propionibacterium acnes (67% of anaerobic isolates).7 Thicker and Buffam6 found no anaerobic bacteria from the lacrimal sac in their study. Huber-Spitzyet al 5 cultured two anaerobic bacteria (onePropionibacterium species and one anaerobicStreptococcus species) from purulent abscesses of the lacrimal sac in their study of 150 patients with acquired dacryocystitis.

Normal flora of human conjunctiva mostly consisted of Gram positive bacteria, which represented up to 97% of cultured aerobic isolates.10 The most common bacterium wasStaphylococcus epidermidis, accounting for 57–87% of isolates,9-12 while Streptococcus species accounted only for 6% of all aerobic isolates of normal conjunctiva.10 Gram negative bacteria represented 0–5% of aerobic isolates.9-12 The most frequent anaerobic bacteria in normal conjunctival flora was Propionibacteriumspecies, accounting for 19% of all isolates and 81% of all anaerobic bacteria.10 An interesting finding in our study was the paucity of Gram negative bacteria and Streptococcusspecies in the cases with SSLD, suggesting that the bacterial flora of this group are comparable with those of normal conjunctiva. This finding may explain why patients with SSLD did not have an increased risk for endophthalmitis after intraocular surgery.13

In conclusion, chronic dacryocystitis in adults was associated with an increased proportion of Gram negative bacteria. These were clearly not related to conjunctival flora. These Gram negative bacteria are potential pathogens in postoperative infections, both in intraocular and lacrimal drainage surgery. For this reason antimicrobial prophylaxis in lacrimal drainage surgery should also cover Gram negative rods.