**5. Microbiology of bleb related infection**

The most common pathogens in blebitis are Staphylococcus aureus and Staphylococcus epidermidis [47, 54, 55]. The microbes most commonly associated with blebitis are less virulent than those in BRE, are part of normal lid/lacrimal flora, and produce no exotoxins; therefore, with successful treatment, visual prognosis is good. In a retrospective study, visual acuity was at least 20/25 in all successfully treated patients [17].

The microbes most commonly associated with early BRE include Staphylococcus epidermidis. Late onset BRE is associated with greater percentage of Streptococcus species 31%, and Gram-negatives such as Haemophilus influenzae 23%, Enterococcus 7%, Pseudomonas 7%, and fewer Staphylococcus species 7–22% [39, 48, 56].

When initiating antibiotic therapy for BRI, it is important to consider antibiotic resistance, which is particularly high in staphylococci; nearly half being resistant to methicillin with a high probability of concurrent resistance among methicillin resistant Staphylococcus aureus to other commonly used antibiotic classes [57]. In such cases it is useful to know that vancomycin is active against all gram-positive organisms, including all the methicillin-resistant staphylococci [57, 58].
