**14. Conjunctivitis due to coinfection**

Conjunctivitis is the most common eye infection in the world. Usually, the normal microbiota in the conjunctiva participates in infectious diseases of the ocular surface, and it has been reported that diversity in the conjunctival microbiota varies depending on geographic region or occupational activity [50, 51, 52, 53]. Moreover, the pathogenesis of infectious conjunctivitis depends on the circumstances and intrinsic mechanisms to the microorganism and the host.

Although there are high diversity of microorganisms on the conjunctiva, few coinfections have been reported. This lack of reports could be due to confusing clinical manifestations or the low sensitivity of the methods used or simply because two or more microorganisms are not usually searched in an infection.

In a patient with conjunctivitis, an uncommon relationship between an adenovirus and *Chlamydia* spp. was reported. The study showed three patients positive for *Chlamydia* spp. in a sample of 100 patients with adenoviral conjunctivitis, using polymerase chain reaction (PCR) [54, 55]. Another report showed the presence of adenovirus type 53 with a multiple resistant strain of *Neisseria gonorrhoeae* in a patient with severe bilateral conjunctivitis.

Iwalokun *et. al*., presented interesting results in a study conducted in Lagos, Nigeria. They analyzed 83 samples from patients with conjunctivitis and isolated 155 bacteria from the samples; the resistance patterns and the plasmid profile were evaluated. The authors found coinfections of two, three, or more pathogens (51.8 % and 18.1 %, respectively) and were able to identify three infection patterns that were significantly different [7]. This work emphasizes the possibility that multiple microorganisms can cause conjunctivitis.
