Bacteria can normally be found in the conjunctival sac. In about 90% of people, bacteria can be isolated from the conjunctival sac, and in 35% of them, more than one type of bacteria can be isolated, mainly Staphylococcus epidermidis (>60%), Corynebacterium diphtheriae (35%) and Propionibacterium acnes anaerobic, which reduce the infestation of other pathogenic bacteria by releasing antibiotic-like substances and metabolites. Infections can occur when the pathogenic bacteria are stronger than the host’s defenses or when the host’s defenses are compromised, such as dry eyes and long-term glucocorticoid use. Bacterial conjunctivitis should be suspected in patients with conjunctival inflammation and purulent exudate in the eye. The disease can be classified as hyperacute (within 24 hours), acute or subacute (hours to days), or chronic (days to weeks). The severity of the disease can be classified as mild, moderate, or severe. Patients with acute conjunctivitis all have varying degrees of conjunctival congestion and conjunctival purulent, mucopurulent, or mucopurulent discharge. Acute conjunctivitis is usually self-limiting, with a duration of about 2 weeks. Effective local treatment can reduce the incidence and duration of the disease, and healing occurs within a few days after administration of sensitive antibiotics. Chronic conjunctivitis is not self-limiting and is more difficult to treat. Other less common bacteria are Mycobacterium tuberculosis and Mycobacterium diphtheriae. Chronic conjunctivitis can evolve from improper treatment of acute conjunctivitis, or it can start as a chronic inflammatory process after infection with Morax-Axenfeld’s bifidobacteria, streptococci, or other less virulent bacteria, with no seasonality in onset. It can also be caused by adverse environmental irritants such as dust and chemical fumes, long-term application of irritating medications to the eye, refractive error, excessive smoking and drinking, and sleep deprivation. Many patients also have lid entropion and impingement, as well as chronic lacrimal sacculitis, chronic rhinitis, and other peripheral tissue inflammation. Clinical manifestations] Acute papillary conjunctivitis with cicatricial or mucopurulent exudate is a characteristic manifestation of most bacterial conjunctivitis. The disease starts in one eye and spreads to both eyes through hand contact. Patients experience irritation and congestion in the eye and wake up in the morning with a discharge from the lid margin that is initially dilute and plagioid, becoming mucopurulent and purulent as the disease progresses. Occasionally, there is eyelid edema and vision is generally unaffected. Corneal involvement with patchy epithelial clouding may cause vision loss. The severity of papillary hyperplasia and follicle formation in bacterial conjunctivitis depends on bacterial virulence including invasiveness. Corynebacterium diphtheriae and Streptococcus haemolyticus can cause lid conjunctival mask or pseudomembrane formation. (i) Hyperacute bacterial conjunctivitis Caused by bacteria of the genus Neisseria (gonococcus or meningococcus). It is characterized by a short incubation period (ranging from 10 hours to 2-3 days), rapid progression of disease, and conjunctival congestion and edema with copious purulent discharge. About 15% to 40% of patients can rapidly develop corneal clouding, infiltration, peripheral or central corneal ulceration, and if not treated promptly, corneal perforation can occur after a few days, seriously threatening vision. Other complications include anterior chamber pus accumulation iritis, lacrimal gland inflammation, and eyelid abscesses. Adults with gonococcal conjunctivitis are primarily infected through genital-ocular contact, and newborns are primarily infected during delivery via the maternal birth canal with gonococcal vaginitis, with an incidence of approximately 0.04%. The most common route of infection for Neisseria meningitidis conjunctivitis is hematogenous transmission, but it can also be transmitted through respiratory secretions. Adult gonococcal conjunctivitis is more common than meningococcal conjunctivitis, which is more common in children, is usually bilateral, has an incubation period of only a few hours to a day, and behaves similarly to gonococcal conjunctivitis, and in severe cases can develop into septic meningitis, which can be life-threatening. The two are often difficult to distinguish clinically, and both causative agents can cause systemic spread, including sepsis. Specific diagnostic methods require culture and sugar fermentation tests. In recent years, penicillin-resistant groups of Neisseria spp. have emerged, making drug sensitivity testing very important. Neonatal gonococcal conjunctivitis (gonococcal conjunctivitis) has an incubation period of 2 to 5 days and is most often an infection of the birth canal, while those with onset 7 days after birth are infected postnatally. Both eyes are often involved at the same time. There is photophobia, lacrimation, and a high degree of eyelid edema, which in severe cases protrudes beyond the lid fissure and may be accompanied by pseudomembrane formation. The secretions quickly change from plasma to pus at the beginning of the disease, with large amounts of pus constantly flowing from the lid fissure, hence the name “pus leaky eye”. There is often enlargement of the lymph nodes in front of the ear and pressure pain. Severe cases may be complicated by corneal ulceration or even endophthalmitis. Infected infants may also have complications with other sites of purulent inflammation, such as arthritis, meningitis, pneumonia, sepsis, etc. (b) Acute or subacute bacterial conjunctivitis, also known as “acute khat conjunctivitis”, commonly known as “pink eye”, is highly contagious and can be disseminated in the spring and autumn, but can also be prevalent in schools, factories and other collective living places. The onset of the disease is rapid, incubation period of 1 to 3 days, two eyes at the same time or 1 to 2 days apart. The disease culminates in 3 to 4 days of onset and gradually decreases later, with the disease lasting more or less 3 weeks. The most common causative agents are S. pneumoniae, S. aureus, and Haemophilus influenzae. The pathogens can change with the seasons, with some studies showing that S. pneumoniae is the main cause of infection in winter, while Haemophilus influenzae conjunctivitis is seen mostly in spring and summer. (1) Staphylococcus aureus causes acute purulent conjunctivitis by releasing exotoxins and activating bioactive substances such as hemolysin, lyso-fibrinolytic enzymes, and coagulase. Patients mostly have blepharitis, which can develop at any age, and have difficulty opening the eyes in the morning due to mucopurulent secretions that paste the eyelids and less often involve the cornea. Conjunctivitis caused by Staphylococcus epidermidis is rare. (2) S. pneumoniae conjunctivitis is self-limiting and has a higher incidence in children than in adults. The incubation period is about 2 days, and symptoms such as conjunctival congestion and mucopurulent discharge culminate after 2 to 3 days. There may be subconjunctival hemorrhage in the upper lid conjunctiva and fornix conjunctiva and bulbar conjunctival edema, but this rarely causes severe purulent conjunctivitis. Upper respiratory symptoms may be present, rarely causing pneumonia. (3) Haemophilus influenzae is the most common pathogen of bacterial conjunctivitis in children, and Haemophilus influenzae symbiosis is seen in the upper respiratory tract of 80% of adults. Haemophilus influenzae spp. can cause two different clinical manifestations of conjunctivitis. The incubation period is about 24 hours, clinical manifestations are conjunctival congestion, edema, subconjunctival hemorrhage, purulent or mucopurulent discharge, symptoms peak in 3 to 4 days, symptoms disappear 7 to 10 days after starting antibiotic treatment, and can recur without treatment. Haemophilus influenzae type III infection can also be complicated by cicatricial marginal corneal infiltration or ulceration. Haemophilus influenzae infection in children can cause periorbital cellulitis, and some patients have systemic symptoms such as elevated body temperature and malaise. (4) Other: acute membranous or pseudomembranous conjunctivitis caused by Mycobacterium diphtheriae, the incidence of which decreased significantly after the use of Mycobacterium diphtheriae toxoid in the early 20th century, nowadays, Mycobacterium diphtheriae conjunctivitis is occasionally seen in children with pharyngeal diphtheria, initially, the eyelids are red, swollen, hot and painful, and there may be swollen lymph nodes in front of the ear. Scar formation after necrosis and exfoliation. Corneal ulcers are rare, but can be easily perforated once they are involved. Diphtheria toxin can cause extraocular and regulatory paralysis, and dry eye, lid adhesions, impingement, and lid entropion are common complications of B. diphtheriae conjunctivitis. The disease is highly contagious and requires systemic antibiotics. Other rare acute purulent conjunctivitis include Moraxella conjunctivitis seen in immunocompromised and alcoholic populations, and Pseudomonas spp., Escherichia spp., Shigella spp. and Clostridium spp. can occasionally cause monocular infections with swollen eyelids, bulbar conjunctival edema, and possible pseudomembrane formation, rarely involving the cornea. (iii) Chronic bacterial conjunctivitis can evolve from acute conjunctivitis or be caused by infection with less virulent pathogens. It is most often seen in patients with nasolacrimal duct obstruction or chronic dacryocystitis, or in those with chronic blepharitis or abnormal function of the lid gland. Staphylococcus aureus and Moraxella catarrhalis are the two most common pathogens of chronic bacterial conjunctivitis. Chronic conjunctivitis progresses slowly, lasts for a long time, and can develop unilaterally or bilaterally. Symptoms are varied and mainly present as itchy eyes, burning sensation, dryness, eye stinging pain and visual fatigue. The conjunctiva is mildly congested, and there may be thickening of the lid conjunctiva, papillary hyperplasia, and a mucus or white foamy discharge. Moraxella can cause canthal conjunctivitis with crusting of the outer canthus, ulcer formation, and hyperplasia of the lid conjunctival papillae and follicles. Staphylococcus aureus often causes ulcerative blepharitis or peripheral corneal punctate infiltration. Diagnosis] Diagnosis can be made based on clinical manifestations and examination of secretion smears or conjunctival scrapings. Conjunctival scrapings and secretion smears can reveal a large number of polymorphonuclear leukocytes and bacteria under the microscope by Gram and Giemsa staining. To clarify the cause and guide treatment, bacterial culture and drug sensitivity testing should be performed for those with large amounts of purulent discharge, children and infants with severe conjunctivitis, and those who have failed treatment, and blood culture should also be performed for those with systemic symptoms. Treatment】Remove the cause, anti-infective treatment, while waiting for the laboratory results, the doctor should start the local use of broad-spectrum antibiotics, and give sensitive antibiotics after determining the genus of the causative organism. Depending on the severity of the disease, conjunctival sac irrigation, topical medication, systemic medication, or a combination of medications may be chosen. Do not bandage the affected eye, but sunglasses may be worn to reduce light irritation. Treatment of hyperacute bacterial conjunctivitis should be performed immediately after diagnostic specimen collection to reduce the occurrence of potential corneal and systemic infections, with equal emphasis on topical and systemic medications. Eye drops are generally chosen for acute or subacute bacterial conjunctivitis in adults. In children, eye ointment is chosen to avoid elimination of the drops with tears when crying, and their duration of action is longer. The basic principles of treatment for chronic bacterial conjunctivitis are similar to those for acute conjunctivitis, requiring long-term treatment, the effectiveness of which depends on the patient’s compliance with the treatment regimen. All types of conjunctivitis involving the cornea should be treated according to the principles of keratitis treatment. Topical treatment (1) When there is a lot of discharge from the affected eye, the conjunctival sac can be flushed with a non-irritating flushing agent such as 3% boric acid or saline. When flushing, be careful to avoid damaging the corneal epithelium and do not flow into the healthy eye to avoid cross-contamination. (2) Apply effective antibiotic eye drops and eye ointment locally. Once every 1 to 2 hours in the acute stage. At present, broad-spectrum aminoglycosides or quinolones are often used, such as 0.3% gentamicin, 0.3% tobramycin, 0.3% ciprofloxacin, 0.3% ofloxacin, 0.3% to 0.5% levofloxacin eye drops or eye ointment. In special cases, synthetic antibiotic eye drops can be used. For example, methotrexate resistant staphylococcal conjunctivitis can be treated with 5mg/ml vancomycin eye drops. Chronic staphylococcal conjunctivitis responds well to bacitracin and erythromycin, and astringents such as 0.25% zinc sulfate ophthalmic solution can also be applied appropriately. Systemic treatment (1) Neisseria conjunctivitis should be treated systemically with an adequate amount of antibiotics administered intramuscularly or intravenously in a timely manner. Gonococcal conjunctivitis cornea is not affected, adults large doses of intramuscular injection of penicillin or ceftriaxone sodium (ceftriaxone, bacteriophage) 1g can, if the cornea is also infected, increase the dose, 1 to 2g / d, for 5 days. For penicillin allergy, Spectinomycin (2g/d, intramuscular injection) can be used. In addition, it can be combined with 1g of azithromycin or 100mg of doxycycline orally twice a day for 7 days; or quinolones (ciprofloxacin 0.5g or ofloxacin 0.4g twice a day for 5 days). Penicillin G 100 000 U/(kg?d) intravenously or intramuscularly in 4 divided doses for 7 days for newborns. Or ceftriaxone sodium (0.125 g, intramuscularly) or cefotaxime sodium (cefotaxime, 25 mg/kg, intravenously or intramuscularly) every 8 or 12 hours for 7 days. Approximately 1 in 5 exogenous (primary) meningococcal conjunctivitis can cause meningococcal bacteremia, and patients treated topically alone are 20 times more likely to develop bacteremia than patients treated with combination systemic agents. Therefore, combination systemic therapy is necessary. Meningococcal conjunctivitis can be treated with intravenous or intramuscular penicillin. Penicillin allergy can be replaced by chloramphenicol, which is effective within 2 days. Prophylactic treatment should be given to patients with a history of contact with meningococcal conjunctivitis, and oral rifampicin can be given twice daily for 2 days. The recommended dose is 600 mg for adults and 10 mg/kg for children. (2) Patients with acute bacterial conjunctivitis due to Haemophilus influenzae infection, or with pharyngitis or acute suppurative otitis media should receive oral cephalosporin antibiotics or rifampicin along with topical medication. (3) In refractory cases of chronic conjunctivitis and patients with rosacea, oral doxycycline 100mg, 1~2 times/day for several months. Prevention】 Pay strict attention to personal hygiene and group hygiene. Promote frequent hand washing, face washing and eye wiping without hands or sleeves. Patients in the acute stage should be isolated to avoid infection and prevent epidemics. When one eye is sick, the other eye should be prevented from being infected. Strictly sterilize the patient’s used washing utensils, handkerchiefs and medical utensils in contact. Health care workers must wash their hands after contact with patients to prevent cross infection. Protective eyewear should be worn when necessary. Newborns should be routinely treated with 1% silver nitrate eye drops or 0.5% tetracycline eye ointment immediately after birth to prevent neonatal gonorrheal conjunctivitis and chlamydial conjunctivitis.