Efficacy of topical povidone-iodine during the first week after ophthalmic surgery

PURPOSE

In the first postoperative day, povidone-iodine ophthalmic solution prevents an increase in conjunctival bacterial colony-forming units and decreases the species compared with antibiotic. We sought to determine whether these beneficial effects of povidone-iodine could be sustained during the first postoperative week.

METHODS

In 42 eyes of 35 consecutive patients, one or two drops of either a broad-spectrum antibiotic (polymyxin B sulfate-neomycin sulfate-gramicidin) or povidone-iodine 1.25% to 2.5% were placed in the treated eye or eyes at the conclusion of surgery and three times daily during the first postoperative week. Bacterial cultures were taken from both eyes at the end of surgery before instillation of either of the eyedrops and again 1 week later. Twenty-eight untreated eyes served as a control group.

RESULTS

During the first postoperative week, the number of colony-forming units and species increased in both treatment groups. Relative to the control group, both medications effectively reduced the mean number of colony-forming units at 1 week (P < .02), but their effects on colony-forming units did not significantly differ from each other (80 +/- 290 for the povidone-iodine-treated eyes and 75 +/- 90 for the antibiotic-treated eyes). At 1 week, the species count increased 281% in the antibiotic group but only 106% in the povidone-iodine group. Compared to the control group, eyes that received povidone-iodine had a significantly lower species count (P = .0097).

CONCLUSION

Povidone-iodine ophthalmic solution is an alternative to postoperative topical antibiotics because of its effectiveness in controlling conjunctival bacterial colony-forming units and species, its relatively low cost, and its availability.

The effect of povidone-iodine solution applied at the conclusion of ophthalmic surgery

PURPOSE

Povidone-iodine 5% solution decreases the incidence of postoperative endophthalmitis when used on the eye for preoperative preparation. We sought to determine whether it also minimized conjunctival bacterial flora immediately after surgery by preventing bacteria present on the surface of the eye from entering surgical wounds.

METHODS

In 42 eyes of 40 patients, at the conclusion of surgery, on an alternating basis, each patient received either a drop of a broad-spectrum antibiotic solution (polymyxin B sulfate-neomycin sulfate-gramicidin) or a 5% povidone-iodine solution in the operated-on eye. Bacterial cultures were taken before and after surgery and 24 hours later. The 38 unoperated-on eyes in the unilateral cases served as control eyes.

RESULTS

Relative to the control group, povidone-iodine was effective in preventing an increase in the number of colony-forming units (P = .035), while the antibiotic was not. At 24 hours after surgery, the species count was lower in the eyes receiving povidone-iodine than in the antibiotic-treated eyes (P = .034) and was increased in the antibiotic group since the completion of surgery (P = .013), but was lower in the povidone-iodine and antibiotic groups than in the control eyes for both groups (P < .01).

CONCLUSIONS

Povidone-iodine 5% solution applied to the eye at the conclusion of surgery was more effective at minimizing the number of colony-forming units and species for the first postoperative day than was a broad-spectrum antibiotic. While not true for the antibiotic, the antimicrobial effect of povidone-iodine lasted for at least 24 hours after the completion of surgery.

Povidone-iodine for ophthalmia neonatorum prophylaxis

PURPOSE

The agents currently used to prevent ophthalmia neonatorum are less than optimal, with reports indicating evidence of bacterial resistance, ineffectiveness, and toxicity. Povidone-iodine ophthalmic solution, which has been shown to be effective in the preoperative preparation of the eye, generates no resistance, is an effective antimicrobial agent, and has low toxicity. We evaluated the effectiveness and safety of povidone-iodine for ophthalmia neonatorum prophylaxis.

METHODS

A bacterial culture was taken from the conjunctiva of each eye of 100 infants within 30 minutes of birth. A drop of 2.5% povidone-iodine solution was then placed on one eye, while the other eye received either one drop of silver nitrate 1% ophthalmic solution or 0.5% erythromycin ointment. Conjunctival bacterial cultures were again taken two to four hours after birth. At each culture and at 24 hours after birth, the eyes were examined for toxic changes. To measure the effectiveness of the medications, the number of bacterial colony-forming units and species from each culture was compared.

RESULTS

All three agents significantly reduced the number of colony-forming units, but povidone-iodine caused the most significant decrease. The number of species was reduced significantly by povidone-iodine (P = .00051) and silver nitrate (P = .007), with povidone-iodine yielding the most significant decrease. Erythromycin did not significantly reduce the number of species. Silver nitrate demonstrated more ocular toxicity at the 24-hour determination point than did either of the other two medications (P < .001).

CONCLUSIONS

Povidone-iodine 2.5% ophthalmic solution is an effective antibacterial agent on the conjunctiva of newborns and causes less toxicity than silver nitrate.

Outpatient topical use of povidone-iodine in preparing the eye for surgery

Povidone-iodine 5% solution placed on the eye immediately before ophthalmic surgery within the preoperative preparation significantly reduces the conjunctival bacterial flora. In 40 patients undergoing ophthalmic surgery, the authors compared the outpatient use of povidone-iodine for 3 days before surgery with a 3-day course of a combination antibiotic ophthalmic solution (Neosporin) placed on the other eye. All patients also received topical povidone-iodine on the operating table directly preceding surgery. Cultures taken just before preparation of the operative field showed a similar reduction of bacteria by each regimen. Cultures taken after preparation but before commencement of surgery showed a further reduction for both regimens, but more for eyes previously treated with the antibiotic (P less than 0.02). To minimize the conjunctival bacterial flora before surgery, the authors continue to recommend instillation of a broad-spectrum antibiotic for 3 days before surgery, followed by application of povidone-iodine solution to the eye immediately before surgery within the preoperative preparation.

Source of the conjunctival bacterial flora at birth and implications for ophthalmia neonatorum prophylaxis

To understand better the source of conjunctival bacteria in neonates, we studied 106 infants immediately after birth before any eyedrops were applied. The 50 infants delivered by cesarean section had significantly fewer species (0.50 +/- 0.85 vs 1.84 +/- 1.33) and colony forming units (272 +/- 1,019 vs 1,790 +/- 3,779) cultured per subject than the 56 infants delivered vaginally. In infants delivered by cesarean section within three hours of membrane rupture, 24 of 30 (80%) of the conjunctival cultures were sterile, while the rest bore a few cutaneous bacteria (0.23 +/- 0.50 species and 2 +/- 9 colony forming units per subject). The conjunctivae of infants delivered vaginally bore significantly more bacteria characteristic of vaginal flora: microaerophilic as Lactobacillus or truly anaerobic as Bifidobacterium. Neonates delivered by cesarean section more than three hours after membrane rupture showed a bacteriologic flora mixture quantitatively and qualitatively midway between those two groups. Infants delivered by cesarean section within three hours of membrane rupture may not need prophylactic eyedrops because of the type and scarcity of conjunctival bacteria.

Bacterial flora of the conjunctiva at birth

In the largest study to date of bacterial flora in newborns, we cultured the conjunctivae of 100 infants within 15 minutes after vaginal delivery and before any antimicrobial agents had been applied to the eye. All cultures were intensively analyzed for anaerobic and aerobic bacteria. By far the largest group of bacteria isolated were microaerophilic, such as Lactobacillus species and diphtheroids, accounting for 46.8% of positive cultures and 62.3% of all bacteria isolated. The second largest group were true anaerobic bacteria, such as Bacteroides and Propionibacterium species. The smallest group were aerobic bacteria. This incidence of non-aerobic bacteria in the conjunctiva of newborns is the highest reported to date. Our finding should alert clinicians to consider non-aerobic, especially microaerophilic, bacteria in the differential diagnosis of ophthalmia neonatorum. The high rate of supposedly sterile cultures reported in other studies may be explained at least partially by improper isolation of non-aerobic bacteria.

Chemical preparation of the eye in ophthalmic surgery. IV. Comparison of povidone-iodine on the conjunctiva with a prophylactic antibiotic

We previously found that half-strength (5%) povidone-iodine solution significantly reduced the bacterial flora of the conjunctiva. To compare the antibacterial effect of a topical combination antibiotic (Neosporin ophthalmic solution) given three times daily for three days preoperatively with that of half-strength povidone-iodine solution given as part of the preoperative preparation, conjunctival cultures were studied from 35 patients undergoing ocular surgery. When used individually, the antibiotic and povidone-iodine solutions caused a similar and substantial decrease in the number of colonies and species of bacteria cultured. When both drugs were used together, the decrease was even more striking, making 83% of the conjunctivae sterile. To minimize bacterial flora before ocular surgery, we recommend that a broad-spectrum topical antibiotic be given for three days preoperatively and that half-strength povidone-iodine solution be used as part of the preoperative preparation.

Antimicrobial preparation of the eye for surgery

An important source of postoperative eye infection is the indigenous flora in and around the eye. Therefore, proper preparation of the operative field is crucial. Through an international survey we determined that ophthalmic surgeons used widely varying techniques in the pre-operative antimicrobial preparation of the eye. On the basis of these survey responses we have studied to date the effect on the bacterial flora of the conjunctiva of three regimens. Irrigation of the conjunctiva with saline tended to increase the ocular flora; instillation of silver protein solution had no significant effect. Povidone-iodine drops (5%) significantly reduced both colony and species counts.

Chemical preparation of the eye in ophthalmic surgery. III. Effect of povidone-iodine on the conjunctiva

A half-strength povidone-iodine (Betadine) solution was used topically as part of the preoperative chemical preparation of the eye. Aerobic and anaerobic bacterial cultures of the conjunctiva were taken before and after the chemical preparation in 30 consecutive patients; the second eye served as a control. In the control eyes, no significant change in the number of colonies or species of bacteria was found. In the povidone-iodine-treated eyes, the numbers of colonies decreased 91% and the number of species decreased 50% (statistically significant). We therefore recommend that a half-strength povidone-iodine solution be used as part of the chemical preparation of the eye for surgery.

Antimicrobial therapy of postpartum endomyometritis. II. Prospective, randomized trial of mezlocillin versus ampicillin

Seventy patients with postpartum endomyometritis were treated with either intravenous mezlocillin (16 gm/day) or ampicillin (8 gm/day) in a prospective, randomized, double-blind comparison. Endocervical dilatation was routinely performed. Clindamycin (2 gm/day) was added if patients failed to improve within 48 hours of beginning therapy. Pretreatment clinical and microbiologic profiles were comparable in the two groups. Bacteremia was documented in 21 patients (30%). Anaerobic cocci and Bacteroides spp. (non-B. fragilis) comprised 19 of 29 (65%) blood isolates. Thirty of 33 mezlocillin-treated patients (91%) and 30 of 37 ampicillin-treated patients (81%) responded to initial therapy (P greater than 0.4). Resolution was noted after the addition of clindamycin in all ten nonresponders; two of these patients also required surgical wound debridement. Objective parameters of clinical response were not significantly different in the two treatment groups. Side effects of mezlocillin therapy were minimal. We conclude that mezlocillin and ampicillin are equally effective and safe for therapy of postpartum endomyometritis. That mezlocillin was not superior to ampicillin, despite expanded activity against B. fragilis and members of Enterobacteriaceae, suggests that these pathogens are less important than was previously considered in postpartum endomyometritis.

Cerebral abscesses complicating neonatal Citrobacter freundii meningitis

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R factor-controlled restriction and modification of deoxyribonucleic acid: restriction mutants

Restriction mutants of two different R factor-controlled host specificities (RI and RII) were isolated. All of the restriction mutants examined had a normal modification phenotype. No complementation was observed between the RI and RII host specificities. It is concluded that for each host specificity no protein subunit is shared by the restriction endonuclease and modification methylase.