Topical antibiotic prophylaxis before intravitreal injections: a pilot study

PURPOSE

To explore whether topical antibiotic prophylaxis in patients scheduled for intravitreal injections achieves surface sterility in a greater proportion of subjects as compared to povidone-iodine alone.

MATERIAL AND METHODS

A randomized, triple-blind clinical trial.

POPULATION

patients scheduled for intravitreal injections for maculopathy.

INCLUSION CRITERIA

any sex and race, age 18 years and above. Subjects were randomized into 4 groups: the first group applied chloramphenicol (CHLORAM), the second netilmicin (NETILM), the third a commercial ozonized antiseptic solution (OZONE), and the fourth applied no drops (CONTROL).

OUTCOME VARIABLE

percentage of non-sterile conjunctival swabs. Specimens were collected before and after the application of 5% povidone-iodine moments before the injection.

RESULTS

Ninety-eight subjects (33.7% females, 64.3% males), mean age: 70.2 ± 9.3 years (54-91). Before povidone-iodine, both the CHLORAM and NETILM group showed a lower percentage of non-sterile swabs (61.1% and 31.3% respectively), as compared to the OZONE (83.3%) and CONTROL (86.5%) groups (p < .04). However, this statistical difference was lost after the application of povidone-iodine for 3 min. Percentage of non-sterile swabs in each group after applying 5% povidone-iodine: CHLORAM 11.1%, NETILM 12.5%, CONTROL 15.4%, OZONE 25.0%. This was not statistically significant (p > .05).

CONCLUSIONS

Topical antibiotic prophylaxis with chloramphenicol or netilmicin drops decreases the bacterial load on the conjunctiva. However, after the application of povidone-iodine, all groups showed a significant reduction in the percentage of non-sterile swabs, and this value was comparable among all groups. For this reason, authors conclude that povidone-iodine alone is sufficient and prior topical antibiotic prophylaxis is not indicated.

Acinetobacter baumannii GC2 Sublineage Carrying the aac(6')-Im Amikacin, Netilmicin, and Tobramycin Resistance Gene Cassette

The aminoglycoside antibiotics amikacin, gentamicin, and tobramycin are important therapeutic options for Acinetobacter iinfections. Several genes that confer resistance to one or more of these antibiotics are prevalent in the globally distributed resistant clones of Acinetobacter baumannii, but the aac(6')-Im (aacA16) gene (amikacin, netilmicin, and tobramycin resistance), first reported in isolates from South Korea, has rarely been reported since. In this study, GC2 isolates (1999 to 2002) from Brisbane, Australia, carrying aac(6')-Im and belonging to the ST2:ST423:KL6:OCL1 type were identified and sequenced. The aac(6')-Im gene and surrounds have been incorporated into one end of the IS26-bounded AbGRI2 antibiotic resistance island and are accompanied by a characteristic 70.3-kbp deletion of adjacent chromosome. The compete genome of the 1999 isolate F46 (RBH46) includes only two copies of ISAba1 (in AbGRI1-3 and upstream of ampC) but later isolates, which differ from one another by <10 single nucleotide differences (SND), carry two to seven additional shared copies. Several complete GC2 genomes with aac(6')-Im in an AbGRI2 island (2004 to 2017; several countries) found in GenBank and two additional Australian A. baumannii isolates (2006) carry different gene sets, KL2, KL9, KL40, or KL52, at the capsule locus. These genomes include ISAba1 copies in a different set of shared locations. The distribution of SND between F46 and AYP-A2, a 2013 ST2:ST208:KL2:OCL1 isolate from Victoria, Australia, revealed that a 640-kbp segment that includes KL2 and the AbGRI1 resistance island replaces the corresponding region in F46. Over 1,000 A. baumannii draft genomes also include aac(6')-Im, indicating that it is currently globally disseminated and significantly underreported. IMPORTANCE Aminoglycosides are important therapeutic options for treatment of Acinetobacter infections. Here, we show that a little-known aminoglycoside resistance gene, aac(6')-Im (aacA16), that confers amikacin, netilmicin, and tobramycin resistance has been circulating undetected for many years in a sublineage of A. baumannii global clone 2 (GC2), generally with a second aminoglycoside resistance gene, aacC1, which confers resistance to gentamicin. These two genes are commonly found together in GC2 complete and draft genomes and globally distributed. One isolate appears to be ancestral, as its genome contains few ISAba1 copies, providing insight into the original source of this insertion sequence (IS), which is abundant in most GC2 isolates. Tracking ISAba1 spread can provide a simple means to track the development and ongoing evolution as well as the dissemination of specific lineages and detect the formation of many sublineages. The complete ancestral genome will provide an essential base point for tracking this process.

High Prevalence of Phenotypic Resistance to Colistin, Tigecycline and Netilmicin in a Region with no History of Colistin Administration in Nigeria

BACKGROUND

Colistin is currently used as a last line antibiotic for the treatment of extensively drug-resistant Gram-negative bacteria. The widespread dissemination of ESBL-producing and carbapenem-resistant Gram-negative bacteria necessitated the re-introduction of colistin which was initially abandoned as a result of high toxicities. This study aimed at determining the epidemiology of Enterobacteriaceae isolates that are resistant to colistin, tigecycline, and netilmicin and the risk factors that may contribute to the resistance observed within Southeastern Nigeria.

METHODS

A total of 400 participants who came to the hospitals for various reasons and suspected to have bacterial infections were enrolled in this study. Phenotypic resistance to colistin was detected using broth microdilution technique on cation - adjusted Mueller-Hinton broth while resistance to colistin and netilmicin was detected using the Kirby-Bauer disk diffusion method using tigecycline disk (10 µg) and netilmicin disk (30 µg). Risk factors were determined by the administration of questionnaires to the participants.

RESULTS

Our study found an overall high prevalence of colistin - resistant Enterobacteriaceae (45.8%) and a high prevalence for colistin and tigecycline (22.2%) and colistin and netilmicin (31.7%) resistant isolates. Among the risk factors that contribute to colistin, non-completion of antibiotics was found to be more significant (p = 0.039 and an odds ratio of 0.324 - 0.972 at 95% confidence interval).

CONCLUSIONS

Our finding is significant in that colistin resistance was determined to be present among populations that have not been exposed to colistin therapy.

Stenotrophomonas maltophilia infections in a general hospital: patient characteristics, antimicrobial susceptibility, and treatment outcome

Introduction

Stenotrophomonas maltophilia is acquiring increasing importance as a nosocomial pathogen.

Methods

We retrospectively studied the characteristics and outcome of patients with any type of S. maltophilia infection at the University Hospital of Heraklion, Crete, Greece, between 1/2005–12/2010. S. maltophilia antimicrobial susceptibility was tested with the agar dilution method. Prognostic factors for all-cause in-hospital mortality were assessed with multivariate logistic regression.

Results

Sixty-eight patients (median age: 70.5 years; 64.7% males) with S. maltophilia infection, not related to cystic fibrosis, were included. The 68 patients were hospitalized in medical (29.4%), surgical (26.5%), hematology/oncology departments (23.5%), or the intensive care units (ICU; 20.6%). The most frequent infection types were respiratory tract (54.4%), bloodstream (16.2%), skin/soft tissue (10.3%), and intra-abdominal (8.8%) infection. The S. maltophilia-associated infection was polymicrobial in 33.8% of the cases. In vitro susceptibility was higher to colistin (91.2%), trimethoprim/sulfamethoxazole and netilmicin (85.3% each), and ciprofloxacin (82.4%). The empirical and the targeted treatment regimens were microbiologically appropriate for 47.3% and 63.6% of the 55 patients with data available, respectively. Most patients received targeted therapy with a combination of agents other than trimethoprim/sulfamethoxazole. The crude mortality and the mortality and the S. maltophilia infection-related mortality were 14.7% and 4.4%, respectively. ICU hospitalization was the only independent prognostic factor for mortality.

Conclusion

S. maltophilia infection in a general hospital can be associated with a good prognosis, except for the patients hospitalized in the ICU. Combination reigmens with fluoroquinolones, colistin, or tigecycline could be alternative treatment options to trimethoprim/sulfamethoxazole.

Stability of drug additives in peritoneal dialysis solutions in a new container

OBJECTIVE

To evaluate the stability of gentamicin, tobramycin, netilmycin, vancomycin, cefazolin, unfractionated heparin, and low molecular weight heparin when added to four different peritoneal dialysis (PD) solutions [Extraneal (Baxter Healthcare, Castlebar, Ireland); Physioneal, Nutrineal, and Dianeal (Baxter Healthcare, Grosotto, Italy)] in new, non-PVC Clear-Flex containers.

MEASUREMENTS

Gentamicin, tobramycin, netilmycin, vancomycin, cefazolin, unfractionated heparin, and low molecular weight heparin were injected into separate bags of PD solution. Samples were withdrawn at predefined sampling times and the concentration of each drug was analyzed using high-performance liquid chromatography (for gentamicin, tobramycin, vancomycin, and cefazolin), or bioassay (for netilmycin, gentamicin, and tobramycin in Nutrineal), or coagulation methods (heparins).

RESULTS

Netilmycin, vancomycin, cefazolin, and heparin in Physioneal, Nutrineal, Extraneal, and Dianeal were stable for at least 24 hours at 25 degrees C and for an additional 4 hours at 37 degrees C. Gentamicin in Nutrineal, Extraneal, and Dianeal was stable for at least 24 hours at 25 degrees C and for an additional 4 hours at 37 degrees C; gentamicin in Physioneal was stable for less than 24 hours at 25 degrees C. Tobramycin in Nutrineal and Extraneal was stable for at least 24 hours at 25 degrees C and for an additional 4 hours at 37 degrees C; tobramycin in Physioneal and Dianeal was stable for less than 24 hours at 25 degrees C.

Doxorubicin reversibly decreases the antithrombogenicity of heparin immobilized on central venous catheters

This is an in vitro study of the effects of doxorubicin on heparin immobilized on polyvinyl chloride (PVC) tubing. Doxorubicin contains an amino group that binds up to 16 heparin molecules, forming insoluble complexes if they are added to the same infusion. Three systems were tested: doxorubicin in perfusing blood, cerebrospinal fluid, and 0.9% sodium chloride (NaCl). The antithrombogenicity of immobilized heparin is impaired on exposure to doxorubicin. However, the reaction is reversible provided the PVC tubing system is thoroughly washed. Heparinized tubing perfused for 12 hours in blood with doxorubicin (0.027 mg/mL) decreased the activity of the immobilized heparin to 6.0% compared with 43% of that exposed to blood only. Exposure to doxorubicin (0.27 mg/mL) for 15 minutes in NaCl decreased the activity to 3% compared with that of NaCl only. Continuous washing for 10 minutes (8 mL/min) resulted in regained activity. This indicated a reversible reaction between immobilized heparin and doxorubicin. Cyclophosphamide, netilmicin, and gentamicin did not affect the antithrombogenicity of heparin in any solution.

Solute kinetics in hypertonic hemodiafiltration and standard hemodialysis

Hemodiafiltration (HDF) is a new dialysis treatment that combines convective and diffusive forces. In order to assess the efficiency of a peculiar model of hypertonic HDF (H HDF), we studied eight uremic patients when they were undergoing five sessions of H HDF of 180 minutes duration and two sessions of standard hemodialysis (HD) of 270 minutes duration with a comparable blood (approximately 400 mL/min) and dialysate flow rate (approximately 520 mL/min). The plasma water clearances (Kw) of small [urea (U), creatinine (C), uric acid (UA), and phosphorus (P)] and middle molecules [netilmicin (N) and inulin (I)] were exceedingly higher in H HDF than in HD; however, because of the different treatment times, U and C removal (R) in HD overcame and UA and P R in HD equalized that in H HDF. The factor time was not sufficient to HD to compensate for the large difference in Kw in the case of I. Additional studies were performed in seven out of the eight patients after two sessions of H HDF and one session of HD. Two significantly higher rebounds were observed when comparing both treatments: for U after HD and for parathyroid hormone (PTH) after H HDF; however, PTH Cx/Cs ratios (ratios of the plasma water concentration of PTH at any postdialysis time to the plasma water concentration of PTH at the start of the run) were not different in both treatments, meaning that there was an increased PTH secretion in the early post H HDF hours in order to compensate for the larger PTH R with H HDF.(ABSTRACT TRUNCATED AT 250 WORDS)

Compatibility of furosemide with aminoglycoside admixtures

The compatibility of furosemide with i.v. admixtures containing each of five different aminoglycosides was studied. Admixtures of amikacin 2 mg/ml, gentamicin 1.6 mg/ml, kanamycin 2 mg/ml, netilmicin 1.5 mg/ml, and tobramycin 1.6 mg/ml (as the sulfate salts) were prepared in both 5% dextrose injection and 0.9% sodium chloride injection in minibags. Furosemide injection 4 ml (40 mg) was then added to each admixture, and the admixtures were examined visually and microscopically for precipitate. The macroscopic and microscopic evaluations were repeated 15 minutes and 24 hours after mixing. To simulate Y-site injection of furosemide, furosemide injection 1 ml (10 mg) was added to 1 ml of each aminoglycoside admixture in a syringe. For admixtures in which precipitates formed, the pH was recorded before and after adding furosemide to subsequent admixtures and also after dropwise addition of 1N sodium hydroxide until the precipitate dissolved. Precipitates were identified using spectrophotometric analysis and melting point determinations. Addition of furosemide resulted in a precipitate only in admixtures containing gentamicin sulfate or netilmicin sulfate; the results for the simulated Y-site injection study were the same. Spectrophotometric analysis and melting point determinations revealed that the precipitate was furosemide. Because furosemide precipitates when added to admixtures containing either gentamicin sulfate or netilmicin sulfate in 5% dextrose injection or 0.9% sodium chloride injection, furosemide should be administered separately or the i.v. tubing should be flushed thoroughly before and after administering this drug via a Y-injection site.

In vitro inactivation of gentamicin, tobramycin, and netilmicin by carbenicillin, azlocillin, or mezlocillin

The in vitro inactivation of gentamicin, tobramycin, and netilmicin, when combined with carbenicillin, azlocillin, and mezlocillin, was studied. Plasma samples containing the aminoglycosides at a concentration of 5-8 micrograms/ml in combination with the penicillins in concentrations of 500, 250, and 50 micrograms/ml were incubated at room temperature and 37 degrees C for 0.3, 1, 3, 6, and 9 days. The aminoglycoside concentration was determined by radioimmunoassay or enzyme immunoassay. The extent of inactivation was dependent on penicillin concentration, contact time, and temperature. Penicillin concentrations of 500 micrograms/ml caused the greatest loss of aminoglycoside, while little loss occurred at the 50-micrograms/ml penicillin level. Carbenicillin, in concentrations of 250 and 500 micrograms/ml, inactivated all three aminoglycosides to a greater extent than either azlocillin or mezlocillin. The initial rate of decline in aminoglycoside concentration was greater at 37 degrees C than at room temperature. The new acylureidopenicillins, azlocillin and mezlocillin, inactivate the aminoglycosides studied, in a similar manner to that previously described for carbenicillin.