Evaluating the ototoxicity of topical piperacillin-tazobactam

Effects of an enrofloxacin-silver sulfadiazine emulsion in the ears of rabbits with perforated tympanic membranes

OBJECTIVE

To determine whether an enrofloxacin-silver sulfadiazine emulsion (ESS) labeled for treatment of otitis externa in dogs has ototoxic effects in rabbits following myringotomy.

ANIMALS

6 healthy adult New Zealand White rabbits.

PROCEDURES

Rabbits were anesthetized for brainstem auditory-evoked response (BAER) tests on day 0. Myringotomy was performed, and BAER testing was repeated. Saline (0.9% NaCl) solution and ESS were then instilled in the left and right middle ears, respectively, and BAER testing was repeated prior to recovery of rabbits from anesthesia. Application of assigned treatments was continued every 12 hours for 7 days, and rabbits were anesthetized for BAER testing on day 8. Rabbits were euthanized, and samples were collected for histologic (6 ears/treatment) and scanning electron microscopic (1 ear/treatment) examination.

RESULTS

Most hearing thresholds (11/12 ears) were subjectively increased after myringotomy, with BAER measurements ranging from 30 to 85 dB in both ears. All day 8 hearing thresholds exceeded baseline (premyringotomy) values; results ranged from 30 to 85 dB and 80 to > 95 dB (the upper test limit) in saline solution-treated and ESS-treated ears, respectively. All ESS-treated ears had heterophilic otitis externa, epithelial hyperplasia of the external ear canal, various degrees of mucoperiosteal edema, and periosteal new bone formation on histologic examination. Scanning electron microscopy revealed that most outer hair cells in the ESS-treated ear lacked stereocilia or were absent.

CONCLUSIONS AND CLINICAL RELEVANCE

Results supported that ESS has ototoxic effects in the middle ear of rabbits. Further research is needed to confirm these findings. Myringotomized laboratory rabbits may be useful to study ototoxicity of drugs used in human medicine.

Effect of piperacillin-tazobactam coated β-tricalcium phosphate for mastoid obliteration in otitis media

BACKGROUND AND OBJECTIVE

β-Tricalcium phosphate (TCP) has good biodegradability and osteoconductivity as a scaffold material for bone tissue engineering. Both block and granular forms are available; however, it has been associated with risk of infection and exposure. To this end, the study evaluated the effect of piperacillin-tazobactam coated β-TCPs for mastoid obliteration in otitis media.

MATERIALS AND METHODS

Ten guinea pigs were divided into the experimental (piperacillin-tazobactam coated β-TCP granules, n=5) and control groups (uncoated β-TCP granules, n=5). After mastoid obliteration, transtympanic injection with a saline suspension of lipopolysaccharide established inflammation. The animals were sacrificed 5 weeks later. Tissue sections were stained with hematoxylin and eosin and examined.

RESULTS

Encapsulation and formation of fibrous capsule by foreign material in the bulla were not evident. The histological evaluation did not reveal inflammatory cells and fibrosis in the piperacillin-tazobactam coated β-TCP group. In contrast, the control group showed numerous inflammatory cells around the implanted uncoated β-TCP granules and incomplete new bone formation.

CONCLUSION

β-TCP is an effective carrier material for piperacillin-tazobactam. The use of piperacillin-tazobactam coated β-TCP may be optimal for mastoid obliteration.

The use of piperacillin-tazobactam coated tympanostomy tubes against ciprofloxacin-resistant Pseudomonas biofilm formation: an in vitro study

BACKGROUND AND OBJECTIVE

Bacterial biofilm formation has been implicated in the high rate of persistent otorrhea after tympanostomy tube insertion. It has been suggested that the tube material may be an important factor in the development of otorrhea. Recently we reported the presence of ciprofloxacin-resistant Pseudomonas aeruginosa (CRPA) biofilms on infected tympanostomy tubes following the use of intractable post-tympanostomy tubes and the onset of otorrhea. In this study, we have evaluated the resistance of piperacillin-tazobactam coated with chitosan on a tympanostomy tube to prevent CRPA biofilm formation in vitro.

MATERIALS AND METHODS

Three sets each of piperacillin-tazobactam coated silicone tubes (n=5), commercial silver-oxide coated silicone tubes (Activent, Silic) (n=5) and control uncoated tympanostomy tubes (Paparella type 1) (n=5) were processed for evaluation. The piperacillin-tazobactam coated tympanostomy tubes were compared with the silver-oxide coated tubes and the uncoated control tubes for resistance to CRPA biofilm formation after in vitro incubation.

RESULTS

Scanning electron microscopy showed that the surface of the silver-oxide coated tube (Activent) formed a thick biofilm with crusts as well as an uncoated tube. In contrast, the surface of a piperacillin-tazobactam coated tympanostomy tube showed virtually no CRPA biofilm formation.

CONCLUSION

The piperacillin-tazobactam coated tympanostomy tube showed resistance to CRPA biofilm formation. The piperacillin-tazobactam coating may be useful to reduce CRPA biofilm formation; however, further in vivo studies are necessary.