Studies of anaerobic bacteria in chronic otitis media

Predominant Bacteria Detected from the Middle Ear Fluid of Children Experiencing Otitis Media: A Systematic Review

BACKGROUND

Otitis media (OM) is amongst the most common childhood diseases and is associated with multiple microbial pathogens within the middle ear. Global and temporal monitoring of predominant bacterial pathogens is important to inform new treatment strategies, vaccine development and to monitor the impact of vaccine implementation to improve progress toward global OM prevention.

METHODS

A systematic review of published reports of microbiology of acute otitis media (AOM) and otitis media with effusion (OME) from January, 1970 to August 2014, was performed using PubMed databases.

RESULTS

This review confirmed that Streptococcus pneumoniae and Haemophilus influenzae, remain the predominant bacterial pathogens, with S. pneumoniae the predominant bacterium in the majority reports from AOM patients. In contrast, H. influenzae was the predominant bacterium for patients experiencing chronic OME, recurrent AOM and AOM with treatment failure. This result was consistent, even where improved detection sensitivity from the use of polymerase chain reaction (PCR) rather than bacterial culture was conducted. On average, PCR analyses increased the frequency of detection of S. pneumoniae and H. influenzae 3.2 fold compared to culture, whilst Moraxella catarrhalis was 4.5 times more frequently identified by PCR. Molecular methods can also improve monitoring of regional changes in the serotypes and identification frequency of S. pneumoniae and H. influenzae over time or after vaccine implementation, such as after introduction of the 7-valent pneumococcal conjugate vaccine.

CONCLUSIONS

Globally, S. pneumoniae and H. influenzae remain the predominant otopathogens associated with OM as identified through bacterial culture; however, molecular methods continue to improve the frequency and accuracy of detection of individual serotypes. Ongoing monitoring with appropriate detection methods for OM pathogens can support development of improved vaccines to provide protection from the complex combination of otopathogens within the middle ear, ultimately aiming to reduce the risk of chronic and recurrent OM in vulnerable populations.

A 16-year survey of changes in bacterial isolates associated with chronic suppurative otitis media

Bacteria were isolated and cultured from the ears of outpatients with chronic suppurative otitis media (OMC) who attended the otologic clinics of Kyushu University Hospital from 1976 to 1991. Bacterial isolates were analyzed retrospectively to determine their incidences and antibiotic sensitivities. Staphylococcus aureus and Pseudomonas aeruginosa were the most commonly isolated organisms. The incidence of S. aureus infections gradually rose over 16 years, while the incidence of Proteus infections gradually declined. The frequency of isolation of glucose non-fermenting gram-negative rod (NF-GNR) species, fungi and anaerobic bacteria gradually increased. The species of bacteria isolated from OMC cases with acute and chronic infections, cholesteatoma and postoperative infections were compared. Over the 16 years, the isolation of S. aureus increased in frequency. The differences in each type of OMC ceased to exist. S. aureus were quite sensitive to most of the antibiotics tested, whereas Ps. aeruginosa and NF-GNR showed poor sensitivity.

Anaerobes and fungi in chronic suppurative otitis media

Microbiology of 102 ears with chronic suppurative otitis media was studied for aerobes, anaerobes, and fungi. Forty-four percent were pure cultures, 33.3% were mixed, and 18.6% had no growth. Seventy-four percent were aerobes, 25% fungi, and only 0.9% anaerobes. Pseudomonas aeruginosa (22.5%) was the most common isolate, followed by Staphylococcus aureus and the Aspergillus species. The possible reasons for low yield of anaerobes and the pathogenic roles of anaerobes and fungi in chronic suppurative otitis media are discussed. It is advocated that in investigating pathogenic organisms in chronic suppurative otitis media, requests should include anaerobes and fungi.

Residual bacterial infection in the tympanic cavity following surgery for ears with chronic discharge

In surgical treatment of ears with chronic discharge, pathogenic microorganisms may remain in the middle ear even after meticulous tympanomastoidectomy, and cause recurrent infection unless an appropriate antimicrobial agent is administered. The present study was conducted to determine the incidence of residual bacterial infection in the tympanic cavity by examining secretions from a drainage tube placed there via the mastoid cavity during surgery. Comparison of the bacterial flora before and after surgery demonstrated that some of the microorganisms continued to be present in the tympanic cavity for up to 2 weeks despite medication, and that the incidence of Pseudomonas aeruginosa and Staphylococcus epidermidis remained fairly high.

Clinical and bacteriological profile of the ear in otogenic tetanus: a case control study

Twenty two patients presented with otogenic tetanus. Seventeen patients had acute histories with only a single episode of otitis media with otorrhoea. Fifteen patients had unilateral central perforations, five had bilateral central perforations and two had no perforations but had acutely congested tympanic membranes which were bulging suggesting the presence of purulent fluid behind them. All patients with perforations had a purulent pulsatile discharge. A coexisting aerobic infection was seen in 85 per cent of the cultures and 59 per cent of these were due to staphylococcus aureus (versus 25 per cent in the controls). Only one patient had received partial immunization. Tetanus resulting from otitis media is not an indication for surgery.

Diagnosis and management of anaerobic infections of the head and neck

Anaerobic bacteria are important pathogens in head and neck infections such as chronic otitis media, chronic sinusitis, chronic mastoiditis, head and neck abscesses, cervical adenitis, parotitis, and postoperative infection. Bacteroides sp (Bacteroides melaninogenicus group, Bacteroides oralis, and Bacteroides fragilis group), Peptostreptococcus sp, and Fusobacterium sp predominate. The observed recent increase in the number of beta-lactamase-producing strains of Bacteroides sp isolated in head and neck infections has been associated with increased failure rates of the penicillins in the management of these infections. The pathogenicity of these organisms is expressed through their ability not only to survive penicillin therapy but also to shield penicillin-susceptible pathogens from the drug. Because of these direct and indirect virulent characteristics of anaerobic bacteria, appropriate antimicrobial therapy must be directed against all pathogens in mixed infections.

Longitudinal studies of experimental otitis media with Haemophilus influenzae in the gerbil

Haemophilus influenzae non-typable strain 119 was found to cause severe otitis media with sequellae when inoculated into the middle ear cavities of the Mongolian gerbil, Meriones unguiculatus. Acute inflammation was followed by the development of highly vascular granulation tissue and formation of new bone within the middle ear bulla. These changes persisted throughout the 14-week study in the untreated animals. The gerbil was variably susceptible to otitis media caused by inoculating 30-3000 bacterial cells and 100% susceptible to greater than 3000 cells. The susceptibility of the gerbil to common etiological agents of otitis media allows its use as an appropriate model of the disease.

Efficacy of Metronidazole in experimental Bacteroides fragilis otitis media

The efficacy of metronidazole in otitis media due to Bacteroides fragilis was evaluated in a guinea pig model. Fifty-nine animals received an injection of 10(8) live B. fragilis bacteria through the tympanic membrane into the right middle ear cavity and metronidazole therapy was started 7 days later. On day 14 after challenge the animals were sacrificed and their middle ears analysed. Intraperitoneal injection of 6 mg metronidazole (about 20 mg per kg) once daily, 6 mg twice daily and 15 mg (50 mg per kg) once daily reduced the incidence of culture positive ears from 13/17 among untreated controls to 7/17 (p = 0.08), 3/10 (p = 0.05) and 2/15 (p = 0.001), respectively. The therapeutic efficacy of metronidazole in experimental otitis media was less than that expected from the concentrations of drug recorded in serum and the drug levels presumed to be achieved in the middle ear effusion.

Experimental otitis media in gerbils and chinchillas with Streptococcus pneumoniae, Haemophilus influenzae, and other aerobic and anaerobic bacteria

To ascertain the usefulness of Mongolian gerbils as an inbred model for otitis media, 52 Mongolian gerbils (Meriones unguiculatus, strain MONT/Tum) were compared with 26 chinchillas (Chinchilla laniger) for susceptibility to Streptococcus pneumoniae type 3. Haemophilus influenzae type b, and a polymicrobic culture including anaerobes (Streptococcus intermedius, Propionibacterium acnes, Staphylococcus epidermidis, and Corynebacterium sp.). Organisms were inoculated percutaneously into the superior chamber of the middle ear bulla. The gerbils and chinchillas shared similar susceptibilities and responses to the inoculated organisms as determined by X-ray, otoscopic, histopathological, and microbiological determinations at 5 to 7 days. Koch's postulate studies proved the role of S. pneumoniae and H. influenzae in the pathology found in both animal models. The animals were also susceptible to the polymicrobic culture, although the relative virulence of the individual members of this mixture was low, suggesting that these species potentiated as a polymicrobic mixture. The Corynebacterium sp. appeared to elicit the greatest histopathological response in chronic (8-week) studies in gerbils. The gerbils were found to be useful as an alternative animal model for the study of otitis media of bacterial etiology.