Otitis media caused by non-typable, ampicillin-resistant strains of Haemophilus influenzae

Acute Otitis Media

A typical case of acute otitis media in a pediatric patient is presented. The pathophysiology of the disorder, as well as its incidence, etiology, complications, and sequelae are discussed. Past treatment methods and current therapeutic recommendations pertaining to antibiotics and other adjuncts are included.

Effect of prior antibiotic treatment on middle ear disease in children

The effect of prior antibiotic treatment on the course of otitis media was assessed in a group of 62 children who experienced 83 episodes of ear infection during 3 years of observation. Bacterial quantitation in middle ear fluids demonstrated a significantly higher colony count in symptomatic children (3.9 x 10(4) +/- 12 bacteria per milliliter) compared to asymptomatic children (6.3 x 10(3) +/- 10 bacteria per milliliter; p = .05). Bacterial counts similarly tended to be higher in children with Streptococcus pneumoniae (4.0 x 10(6) +/- 16 bacteria per milliliter) and Hemophilus influenzae (2.0 x 10(6) +/- 16 bacteria per milliliter), who were more often symptomatic (73% and 55%, respectively, versus 38%) than children with Moraxella catarrhalis (7.9 x 10(3) +/- 2). Antibiotic therapy between 3 and 30 days prior to bacterial diagnosis was associated with a reduction in symptoms from 70% to 38% (p less than .025). However, prior treatment did not statistically reduce bacterial colony counts, although S pneumoniae decreased 90% in the previously treated group. Resistance to ampicillin occurred in 0% of S pneumoniae, 39% of nontypeable H influenzae, and 80% of M catarrhalis subjects without prior treatment and in 0%, 46%, and 100%, respectively, of subjects previously treated (p less than .025). These data suggest that prior treatment has a significant impact on the subsequent course of otitis media in children.

A randomized controlled trial of amoxicillin plus clavulanate compared with cefaclor for treatment of acute otitis media

We performed a randomized controlled trial of amoxicillin plus clavulanate versus cefaclor for treatment of acute otitis media. Total daily doses given in three divided doses were 40 mg/kg amoxicillin plus 10 mg/kg clavulanate, and 40 mg/kg cefaclor. Pathogens were eradicated from the middle ear exudate after 3 to 6 days of therapy in 35 (97%) of 36 patients given amoxicillin-clavulanate compared with 24 (75%) of 32 given cefaclor (P = 0.028). When analysis was restricted to patients with positive urine or serum drug assays during therapy, pathogens were eliminated in 33 (97%) of 34 patients given amoxicillin-clavulanate compared with 21 (75%) of 28 given cefaclor (P = 0.026). Bacterial isolates associated with bacteriologic failure of cefaclor therapy were Streptococcus pneumoniae (two patients), beta-lactamase-negative Haemophilus influenzae (four), and beta-lactamase-positive Branhamella catarrhalis (two). The single failure with amoxicillin-clavulanate therapy was associated with non-beta-lactamase-producing H. influenzae isolated from the middle ear exudate. We conclude that cefaclor is less efficacious than amoxicillin-clavulanate for the treatment of acute otitis media.

Capsular variation in experimental strains of Haemophilus influenzae

This study sought to demonstrate that clinically untypable strains of Haemophilus influenzae are derivable from previously capsulated ones. Penicillin-induced forms were employed to explore in vivo and in vitro a possible mechanism of the reversible cycle vegetative to L-phase revertant. Normal H. influenzae type b (Rab), capsule-deficient strain ATCC 9333, and experimental L-phase and its revertants were used in this investigation. Capsular antigens, polyribose phosphate (PRP) content of each strain was assayed by orcinol and rocket immunoelectrophoretic methods. Intra- and inter-strain PRP differences were statistically analysed. Strain differences between in vivo and in vitro passaged extracts of strain 9333 and 9333 were significant (t-test P less than 0.01). There were also significant differences in vivo and in vitro between penicillin-treated, L-phase infected mouse isolates and penicillin-free, L-phase infected mouse isolates; and also between penicillin-treated, L-phase infected mouse isolates and revertant Rab infected mouse isolates (Mann-Whitney U-test P less than 0.02, P less than 0.01, respectively). These findings suggest that untypable isolates of H. influenzae are derivable from otherwise capsulated strains, depending on decapsulating factors in the microenvironment. Clinical implications of the findings are discussed.

A randomized controlled trial of cefaclor compared with trimethoprim-sulfamethoxazole for treatment of acute otitis media

We performed a randomized controlled trial of cefaclor administered twice daily compared with trimethoprim-sulfamethoxazole (TMP-SMZ) administered twice daily for the treatment of acute otitis media. Pathogens were eradicated from the middle ear exudate after 3 to 6 days of therapy in 35 of 37 (95%) patients given TMP-SMZ compared with 28 of 40 (70%) given cefaclor (P = 0.017). Haemophilus influenzae was eliminated in 13 of 14 (93%) patients given TMP-SMZ compared with 10 of 18 (56%) given cefaclor (P = 0.047). Clinical outcomes failed to distinguish between patients given TMP-SMZ or cefaclor. Symptoms improved despite persistent infection in 11 of 13 (85%) patients; middle-ear effusion persisted after therapy in 38 of 61 (62%) patients despite eradication of pathogens. We conclude that twice daily TMP-SMZ is more efficacious than twice daily cefaclor for the treatment of acute otitis media and that clinical outcomes may fail to detect differences between antibacterial agents in comparative drug trials in acute otitis media.

Rapid species identification and biotyping of respiratory isolates of Haemophilus spp

Three commercially available systems, the 4-h Minitek Enterobacteriaceae III, the Haemophilus Trio-Tube, and the Micro-ID, were evaluated for their capacities to identify and biotype 308 respiratory isolates of Haemophilus spp. When compared with aminolevulinic acid test results, the definitive identification method used in this study, these systems demonstrated no significant differences in their capacities to differentiate Haemophilus influenzae from Haemophilus parainfluenzae. They were in agreement with the standard method of species identification approximately 50% of the time. When sucrose was added to the Minitek and Trio-Tube configurations, the efficiency rate of species identification increased to more than 95%. The Micro-ID could not be modified to incorporate this additional biochemical parameter. The performance of the sucrose-supplemented Minitek and Trio-Tube systems, compared to the combined results of Micro-ID and aminolevulinic acid, produced correlations of 94 and 90%, respectively. Rapid and accurate methodologies are available for combined species identification and biotyping of Haemophilus spp.

Otitis media: update on etiology and management

Thirty children with clinical evidence of otitis media underwent tympanocentesis. Streptococcus pneumoniae was the predominant organism recovered (63%). Three cases of Hemophilus influenzae, alone or in combination with S pneumoniae, were identified. Other organisms found were Staphylococcus albus, Neiserria species. Group A B-hemolytic Streptococcus, and anaerobes. In four patients (13%) no organism was recovered. All isolates were ampicillin susceptible. No relationship was found between WBC, temperature, or age and the organism recovered. Tympanocentesis did not provide any information resulting in an alteration of therapy. Tympanocentesis may be indicated for relief of pain or for periodic surveillance of organism sensitivities, but is not justified in the emergency department for uncomplicated acute otitis media. [Friedman A, Fleisher GR, Henretig F, Handler S, Campos JM: Otitis media: Update on etiology and management. Ann Emerg Med 11:181-183, April 1982.]

Differentiation of Haemophilus spp. in Respiratory isolate cultures by an indole spot test

Indole spot tests using isolated, nonhemolytic colonies of Haemophilus species were positive for 90 of 151 (60%) respiratory isolates of Haemophilus influenzae, whereas 67 to 72 (93%) isolates of H. influenzae from cerebrospinal fluid and blood specimens were indole positive. Only 4 of 117 (3%) Haemophilus parainfluenzae isolates were positive for indole spot tests. Thus, indole-positive, nonhemolytic Haemophilus isolates in respiratory cultures can be presumptively identified as H. influenzae.

Trimethoprim-sulfamethoxazole compared with ampicillin in the treatment of acute otitis media

We treated 132 children with acute otitis media in a randomized trial comparing trimethoprim-sulfamethoxazole and ampicillin. The antibacterial efficacy of the drugs was assessed primarly from the results of cultures of middle ear aspirates obtained during or after the course of therapy; persistent, recurrent, and new infections of the middle ear were documented in both groups of patients but did not differ significantly. Both drug regimens were well accepted by the patients and were not associated with serious side effects or toxicity. TMP-SMZ is an effective alternate to AMP or to other accepted regimens for initial treatment of acute otitis media.

Non-type b Haemophilus influenzae infections in adults with reference to biotype

We report three cases of serious non-group b Haemophilus influenzae infections. The significance of these isolates with respect to both biotypes and serotypes is discussed.

Antibiotic-resistant bacteria in otitis media with effusion

Eighty-two bacterial isolates recovered from the middle ear effusions (192) of children with otitis media with effusion (OME) were tested for antibiotic sensitivity. Nearly 50% of all bacteria isolated were found to be resistant to penicillin, and in particular, 61% of the Haemophilus isolates were penicillin-resistant; 48% of the Haemophilus isolates were ampicillin-resistant. In addition, we we compared the bacterial recovery rate from effusions of patients who were receiving antibiotics with those who were not. Among patients who were receiving antibiotics, 33% of the effusions were culture positive, while 82% of the effusions were culture positive in the patients who were not given antibiotics. These results are discussed with respect to the possible role of bacteria in the pathogenesis of OME.

Incidence of ampicillin-resistant Hemophilus influenzae in otitis media

Ampicillin resistance in Hemophilus influenzae type b causing serious infections is appreciated, but little is known about ampicillin resistance in nonencapsulated strains causing otitis media. The ampicillin sensitivity of 984 middle-ear isolates of H. influenzae from children in Huntsville, Ala. obtained from 1970-1976, was examined: Nine AmpR isolates were found: one in 1973, two in 1974, three in 1975, and three in the first five months of 1976. Seven strains were nonencapsulated; two were type b. All nine produced beta-lactomase. The incidence of ampicillin resistance in strains causing otitis media increased from 0.6% in 1973 to 2.4% in 1976. AmpR H. influenzae infection should be suspected in situations where ampicillin therapy of otitis media is unsuccessful.