Sensitivity of Haemophilus influenzae to antibiotics

Cefamandole, a cephalosporin antibiotic with an unusually wide spectrum of activity

The in vitro activity of cefamandole, 7-d-mandelamido-3-(1 methyl-1H-tetrazol-5 yethiomethyl)-3-cephem-4 carboxylic acid, was investigated. The majority of streptococci and pneumococci were inhibited by 0.1 mug/ml. Activity against Staphylococcus aureus was below that of cephalothin, but most strains were inhibited by 0.4 mug/ml. Enterococci were not inhibited by less than 25 mug/ml. Cefamandole was very active against most members of the Enterobacteriaceae, with 70% of Escherichia coli, 86% of Klebsiella pneumoniae, and 88% of Proteus mirabilis inhibited by 1.6 mug/ml. A number of Enterobacter aerogenes, Proteus vulgaris, and Serratia marcescens strains were inhibited by less than 25 mug/ml. Pseudomonas species were resistant. Cefamandole was more active than cephalothin, cephaloridine, or cephalexin against members of the Enterobacteriaceae. Inoculum size and type of medium had variable effects on the minimal inhibitory concentration, depending upon the particular strain tested. Strains of Enterobacter, Serratia, indole-positive Proteus species showed the greatest inoculum effect. Similarly, these species showed a several-fold difference of bactericidal and inhibitory levels. Resistance of cefamandole to hydrolysis by gram-negative beta-lactamase played a partial role in its activity, but some strains that hydrolyzed the agent were susceptible.

Antimicrobial resistance among clinical isolates of Haemophilus influenzae in northern Italy. Collaborative Study on Pediatric Infectious Diseases

Only scanty data are available on the susceptibility of Haemophilus influenzae in Italy. The in vitro activity of ampicillin, ampicillin-sulbactam, cefaclor, cefuroxime, cefotaxime, chloramphenicol, erythromycin and trimethoprim-sulfamethoxazole against 327 strains of Haemophilus influenzae (55 encapsulated, 272 non-typeable) isolated from adults and children in northern Italy, between January 1984 and December 1989, was compared. Patients were affected by meningitis or other invasive infections, conjunctivitis, otitis, sinusitis, pneumonia or bronchitis. Minimal inhibiting concentrations were determined by a microdilution technique in Mueller Hinton broth supplemented with 10 microliters/ml NAD and 2-5% lysed horse blood. A concentration of 1 x 10(5) to 5 x 10(5) CFU/ml was used as the inoculum. The antibiotics were tested at concentrations ranging from 0.03 to 64 microliters/ml with the exception of trimethoprim-sulfamethoxazole, for which the range of concentrations examined were 0.01/0.25 to 32/512 microliters/ml. All the strains tested were susceptible to ampicillin-sulbactam, cefuroxime and cefotaxime, and more than 95% were susceptible to ampicillin, cefaclor and chloramphenicol. Only 4% were susceptible to erythromycin but most minimal inhibiting concentrations fell into the intermediate category. Strains isolated from adults were more susceptible to trimethoprim-sulfamethoxazole than strains isolated from children (85% vs 66%; p = 0.011).

Mechanisms of beta-lactam resistance in Haemophilus influenzae

Haemophilus influenzae has become increasingly resistant to beta-lactam antibiotics. Three major mechanisms, both enzymatic and non-enzymatic, are involved. Enzymatic resistance is mainly due to production of a TEM-1 plasmid-mediated beta-lactamase, and in some cases to a new enzyme ROB-1. Of the non-enzymatic mechanisms, decreased permeability due to alteration of outer membrane proteins seems to be rare in comparison to decreased affinity of penicillin-binding proteins for beta-lactam antibiotics. Enzymatic resistance is present in about 10-20% of clinical isolates, while non-enzymatic resistance is present only in 2-4%.

Influence of growth medium and supplement on growth of Haemophilus influenzae and on antibacterial activity of several antibiotics

In the present study, five non-beta-lactamase- and five beta-lactamase-producing strains of Haemophilus influenzae were used to determine whether three different growth media, Mueller-Hinton broth and agar, brain heart infusion broth and agar, and tryptic soy broth and agar, and their added supplements (0.2% hemin-0.1% IsoVitaleX, 1% hemin-1% IsoVitaleX, 2% sheep blood, 10% Fildes enrichment, 5% Fildes enrichment, 1% supplement B, 5% horse erythrocytes, and 2% hemoglobin-1% IsoVitaleX) would influence the growth rate of this microorganism and the antibacterial activity of eight antibiotics, including ampicillin, tetracycline, chloramphenicol, gentamicin, cefamandole, erythromycin, trimethoprim-sulfamethoxazole (TMP-SMX), and cefoperazone. The growth curve studies were carried out with an initial inoculum of 10(4) bacteria per ml, and MICs were determined with an inoculum of 5 X 10(5) microorganisms. Mueller-Hinton broth, brain heart infusion broth, and tryptic soy broth enriched with 5% Fildes resulted in a maximal growth of more than 10(8) CFU/ml at 24 h. When 10% Fildes or 2% sheep blood was added as enrichment to Mueller-Hinton broth, a considerable reduction in the growth rate of H. influenzae strains resulted (P less than 0.01). Significant variations in MICs (P less than 0.01) were observed with chloramphenicol, TMP-SMX, erythromycin, and cefoperazone when brain heart infusion agar, Mueller-Hinton agar, or tryptic soy agar was used. Chloramphenicol, gentamicin, erythromycin, and TMP-SMX were all affected by the different enrichments added to Mueller-Hinton agar. MICs were in general higher with 5% Fildes enrichment and lower with 1% supplement B. Cefoperazone was the only drug which exhibited a lower MIC in 5% Fildes enrichment for ampicillin-resistant H. influenzae strains.

Pericarditis caused by beta-lactamase-producing Haemophilus influenzae: report of two cases in adults and review of the literature

Two adult patients with pericarditis caused by beta-lactamase producing Haemophilus influenzae are reported and their management reviewed. Both had pharyngitis, epiglottitis, pneumonia, empyema, or septicemia and were cured with antimicrobics and pericardial drainage (one by catheter and one by surgery). Eleven previously reported cases of pericarditis caused by Haemophilus influenzae are also reviewed. In reviewing this rare cause of bacteria pericarditis, it is important to recognize the antibiotic resistance profile, the incidence of pericardial tamponade, and the use of surgical drainage. Antibiotic selection for this organism is also discussed, as well as the importance of biotyping.

Rifampin alone or with trimethoprim for contacts of children with Haemophilus influenzae type b infections

We carried out a nonrandomized, unblinded study to compare the efficacy of rifampin alone with that of rifampin in combination with trimethoprim in the eradication of the Haemophilus influenzae type b (HIB) carrier state among contacts of patients with invasive HIB infection. The study population comprised 17 index patients admitted to hospital with severe HIB infections and 233 contacts, 43 of whom had nasopharyngeal colonization with HIB of the same biotype as that of the index patient. Rifampin in a daily dose of 20 mg/kg (maximum 600 mg) for 4 days eradicated the carrier state in 86% of cases, as did the combination of rifampin at the same dosage and trimethoprim in a daily dose of 5 mg/kg (maximum 160 mg) for 4 days.

Erythromycin: a microbial and clinical perspective after 30 years of clinical use (1)

Erythromycin is a macrolide that acts by inhibiting the translocation reaction during protein synthesis. Erythromycin is inactive against the Enterobacteriaceae and Pseudomonas aeruginosa except under alkaline conditions. Erythromycin is active against most gram-positive bacteria; some gram-negative bacteria, including Neisseria, Bordetella, Brucella, Campylobacter, and Legionella; and Treponema, Chlamydia, and Mycoplasma. The emergence of resistance to erythromycin is closely associated with its use and is often plasmid mediated. After its oral or parenteral administration, erythromycin diffuses readily into intracellular fluids and is actively concentrated intracellularly by polymorphonuclear leukocytes and alveolar macrophages.

The bactericidal activity of ampicillin, amoxicillin, tetracycline, and doxycycline against H. influenzae under various conditions of culture

The bactericidal activities of ampicillin, amoxicillin, tetracycline, and doxycycline at a concentration of 1 mg/l were compared for 13 strains of H. influenzae with a typical minimal inhibitory concentration of these drugs. Conditions of culture used were: liquid medium in shaken flasks, stationary flasks and stationary tubes, with and without the addition of 30% human serum. Ampicillin and amoxicillin exerted the same bactericidal activity. Survival rates at 5 h were on the average near 1%, however, with large variations. At 24 h survival rate was uniformly below 0.12%. The bactericidal activity of the tetracyclines depended more on the cultural conditions. A marked reduction of the bacterial population below 1% was found at 24 h between 12 of 12 and 5 of 13 strains according to the experimental circumstances. Tetracycline was more bactericidal than doxycycline, especially in the presence of serum.

Antibiotic susceptibility pattern and capsular types of Haemophilus influenzae recovered from clinical specimens in northern Norway

One hundred and nine strains of Haemophilus influenzae recovered from clinical specimens were examined for antibiotic sensitivity pattern and capsular types. All strains from blood cultures, cerebrospinal fluid and a joint aspirate were type b whereas most of the isolates were acapsular when recovered from other specimens viz. wound secretions (67%), maxillary sinus (75%), lower resp tract (86%), nasal cavity (90%). Out of the 109 strains 88 (81%) were non-typable, and 3.6% were beta-lactamase-producing, two of which were type e, one was type b and one was acapsular. Three beta-lactamase-producing strains were isolated from specimens from the respiratory tract and one from blood cultures. Beta-lactamase-producing strains including one chloramphenicol-resistant strain harboured similar plasmids, as judged by agarose gel electrophoresis. The strains showed quite a uniform sensitivity to antibacterial agents with the exception of sulphonamides to which the capsular strains, particularly type b strains, were less susceptible.

Efficacy and tolerance of enteric-coated erythromycin base (Ery-Max) administered twice or four times daily in patients with acute bronchitis

We performed a double-blind trial of a new formulation of erythromycin base as enteric-coated pellets (Ery-Max) in the treatment of acute bronchitis in 220 patients. Subjects were randomized to receive either 500 mg twice or 250 mg four times a day for 10 days. The response to treatment as assessed clinically and by changes in sputum purulence was the same in the two groups. Thus 97% and 98% of the patients had a good or improved clinical effect. Treatment was well tolerated, but side-effects were encountered more often in the q.i.d. group (p greater than 0.05). In conclusion, the study showed that the enteric-coated erythromycin as pellets, given twice or four times daily for 10 days, was well tolerated and equally effective in acute bronchitis. Hence, the more convenient b.i.d. regimen can be recommended.

Bacampicillin in acute maxillary sinusitis: concentration in sinus secretion and clinical effect. A randomized, double-blind study of two dosage regimens

The clinical effect and the penetration of ampicillin into sinus secretion after oral administration of bacampicillin was studied in 47 patients with acute maxillary sinusitis allocated at random in treatment with 400 mg bacampicillin 3 times or 1200 mg twice daily. The overall clinical effect was similar and was assessed as "good" in 23/25 patients treated with 400 mg doses and in 19/22 treated with 1200 mg. Adverse reactions were reported by 4 patients. The concentrations of ampicillin obtained in sinus secretion were proportional to the dose given. The highest values after 400 mg bacampicillin were approximately 0.6 mg/l and after 1200 mg about 2 mg/l. Both dosages are applicable to treatment of acute maxillary sinusitis.

Activity of erythromycin against Haemophilus influenzae from respiratory tract infections

Ampicillin and amoxycillin are very frequently used for treating respiratory infections due to Haemophilis influenzae, but the emergence of beta-lactamase producing strains of this organism may limit their use. Erythromycin would be a suitable alternative but to date variable absorptions and reported minimal inhibitory concentrations (MICs) outside the range of achievable blood levels of erythromycin have prevented its use. The purpose of this study was to determine the MICs of erythromycin for strains of H. influenzae isolated from patients with lower respiratory tract infection and the frequency of beta-lactamase production in these strains. Eighty-five of 100 strains were sensitive to erythromycin (MIC much less than 2.00 mg/L). Eleven strains were resistant to ampicillin and 10 of these produced beta-lactamase. Nine beta-lactamase producing strains had MICs to erythromycin of 2.0 mg/L or less. With the blood levels of erythromycin obtainable with new formulations, this antibiotic should prove of use in the treatment of respiratory infections due to H. influenzae.

Limited in vitro activity of cefamandole against 100 beta-lactamase- and non-beta-lactamase-producing Haemophilus influenzae strains: comparison of moxalactam, chloramphenicol, and ampicillin

In the present study, the minimal inhibitory concentrations and minimal bactericidal concentrations of moxalactam, cefamandole lithium, ampicillin, and chloramphenicol were determined, both in broth and on solid medium, against 75 non-beta-lactamase-producing and 25 beta-lactamase-producing strains of Haemophilus influenzae. Most of the 75 strains were inhibited or killed by 2 microgram or less of ampicillin, chloramphenicol, or moxalactam per ml, but cefamandole exhibited poor bactericidal activity against 11 non-beta-lactamase-producing strains, of which 9 were non-type B H. influenzae. Most of the 25 beta-lactamase-producing H. influenzae were resistant to 128 microgram of ampicillin per ml. Both moxalactam and chloramphenicol, which had minimal inhibitory concentrations of less than 0.25 and 2 microgram/ml, respectively, were more active than cefamandole, which had a minimal inhibitory concentration ranging from 2 to greater than or equal to 128 microgram/ml.

Antibiotic sensitivity of Haemophilus influenzae strains including three recent chloramphenicol-resistant isolates

The antibiotic sensitivity of 100 recent isolates of Haemophilus influenzae was determined. Three strains were resistant to chloramphenicol with minimal inhibitory concentrations of 16 microgram/ml. Of these three resistant strains, one produced betalactamase and one was resistant to sulfamethoxazole-trimethoprim. The remaining strains were inhibited by 0.25-2.0 microgram/ml of chloramphenicol. Ampicillin and benzylpenicillin were found to inhibit all but the betalactamase-producing strains at low concentrations. Regarding sulfamethoxazole-trimethoprim 96% had minimal inhibitory concentrations of 2.5-0.12 microgram/ml or less, while two strains were resistant. The invitro efficacy of erythromycin against H. influenzae was low. The majority of the strains was inhibited by low concentrations of doxycycline and cefuroxime while cefoxitin exhibited minimal inhibitory concentrations values usually exceeding 1 microgram/ml. The minimal inhibitory concentrations registered are compared to the concentrations of the different antibiotics attainable in certain body fluids.

Chromosomally integrated conjugative plasmids are common in antibiotic-resistant Haemophilus influenzae

Twenty-three highly antibiotic-resistant strains of Haemophilus influenzae and two of Haemophilus parainfluenzae without detectable large plasmids were examined for conjugative transfer of their resistance to H. influenzae strain Rd or to other strains. Very inefficient transfer was observed for 18 H. influenzae strains and 1 H. parainfluenzae strain. All H. influenzae transcipients carried a large plasmid, and they were in turn efficient donors of their resistances in standard conjugation crosses with isogenic recipients. This was not seen for the H. parainfluenzae transcipients. It is concluded that most of the original antibiotic-resistant cultures carried an integrated conjugative R plasmid which had been excised in a few cells in each population. It was these cells which transferred resistance in the primary crosses.

The aminopenicillins: development and comparative properties

In this review we have compared and contrasted the antibacterial and pharmacological properties of the aminopenicillins currently available. It is apparent that there is little hard evidence (except in the case of thphoid fever) that either amoxycillin or the pro-drug esters of ampicillin are significantly more effective than ampicillin itself, despite their better absorption and higher serum levels. However, amoxycillin and the ampicillin pro-drug esters do cause fewer bowel side-effects than ampicillin, which may justify their use despite the extra cost involved. The problem of susceptibility to penicillinases is unlikely to be solved by modification of the aminopenicillin molecule. A more likely solution is administration of these substances with beta-lactamase inhibitors such as clavulanic acid. Trials with such combinations are already under way.

Serum and sputum antibiotic levels after ampicillin, amoxycillin and bacampicillin chronic bronchitis patients

Serum and sputum concentrations of ampicillin or amoxycillin were measured in patients admitted to hospital for acute exacerbations of chronic bronchitis with purulent sputum. Mean peak serum levels of nearly 12 mg/l were found after 1600 mg bacampicillin (mean peak level in sputum 0.85 mg/l). The serum and sputum concentrations after 750 mg amoxycillin and 800 mg bacampicillin were comparable (mean peak serum levels approximately 9.5 mg/l, sputum concentrations 0.4 to 0.5 mg/l) although the drugs were not given in equimolar doses. Results after 1000 mg ampicillin by mouth were less satisfactory (mean peak serum level 7.8 mg/l) and only 0.25 mg/l was attained in the sputum. Minimum inhibitory concentrations of ampicillin and amoxycillin were measured for 177 Haemophilus influenzae strains. Most of the ampicillin MIC values were between 0.125 and 0.5 mg/l but more of the strains required 0.5 mg/l of amoxycillin. The amoxycillin MIC values were often one or two dilutions higher than those of ampicillin (p less than 0.001).

A clinical comparison of ampicillin, ampicillin esters (bacampicillin and pivampicillin) and amoxycillin in acute exacerbations of chronic bronchitis

The results of antibiotic therapy in 271 patients suffering from acute exacerbations of chronic bronchitis are presented. The effectiveness of the better absorbed ampicillin esters (pivampicillin and bacampicillin) is confirmed, but side-effects from the pivampicillin present problems whereas bacampicillin is excellently tolerated, even in twice daily doses of 1600 mg. Amoxycillin, if given in 750 mg doses three times daily by mouth, is also safe and effective against Haemophilus influenzae. However, if accurate MIC results are not available for both ampicillin and amoxycillin, the lesser degree of sensitivity to amoxycillin suggests that use of an ampicillin ester (such as bacampicillin) is to be preferred. Prophylactic use of antibiotics in chronic bronchitis patients does not seem logical to us.

Ampicillin concentration in normal and pathological lung tissues after oral administration of bacampicillin

Following oral administration of 800 mg bacampicillin, the concentrations of ampicillin were determined in normal (n = 16) and pathological (n = 12) lung tissue after 3.6 and 9 hours in a total of 28 patients. The serum concentration was determined simultaneously. The mean peak serum concentration (+/- SD) after one hour was 9.7 +/- 7.2 micrograms/ml. The mean concentration (+/- SD) in normal lung tissues were, after 3, 6 and 9 hours, 3.73 +/- 1.10 micrograms/ml, 1.06 +/- 0.99 micrograms/ml, 0.15 +/- 0.30 microgram/ml respectively, and in pathological lung tissues 0.95 +/- 0.31 microliters/ml, 0.86 +/- 1.11 micrograms/ml and 0.40 +/- 0.24 micrograms/ml respectively. Thus bacampicillin produced concentrations well above the MIC of the most important pathogen, Haemophilus influenzae, in both pathological and normal lung tissue.

Ampicillin dosage in bacterial meningitis with special reference to Haemophilus influenzae

Ampicillin remains the preferred drug for most cases of bacterial meningitis, including those due to Haemophilus influenzae type b. A prospective study was performed comparing high (400 mg/kg per day)- and low (150 mg/kg per day)-dosage regimens of ampicillin in the treatment of 172 patients with bacterial meningitis. Response to both regimens was equivalent in terms of average hospital stay, duration of ampicillin therapy, microbiological response, and death and residua. Patients with H. influenzae infections treated with low-dosage regimens had slightly prolonged febrile courses. This study suggests that high-dosage regimens of ampicillin offer no benefit over low-dosage regimens in the treatment of bacterial meningitis.

Plasmid transfer in Haemophilus influenzae

Twenty-nine strains of Haemophilus influenzae highly resistant to ampicillin, chloramphenicol, or tetracycline were examined for the presence of plasmids. Agarose gel electrophoresis of ethanol-precipitated cell extracts revealed large plasmids in 11 strains, of which 7 were conjugative. Plasmid transfer by conjugation between isogenic strains was quite efficient, but transfer between different serotypes was nearly always much more inefficient. Type I or II restriction enzymes do not appear to be barriers to this transfer. Encapsulated cells can be both efficient donors and recipients. Small plasmids were seen in three strains, but only two of the three are resistance factors (RSF0885, pUB703). Thus, in 17 isolates antibiotic resistance genes are believed to be located in the bacterial chromosome. Most of these resistances could be transferred by genetic transformation into the widely used Rd strain. In some cases transfer of chromosomal resistance into conjugative plasmids was observed in both rec+ and rec host cells. Since transfer by conjugation seems to be the more efficient process, it is puzzling that in the majority of the 29 isolates studied resistance genes appeared to be in the chromosome.

[Tissue penetration of erythromycin (author's transl)]

Although erythromycin has been used in therapy for more than 25 years, until now there has been no paper summarizing the data on tissue penetration. The present review documents in detail dose- and time-related peak serum levels of erythromycin derivatives after oral administration, in addition to the erythromycin tissue levels. The erythromycin tissue levels often manifoldly exceed the corresponding MIC values of pathogens sensitive to erythromycin. However, erythromycin does not penetrate the central nervous system, or only penetrates in small, incalculable amounts. The same applies for the placental passage of erythromycin. The tissue levels confirm, with respect to the MIC values of the pathogen spectrum, clinical experience with erythromycin in the treatment of ear, nose and throat infections, respiratory tract infections and, with some limitations Chlamydia urethritis.

Growth curves, microscopic morphology, and subcultures of beta-lactamase-positive and -negative Haemophilus influenzae under the influence of ampicillin and cefamandole

In contrast to the results obtained with ampicillin, the minimum inhibitory concentrations of cefamandole against Haemophilus influenzae were within the same range (0.5 to 1.5 mug/ml) whether or not the strains were beta-lactamase producers. The minimum bactericidal concentrations were somewhat higher for beta-lactamase-positive strains (6.4 mug/ml) than for negative strains (1.2 mug/ml). In a culture with high initial microbial density, monitored by recording optical densities, the addition of 10 mug of cefamandole per ml brought about rapid lysis of a beta-lactamase-negative strain. Observation of a beta-lactamase-positive strain revealed, in the early part of the growth curve, absence of lysis and an increase of biomass similar to that observed in a drug-free control curve. In contrast to the results obtained with ampicillin, the culture consisted uniformly of spherical forms, probably in the process of division, which were capable of generating colonies. When the microbial density exposed to cefamandole was increased still further, persistent bacillary forms were observed, and after 24 h hydrolysis had eliminated every trace of microbiologically active cefamandole.

Antibiotic resistance in Streptococcus pneumoniae and Haemophilus influenzae. Report of a study group on bacterial resistance

Twenty laboratories in England and Scotland took part in 1977 in a survey of antibiotic resistance in Streptococcus pneumoniae and Haemophilus influenzae. In Str pneumoniae 59 (6.8%) of the 866 strains studied were resistant to tetracycline and three to chloramphenicol, and one strain showed a decreased susceptibility to penicillin. The prevalence of resistance to tetracycline was lower than that found in a similar study performed in 1975. Nine hundred and fifty-two strains of H influenzae were examined: 15 (1.6%) were resistant to ampicillin (all were beta-lactamase producers) and 26 (2.7%) to tetracycline. Only two strains were resistant to chloramphenicol and two to trimethoprim. Sixty-three H influenzae strains were capsulated. Thirty-four of these were of Pittman type b, and antibiotic resistance, particularly to ampicillin, was more common in these than in other serotypes or non-typable strains. Some variation was seen in the resistance rate of both H influenzae and Str pneumoniae to tetracycline in strains from different centres, but too few were isolated to assess whether this represented a true geographical difference.

Susceptibility of Haemophilus influenzae type b to rifampin and sulfisoxazole

A total of 100 and 97% of Haemophilus influenzae type b strains from major infections were susceptible, respectively, to levels of rifampin and sulfisoxazole attainable in saliva. It is theoretically feasible to eliminate Haemophilus influenzae from the nasopharynx with these drugs.

Pharmacokinetics of bacampicillin compared with those of ampicillin, pivampicillin, and amoxycillin

Bacampicillin, a new oral prodrug which in vivo is rapidly transformed to ampicillin, was compared with ampicillin, pivampicillin, and amoxycillin in a randomized cross-over study on 11 healthy volunteers. All drugs were given in oral doses equimolar to 400 mg of bacampicillin (800 mumol). The mean of the individual peak concentrations in serum was 8.3 mug/ml for bacampicillin, 7.1 mug/ml for pivampicillin, 7.7 mug/ml for amoxycillin, and 3.7 mug/ml for ampicillin. Furthermore, bacampicillin had a higher absorption rate than all the other drugs, although there were statistically significant differences only versus ampicillin. The peak serum levels of the individual subjects were more dispersed with ampicillin and amoxycillin, suggesting a more uniform absorption of bacampicillin and pivampicillin. The relative bioavailability of bacampicillin and pivampicillin was comparable, whereas ampicillin was only 2/3 that of the others.

Quantitative inhibition of Haemophilus influenzae by trimethoprim/sulfamethoxazole

We evaluated the inhibitory effect of trimethoprim (TMP) and sulfamethoxazole (SMZ), alone and in combination, against 34 strains of Haemophilus influenzae. Growth inhibition was determined after incubation for 18 h by comparing viable counts of cultures in drug-containing medium with corresponding counts of control cultures in drug-free medium. In a modified, thymidine-deficient Levinthal broth, the numbers of colony-forming units of all the isolates tested were reduced 100-fold or more by TMP/SMZ (1.25/25 mug/ml) as compared with growth without drug. Inhibition was significantly greater with TMP/SMZ than with either TMP or SMZ alone. Ampicillin-susceptible and ampicillin-resistant strains were equally susceptible to TMP/SMZ. Growth of nontypable strains was inhibited more than growth of type b organisms.

Bacteremic hemophilus influenzae type B cellulitis in the adult

Described herein are three patients over the age of 50 years who had cellulitis of the neck and the upper portion of the chest, associated with Hemophilus influenzae type B bacteremia and respiratory tract infection--particularly that of the upper airway. Only one of the patients with cellulitis had the classic bluish-purple hue commonly seen in children affected with this syndrome. In the other two, the H. influenzae type B cellulitis could not be distinguished clinically from the more common group A streptococcal or staphylococcal cellulitis. Since the antibiotics employed in treating patients with infection due to the latter two organisms differ significantly from those used to treat patients with H. influenzae type B infection, the possibility of disease due to H. influenzae type B must be considered in any adult or child in whom cellulitis of the neck, chest and possibly face is associated with a respiratory tract infection, especially of the upper airway.

Haemophilus influenzae in otitis media and sinusitis: serotypes and susceptibilty to ampicillin and amoxycillin in vitro

In order to obtain Haemophilus influenzae, other than Type b, with highly probable human pathogeniticy strains were collected that had been isolated in abundant numbers from middle ear or maxillary sinus secretions of 157 patients with otitis media or sinusitis. The distribution of serotypes was as follows: nontypable 33.8%, Type b 26.1% Type a 19.1%, Type c 7.6%, Type e 5.7%, Type f 5.1%, and Type d 2.5%. The type distribution did not depend on the source of the strains. All strains were susceptible to ampicillin and amoxycillin in vitro; the broth dilution minimum inhibitory concentrations (MIC) of both antibiotics varied only fourfold; typical MIC values were 0.125 microgram/ml and 0.25 microngram/ml, respectively. Susceptibility did not vary with the source or type of the strains nor with the presence or absence of concomitant penicillin therapy.

Antimicrobial susceptibility of Haemophilus parainfluenzae

Fifty random clinical isolates of Haemophilus parainfluenzae were tested for their susceptibility to 10 antibiotics by a microtiter broth dilution method. Three of the strains tested were resistant to ampicillin, whereas eight were resistant to tetracycline. All strains tested were susceptible to chloramphenicol, kanamycin, gentamicin, cephalothin, and colistin. The ranges of minimal inhibitory concentrations for the three remaining antibiotics were: 0.5 to >/=128 mug of penicillin G per ml, 0.03 to 4 mug of carbenicillin per ml, and 1 to 16 mug of erythromycin per ml. Elevated minimal inhibitory concentrations for penicillin and carbenicillin were noted for the three ampicillin-resistant strains. Tests for beta-lactamase production demonstrated the presence of this enzyme in each of the three ampicillin-resistant strains.

Comparative acitivity of ampicillin and cefuroxime against three types of Haemophilus influenzae

On the basis of their susceptibility to ampicillin, strains of Haemophilus influenzae can be divided into three types: type 1 are normally susceptible strains, type 2 produce stable spheroplasts from low inocula, and type 3 are beta-lactamase producers. Because of the production of spheroplasts, standard broth and agar dilution techniques have failed to differentiate between the responses of type 2 and 3 strains to ampicillin, or to identify the superiority of cefuroxime over ampicillin against the beta-lactamase-producing strains. Disk susceptibility tests with heavily seeded plates were also difficult to interpret. To overcome these problems, we developed a medium that supports the growth of H. influenzae, but not survival of spheroplasts, thereby reducing the complicating influence of spheroplast formation. Utilization of the medium made it possible to identify beta-lactamase-producing strains via both minimal inhibitory concentration and disk susceptibility techniques, as well as the superiority of cefuroxime over ampicillin against such strains. In vivo experiments showed that cefuroxime and ampicillin are equally active against infections with type 1 and 2 strains, but that cefuroxime is superior to ampicillin against infections with type 3 beta-lactamase-producing strains.

Comparative trial of carbenicillin and ampicillin therapy for purulent meningitis

A randomized therapeutic trial of carbenicillin (CB) or ampicillin (AMP) in purulent meningitis was performed in 86 pediatric and adult patients (41 Haemophilus influenzae, 22 Streptococcus pneumoniae, 13 Neisseria meningitidis, and 10 of unknown etiology). All isolates, incuding H. influenzae, were susceptible to CB and AMP. Median cerebrospinal fluid (CSF) antibiotic concentrations were 0.85 and 1.60 mug/ml for CB and AMP, respectively, during administration of daily doses of 400 mg/kg and 0.65 and 0.45 mug/ml, respectively, on daily doses of 200 mg/kg. Higher CSF concentrations, up to a median concentration of 4.5 mug/ml, were observed in patients with CSF protein concentrations >/=75 mg/100 ml. Clinical responses were equivalent on either antibiotic regimen. Among AMP patients (45), 8 had significant residua and 3 died; among CB patients (41), 5 had residua and none died. However, 38% of H. influenzae patients treated with CB had positive CSF cultures on day 1 follow-up lumbar punctures, compared with only 5.8% of AMP patients with H. influenzae. The significance of a delay of CSF sterilization among CB-treated patients is unknown, since there was no correlation between persistence of hemophilus organisms and the frequency of adverse outcome. AMP and CB are equivalent for the treatment of bacterial meningitis due to susceptible organisms.

Activity of cefamandole and other cephalosporins against aerobic and anaerobic bacteria

The activity of cefamandole was comparable to that of cephalothin, cefazolin, and cephaloridine against Staphylococcus aureus, Streptococcus pyogenes, and Diplococcus pneumoniae. In contrast, cefamandole was considerably more active than cephalothin, cefazolin, or cephaloridine against gram-negative facultative bacilli, including Haemophilus influenzae, the most striking disparities being noted with indole-positive Proteus and Enterobacter. Bacteroides fragilis was more susceptible to cefoxitin than to cefamandole or cefazolin (median minimal inhibitory concentration, approximately 8, 32, and 32 mug/ml, respectively); cephalothin exhibited still less activity against this species. The majority of other anaerobes were inhibited by relatively low concentrations of all four cephalosporins. The results indicate a potentially valuable role for cefamandole against facultative gram-negative bacilli, including H. influenzae, but no exceptional activity against anaerobes.

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

Strains of Haemophilus influenzae, which did not belong to any of the known capsular serotypes and which were resistant in vitro to ampicillin, have been isolated from middle ear exudates of two children with otitis media. These children failed to improve with ampicillin therapy, and the resistant organisms persisted at the site of infection. Patients infected with such ampicillin-resistant organisms require therapy with antimicrobial agents which are not susceptible to degradation by penicillinase.