Revised disk diffusion interpretive criteria for cefaclor, loracarbef, cefprozil and cefixime when testing Haemophilus influenzae on haemophilus test medium

The aim of the current five-center collaborative study was to reassess the interpretive criteria for cefaclor, loracarbef, cefprozil and cefixime previously adopted or proposed by the National Committee for Clinical Laboratory Standards (NCCLS) for disk diffusion susceptibility tests with Haemophilus influenzae on Haemophilus Test Medium (HTM) agar. MICs and zones of inhibition were determined using NCCLS methods, HTM and two collections of strains of Haemophilus influenzae. One group of strains consisted of 118 stock organisms taken largely from various recent U.S. antibiotic resistance surveillance studies. The emphasis in this selected group of organisms was on strains that were beta-lactamase negative but ampicillin resistant (BLNAR) by some other mechanism. The second collection of test organisms consisted of 50 recent clinical isolates of Haemophilus influenzae obtained from each of the five participating study centers. This group was considered representative of the type of Haemophilus influenzae currently recovered from clinical sources in the USA. Frequency distribution assessment and error-rate bounded analysis of scattergram comparisons of MICs and zone sizes were used to develop the following zone diameters interpretive for disk diffusion susceptibility tests with Haemophilus influenzae on HTM agar: cefaclor, > or = 20 mm (susceptible, S) and < or = 16 mm (resistant, R); loracarbef, > or = 19 mm (S) and < or = 15 mm (R); and cefprozil, > 18 mm (S) and < 14 mm (R). The respective MIC correlates for all three antimicrobial agents were < or = 8 micrograms/ml (S) and 32 micrograms/ml (R).(ABSTRACT TRUNCATED AT 250 WORDS)

[Beta-lactamase-producing Haemophilus influenzae isolated in Portugal, 1989-1992]

Within the framework of a national multicentric study between 1989 and 1992, 118 strains of betalactamase producing Haemophilus influenzae were isolated. Biotyping demonstrated the predominance of biotypes I, II and III, with 22, 36 and 24% of the strains, respectively. Encapsulated strains accounted for 13% of the total; all, but one, were serotype b. The antimicrobial susceptibility test (dilution method) of the 118 ampicillin--resistant strains showed: 33.9% resistance to tetracycline, 29.7% to chloramphenicol, 10.2% to erythromycin, 9.3% to trimethoprim, 0.8% to rifampicin, and 29.7% of multiresistance. All strains were susceptible to augmentin, cefotaxime, ceftriaxone and ceprofloxacin. Ninety strains were screened for resistant plasmids. A large plasmid (30-50 Mdal) was isolated in 38.9% of the strains and a small plasmid (3-4.4 Mdal) in 10%. No plasmid was found in 51% of the strains. Isoelectric focusing of 54 beta-lactamases showed that all were type TEM-1 (pI = 5.4), with the exception of one, which was type TEM-2 (pI = 5.6).

[Comparative activity of oral beta-lactam antibiotics against fifty strains of Haemophilus influenzae producing a beta-lactamase according to bacterial inoculum]

Minimal inhibitory concentrations (MICs) of amoxycillin alone and in combination with 2 mg/l or 4 mg/l clavulanic acid, ampicillin alone and in combination with 4 mg/l or 8 mg/l sulbactam, cefuroxime and cefaclor, were determined by the agar dilution method, with bacterial inoculum size ranging from 3 x 10(7) to 3 x 10(9) colony-forming units per ml. As expected, an inoculum effect was observed with cefaclor. In contrast, MICs of amoxycillin in combination with clavulanic acid did not significantly increase with the inoculum size. Ampicillin combined with sulbactam, and cefuroxime were less efficient at the highest bacterial concentration tested.

[Comparative antibacterial activity of cefpodoxime against Haemophilus influenzae, Streptococcus pyogenes, Streptococcus pneumoniae and Moraxella catarrhalis]

The antimicrobial activity of cefpodoxime (Podomexef, CAS 80210-62-4) against 236 clinical isolates of H. influenzae, Moraxella catarrhalis, Streptococcus pyogenes and Streptococcus pneumoniae was investigated and compared with that of another 8 commonly used oral antibiotics. beta-Lactamase negative, beta-lactamase positive and multiresistant strains of H. influenzae were inhibited by cefpodoxime at a concentration of 0.13 mg/l. 10% of Moraxella catarrhalis isolates were moderately susceptible to cefpodoxime, with minimum inhibitory concentration (MIC) of cefpodoxime ranging between 0.13 and 2.0 mg/l. All isolates of Streptococcus pyogenes and Streptococcus pneumoniae were susceptible to < or = 0.25 mg/l cefpodoxime. Cefpodoxime was clearly more active than the older oral cephalosporins against all species tested. The activity was comparable to that of cefixime against all species except Streptococcus pneumoniae, against which cefpodoxime was more active than cefixime.

Validation of NCCLS macrolide (azithromycin, clarithromycin, and erythromycin) interpretive criteria for Haemophilus influenzae tested with the Haemophilus test medium. National Committee for Clinical Laboratory Standards

Some recently marketed macrolide antimicrobial agents possess physiochemical, antimicrobial, and pharmacokinetic advantages that enable their wider clinical use against Haemophilus influenzae infections. A five-laboratory study assessed the validity of existing or proposed azithromycin, clarithromycin, and erythromycin interpretive criteria for tests with H. influenzae isolates. National Committee for Clinical Laboratory Standards (NCCLS) methods, criteria, and quality-control guidelines were used. A total of 350 H. influenzae strains were processed, including fresh clinical isolates (250 strains) and replicate tests of 100 stock cultures sampling strains isolated from 1984 to 91. Azithromycin interpretive criteria (susceptible at < or = 4 micrograms/ml, > or = 12 mm) produced a 99.8% absolute agreement between the minimum inhibitory concentrations and disk diffusion results (0.2% false-susceptible error). Clarithromycin breakpoint criteria (susceptible at < or = 8 micrograms/ml, > or = 13 mm; and resistant at > or = 32 micrograms/ml, < or = 10 mm) produced high minor interpretive error, but < or = 1% combined false-susceptible and false-resistant discrepancies. Erythromycin interpretive guidelines were initially proposed for susceptible at < or = 0.5 microgram/ml, > or = 26 mm. This categorizes nearly all H. influenzae strains as resistant to this older macrolide. The NCCLS should consider the proposed erythromycin criteria for publication in appropriate tables, and a class drug should also be selected (azithromycin) that would best predict macrolide-class susceptibility for those agents indicated by the US Food and Drug Administration for H. influenzae infection chemotherapy (azithromycin and clarithromycin). No serious interpretive problems were observed with the current NCCLS criteria using Haemophilus test medium.

Progress in the prevention of hearing loss in infants

Two leading causes of hearing loss in infants and young children have been bacterial meningitis due to Haemophilus influenzae Type b (Hib) and congenital toxoplasmosis. In this two-part review, we describe the essential nature and incidence of these two diseases and how the availability of a Hib vaccine effective and safe with infants as young as 2 mo of age; the prospect of universal immunization against Hib disease; the introduction of cephalosporin antibiotic and corticosteroid treatment; and the use of early and prolonged antimicrobial therapy with children with congenital toxoplasmosis promises significant reduction, if not complete eradication, of hearing loss in infants and toddlers attributable to Hib bacterial meningitis and congenital toxoplasmosis. As a result, there may be up to a third fewer children under the age of five with severe hearing impairment annually in the United States.

[Antimicrobial activities of cefuroxime against recent clinical isolates]

Antimicrobial activity of cefuroxime axetil (CXM-AX) was compared with those of other cephem antibiotics against clinically isolated strains obtained mainly from outpatients of our center in a period from January to September of 1990 and 1993. Minimum inhibitory concentrations were determined and the following results were obtained. 1. The results suggested that, compared with reports of studies conducted with clinical isolates in early 1980's, MIC80 of CXM were equal to or lower against Staphylococcus spp., Streptococcus pyogenes, Escherichia coli, Klebsiella spp., Proteus mirabilis, Haemophilus influenzae, Moraxella subgenus Branhamella catarrhalis, Neisseria gonorrhoeae, Peptostreptococcus spp., and Propionibacterium acnes, except for Streptococcus pneumoniae, MIC80 which was slightly higher. 2. MIC90 of comparator drugs reflected those of new resistant organisms recently appeared, such as benzylpenicillin (PCG)-insensitive S. pneumoniae (PISP), cephem-resistant E. coli and Klebsiella spp., new quinolone-resistant H. influenzae and N. gonorrhoeae. Methicillin-resistant Staphylococcus aureus (MRSA) was detected also from specimens of community acquired infections. From the nature of MRSA detected in those situations MRSA appeared to present a continuing problem. 3. MIC90 against strains obtained from patients with community acquired infections was a good index of increases of multidrug-resistant organisms in the past. Therefore, the determination of MIC90 is important in examining changes with time of sensitivities or resistances of clinically isolated strains to antimicrobial drugs. 4. Antimicrobial activities of CXM against recent clinical isolates showed the existence of problems as mentioned above. However, MIC of CXM as well as those of comparator drugs indicated that antimicrobial activities of CXM against Staphylococcus spp., Streptococcus spp., H. influenzae appeared to be relatively strong, and it is concluded that cefuroxime axetil still is one of the clinically useful oral antimicrobial drugs in the 1990's.

Antimicrobial susceptibility of bacterial isolates in south Sweden including a 13-year follow-up study of some respiratory tract pathogens

The antibiotic susceptibility of consecutive isolates of the upper respiratory tract pathogens Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae, Branhamella catarrhalis, and Staphylococcus aureus, (100 strains of each species collected each year during March through April 1985, 1988 and 1992) to penicillin V, amoxycillin, cefaclor, cefuroxime, doxycycline, erythromycin, and cotrimoxazole was investigated by MIC determination on PDM and PDM II agar. The MICs of the upper respiratory isolates from 1992 supplemented with 100 isolates each of Escherichia coli, Klebsiella spp., Enterobacter cloacae, Proteus mirabilis and Staphylococcus saprophyticus collected during 1992 were determined against the above antibiotics plus cefadroxil, cefpodoxime, roxithromycin, ciprofloxacin, ofloxacin, and BAY Y 3118. Beta-lactamase production was found in 10% of H. influenzae and 80-90% of S. aureus and B. catarrhalis in 1992. Among H. influenzae isolates, non-beta-lactamase-induced resistance to all beta-lactam antibiotics was first detected in 1988 and amounted to 3% of isolates in 1992. Decreased susceptibility of S. preumoniae to penicillin (> or = 0.12 mg/l), co-trimoxazole > or = 32 mg/l, doxycycline (> or = 2 ml/l) and erythromycin (> or = 1 mg/l) was detected in 11%, 7%, and 8%, respectively, in 1992, which is significantly higher than in previous years at the same laboratory. Decreased susceptibility of S. pyogenes to doxycycline and erythromycin was detected in 11% and 9% in 1992. The two most recently developed antibiotics, cefpodoxime and BAY Y 3118, showed high antibacterial activity. The study emphasizes the need to screen for resistance mechanisms such as beta-lactamase production and lowered penicillin affinity.

Carriage of Haemophilus influenzae in Cape Town children

Little is known about the epidemiology of Haemophilus influenzae infections in South Africa. This study was designed to determine the prevalence, serotype distribution, antimicrobial susceptibility pattern and effect of age and hospitalisation on the carriage of H. influenzae in 322 Cape Town children. The overall and type b specific carriage rates in normal children (N = 107) were 45.8% and 4.7% respectively. The yield following nasopharyngeal culture was twice that following throat culture (P < 0.001). Children hospitalised with tuberculosis (N = 62) had significantly greater carriage rates, 66.1% and 37.1% respectively (P = 0.02). Institutionalised mentally handicapped children (N = 77) and children with tuberculosis attending an outpatient clinic (N = 76) had lower carriage rates (P < 0.02). Antimicrobial resistance was a major problem only in children hospitalised with tuberculosis (rifampicin 100%, penicillin 43.9%, erythromycin 85.4%, co-trimoxazole 82.9%). This universal resistance to rifampicin has not been reported previously. There was no difference in the mean age of children with positive or negative cultures, with the exception of those hospitalised with tuberculosis. In this group children infected with type b were much younger (mean 19.7 months) than those with other and non-typeable infections (32.1 months) and the non-infected (50.1 months) (P = 0.04). Duration of hospitalisation or outpatient therapy in the patients with tuberculosis did not influence carriage rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Penetration of clarithromycin and its 14-hydroxy metabolite into middle ear effusion in children with secretory otitis media

Clarithromycin suspension was given at a dosage of 7.5 mg/kg bd for 7 days to 31 children with secretory otitis media, scheduled for insertion of grommets. The fifth dose was given approximately 2.5 h before myringotomy and aspiration of the middle ear effusion at which time a blood sample also was taken. In addition, in 16 children blood samples were taken at 1, 1.5 and 4 h after the fifth dose. The concentrations of clarithromycin and its active 14-hydroxylated metabolite, in middle ear effusion and serum, were determined by HPLC. Before therapy, at surgery on day 3 and after completion of treatment, nasopharyngeal samples were taken for culture and susceptibility testing. In the middle ear effusions mean concentrations of clarithromycin (2.5 mg/L) and metabolite (1.3 mg/L) were considerably higher than the serum concentrations (1.7 and 0.8 mg/L, respectively). The mean concentrations in middle ear effusion exceeded the MICs for most respiratory pathogens. Complete eradication of Streptococcus pneumoniae, Moraxella catarrhalis and Streptococcus pyogenes from the nasopharynx was achieved after three days of therapy. Approximately 50% of the isolates of Haemophilus influenzae were eradicated from approximately 50% of the patients and the growth of the persisting strains was decreased from abundant or moderate to sparse. Adverse events were mild and transient and were experienced by only two of the 31 children.

[Pharmacokinetic, bacteriological and clinical evaluation of cefditoren pivoxil in pediatrics]

Pharmacokinetic, bacteriological, and clinical studies were performed in pediatrics on cefditoren pivoxil (CDTR-PI, ME1207) in granules. 1. Serum concentrations and urinary excretions of CDTR after administration of CDTR-PI to children (ages between 1 and 10) were investigated. Five cases were administrated with CDTR-PI at a dose level of 3 mg/kg 30 minutes after meal. Serum concentrations in these cases reached their peaks at 2 hours after administration with an average level of 1.23 +/- 0.34 micrograms/ml and diminished to 0.04 +/- 0.04 micrograms/ml at 8 hours after administration with a half-life of 1.60 +/- 0.38 hours. Urinary recovery rates of CDTR in the first 8 hours after administration of CDTR-PI averaged 14.9 +/- 0.9%. Five cases were administered with CDTR-PI at a dose level of 6 mg/kg 30 minutes after meal. Serum concentrations with the drug after meal reached their peaks at 1 hour after administration with an average level of 2.62 +/- 0.42 micrograms/ml and diminished to 0.21 +/- 0.11 micrograms/ml at 8 hours after administration with a half-life of 1.58 +/- 0.31 hours. Urinary recovery rates of CDTR in the first 8 hours after administration of CDTR-PI averaged 17.0 +/- 0.7%. These data also showed that serum and urinary concentrations of the drug depended on dose levels. 2. CDTR-PI was administered to 31 pediatric patients (their ages ranged between 1 year and 10 years) with various infections, and clinical and bacteriological effects and adverse reactions were investigated. Clinical effects were evaluable in 24 cases including 2 cases of scarlet fever, 1 case of acute pharyngitis, 12 cases of acute purulent tonsillitis, 4 cases of acute bronchitis, 5 cases of acute pneumonia. Clinical responses were excellent in 16 cases, effective in 8 cases, with an efficacy rate of 100%. Antimicrobial effects against a total of 16 strains identified or assumed to be pathogenic bacteria were evaluated. The 16 strains of bacteria included 4 strains of Staphylococcus aureus, 6 strains of Streptococcus pyogenes, 2 strains of beta-Streptococcus, 4 strains of Haemophilus influenzae. All the bacteria listed here were judged to have been eradicated except 2 strains of H. influenzae (1 was decreased and 1 was unchanged) thus, the eradication rate was 87.5%. Two strains of bacteria replaced infection causing bacteria. Streptococcus pneumoniae replaced S. pyogenes and S. aureus replaced H. influenzae. No adverse side reactions were observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Neonatal meningitis due to non-encapsulated Haemophilus influenzae in a set of twins--a case report

A set of twins born to a 24-year-old primigravida had evidence of sepsis 24 to 60 hours after birth and were treated empirically with penicillin and gentamicin. A non-encapsulated H. influenzae biotype IV strain was isolated from the blood cultures of both and from the CSF of twin II. The isolates were beta-lactamase positive and hence showed resistance to ampicillin and therapy was changed to chloramphenicol only. Twin II recovered but Twin I developed a brain abscess in the left occipital region which resolved with extended antibiotic treatment. Although ampicillin-resistant H. influenzae have been reported in Malaysia, invasive disease by such strains are rare.

In vitro evaluation of cefodizime, cefuroxime, ceftriaxone against respiratory pathogens

The in vitro activity of cefodizime and two comparative cephalosporins, cefuroxime and ceftriaxone were studied against respiratory pathogens. MIC90s of cefodizime were 0.06-0.512 microgram/ml for Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae. MIC50s of cefodizime for Klebsiella pneumoniae and Staphylococcus aureus isolates were 2 micrograms/ml and 8 micrograms/ml respectively. Cefuroxime and ceftriaxone at a concentration of 2 micrograms/ml and 1 microgram/ml inhibited 50% of Klebsiella pneumoniae and 50% of Staphylococcus aureus strains studied respectively. Cefodizime inhibited many of the important respiratory pathogens and can be suggested as an active antimicrobial agent for respiratory tract infections.

The intrabronchial microbial flora in chronic bronchitis patients: a target for N-acetylcysteine therapy?

Chronic bronchitis is common among smokers, often together with recurrent infectious exacerbations. Streptococcus pneumoniae and Haemophilus influenzae are the pathogens traditionally considered most important. N-acetylcysteine (NAC) treatment has been shown to reduce the number of infectious exacerbations in patients with chronic bronchitis. The mechanism behind this is unknown. We attempted to characterize the intrabronchial bacterial flora in patients with chronic bronchitis in an infection-free interval, and to determine whether pharmacological and immunological factors effected the bacterial occurrence. Twenty two smokers with non-obstructive chronic bronchitis, 19 smokers with chronic bronchitis and chronic obstructive pulmonary disease (COPD) and 14 healthy nonsmokers underwent bronchoscopy. To obtain uncontaminated intrabronchial samples, a protected specimen brush was used. Quantitative bacterial cultures and virus isolations were performed. Significantly positive bacterial cultures (> 1,000 colony-forming units (cfu).ml-1) were found only in the patients. S. pneumoniae and H. influenzae were found in five patients, and only in the patients without NAC treatment. The most common bacterium was alpha-haemolytic streptococcus. Negative cultures were more common in the healthy controls. Of the various factors examined, only NAC medication had an influence on bacterial numbers. Significantly fewer patients with NAC medication had positive cultures (3 out of 16) than in the group of patients without NAC therapy (15 out of 21). Our results confirm that chronic bronchitis in smokers leads to increased intrabronchial bacterial colonization. We could also confirm that 1,000 cfu.ml-1 is an adequate cut-off level for significant bacterial growth when using the protected specimen brush. NAC medication was associated with low bacterial numbers.

[The biological properties of Haemophilus influenza isolated from healthy children and from patients with acute and chronic respiratory diseases]

The comparative study of the biological properties of H. influenzae strains isolated from healthy children and from patients with acute and chronic respiratory diseases has been made, taking into account the biochemical features (biotypes) and adhesive activity of these strains. Differences in various biotypes of H. influenzae strains isolated from patients with bronchopulmonary diseases and from healthy carriers have been established. H. influenzae strains isolated from various sources differ by their adhesive properties: strains isolated from patients with acute bronchopulmonary diseases have the highest adhesive activity, while strains isolated from healthy controls have the lowest adhesive activity. The data thus obtained indicate the possible dependence of the degree and duration of the colonization of the respiratory tract by H. influenzae on the biological properties of these microorganisms. The monitoring of the sensitivity of H. influenzae strains to antibiotics has demonstrated that these strains retain high sensitivity to ampicillin, chloramphenicol, gentamicin and exhibit a tendency towards an increase in resistance to penicillin and erythromycin.

[Bacteremia caused by Haemophilus influenzae with special reference to its relation to HIV infection]

BACKGROUND

The association between infection by Haemophilus influenzae and infection by the human immunodeficiency virus (HIV) has been clearly demonstrated. However, some characteristics of this association still remain poorly defined.

METHODS

The medical records of all adult patients admitted to a general hospital over a period of four years with blood cultures positive for Haemophilus influenzae were reviewed. Patients were grouped according to whether HIV infection or no evidence of HIV infection existed. Clinical and epidemiologic data were collected and compared. The main features of data corresponding to seropositive patients are reported.

RESULTS

Of a total of 29 cases of bacteremia by Haemophilus influenzae, 19 were diagnosed in adults: 5 in patients with HIV infection and 14 in patients without HIV infection. Over the following 18 months one additional case was reported. The incidence (calculated in cases per 100,000 people/year) was 1.9 in the general population, 1.5 in adults, 70 in adults with HIV infection and 360 in AIDS patients. All the cases diagnosed in adults below the age of 30 years were reported in HIV carriers. Five of the 16 (31%) H. influenzae strains tested were resistant to ampicillin, with a significant difference being found between those isolated from HIV positive patients (4/5) and from HIV negative patients (1/11). No patient with HIV infection died during the episode. But five of the HIV negative adults died.

CONCLUSIONS

HIV infection seems to be frequent risk factor for bacteremia by Haemophilus influenzae. It should always be considered on diagnosis in adults under the age of 30. Likewise, the high probability of resistance to ampicillin should also be taken into account for the empiric treatment.