Prospective epidemiological study of invasive Haemophilus influenzae disease in adults

The incidence and characteristics of invasive Haemophilus influenzae disease were studied in 43 adult patients admitted to the acute care hospitals in El Vallés County (Barcelona, Spain) between January 1987 and June 1992. The annual incidence of Haemophilus influenzae disease was 1.2 per 100,000 inhabitants. Pneumonia occurred in 24 patients, meningitis in five, intraabdominal infections in three, obstetric infections in two, epiglottitis in two and cellulitis in one. In six patients the source of infection was unknown. Ten (23%) of the infections were hospital acquired. Underlying conditions were diagnosed in 30 (70%) patients. Nontypeable Haemophilus influenzae strains predominated in all adult age groups. Sixty-one percent of type b and 34% of nontypeable strains were ampicillin resistant (p = 0.08). Multiple antibiotic resistance was also high among type b (53%) and nontypeable (18%) strains. The mortality rate was significantly higher in patients with pneumonia, bacteremia from an unidentified focus or shock at presentation.

Surveillance of susceptibility testing methodologies for Haemophilus influenzae in Canada, including evaluation of disk diffusion test

We surveyed 75 clinical laboratories to determine if National Committee for Clinical Laboratory Standards (NCCLS) were being used for the susceptibility testing of Haemophilus influenzae. Of the 66 laboratories that performed susceptibility testing, all claimed to follow current NCCLS guidelines. However, upon further questioning, only 23, all of which used disk diffusion testing, accurately interpreted and followed the guidelines. Proficiency testing of 22 of these laboratories found that an unacceptable number of interpretive errors (> 10%) occurred. These results query the merit of routine disk diffusion susceptibility testing of H. influenzae to beta-lactam agents.

[Ampicillin-resistant Haemophilus influenzae. Prevalence in isolates from Danish children]

The prevalence of ampicillin-resistance was assessed among a total of 2766 strains of H. influenzae isolated from lower respiratory tract secretions, middle ear secretions, spinal fluid specimens, and blood cultures from children 0-15 years of age tested in two separate counties in Denmark during the period from 1986 to May, 1993. All strains were tested for susceptibility to ampicillin with disc or tablet diffusion technique and strains were examined for beta-lactamase production with a chromogenic cephalosporinase test. In the county of Northern Jutland the rate of beta-lactamase production in non-encapsulated H. influenzae was 2.5% in 1986 rising to 9.3% in 1993. The rate of beta-lactamase production in H. influenzae type b was 4.1% without any rise. In the county of Copenhagen the rate of beta-lactamase production in non-encapsulated H. influenzae rose from 6.3% in 1986 to 10.6% in 1992. In 1993 a further increase to 20.7% was noticed. This year the number of specimens sent to the laboratory and the number of H. influenzae isolated were lower compared to previous years. Thus a different selection of patients may explain the increase in the rate of beta-lactamase production in 1993. The rate of beta-lactamase production in H. influenzae type b was 8.5%. No strains were resistant to ampicillin in diffusion test other than the beta-lactamase producers.

Determination of antimicrobial susceptibilities of Canadian isolates of Haemophilus influenzae and characterization of their beta-lactamases. Canadian Haemophilus Study Group

Susceptibility testing of 1,688 Haemophilus influenzae isolates found 484 ampicillin-resistant strains; 474 strains (28.4%) were beta-lactamase positive, and 5 strains (0.4%) were non-beta-lactamase producers. Restriction enzyme digestion of the beta-lactamase amplicon determined that, of 157 strains, 11 (7.0%) contained ROB-1 beta-lactamase and 146 (93.0%) contained a TEM-type beta-lactamase.

[Antimicrobial susceptibilities of Haemophilus influenzae isolated from the nasopharynx of children]

Changes in susceptibilities to oral antimicrobials were investigated in 189 children, in whom Haemophilus influenzae was detected by nasopharyngeal culture, among the children who were diagnosed as having acute otitis media or chronic sinusitis with acute exacerbation in the Department of Otolaryngology in 1986, 1988 and 1991. The minimum 50% inhibitory concentration (MIC50) and minimum 90% inhibitory concentration (MIC90) of ampicillin (ABPC), cefaclor (CCL) and erythromycin (EM) in the subjects examined in 1986 were almost the same as the levels in those examined in 1991. The MIC50 level of minocycline (MINO) in the subjects examined in 1991 was lower by 2 test tubes than that determined in 1986, showing improvement in susceptibilities. The prevalence of resistance to antimicrobials was compared between 1986 and 1991. The prevalence to ABPC tended to decrease very slightly, while the prevalence to CCL tended to increase very slightly. The prevalence of EM tended to increase slightly. Many CCL-resistant strains detected in 1991 showed resistance to ABPC and EM, but showed favorable susceptibilities to cefixime and norfloxacin. Future trends of CCL-resistant strains should be carefully observed. There was no marked change in the prevalence of resistance to ABPC or CCL. ABPC and CCL were considered to be the first choice drugs, even at present, for pediatric patients with acute otitis media due to infection with H. influenzae and in those with acute exacerbation of chronic sinusitis due to the infection.

Aggregation and opsonization of type A but not type B Hemophilus influenzae by surfactant protein A

The ability of surfactant protein A (SP-A) to aggregate and opsonize type a and b Hemophilus influenzae was investigated. Type a, but not type b, was aggregated by SP-A. Aggregation was maximal at 24 micrograms SP-A/ml and was Ca(2+)-dependent. Aggregation of type a was inhibited by D-glucosyl-BSA but not by high concentrations of monosaccharides (D-mannose, D-galactose, D-glucose, or L-fucose) or by sialic acid, purified type a capsular polysaccharide, or type IV collagen. In Western blots, 125I-labeled SP-A bound to the major outer membrane protein (putatively P2) of type a hemophilus by a Ca(2+)-dependent mechanism. This binding was competitively inhibited by excess unlabeled SP-A. 125I-labeled SP-A also bound to the major membrane protein of type b, but at less than 5% of the level observed for type a. SP-A did not bind to lipooligosaccharides of either type a or type b. SP-A increased association of type a, but not type b, hemophilus with alveolar macrophages. After opsonization with SP-A, type a hemophilus were killed by alveolar macrophages, as indicated by bactericidal assays and the release of soluble, radiolabeled products from leukocytes. It is concluded that SP-A aggregated and opsonized type a hemophilus, but not type b, possibly because SP-A bound to the P2 outer membrane protein of type a to a greater extent.

Antimicrobial susceptibility of nasopharyngeal isolates of potential pathogens recovered from infants before antibiotic therapy: implications for the management of otitis media

Antimicrobial susceptibility was determined for strains of Streptococcus pneumoniae, nontypable Haemophilus influenzae and Moraxella catarrhalis recovered from the nasopharynxes of children followed from birth. The bacteria tested were the first potential pathogens isolated from each child before any treatment with antibiotics. Minimal inhibitory concentrations of commonly used oral antibiotics demonstrated the following overall rates of resistance for (1) S. pneumoniae: penicillin 1.2% (intermediate susceptibility 4.8%), trimethoprim-sulfamethoxazole 20%; (2) nontypable H. influenzae: ampicillin 32%, cefaclor 17%; (3) M. catarrhalis: ampicillin 90%, trimethoprim-sulfamethoxazole 19%. Antibiotic regimens used for treatment of otitis media may have to be evaluated in light of changing antibiotic susceptibilities.

Interpretive criteria for susceptibility tests with DU-6859a and FK-037 tested against Haemophilus influenzae and Neisseria gonorrhoeae

Preliminary susceptibility testing interpretive criteria were determined for two investigational drugs, DU-6859a and FK-037, when tested against Haemophilus influenzae and Neisseria gonorrhoeae strains. National Committee for Clinical Laboratory Standards (NCCLS) methods with the Haemophilus Test Medium and GC agar base were utilized, and the study design conformed to the NCCLS M23-A guidelines. The proposed H. influenzae susceptibility testing criteria were for DU-6859a susceptible at < or = 1 microgram/ml (5-micrograms disk zone diameter correlate, > or = 19 mm) or < or = 2 micrograms/ml (disk zone diameter correlate, > or = 16 mm) and for FK-037 susceptible at < or = 2 micrograms/ml (30-micrograms disk zone diameter correlate, > or = 19 mm). No other susceptibility categories were proposed. The gonococcal susceptibility testing criteria were for DU-6859a susceptible at < or = 0.12 microgram/ml (disk zone diameter correlate, > or = 34 mm) and for FK-037 susceptible at < or = 0.5 microgram/ml (disk zone diameter correlate, > or = 30 mm) and resistant at > 1 microgram/ml (disk zone diameter correlate, < or = 26 mm). No resistant criterion was proposed for N. gonorrhoeae tests with DU-6859a. No interpretive discrepancies were observed between methods using these proposed testing criteria.

Comparison of agar dilution, broth dilution, and disk diffusion testing of ampicillin against Haemophilus species by using in-house and commercially prepared media

An evaluation to determine the optimal method for the in vitro susceptibility testing of Haemophilus strains to ampicillin was undertaken. In our hands, in-house-prepared Haemophilus Test Medium used by either the broth macrodilution or agar dilution method produced the most consistent results, especially for beta-lactamase-negative, ampicillin-resistant H. influenzae strains.

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)