Rapid biochemical characterization of Haemophilus species by using the micro-ID

Comparison of three commercial test systems for biotyping Haemophilus influenzae and Haemophilus parainfluenzae

The biotypes of Haemophilus influenzae and Haemophilus parainfluenzae isolates were determined with three commercially available biochemical test kits: the IDS RapID NH system, the Neisseria-Haemophilus identification test (NHI card), and the API NH strip. The API NH strip performed best, correctly classifying the biotypes of 371 of 380 (97.6%) different challenge strains.

Evaluation of four commercial methods for identification and biotyping of genital and neonatal strains of Haemophilus species

Four commercial methods for identification of Haemophilus species were evaluated in comparison to conventional methods using 188 genital and neonatal Haemophilus strains. In the case of discrepancies between results obtained by the different methods, DNA-DNA hybridization was performed. The four commercial systems and conventional methods showed excellent correlation of results in 167 strains (88%). DNA-DNA hybridization was performed in 8 strains with discrepant identification results and 13 strains with discrepant biotyping results. In 15 cases discrepancies could be explained by the fact that the strains belonged to a newly recognised species of Haemophilus.

Comparison of the RIM-H rapid identification kit with conventional tests for the identification of Haemophilus spp

A commercially available system, the RIM-H system (Austin Biological Laboratories, Austin, Tex.), was evaluated for its ability to rapidly and accurately identify various Haemophilus spp. A total of 110 clinical isolates were tested by both the RIM and conventional identification procedures. The RIM agreed with the standard identification for 100% of the Haemophilus influenzae (76 of 76) and 92.0% of the Haemophilus parainfluenzae (23 of 25) isolates tested. The identifications of Haemophilus parahaemolyticus, Haemophilus aphrophilus, and Haemophilus haemolyticus also correlated with those obtained by conventional methods. The RIM was found to be rapid and easy to use and was considered a suitable alternative to conventional identification procedures.

Evaluation of two rapid methods for identifying and biotyping Haemophilus influenzae

Several rapid method kits (one to four hours) have become available for the identification of Haemophilus and related genera. Two kits (the "Rapid NH" system and the "RIM Haemophilus" system), which include the identification and biotyping of H influenzae, were investigated for the rapid identification and biotyping of 193 isolates of H influenzae and the results compared with those obtained by more standard overnight methods. The kits were convenient to use and gave reliable and rapid speciation of all isolates. Both test systems were unreliable for biotyping: 42 isolates were wrongly biotyped by the RIM kit and 40 isolates wrongly biotyped by the rapid NH kit. It is concluded that the test kits may be useful for the rapid identification of H influenzae but that they are not reliable for the biotyping of this species.

Identification of Neisseria spp., Haemophilus spp., and other fastidious gram-negative bacteria with the MicroScan Haemophilus-Neisseria identification panel

The Haemophilus-Neisseria identification (HNID) panel (American MicroScan, Sacramento, Calif.) is a 4-h microdilution format system for identification of Haemophilus and Neisseria spp., Branhamella (Moraxella) catarrhalis, and Gardnerella vaginalis. The HNID panel was evaluated by using 423 clinical isolates and stock strains of these organisms, and HNID identifications were compared with those obtained by conventional methods. In addition, 32 isolates representing six genera not included in the HNID data base were tested to determine whether these organisms would produce unique biotype numbers for possible inclusion in the data base. The HNID panel correctly identified 95.3% of 86 Neisseria gonorrhoeae strains, 96% of 25 G. vaginalis strains, and 100% of 28 Neisseria lactamica strains and 48 B. catarrhalis strains. Only 64.7% of 68 Neisseria meningitidis isolates were identified correctly owing to false-negative or equivocal carbohydrate and/or aminopeptidase reactions. Among the Haemophilus spp., 98.8% of 83 H. influenzae strains, 97.1% of 34 H. parainfluenzae strains, and 80% of 15 H. aphrophilus and H. paraphrophilus strains were correctly identified. Eight strains of Neisseria cinerea, a species not included in the data base, produced profiles identical with those for B. catarrhalis and N. gonorrhoeae. Isolates of other species not included in the data base, including Eikenella corrodens, Kingella spp., and Cardiobacterium hominis, produced unique biochemical reaction patterns on the panel. Modification of interpretative criteria for certain tests, expansion of the data base to include other species, and suggestions for additional confirmatory tests will increase the accuracy and utility of the HNID panel.

Clinical evaluation of the Vitek Neisseria-Haemophilus Identification card

A clinical evaluation of the Vitek Neisseria-Haemophilus Identification (NHI) card (Vitek Systems, Inc., Hazelwood, Mo.) was performed with 480 clinical isolates and stock strains of Neisseria spp., Haemophilus spp., and other fastidious microorganisms included in the data base of the system. Identifications obtained with the NHI card were compared with those determined by conventional methods. The card identified 83.2% of 244 Neisseria spp. and Branhamella catarrhalis, 54.9% of 164 Haemophilus spp., and 84.7% of 72 fastidious gram-negative species with no further testing required. Some isolates produced good confidence-marginal separation identifications, in which the correct identification was listed with one or two other possible identifications and extra tests were required and suggested. When isolates producing good confidence-marginal separation identifications were included, correct identifications of these organism groups increased to 97.1, 92.7, and 94.4%, respectively. Among the commonly isolated microorganisms, the NHI card identified 99.1% of 110 N. gonorrhoeae, 98.5% of 68 N. meningitidis, 93.9% of 98 H. influenzae, and 95.6% of 46 H. parainfluenzae strains. All of these organisms produced excellent to very good confidence level identifications except for H. influenzae biotypes II, III, and VII, for which hemolytic reactions were required for differentiation from H. haemolyticus. The NHI card reliably identified other fastidious gram-negative species, including H. aphrophilus, Eikenella corrodens, Gardnerella vaginalis, and Kingella denitrificans.

Four hour identification of Enterobacteriaceae with the API Rapid 20E and Micro-ID systems

One hundred strains of Enterobacteriaceae were examined in parallel with the API Rapid 20E and Micro-ID commercial four hour identification systems. With the API Rapid 20E system 78% of the strains were correctly identified, 15% were not identified, and 7% were misidentified. The respective figures with the Micro-ID system were 74%, 11%, and 15%.

In vitro susceptibilities of Haemophilus influenzae isolates from a Veterans Administration Medical Center

One hundred and one consecutively occurring clinical isolates of H. influenzae, from adult male patients, were tested for quantitative antimicrobial susceptibility (by broth microdilution) and classification properties. Almost all were susceptible to a variety of antimicrobials, except erythromycin and ampicillin; 14% were ampicillin resistant. Beta-lactamase was produced by all the ampicillin-resistant strains. Most isolates were biotype II (68%) or III (24%). Only 6% were serotype b, while 94% were from the lower respiratory tract. When isolates were grouped according to biotype, serotype, B-lactamase production and site of isolation, there were some significant differences in susceptibilities among the groups.

Development of a test system for rapid differentiation of Neisseria and Haemophilus spp

A qualitative micromethod (IDS Rapid NH system) employing conventional and single-substrate enzyme tests was developed for the biochemical characterization of Neisseria spp., Haemophilus spp., and other gram-negative species. A total of over 140 dehydrated, miniaturized biochemical tests were investigated for their ability to distinguish species. Computer-assisted test selection and pair separation analysis of the data allowed the selection of 11 4-h tests that would identify Haemophilus and Neisseria spp. implicated as etiological agents as well as differentiate them from other Neisseria spp., Moraxella spp., Branhamella catarrhalis, Centers for Disease Control M groups, and Kingella spp. The final test configuration included modified glucose, sucrose, galactosidase, nitrate, phosphatase, resazurin reduction, and two arylamidase tests. In addition, indole, urea, and ornithine decarboxylase tests were included to biochemically type strains of Haemophilus influenzae and Haemophilus parainfluenzae.

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.

Primary peritonitis due to Haemophilus influenzae type b in a previously healthy child

A case of primary peritonitis caused by Haemophilus influenzae type b biotype 2 in a 3-year-old child is described. The organism was isolated from peritoneal fluid. This is the first case of documented peritoneal infection due to this species in a patient who showed no evidence of being immunocompromised.

Comparison of four rapid methods for identification of Enterobacteriaceae from blood cultures

Positive blood cultures containing gram-negative bacilli were utilized for direct identification by two automated systems, the AutoMicrobic system (Vitek Systems, Inc., Hazelwood, Mo.) and the MS-2 (Abbott Diagnostics, Dallas, Tex.), and two commercial kits, the Micro-ID system (General Diagnostics, Warner-Lambert Co., Morris Plains, N.J.) and the same-day API 20E (Analytab Products, Plainview, N.Y.). Samples of 10 to 15 ml were aseptically removed from radiometrically positive BACTEC bottles (Johnston Laboratories, Cockeysville, Md.) and divided among four sterile tubes. The tubes were centrifuged at 107 X g for 10 min. The supernatants were centrifuged at 1,510 X g for 10 min, and pellets were tested for cytochrome oxidase by means of Pathotec strips. Oxidase-negative pellets were suspended in appropriate media as suggested by the manufacturers. All systems were inoculated, incubated, and interpreted according to the instructions of the manufacturers. The Micro-ID system was read after 4 h of incubation; the three remaining systems were read after 5 h. Results were compared with those of the 18-h API 20E inoculated from pure subcultures of the organisms. Correlation of 90% or more with the API 20E was achieved by the AutoMicrobic and Micro-ID systems. The same-day API 20E and the MS-2 demonstrated 60 and 44% correlation, respectively, with the 18-h API 20E.

Biotyping of Haemophilus using API 10S--an epidemiological tool?

One hundred and ninety-nine strains of Haemophilus isolates were biotyped by Kilian's method(1) and a modified API 10S strip and the results compared. One hundred percent correlation was found between the two systems. The ONPG test proved of value in differentiating between Haemophilus influenzae and Haemophilus parainfluenzae when there was growth factor disc failure.

Novel method of biotyping Haemophilus influenzae that uses API 20e

One hundred Haemophilus influenzae isolates from various body sites were biotyped by conventional methods and by the API 20E system (Analytab Products, Plainview, N.Y.). By using a hemin- and a nicotinamide adenine dinucleotide-enriched saline solution as the inoculating fluid for the API 20E, a 100% correlation of results was obtained between the two methods. Ninety percent of the blood and cerebrospinal fluid isolates were biotype I. Biotype II was the predominant biotype encountered overall. No correlation was observed between beta-lactamase production and biotype. The API 20E is a reliable method and should prove useful for routine biotyping of H. influenzae in the clinical laboratory.

Rapid biotyping of Haemophilus influenzae and Haemophilus parainfluenzae with PathoTec strips and spot biochemical tests

PathoTec strips and spot biochemical tests were evaluated for the ability to biotype Haemophilus influenzae and Haemophilus parainfluenzae. Indole, urease, and ornithine decarboxylase reactions were tested. The results of PathoTec strips compared favorably with those conventional methods; the percent agreements were as follows: indole, 100; urease, 99.5; and ornithine, 95.5. Spot tests were simple and rapid, and the results also compared favorably with those of conventional tests; the percent agreements were as follows: indole, 99; urease, 100; and ornithine, 96.

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.

Evaluation of the four-hour Micro-ID technique for direct identification of oxidase-negative, Gram-negative rods from blood cultures

A 4-h Micro-ID technique for direct identification of oxidase-negative gram-negative rods from positive blood cultures was compared to subculture and species identification of single colonies by API 20E and Micro-ID, using standardized inocula. A total of 127 patients (220 positive cultures) were studied. Isolates included 96 Escherichia coli, 46 Klebsiella pneumoniae, 7 Klebsiella oxytoca, 8 Enterobacter aerogenes, 17 Enterobacter cloacae, 19 Serratia marcescens, 2 Serratia liquefaciens, 8 Proteus mirabilis, 1 Salmonella species, 1 Morganella morganii, 6 Haemophilus influenzae, 2 Haemophilus parainfluenzae, 3 Bacteroides fragilis, 3 Acinetobacter calcoaceticus biotype anitratus, and 1 Pseudomonas maltophilia. In 90% of the cultures, identification by Micro-ID was identical to that obtained after subculture; if the 15 non-enterobacterial isolates were excluded, the corresponding figure was 96.6%. Enterobacteria identified incorrectly by direct Micro-ID were three S. marcescens (two identified as S. liquefaciens, one as Hafnia alvei), two S. liquefaciens (both identified as E. cloacae), and two K. pneumoniae (one identified as Klebsiella ozaenae, the other as Serratia rubidaea). None of the 15 non-enterobacterial cultures were correctly identified by Micro-ID (non-identifiable, or classified as Providencia/Yersinia/Klebsiella species). Although biochemical discrepancies between direct and final Micro-ID tests occurred in 41% of the enterobacterial cultures, this did not seriously interfere with identification. Direct species identification of Enterobacteriaceae from blood cultures by direct Micro-ID is accurate and easily performed and identified organisms within 4 h compared to at least 24 h by most other methods; the direct Micro-ID technique would be rendered even more valuable by the additional capability of identifying non-enterobacterial gram-negative isolates.