The performance of Luminex ARIES® Flu A/B & RSV and Cepheid Xpert® Flu/RSV XC for the detection of influenza A, influenza B, and respiratory syncytial virus in prospective patient samples

BACKGROUND

The demand for rapid, accurate viral testing has increased the number of assays available for the detection of viral pathogens. One of the newest FDA cleared platforms is the Luminex ARIES^® Flu A/B & RSV, which is a fully automated, real-time PCR-based assay used for detection of influenza A, influenza B, and respiratory syncytial virus (RSV).

OBJECTIVES

We sought to compare the performance of Luminex ARIES^® Flu A/B & RSV assay to the Cepheid Xpert^® Flu/RSV XC assay for rapid Flu and RSV testing.

STUDY DESIGN

A series of consecutive nasopharyngeal specimens received in the clinical microbiology laboratory during peak influenza season at a major academic center in Chicago, IL, were prospectively tested, using both the ARIES^® Flu A/B & RSV and Xpert^® Flu/RSV XC assays, side by side. Discrepant results were tested on the BioFire FilmArray^® Respiratory Panel for resolution.

RESULTS

A total of 143 consecutive nasopharyngeal specimens, obtained from patients ranging from six months to ninety-three years in age were received between January 1st, 2017 and March 21st, 2017. There was 96.6% agreement between the two assays for detection influenza A, 100% agreement for detection influenza B and RSV, and 98.9% agreement for negative results. The Xpert^® Flu/RSV XC performed with an average turn-around time of approximately 60min, compared to the ARIES^® Flu A/B & RSV of approximately 120min. Both assays were equally easy to perform, with a similar amount of hands-on technologist time for each platform.

CONCLUSIONS

Overall, these results indicate that both tests are comparable in terms of result agreement and technical ease-of-use. The Xpert^® Flu/RSV XC assay did produce results with less turn-around-time, approximately 60min quicker than the ARIES^® Flu A/B & RSV.

Prospective evaluation of the VITEK MS for the routine identification of bacteria and yeast in the clinical microbiology laboratory: assessment of accuracy of identification and turnaround time

This study assessed the accuracy of bacterial and yeast identification using the VITEK MS, and the time to reporting of isolates before and after its implementation in routine clinical practice. Three hundred and sixty-two isolates of bacteria and yeast, consisting of a variety of clinical isolates and American Type Culture Collection strains, were tested. Results were compared with reference identifications from the VITEK 2 system and with 16S rRNA sequence analysis. The VITEK MS provided an acceptable identification to species level for 283 (78 %) isolates. Considering organisms for which genus-level identification is acceptable for routine clinical care, 315 isolates (87 %) had an acceptable identification. Six isolates (2 %) were identified incorrectly, five of which were Shigella species. Finally, the time for reporting the identifications was decreased significantly after implementation of the VITEK MS for a total mean reduction in time of 10.52 h (P<0.0001). Overall, accuracy of the VITEK MS was comparable or superior to that from the VITEK 2. The findings were also comparable to other studies examining the accuracy of the VITEK MS, although differences exist, depending on the diversity of species represented as well as on the versions of the databases used. The VITEK MS can be incorporated effectively into routine use in a clinical microbiology laboratory and future expansion of the database should provide improved accuracy for the identification of micro-organisms.

Outbreak of human adenovirus type 3 infection in a pediatric long-term care facility--Illinois, 2005

BACKGROUND

Human adenovirus type 3 (HAdV-3) causes severe respiratory illness in children, but outbreaks in long-term care facilities have not been frequently reported. We describe an outbreak of HAdV-3 infection in a long-term care facility for children with severe neurologic impairment, where only 3 of 63 residents were ambulatory.

METHODS

A clinical case of HAdV-3 was defined as fever (temperature, > or = 38.0 degrees C) and either a worsening of respiratory symptoms or conjunctivitis in a resident, with illness onset from June through August 2005. We reviewed medical records; conducted surveillance for fever, conjunctivitis, and respiratory symptoms; and collected nasopharyngeal and conjunctival specimens from symptomatic residents. Specimens were cultured in HAdV-permissive cell lines or were analyzed by HAdV-specific polymerase chain reaction assay.

RESULTS

Thirty-five (56%) of 63 residents had illnesses that met the case definition; 17 patients (49%) were admitted to intensive care units, and 2 (6%) died. Patients were hospitalized in the intensive care unit for a total of 233 patient-days. Illness onset dates ranged from 1 June through 24 August 2005. Thirty-two patients (91%) had respiratory infection, and 3 (9%) had conjunctivitis. HAdV was identified by culture or PCR in 20 patients. Nine isolates were characterized as HAdV-3 genome type a2.

CONCLUSIONS

Considering the limited mobility of residents and their reliance on respiratory care, transmission of HAdV-3 infection during this outbreak likely occurred through respiratory care provided by staff. In environments where patients with susceptible underlying conditions reside, HAdV infection should be considered when patients are identified with worsening respiratory disease, and rapid diagnostic tests for HAdV infection should be readily available to help identify and curtail the spread of this pathogen.

Reduction of preoperative conjunctival bacterial flora with the use of mupirocin nasal ointment

PURPOSE

To determine whether the use of mupirocin ointment for preoperative eradication of nasal bacterial carriage was effective in reducing conjunctival bacterial flora.

METHODS

Prospective, double-arm, blinded clinical trial of 37 eyes of 37 patients undergoing intraocular surgery (cataract extraction or pars plana vitrectomy) randomized to either control or mupirocin treatment groups. Treated patients received mupirocin nasal ointment twice daily for 5 days prior to surgery. Nasal cultures were obtained in all patients. All patients received a standard 5% povidone-iodine preparation before the surgical procedure, and conjunctival cultures were obtained in all patients before and after the povidone-iodine preparation.

RESULTS

All 37 patient nasal swabs were positive for bacterial growth (cultures were obtained prior to the use of mupirocin ointment in the treatment group). One of 15 eyes (6.7%) in the treatment group had positive conjunctival cultures prior to povidone-iodine preparation, compared with nine of 22 eyes (41%) in the control group (P < .05). Even after povidone-iodine preparation, eight of 22 eyes (36%) in the control group demonstrated persistent positive cultures, whereas one (6.7%) of the treatment eyes exhibited growth (P < .05).

CONCLUSIONS

Prophylactic use of mupirocin nasal ointment resulted in significant reduction of conjunctival flora with or without preoperative topical 5% povidone-iodine preparation. The use of mupirocin nasal ointment prior to intraocular surgery or intravitreal injections is a novel method for reducing conjunctival contamination rates, which theoretically should reduce the incidence of endophthalmitis.

Allergic inflammation enhances bacterial sinusitis in mice

BACKGROUND

Although it is not proven, one factor considered important in the development of sinusitis is allergic rhinitis.

OBJECTIVE

The purpose of this study was to determine whether ongoing allergic rhinitis enhances the infection and inflammation associated with Streptococcus pneumoniae acute sinus infection.

METHODS

BALB/c mice were sensitized to ovalbumin by intraperitoneal injection. After infection of the sinuses by S pneumoniae, either with or without concomitant administration of ovalbumin to induce allergic inflammation, mice were killed at various times and their heads were prepared for histologic evaluation of the sinuses.

RESULTS

Mice became allergic to ovalbumin and developed eosinophilia in the sinus and lung cavities in response to ovalbumin administration to each of the respective cavities. In comparison with controls, the mice with ongoing nasal allergic inflammation that were inoculated with S pneumoniae had significantly more bacteria recovered at sacrifice and had significantly more inflammation, as indicated by neutrophil, eosinophil, and mononuclear influx into the sinus mucosa. The percentage of the sinus area occupied by neutrophil clusters was also increased after infection in the allergic mice in comparison with the control mice.

CONCLUSION

Our data demonstrate that mice can be sensitized to ovalbumin and develop a localized allergic reaction in the skin, nose, or lung. An ongoing local allergic response augments bacterial infection in these animals. We also demonstrate that allergic sensitization alone, allergen exposure alone, or an allergic response at a distal site, the lung, does not augment the sinus infection.

C57Bl/6 and BALB/c mice have similar neutrophil response to acute Streptococcus pneumoniae sinus infections

BACKGROUND

Previous investigations have shown that mice with a tendency toward a T(H)1 or T(H)2 lymphocyte response manifest different reactions to inoculation with the parasite Leishmania major. BALB/c mice (with a tendency for a T(H)2 response) showed evidence of systemic infection, whereas C57Bl/6 mice (with a tendency for a T(H)1 response) showed only a local reaction.

OBJECTIVE

To investigate whether BALB/c and C57Bl/6 mice respond differently to acute bacterial infection of the sinuses.

METHODS

We inoculated the nasal cavities of C57Bl/6 and BALB/c mice with Streptococcus pneumoniae (type ATCC59), or with broth as a control. The mice were humanely killed 2, 5, 10, and 14 days after inoculation. Their heads were fixed, decalcified, and embedded in paraffin blocks. Sections were stained with hematoxylin and eosin, and the degree of inflammation was quantified by the number of neutrophils per square millimeter of the sinus mucosa and the percentage of the sinus cavity occupied by neutrophil clusters.

RESULTS

Both groups of mice showed evidence of inflammation that was significantly greater than controls (P =.01), with no difference between groups. There was a correlation between the number of neutrophils per square millimeter in the sinus mucosa and the percentage of neutrophil clusters (C57Bl/6 mice, r = 0.37, P<.001; BALB/c mice, r = 0.20, P<.001). In the infected mice, the number of infiltrating neutrophils was significantly greater (P<.001) in anatomically lower (dependent) areas of the sinuses compared with the upper areas.

CONCLUSION

Unlike leishmaniasis, acute bacterial sinusitis is not affected by the tendency of the host to favor either a T(H)1 or T(H)2 response.

Bactrim reduces the inflammatory response in a murine model of acute rhinosinusitis

OBJECTIVE

To determine whether treatment with an antibiotic (trimethoprim-sulfamethoxazole) reduced the inflammatory response in a murine form of Streptococcus pneumoniae-induced rhinosinusitis.

DESIGN

We randomized 18 C57BL/6 mice to either treatment with intraperitoneal trimethoprim-sulfamethoxazole (Bactrim, 30 mg/kg) or no treatment (control). After 2 days, we inoculated all C57BL/6 mice intranasally with a Bactrim-susceptible strain of Streptococcus pneumoniae, ATCC 49619, suspended in Trypticase soy broth. At day 5 after bacterial inoculation, we sacrificed the mice and prepared histopathologic sections of their sinuses after culturing their nasal cavities by lavage.

SETTING

Animal care facility at a tertiary, academic institution.

METHODS

The histopathologic sections of the sinuses were examined in a blind manner for the percent of sinus cavity area occupied by neutrophil clusters, and for the number of neutrophils per square millimeter of sinus mucosa.

RESULTS

The Bactrim group had a significantly smaller sinus area occupied by neutrophil clusters (1.58% +/- 1.13 vs 4.38% +/- 3.41; P < 0.05), significantly fewer neutrophils infiltrating the mucosa (58.81 +/- 29.63/mm2 vs 105.85 +/- 48.49/mm2; P < 0.05), and significantly less growth of Streptococcus pneumoniae colonies in the intranasal cultures (8 few and 1 moderate vs 3 few, 3 moderate, and 1 many; P = 0.05) compared to the control group.

CONCLUSION

In our murine model of acute rhinosinusitis, Bactrim decreased the number of neutrophil clusters in the sinus cavities, the number of neutrophils infiltrating the sinus mucosa, and the growth of Streptococcus pneumoniae. We propose that our murine model can be used for the study of the pathophysiology and treatment of acute rhinosinusitis.

A mouse model of acute bacterial rhinosinusitis

OBJECTIVE

To develop a mouse model of acute bacterial rhinosinusitis.

DESIGN

Study mice (C57BL6/J) were inoculated intranasally with Streptococcus pneumoniae, ATCC 49619 suspended in trypticase soy broth, and controls were inoculated with trypticase soy broth alone. After 2, 5, or 14 days, intranasal cultures were obtained and mice were killed. The sinuses were prepared for histological investigation.

SETTING

Animal care facility at a tertiary, academic institution.

METHOD

The histological sections of the sinuses were examined in a blinded manner for the percentage of sinus cavity occupied by neutrophil clusters, and for the number of neutrophils per square millimeter of sinus mucosa.

RESULTS

Infected mice killed at 5 days had significantly more sinus area occupied by neutrophil clusters, significantly more neutrophils within the mucosa, and significantly more S pneumoniae growth in the intranasal cultures compared with controls (15/15 vs 0/6; P<.01). The amount of inflammation had decreased at 2 weeks.

CONCLUSION

Streptococcus pneumoniae induces acute bacterial rhinosinusitis in C57BL6/4 mice as measured by culture and influx of neutrophils, and can be used as a model of acute bacterial rhinosinusitis.

Detection of high-level aminoglycoside resistance in enterococci other than Enterococcus faecalis

The ability of six screening methods to detect high-level aminoglycoside resistance in enterococcal species other than Enterococcus faecalis was investigated. The 85 Enterococcus isolates, which included 55 E. faecium, 11 E. gallinarum, 9 E. casseliflavus, 5 E. raffinosus, 4 E. avium, and 1 E. mundtii, were tested by using aminoglycoside-supplemented brain heart infusion agar (BHI), Remel EF Synergy Quad plates, high-content aminoglycoside diffusion disks, standard (prepared in-house) microdilution panels, Pasco MIC Gram Positive microdilution panels, and Vitek GPS-TA cards. When tested on BHI, 32 and 35 strains showed resistance to gentamicin and streptomycin, respectively. Resistance profiles obtained with Remel EF Synergy Quad plates were in complete agreement with those obtained on BHI. However, growth on Mueller-Hinton agar-based plates was not as heavy. Some isolates showed only weak growth and required 48 h for resistance to become evident, especially with swab inoculation of quadrants containing 2,000 micrograms of gentamicin per ml. Profiles obtained by use of the agar-based screens were used as the basis for evaluating the other methods. Disk diffusion showed complete agreement. No false resistance occurred by either microdilution method, but 48 h of incubation was needed for detection of some gentamicin-resistant isolates, and 14% of the streptomycin-resistant strains were not detected by standard microdilution. The Vitek GPS-TA card detected 81 and 100% of the gentamicin- and streptomycin-resistant isolates, respectively. In general, most methods used to detect high-level aminoglycoside resistance in E. faecalis appear to be reliable for the testing of the other enterococcal species. However, further investigations with a greater number of resistant E. raffinosus, E. avium, and E. mundtii isolates, when they are available, will be useful for establishing the full range of enterococci that can reliably be tested by the various methods.

Factors influencing determination of high-level aminoglycoside resistance in Enterococcus faecalis

The ability of seven methods to detect high-level gentamicin (58 strains) and streptomycin resistance (56 strains) among 107 Enterococcus faecalis isolates was investigated at the University of Chicago Medical Center and the University of Nebraska Medical Center. Methods included a standard agar screen plate, high-content disk diffusion, Remel (Lenexa, Kans.) EF Synergy Quad plates, standard microdilution panels prepared in house, Pasco MIC Gram-Positive panels (Difco Laboratories, Detroit, Mich.), MicroScan MIC Type 5 dry panels (Baxter Healthcare Corp., MicroScan Div., West Sacramento, Calif.), and Vitek GPS-TA cards (Vitek Systems Inc., Hazelwood, Mo.). Results indicating false resistance were not obtained by any method, and there was 100% agreement between the results of the disk diffusion and standard agar screen methods. Prolonging incubation from 24 to 48 h increased resistance detection for both agar and microdilution screens. EF Synergy Quad plates inoculated with micropipettes detected 100% of the streptomycin- and gentamicin-resistant isolates. Resistance detection for streptomycin and gentamicin, respectively, was 93 and 96% by standard microdilution, 93 and 98% by Pasco panels, 88 and 89% by MicroScan panels, and 88 and 91% by Vitek GPS-TA cards. False susceptibility occurred more frequently with streptomycin-resistant isolates than it did with gentamicin-resistant strains and appeared to be strain related in some instances. The use of an increased inoculum size enhanced resistance detection with these strains, but it complicated interpretation of results and led to the selection of streptomycin-resistant mutants. Until results of further studies delineate optimum test conditions, a delay in the final interpretation of agar and microdilution screen results until 48 h for isolates showing no or light growth at 24 h may help to minimize the occurrence of false susceptibility reporting.

Direct susceptibility testing of blood culture isolates with the AutoMicrobic System (AMS)

To decrease the time needed to obtain preliminary antimicrobial susceptibility results with blood culture isolates, we inoculated a suspension of centrifuged organisms from blood culture broth directly into the AutoMicrobic System Gram-Positive (GPS) and Gram-Negative (GSC+) susceptibility cards (AMS, Vitek Systems Inc., Hazelwood, MO). Interpretive category results (susceptible, moderately susceptible, resistant) obtained by this direct method (DAMS) were then compared with results obtained by conventional inoculation (i.e., using 18-hr subcultures) of both AMS cards (CAMS method) and broth microdilution panels (MIC method, Micro-Media Systems Inc., Potomac, MD). Ninety-six Gram-positive cocci (951 antimicrobial agent--organism combinations) and 112 Gram-negative bacilli (1006 antimicrobial agent-organism combinations) were tested. When only very major (false susceptible DAMS results) and major (false resistant DAMS results) discrepancies were considered, 95% of the DAMS results for Gram-positive cocci agreed with CAMS results and 93% agreed with MIC results. Most discrepancies were observed when staphylococci were tested against oxacillin and when enterococci were tested against several antimicrobial agents. For Gram-negative bacilli, 94% of DAMS results agreed with CAMS results and 93% agreed with MIC results. Most discrepancies occurred when Enterobacter spp. and Serratia marcescens were tested against ampicillin and cefamandole. The DAMS method provides accurate and rapid preliminary susceptibility test results, usually within 6 to 7 hr of the time a positive blood culture is first detected.

Detection of Mycoplasma hominis septicemia by radiometric blood culture

The ease with which Mycoplasma hominis can be recovered and the frequency of its occurrence in septicemia may not be fully appreciated. We detected the growth of M. hominis radiometrically with an automated blood culture instrument. The organism grew in both aerobic and anaerobic culture media, but the cultures were not visibly positive. It was necessary to stain the cultures with acridine orange to visualize M. hominis and to subculture them on Columbia base sheep blood agar to confirm the positive growth index indicated by the instrument. Sodium polyanetholesulfonate inhibited the growth of M. hominis and is not recommended for use as the anticoagulant when blood is cultured for Mycoplasma spp.

Cryopreservation of human granulocytes: study of granulocyte function and ultrastructure

Human granulocytes can be cryopreserved with dimethyl sulfoxide (DMSO) at--80 degrees C. However, the percent recovery of functional cells has been unsatisfactory to date. Throughout this study we have been able to prepare relatively pure granulocytes approximately equal to 85%), cryopreserve them with 5%--10% DMSO with and without serum, and store them at--80 degrees C for up to 4 mo. The parameters studied were absolute cell counts and viability determination, myeloperoxidase activity, phagocytosis, candidacidal activity, bactericidal activity, nitroblue tetrazolium reduction, chemiluminescence, and cell morphology by transmission and scanning electron microscopy. Based on our investigation, granulocytes cryopreserved without serum showed an intact membrane of superior integrity as compared with those preserved with serum. At least 50% of the cells recovered were functional after 2 mo of storage, but there was a progressive loss of viability and function on prolonged storage. The property of phagocytosis was the best preserved after storage for 4 mo, whereas myeloperoxidase activity, killing activity, nitroblue tetrazolium reduction, and chemiluminescence were maintained less efficiently. Morphological studies of cryopreserved granulocytes revealed that the nuclear, cytoplasmic, and cell surface architectures were altered by storage. Depletion of nuclear and cytoplasmic material, as well as changes in configuration, were also noted.