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Clinical Infection & Immunity

Original Article

Volume 5, Number 2, June 2020, pages 31-38

Bacterial Distribution Pattern of Urine in Men With Gonococcal Urethritis

The Sysmex UF500i instrument measures urine parameters that include leukocyte, erythrocyte and bacterial counts using a red semiconductor laser that quantifies cells. The instrument also includes an improved staining technique with the use of polymethine dyes (fluorophores) that identifies the four most prevalent uropathogens [1, 2]. Sysmex UF500i has a cut-off value of 200 bacterial cells/µL and has a sensitivity of 82% and specificity of 96% [1] based on the negative culture colony count of either < 10⁴ or < 10⁵ colony-forming unit (CFU)/mL. However, in the study of Erdman et al [3] and Wang et al [4], the instrument had a specificity of 97%, making the said urine analyzer able to discriminate better the negative and positive urine cultures using bacterial count [1].

Discrimination of bacteria as to gram-positive and gram-negative is important for one single reason; that is for the choice of antibiotic for empiric use. Studies discriminating the two groups utilizing the Sysmex UF series of instruments were already seen in the study of Wada et al [5], Ozawa et al [6], Muratani et al [7], and Agpaoa et al [8]. NaOH-SDS was utilized in the study of Wada et al [5], where it lyses gram-negative groups while leaving the gram-positive unlysed. This was performed by analyzing the urine twice, untreated then treated, to observe bacterial count and its corresponding scattergram. The study of Agpaoa et al [8] however, mainly used the pattern observed on the scattergram among 104 culture-positive (24 gram-positive, 80 gram-negative) untreated urine samples using the B-FSC and B-FLH histograms. The findings of Agpaoa et al [8] indicated that samples with bacterial distribution of less than 30° angle are most likely gram-negative bacteria, while those above the 30° angle are gram-positive bacteria.

Observations to discriminate urinary pathogens using automated analyzers can already be seen in a number of published papers. However, the pattern of observations of urine with gonococcal urethritis using Sysmex UF500i is limited. Hence, it is with this reason, that the bacterial distribution pattern of urine containing gonococcus using the Sysmex UF500i and its concordance with microbial studies of urine or urethral discharges were determined.

The study was conducted from December 2017 to August 2019. Only specimens from men with or without manifestation of urethritis were requested for urinalysis, and microbial studies were included. Microbial studies included culture of urethral discharges or urine and gram stain of urethral discharges or sediments of urine. Additional criteria for inclusion is that the urine should contain at least 10 (white blood cell) WBC/µL [6, 9-11] as indicated by the UF500i. Specimens that were noted to contain less than 10 WBC/µL, no microorganisms seen on gram stained smears or to growth was observed on culture were automatically excluded. Data collected only included the patient’s accession number, WBC count (per µL), bacterial count (per µL) and gram stain or culture result of the urethral discharges or urine specimens. Neither the patient’s name nor any of the patient’s data that leads to his identification were included.

Patients with or without manifestations of urethritis were instructed by their physicians to go to the laboratory for urine and microbial analysis. Patients collected their specimens on their own. Specimens were not marked as on the manner of collection; may it be mid-stream clean-catch, first void or first pass (the first 10 - 20 mL) collection. The specimens were labeled appropriately and were sent to the clinical laboratory for cellular content analysis using the UF500i instrument and microbial studies.

The specimens are analyzed within 15 min after collection. Approximately 12 - 15 mL of well-mixed urine is transferred into a conical tube and analyzed immediately using the manual module of the UF500i. Cellular count for WBCs and bacterial cells per µL were noted, so as the scatter plot graph for bacterial distribution.

Bacterial distribution patterns were determined as to the classification of Agpaoa et al [8] as to (A) less than 30°, (B) more than 30°, (C) widespread and (D) non-specific. Another pattern (E) however is added which is crawling, or as defined that the majority of the bacterial distribution is near the zero limit of the x-axis or does not go higher than 10°.

Urine cultures were performed by inoculating 0.01 mL of urine using a standardized sterile loop on a blood agar plate and Mac Conkey agar. After 24 - 48 h of mesothermic incubation, isolated colonies are then purified and identified through the Vitek Compact 2 instrument.

Urine gram stain was performed by concentrating 10 - 15 mL of urine by centrifugation. Smears were made using the sediments and stained as described by Basit and Juayang [12]. Microscopic examinations were then made to preliminary identify gram-negative and gram-positive organisms.

Urethral discharges were collected by trained personnel from patients suspected to have gonococcal urethritis using a sterile cotton swab for culture and direct touch imprint of the glass slides to the meatus for gram staining. Swabs and smears were then sent to microbiology laboratory for microbial analysis [11].

Collected smears are allowed to air dry followed by heat fixing. Smears are then gram stained [12] and viewed microscopically for the presence of gram-negative diplococci that are seen intracellularly within polymorphonuclear leukocytes [11, 13, 14]. Finding of gram-negative diplococci intracellularly is considered diagnostic for infection of Neisseria gonorrhoeae (N. gonorrhoeae) among symptomatic men. Furthermore, it has a high specificity of > 99% and sensitivity of > 95% [11].

Cultures for N. gonorrhoeae were performed as described by Ng et al [14]. Swabs that contain the substances from the patient’s urethra were inoculated directly on chocolate agar plate (Oxoid) and incubated in a carbon dioxide incubator at 35 - 37 °C for 18 - 24 h. Colonies that are small and greyish are gram stained and were tested for oxidase and superoxol, and then subjected for identification using the Vitek Compact 2 instrument.

Test sensitivity and specificity are determined using the formula by Strohl et al [15]. The sensitivity of a test is the probability that it will be positive in the presence of a pathogen. When the number of false-negative reaches zero, the sensitivity approaches 100%. The specificity is the probability that a test will be negative if the pathogen is not present. When the number of false-positive reaches zero, the specificity approaches 100%.

Sensitivity was further evaluated by direct dilution methods. Dilutions were prepared as follows: 1:2, 1:4, 1:6, 1:8, 1:10, and 1:12. Each dilution was analyzed for its WBC count, bacterial count and bacterial scatter plot or diagram.

Daily running of controls were made to ensure result quality. This includes high and low counts of erythrocytes, leucocytes, epithelial cells, casts, bacteria and even conductivity. In situations where in one or more readings are out of control twice consecutively, recalibration is performed. Additionally, background or blank checks were executed every 8 h for the same aforementioned cellular elements.

Aside from the routine controls of the Sysmex UF500i, bacterial suspensions equivalent to 0.5 - 0.63 McFarland standards on a 0.4% normal saline solution were also used as controls. This include the following ATCC strains: Staphylococcus aureus (S. aureus) (29213, 43300, 25922), Enterococcus faecalis (E. faecalis) (29212), Pseudomonas aeruginosa (P. aeruginosa) (27853), Klebsiella pneumoniae (K. pneumoniae) (1705, 700603), N. gonorrhoeae (49226) and Escherichia coli (E. coli) (35218, 25922). These bacterial suspensions are treated as urine and were analyzed as well using the Sysmex UF500i instrument for its pattern.

The study had undergone research review through the Ethics Committee of Riverside Medical Center with RERC protocol number DPOTMH-REC 2019-09 approved on July 05, 2019.

Percentage distribution and concordance rate were utilized in this study. Percentage distribution was used to describe the frequency of observation, while concordance rate was used in order to measure the agreement or predictive accuracy of the bacterial scatterplot observed in the UF500i and the gonococcal microbial results in urine.

A total of 194 randomly collected urine specimens made up this study; 106 (54.64%) were from patients with obvious manifestation of urethritis as diagnosed by clinicians, 38 (19.59%) were from those who did not show any manifestations of urethritis but diagnosed with urinary tract infection (UTI), and 50 (25.77%) were from those noted to contain normal cellular counts with negative culture results. All isolates were identified using Vitek Compact 2 (bioMerieux) with ≥ 95% probability. Tables 1 and 2 show the summary of data taken from Sysmex UF500i and Vitek Compact 2 instrument.

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Table 1. Summary of Bacteria Scatterplot Pattern From Patient’s Urine With Manifestations of Urethritis

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Table 2. Summary of Bacteria Scatterplot Pattern From Patient’s Urine Without Manifestations of Urethritis

The capability of the instrument to detect the gram reactions as discussed by Agpaoa et al [8], were also determined. Her findings also served as a quality control for the utilized machine and as expected pattern matched the isolate. A total of 38 specimens were analyzed and yielded the following results in Table 2.

Out of the 38 urine specimens diagnosed with UTI, 33 were identified with causative agents that of gram-negative bacteria by culture results, five were noted to be of gram-positive bacteria, and one with mixed results. Majority of the isolates were identified as E. coli (47.37%), followed by K. pneumoniae (13.16%), and Enterobacter cloacae (E. cloacae) complex (15.79%). All specimens that contained gram-negative bacilli had a pattern of either A (less than 30°) or C (widespread). Gram-positive agents however were not that consistent as observed. This is because Streptococcus or Enterococcus species were noted to have a pattern that is of C (wide spread) probably because of their arrangements that are in chains.

Known bacterial isolates inoculated onto 4% NaCl were also utilized to observe its pattern where the same patterns were also noted with those specimens as mentioned in Table 3.

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Table 3. Data Collected Using Known Standardized Bacterial Suspensions

Interestingly, all urine specimens that contain gram-negative cocci exhibited the pattern E, that is most of the scatter plot were below the 10° and sticks low to the B-FLH (x-axis) as seen in Figure 1.

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Figure 1. Scattergram pattern samples of urine containing E. coli (a), S. epidermidis (b), K. pneumoniae (c), control low (d), control high (e) and gonococcus (f and g). S. epidermidis: Staphylococcus epidermidis; E. coli: Escherichia coli; K. pneumoniae: Klebsiella pneumoniae.

A total of 50 in-house specimens from newborns that did not show any indication of infection were used to test for the equipment’s specificity. In this study, none of the samples was noted to have a false-positive result. This then showed 100% specificity for the test.

Using the same samples in Table 1, a total of 106 samples were noted to be positive using both clinical manifestations of urethritis and culture results. However, only 105 samples indicated a bacterial scatterplot pattern of E, whereas one sample indicated a scatterplot of C. This results to 99.07% sensitivity of UF500i for this study. Furthermore, at 1:12 dilution, where bacterial count ranges from 9 - 43.9/µL, bacterial scatter plot pattern of E can still be observed (Table 4).

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Table 4. Cell Counts and Pattern of Directly Diluted Urine Containing Gonococci

Automation in the analysis of urine has been encouraged not just to promote efficient turnaround time of results but specifically for standardization among laboratories. Sysmex UF500i is an equal of Sysmex UF1000i in urine analysis, and has the capacity of selecting out nonpathologic or normal urine samples from pathologic ones. It can further explore specifically for clues that can aid the operator in detecting causative agents which may be found in urine specimens.

Recently, a number of published articles using automated urine analyzers have set different cut-offs as to WBC counts and bacteria counts to exclude specimens who are normal and with significant bacteriuria [4, 16, 17]. These findings however are set for UTIs and none of which were indicated for urethritis. Although the Centers for Disease Control and Prevention (CDC) [11] has diagnostic considerations for urine with urethritis, this is however restricted to gram-stained urethral discharges of having > 2 WBC per oil immersion field and urine sediments of > 10/high-power field (HPF), but none with unspun urine. Unspun urine is the sample of choice for standardized automated urinalysis procedures. The study of Grosso et al [18], however indicated cut-off values of 200/µL for bacterial count and 500/µL for WBC count can obtain a specificity and sensitivity of more than 80% in ruling out non-gonococcal urethritis only.

Urine that contains different types of pathogens must be identified for proper medication. Treatment for gonococcal urethritis is different from treating common UTIs, noting that there are other urethritis causing bacteria as well. These include Chlamydia trachomatis (C. trachomatis), Mycoplasma genitalium (M. genitalium), Ureaplasma species, Neisseria meningitidis (N. meningitides), Haemophilus influenzae (H. influenzae), Moraxella catarrhalis (M. catarrhalis), Streptococcus pneumoniae (S. pneumoniae) [9], Gardnerella vaginalis (G. vaginalis) [18] and E. coli [19]. As per CDC [11] and WHO’s [20] recommendation, gonococcal urethritis must be treated with ceftriaxone or cefexime coupled with azithromycin. This also holds to be true for the reason that, not all urine specimens sent to laboratory are for the diagnosis of UTI but for urethritis as well.

As with results in Table 1, urine specimens were all taken from patients with obvious manifestation of urethritis, which is with urethral discharges. However, the urinary WBC content of 26 specimens (13.9%) exceeded the normal range of 10/µL [10] were also found to be less than 40/µL [21], and is not as high as expected in patients with urethritis. This is probably because patients were not instructed to collect their urine specimen properly, that is of first pass (first stream of about 10 - 20 mL of the urine) [11, 22], and not mid-stream clean-catch. Collecting mid-stream clean-catch samples tends to wash off the WBCs in the urethra and further dilutes the sample resulting to low numbers of WBCs in the urine sample though patients have obvious manifestations of urethritis. Although low numbers of urinary WBCs were noted on 26 samples, the Sysmex UF500i was still able to classify or indicate the urine specimen to be pathologic based on its WBC content.

Several specimens have bacterial counts noted to be low if compared to the suggested cut-off of 89.4/µL [16, 17, 21]. This means, 41 (29.7%) samples will not be considered with significant bacteriuria if 89.4/µL cut-off is used, 33 (23.91%) samples if 58/µL, and eight (5.79%) samples if 15/µL. The number of bacteria per µL however is expected noting that some samples were collected mid-stream clean-catch with possible volumes greater than 20 mL. This leads to washing out not just of the WBCs but bacteria as well. Moreover, N. gonorrhoeae when examined on smears is commonly intracellular rather than extracellular, or both. This also means that only those gonococci found outside the cells are the ones counted by the instrument, leaving those inside the cells uncounted.

By principle, the UF500i analyzer has a separate channel for detecting bacteria. It stains the nucleic acid of the bacteria and delivers it into the flow cell for particle analysis with the use of red semiconductor laser. The particles are then characterized according to impedance scattering; fluorescence light from forward- to side-scatter lights. The forward scatter light provides information on particle size; while side-scatter light provides information on the internal complexity and internal surface. Additionally, florescence intensity provides information on the nucleic acid of the bacteria [22]. In the condition where there is a proliferation of substances that reduce nitrite ions, like N. gonorrhoeae, decomposition of the dye is inhibited resulting to enhanced dye transmissivity [23]. Enhanced dye transmissivity will show the scatterplot to be near the B-FLH axis.

Urine that contains different types of organisms can be identified by Sysmex UF series instrument as to its gram reaction for it provides bacterial scatter plot for easy detection even at counts of 9.1/µL (Table 4). The two-dimensional scattergram is created by the intensity of forward scatter light which reflects the size of the particle, and fluorescent light intensity that reflects the level of staining [6, 7, 24]. Forward scatter light reading is somewhat higher in most gram-positive bacteria since they tend to be bigger compared to gram-negative. Most gram-positive bacteria are noted to be bigger because they aggregate with each other either as clustered or in chains. Most gram-negative bacilli like E. coli has cell sizes that ranges 1 - 2 µm, K. pneumoniae at 2 µm, P. aeruginosa at 1 - 5 µm, and Enterobacter species at 1 - 3 µm. Also, the aforementioned gram-negative bacilli are able to reduce nitrates to nitrites. Thus in this study, urine that contains gram-negative bacilli will almost always result to pattern A or pattern C. On the other hand, Neisseria species ranges 0.6 - 1 µm and is able to reduce nitrite. Hence, pattern E was noted to be produced by Neisseria species (Fig. 1). Majority of N. gonorrhoeae containing urine specimens exhibited type E pattern (98.97%), while those of the E. coli exhibited type A pattern. These observations were also noted on the study of Fujinami et al [24] and Muratani et al [7]. When compared to culture results, the pattern exhibited by urine containing gonococcus has a concordance rate of 98.97% while those containing E. coli had a rate of 100%. If based on the criteria of urethritis alone, this will have a concordance rate of 99.06%.

Looking onto Table 3 however, it indicates that three species exhibit the same pattern. These include N. gonorrhoeae, Haemophilus species and Acinetobacter species. In this table, bacterial suspensions are emulsified on 0.9% normal saline solution (NSS). Acinetobacter species on actual clinical specimens are noted to be coccobacilli in morphology. On environment with growth promoters, Acinetobacter species tend to be more of the diplococcoid type. As for N. gonorrhoeae and H. influenzae, this is probably because the two share some similarities such as the size of their cells which is up to 1 µm, whereas most bacterial cells are more than 1 µm; both organisms are also highly fastidious, containing lipooligosaccharides on their cell surface [25], and produce IgA1 protease [26]. A number of bacteria also have the lipooligosaccharides on their cell surface that include Neisseria, Haemophilus, Bordetella, Campylobacter and Branhamella [27]. However, out of these five species, Neisseria species is frequently associated as the causative agent for urethritis. Though there are a couple of studies that Haemophillus species causes urethritis [9, 18], its frequency is very rare when compared to Neisseria species especially in our local setting. There are also some bacteria that produce IgA1 protease that are considered human-restricted pathogens that include S. pneumoniae, N. meningitides, N. gonorrhoeae and H. influenzae. However, N. meningitides, N. gonorrhoeae and H. influenzae produce homologous serine protease while S. pneumoniae produce a functionally homologous, but evolutionary distinct metalloprotease [26].

This study suggests the utilization of Sysmex UF500i, including its succeeding machines that have similar principles, to help laboratory technologists in diagnosing specimens with UTI and urethritis with causative agents using the bacterial scatter plot or distribution pattern and not merely relying on the WBC and bacterial counts. The machine produces five types of bacterial distribution pattern, wherein the first four were mentioned in the study of Agpaoa et al [8] and Kim et al [16]. Urine specimens that contain N. gonorrhoeae produce a bacterial distribution pattern in which majority of the bacteria are noted below 10°.

Analysis of bacterial distribution patterns generated by the UF500i seemed to provide new analytical information which can serve as a useful kit for screening urethritis specifically those caused by N. gonorrhoeae. Also, bacterial scattergram displays distribution of bacterial cells below 10° which is a helpful guide in the diagnosis and treatment of infections and low bacterial counts do not rule out infection. It is thereby necessary that clinical laboratories should also release the bacterial scattergram results of Sysmex UF series analyzers together with other urine parameters for more substantial patient results.

Acknowledgments

The authors would like to thank Mr. Michael Angelo Acosido, Ms. Lucille Joy Alulod, Ms. Jo-Anne Lagotang and Mr. Jericho Carmona for their comments and suggestions.

Financial Disclosure

None to declare.

Conflict of Interest

None to declare.

Informed Consent

Not applicable.

Author Contributions

This work was carried out in collaboration with all authors. ACJ and JPTL designed the proposed study. ACJ and RR wrote the protocols. RVdR and PCVM did the literature search, processing of specimens and managed other requirements for ethics review. ACJ, JPTL and RR managed the analysis and discussions of the study. ACJ and JPTL wrote the first draft of the manuscript. All authors have read and approved the final manuscript.

Data Availability

The authors declare that the data supporting the findings of this study are available within the article.

1. Broeren MA, Bahceci S, Vader HL, Arents NL. Screening for urinary tract infection with the Sysmex UF-1000i urine flow cytometer. J Clin Microbiol. 2011;49(3):1025-1029.
   doi pubmed
2. Pieretti B, Brunati P, Pini B, Colzani C, Congedo P, Rocchi M, Terramocci R. Diagnosis of bacteriuria and leukocyturia by automated flow cytometry compared with urine culture. J Clin Microbiol. 2010;48(11):3990-3996.
   doi pubmed
3. Erdman P, Anderson B, Zacko JC, Taylor K, Donaldson K. The accuracy of the sysmex UF-1000i in urine bacterial detection compared with the standard urine analysis and culture. Arch Pathol Lab Med. 2017;141(11):1540-1543.
   doi pubmed
4. Wang J, Zhang Y, Xu D, Shao W, Lu Y. Evaluation of the Sysmex UF-1000i for the diagnosis of urinary tract infection. Am J Clin Pathol. 2010;133(4):577-582.
   doi pubmed
5. Wada A, Kono M, Kawauchi S, Takagi Y, Morikawa T, Funakoshi K. Rapid discrimination of Gram-positive and Gram-negative bacteria in liquid samples by using NaOH-sodium dodecyl sulfate solution and flow cytometry. PLoS One. 2012;7(10):e47093.
   doi pubmed
6. Ozawa H, Yajima N, Kobayashi H. Estimation of the causative bacterial group from bacterial scattergrams of fully automated urine particle analyzer UF-1000i. Sysmex Journal International. 2012;22(1):6.
7. Muratani T, Kobayashi T, Minamoto Y, Ikuno Y, Migita S. The possibility of the bacterial class estimate using urine from patients with urinary tract infection by the fully automated urine particle analyzer UF-1000i. Sysmex Journal International. 2013;23(1):9.
8. Agpaoa V, Mendoza J, Fernandez AJ, Veloso J, Bhatnagar S. Predict urinary tract infection and to estimate causative bacterial class in a Philippine subspecialty hospital. Nephrology and Therapeutics. 2015;5(2):6.
9. Frolund M, Lidbrink P, Wikstrom A, Cowan S, Ahrens P, Jensen JS. Urethritis-associated pathogens in urine from men with non-gonococcal urethritis: a case-control study. Acta Derm Venereol. 2016;96(5):689-694.
   doi pubmed
10. Burd E, Sue Kehl K. A critical appraisal of the role of the clinical microbiology laboratory in the diagnosis in the urinary tract infections. Journal of Clinical Microbiology. 2011;49(9):534-538.
    doi
11. Centers for Disease Control and Prevention (CDC). Recommendations for the Laboratory-based detection of chlamydia trachomatis and Neisseria gonorrhoeae - 2014. Morbidity and Mortality Week Report (MMWR). Retrieved from: https://www.cdc.gov/mmwr/preview/mmwrhtml/rr6302a1.htm.
12. Basit S, Juayang A. Outcomes-based education manual in clinical bacteriology. APD Educational Publishing House. Philippines. 2016.
13. Torpy J, Lynm C, Golub R. Gonorrhea. The Journal of the American Medical Association. 2013;309(2):1.
    doi pubmed
14. Ng LK, Martin IE. The laboratory diagnosis of Neisseria gonorrhoeae. Can J Infect Dis Med Microbiol. 2005;16(1):15-25.
    doi pubmed
15. Strohl W, Rouse H, Fisher B. Lippincott's illustrated reviews microbiology. Pennsylvania. Lippincott William and Wilkins. 2001:21-22.
16. Kim S, Park Y, Kim H, Kim J, Koo S, Kwon G. Rapid screening of urinary tract infection and discrimination of gram-positive and gram-negative bacteria by automated flow cytometric analysis using Sysmex UF 5000. Journal of Clinical Microbiology. 2018;56(8):14.
    doi pubmed
17. Millan-Lou MI, Garcia-Lechuz JM, Ruiz-Andres MA, Lopez C, Aldea MJ, Revillo MJ, Rezusta A. Validation and search of the ideal cut-off of the sysmex UF-1000i((R)) flow cytometer for the diagnosis of urinary tract infection in a tertiary hospital in Spain. Front Med (Lausanne). 2018;5:92.
    doi pubmed
18. Grosso S, Bruschetta G, Camporese A. Utilizzo Sperimentale di Sysmex UF1000i nello Screening di Uretrite non Gonococcica. Le Infezioni in Medicine. 2012;3:188-194.
19. Dan M, Gottesman T, Schwartz O, Tsivian A, Gophna U, Rokney A. Sexually transmitted Escherichia coli urethritis and orchiepididymitis. Sex Transm Dis. 2012;39(1):16-17.
    doi pubmed
20. World Health Organization. WHO Guidelines in the treatment of gonorrhoeae. 2016:17-18.
21. De Rosa R, Grosso S, Lorenzi G, Bruschetta G, Camporese A. Evaluation of the new Sysmex UF-5000 fluorescence flow cytometry analyser for ruling out bacterial urinary tract infection and for prediction of Gram negative bacteria in urine cultures. Clin Chim Acta. 2018;484:171-178.
    doi pubmed
22. Monsen T, Ryden P. Flow cytometry analysis using sysmex UF-1000i classifies uropathogens based on bacterial, leukocyte, and erythrocyte counts in urine specimens among patients with urinary tract infections. J Clin Microbiol. 2015;53(2):539-545.
    doi pubmed
23. Sakai Y, Kawashima Y, Inoue J, Ikeuchi Y. Method of staining, detection and counting bacteria and a diluent for bacterial stain. US 7,309,581 B2. United States Patent. 2007.
24. Fujinami S, Inamitsu S, Tokushige C, Yoshimura H, Futata Y, Kawashima H, Matsunaga A. Comparisons of the fully automated urine particle analyzer (UF-1000i) to quantitative urine culture and nitrite reaction in urinary tract infection test. Sysmex Journal International. 2013;23(1):5.
25. Phillips N, John C, Reinders L, Gibson B, Apicella A, McLeod Grifiss J. Structural models for the cell surface lipooligosaccharides of Neisseria gonorrhoeae and Haemophillus influenzae. Biomed Environ Mass Spectrom. 1990;19(11):731-745.
    doi pubmed
26. Vidarsson G, Overbeeke N, Stemerding AM, van den Dobbelsteen G, van Ulsen P, van der Ley P, Kilian M, et al. Working mechanism of immunoglobulin A1 (IgA1) protease: cleavage of IgA1 antibody to Neisseria meningitidis PorA requires de novo synthesis of IgA1 Protease. Infect Immun. 2005;73(10):6721-6726.
    doi pubmed
27. Preston A, Mandrell RE, Gibson BW, Apicella MA. The lipooligosaccharides of pathogenic gram-negative bacteria. Crit Rev Microbiol. 1996;22(3):139-180.
    doi pubmed

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