SPECIMEN COLLECTION AND TRANSPORT

No special considerations are required for specimen col lection and transport of the organisms discussed in this chapter.

SPECIMEN PROCESSING

No special considerations are required for processing of the organisms discussed in this chapter.

DIRECT DETECTION METHODS

 No specific procedures other than microscopy are required for direct detection of these organisms in clinical material.

 CULTIVATION

Media of Choice

Sphingomonas spp., Sphingobacterium spp., Acidovorax facilis, and all CDC groups considered in this chapter grow well on routine laboratory media, such as 5% sheep blood and chocolate agars; however, most fail to grow on MacConkey agar. They usually grow well in thioglycollate and brain-heart infusion broths and in broths used in blood culture systems.

Incubation Conditions and Duration

Within 24 to 48 hours of inoculation and incubation, most of these organisms produce detectable growth on media incubated at 35° to 37°C in 5% carbon dioxide (CO2) or ambient air.

Colonial Appearance

 Table 1 describes the colonial appearance and distinguishing characteristics (e.g., pigment) of each organ ism on 5% sheep blood agar. When these organisms do grow on MacConkey agar, they appear as lactose nonfermenters.

Table1. Colonial Appearance and Characteristics

APPROACH TO IDENTIFICATION

 The ability of many commercial identification systems to identify accurately the organisms discussed in this chapter may be limited or uncertain. Tables 2 through 5 show some biochemical tests that are helpful for presumptive differentiation among the various organisms in this group.

Table2.  Key Biochemical and Physiologic Characteristics

Table3. Specific Biochemical Characteristics for  Differentiation of CDC groups IIc, IIe, and IIh *

Table4. Specific Biochemical Characteristics for  Differentiation of the Sphingobacterium spp.

Table5. Specific Biochemical Characteristics for  Differentiation of the Sphingomonas spp.

Comments Regarding Specific Organisms

Acidovorax facilis. A. facilis is a straight to slightly curved, gram-negative rod that occurs singly or in short chains. It is aerobic and has a single polar flagellum, which makes it motile. On nutrient agar, it forms unpigmented colonies, and 30°C is its optimum temperature. A. facilis is oxidase positive and urease variable (some grow on Christensen urea agar but lack urease activity). Key characteristics are shown in Table 2. A. facilis is commonly found in soil, and no evidence of pathogenicity in healthy humans has been identified. A role for A. facilis as an opportunistic pathogen has not been proven or rejected.

CDC groups IIc, IIe, IIh, IIi, O-1, O-2, and O-3. CDC groups IIc, IIe, IIh, IIi, O-1, and O-2 are short, straight rods that may appear as “II-forms” (i.e., bacteria with thickened ends and thin centers). The phenotypic characteristics of CDC group IIc are most similar to those of CDC groups IIe and IIh, the major difference being that CDC group IIc produces acid from sucrose, hydrolyzes esculin, and usually reduces nitrate. Strains of CDC groups IIe and IIh are similar to Empedobacter brevis in that they oxidize glucose and maltose and produce indole. CDC group IIi resembles S. multivorum but pro duces indole. S. parapaucimobilis resembles CDC group O-1 in that both are motile, esculin positive, and positive for hydrogen sulfide (H2S) in lead acetate; however, S. parapaucimobilis oxidizes more carbohydrates (CDC O-1 is weakly positive in OF glucose and negative in OF xylose, maltose, and mannitol).

CDC groups O-1 and O-2 are similar in that they are motile, oxidase-positive, esculin-positive, gram-negative rods that grow with yellow pigment and do not grow on MacConkey agar. CDC groups O-1 and O-2 have been isolated from clinical sources; antimicrobial susceptibility testing on these organisms has not been reported. CDC group O-2 does not oxidize xylose, mannitol, or lactose; this can help distinguish it from the other yellow pigmented organisms growing on blood agar discussed in this chapter.

CDC O-3 bacteria, which are predominantly curved rods, do not produce yellow pigment. They are motile by a single polar flagellum. They grow well on a Campylobacter selective medium and may be misidentified as a Campylobacter sp. CDC group O-3 are aerobic, glucose-oxidizing organisms that utilize xylose, sucrose, and maltose. They do not grow on MacConkey agar. They are oxidase positive, hydrolyze esculin, and are negative for urease, indole, nitrate, and gelatin. Key characteristics of the CDC groups are shown in Tables 2 and 3. CDC O-3 has been reported as susceptible to aminoglycosides, imipenem, chloramphenicol, and trimethoprim-sulfamethoxazole and resistant to beta-lactam antimicrobials.

Sphingobacterium mizutaii. S. mizutaii exhibits II-forms. It can produce a yellow pigment, and it does not grow on MacConkey agar. Although aflagellate and therefore frequently classified as nonmotile, it can be motile by gliding movement. It is able to grow in the presence of 40% bile; it also is oxidase positive, catalase positive, esculin positive, indole negative, and urease negative (although a report exists that 20% are positive for Christensen urease). Key characteristics are shown in Tables 2 and 4. Reported infections in humans have included septicemia (blood culture), meningitis (CSF specimen), and cellulitis (wound source). This bacterium has been reported to be susceptible to erythromycin, trimethoprim-sulfamethoxazole, and pefloxacin.

Sphingobacterium multivorum. S. multivorum is yellow pigmented, oxidase positive, and esculin positive. It is OF glucose positive; it does not produce acid from mannitol, ethanol, or rhamnose; and it is Christensen urease positive. This bacterium grows on blood agar plate (BAP), Mueller-Hinton agar, Burkholderia cepacia–selective agar (BCSA), and MacConkey agar. Key characteristics are shown in Table4. These organisms are ubiquitous in nature and rarely associated with serious infection; however, cases of septicemia and peritonitis have been reported. This bacterium is nonmotile and resistant to polymyxin B, characteristics that distinguish it from S. paucimobilis. Susceptibility to amikacin, gentamicin, aztreonam, cefepime, cefotaxime, ceftazidime, meropenem, piperacillin, and chloramphenicol has been reported in a small study of eight isolates.

Sphingobacterium spiritivorum. S. spiritivorum is yellow pigmented and positive for oxidase and esculin. It does not grow on MacConkey agar but does grow on BAP, Mueller-Hinton agar, and BCSA. It produces acid in OF glucose and in mannitol, ethanol, and rhamnose. Like S. multivorum, this bacterium is ubiquitous in nature but rarely pathogenic for humans. It can be distinguished from S. paucimobilis by the fact that it is nonmotile and resistant to polymyxin B. Key characteristics are shown in Table 4. S. spiritivorum has been isolated environmentally from hospitals, most commonly from blood and urine. Susceptibility testing by Kirby-Bauer (KB) disk diffusion on 13 isolates showed susceptibility to amikacin, gentamicin, aztreonam, cefepime, cefotaxime, and chloramphenicol.

Sphingomonas paucimobilis. S. paucimobilis is a medium size, straight, gram-negative rod with a single polar flagel lum; growth requires at least 48 hours’ incubation on sheep blood agar (Figure 1). Optimal growth occurs at 30°C in 5% CO2 or ambient air; it does grow at 37°C but not at 42°C. It grows as a deep yellow colony on tryptic soy and blood agars. It is obligately aerobic, grows in broth (e.g., brain-heart infusion, thioglycollate, blood culture media), and does not grow on MacConkey agar (90% do not grow; 10% grow as lactose nonfermenters). S. paucimobilis oxidatively utilizes glucose, xylose, and sucrose. Biochemical test results of interest include the following: esculin hydrolysis positive; motile by wet mount or in motility medium when incubated at 18° to 22°C (nonmotile when incubated at 37°C); oxidase positive (90% to 94% positive); catalase positive; urease negative; and indole negative. S. paucimobilis is susceptible to polymyxin B, a trait that distinguishes it from Sphingobacterium spp. Key characteristics are shown in Table5.

Fig1. Sphingomonas paucimobilis growth on BAP. (From  Seo SW, Chung IY, Kim E, Park JM: A case of postoperative Sphingomonas paucimobilis endophthalmitis after cataract extraction,  Kor J Ophthalmol 22:63, 2008.)

Antimicrobial susceptibility testing indicates that S. paucimobilis is susceptible to tetracycline, chloramphenicol, trimethoprim-sulfamethoxazole, and aminoglycosides. Susceptibility to vancomycin has been noted when the organism is grown on sheep blood agar with a vancomycin disk (30 µg). S. paucimobilis is ubiquitous in soil and water and has been isolated environmentally from swim ming pools, hospital equipment, and water and laboratory supplies. It has been associated with human infections and found in a variety of clinical specimens, specifically, peritonitis associated with wound infections (chronic ambulatory peritoneal dialysis, leg ulcer, empyema, splenic abscess, brain abscess), blood cultures, and CSF, urine, vaginal, and cervical samples. Recent literature indicates that S. paucimobilis is usually regarded as having minor clinical significance; however, community-acquired infection, diabetes mellitus, and alcoholism have been identified as significant risk factors for primary bacteremia. A retrospective study suggests that the prevalence of S. paucimobilis infection in humans seems to have increased in recent times, and although it has low virulence, infection can lead to septic shock, particularly in immunocompromised patients. Another report indicates that although this bacterium has low mortality associated with infection, it frequently causes complications in hospitalized patients.

Sphingomonas parapaucimobilis. S. parapaucimobilis is similar to S. paucimobilis in many ways. It is a medium-size, straight, gram-negative rod that grows with a deep yellow pigment. It is obligately aerobic, motile, and does not grow on MacConkey agar. S. parapaucimobilis can be distinguished from S. paucimobilis by several characteristics. S. parapaucimobilis is H2S positive, as indicated by blackening of lead acetate paper suspended over Kligler iron agar (KIA); it is Simmons citrate positive (S. paucimobilis is negative); and it is negative for extracellular DNAse (S. paucimobilis is positive). Like S. paucimobilis, S. parapaucimobilis is acid in OF glucose, OF xylose, and OF maltose but negative in OF mannitol. It has been distinguished from Sphingobacterium spp. by its susceptibility to polymyxin B; however, S. parapaucimobilis is sometimes variable to polymyxin B. Key characteristics are shown in Table 5. Antimicrobial susceptibility testing indicates that S. parapaucimobilis displays variable resistance but is usually susceptible to tetracycline, chloramphenicol, sulfamethoxazole, aminoglycosides, third-generation cephalosporins, and fluoroquinolone. S. parapaucimobilis has been associated with human infections; specifically, it has been isolated from sputum, urine, and the vagina.

ANTIMICROBIAL SUSCEPTIBILITY

 Antimicrobial susceptibility for this group of bacteria ranges from variable resistance to identifiable patterns of susceptibility. Standardized guidelines are not available. However, when clinically necessary, susceptibility testing should be completed using an overnight MIC or E-test method.

SERODIAGNOSIS

Serodiagnostic techniques are not generally used for the laboratory diagnosis of infections caused by the organ isms discussed in this chapter.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم الشؤون الفكرية يضمّ جامعتي العميد والكفيل إلى مشروعي الملف الاستنادي والبوابة العراقية

المجمع العلمي يطلق المشروع التطويري الصيفي لطلبة حفظ القرآن الكريم في كربلاء

المجمع العلمي يُحيي ذكرى شهادة الإمام محمد الجواد (عليه السلام) في بغداد

تكريم إدارات المدارس المشاركة في مسابقة بصائر العلم الوطنية الأولى

المزيد

الآخبار الصحية

طريقة مبتكرة للكشف المبكر عن أمراض القلب والشرايين

منظمة الصحة تحذر من خطر إدمان الشباب لأكياس النيكوتين

خبراء يحذرون من عادة شائعة تهدد صحة الملايين

خبير يكشف 5 حقائق طبية صادمة وغير معروفة

المزيد

الآخبار التكنلوجية

الأولى في العالم.. الصين تجري تجربة رائدة في الفضاء باستخدام "جنين اصطناعي"

دراسة حديثة تفند ربط التستوستيرون بالمخاطرة لدى الرجال

ميتا تضيف وضع "المحادثة المخفية" إلى تطبيق "واتساب"

فوبيا المرتفعات ليست من الدماغ.. دراسة تكشف السبب

المزيد

مواضيع ذات صلة

Moraxella and Related Organisms

Alcaligenes, Bordetella (Non-pertussis), Comamonas, and Similar Organisms : Pathogenesis and Spectrum of Disease

Chryseobacterium, Sphingobacterium, and Similar Organisms

Pseudomonas, Burkholderia, and Similar Organisms : Epidemiology

Acinetobacter, Stenotrophomonas, and Similar Organisms : Pathogenesis and Spectrum of Disease

Nocardia, Streptomyces, Rhodococcus, and Similar Organisms: Antimicrobial Susceptibility Testing and Therapy

Erysipelothrix, Lactobacillus, and Similar Organisms : Antimicrobial Susceptibility Testing and Therapy

Erysipelothrix, Lactobacillus, and Similar Organisms : Approach to Identification

Staphylococcus, Micrococcus, and Similar Organisms : Pathogenesis and Spectrum of Disease

Strategies to Control Bacteria at the Environmental Level

Definition and Measurement of Bacterial Death

Growth in Biofilms