Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Pseudomonas and related organisms
Document related concepts
no text concepts found
Transcript
Pseudomonas and related organisms Pseudomonas and related organisms Pseudomonas aeruginosa Burkholderia cepacia Stenotrophomonas maltophilia Acinetobacter baumannii Acinetobacter lwoffi Moraxella catarrhalis Pseudomonas Ubiquitous Soil, decaying organic matter, vegetation, water Hospital environment Moist reservoirs, food, cut flowers, sinks, toilets, floor mops, respiratory therapy & dialysis equipment EVEN “disinfectant solutions” Simple growth requirements (can even grow in distilled water) Pseudomonas /Physiology & structure Small gram-negative bacilli, motile Strict aerobe Nonfermenter Also able to use nitrate or arginine an alternate electron acceptor Simple nutritional requirements Mucoid capsule Oxidase positive = enterobactericeae > 10 species P. aeruginosa most common Pseudomonas /Pathogenesis & immunity Virulence factors Structural components Capsule mucoid polysaccharide; adhesin; inhibits antibiotic (e.g., aminoglycoside) killing; suppresses neutrophil and lymphocyte activity Pili: Adhesin LPS: Endotoxin activity Pyocyanin: Impairs ciliary function; increases release of IL-8, leading to stimulation of inflammatory response; mediates tissue damage through production of toxic oxygen radicals Pathogenesis & immunity: Toxins and enzymes Exotoxin A: Inhibits protein synthesis; produces tissue damage (e.g., skin, cornea); immunosuppressive Exotoxin S: Inhibits protein synthesis; immunosuppressive Cytotoxin (leukocidin) Elastase Alkaline protease Phospholipase C Antibiotic resistance: resistant to many antibiotics Pseudomonas /Epidemiology Opportunistic pathogens Tolerate a wide range of temperatures (4° to 42°C) Resistant to many antibiotics and disinfectants Isolation of pseudomonads from a hospitalized patient is worrisome but does not normally justify therapeutic intervention unless there is evidence of disease Pseudomonas /clinical diseases Pulmonary infections: asymptomatic colonization, benign tracheobronchitis to severe necrotizing bronchopneumonia Burn wound & other skin & soft tissue inf. UTI External otitis Eye inf. (contaminated contact lens cleaning fluids) Bacteremia & endocarditis Pseudomonas /diagnosis & identification Culture Simple Identification Colonial morphology colony size, hemolysis, pigmentation, odor Biochemical tests Positive oxidase test TREATMENT, PREVENTION, AND CONTROL The bacteria are typically resistant to most antibiotics and Susceptible organisms can become resistant during therapy by inducing the formation of antibioticinactivating enzymes (e.g., β-lactamases) or The mutation of the genes coding the outer membrane pore proteins or Tthrough the transfer of plasmid-mediated resistance from a resistant organism to a susceptible one. A combination of active antibiotics is generally required Burkholderia (Formerly classified as Pseudomonas) B. cepacia, B. pseudomallei, B.mallei, B.galidei Important human pathogens Burkholderia cepacia Like P. aeruginosa is commonly associated with nosocomial infections relatively low level of virulence, rarely cause death is susceptible to trimetoprimsulfamethoxazole Burkholderia cepacia Respiratory tract infections in patients with cystic fibrosis or chronic granulomatous disease UTIs in catheterized patients Septicemia, particularly in patients with contaminated intravascular catheters Other opportunistic infections Burkholderia pseudomallei Found in soil, water, vegetation Endemic is Southeast Asia, India, Africa and Australia Opportunistic Melioidosis: (acute suppurative infection or a chronic pulmonary infection) “highly infectious” , ‘careful isolation’ TMP_SMX+Cephalosporin Burkholderia mallei Small, nonmotile, nonpigmented, aerobic Gr- rod Grows readily most media Glanders: Horses, donkeys Human infection may be fatal Ulcer on the skin, lymphangitis and sepsis Tetracycline+aminoglycozide “Stenotrophomonas maltophilia” The clinical importance of this opportunistic pathogen is well known Nosocomial infections; bacteremia, pneumonia, meningitis, wound infections, and UTIs Antimicrobial therapy: Trimethoprimsulfamethoxazole Acinetobacter A.baumannii, A. lwoffii, the most common isolated Aerobic, oxidase negative, gr- coccobacilli Ubiquitous, recovered in nature & hospital Survive on moist and dry surfaces (!skin!) Part of the normal oropharyngeal flora Resistant to antibiotics Moraxella Moraxella catarrhalis is the most important human pathogen within this genus Aerobic, oxidase +, Gr- diplococci Common cause of bronchitis and bronchopneumonia, sinusitis, otitis most isolates are resistant to penicillin (produce β-lactamase) Anaerobic, Non-Spore-Forming, Gram-Positive Bacteria Heterogeneous group of bacteria that characteristically colonize the skin and mucosal surfaces. Opportunistic pathogens; recovered in mixtures of aerobic and anaerobic bacteria. Have fastidious nutritional requirements and grow slowly Thus the isolation and identification of individual strains are difficult and often time consuming. Anaerobic Gram-Positive Cocci Peptostreptococcus, Finegoldia, Micromonas spp. The anaerobic gram-positive cocci normally colonize the oral cavity, gastrointestinal tract, genitourinary tract, and skin. They produce infections when they spread from these sites to normally sterile sites. For example, bacteria colonizing the upper airways can cause sinusitis and pleuropulmonary infections; bacteria in the intestines can cause intraabdominal infections; Laboratory confirmation of infections with anaerobic cocci is complicated by the following three factors: (1) care must be taken to prevent contamination of the clinical specimen with the anaerobic cocci that normally colonize the mucosal surface; (2) the collected specimen must be transported in an oxygen-free container to prevent loss of the organisms; and (3) specimens should be cultured on nutritionally enriched media for a prolonged period (i.e., 5 to 7 days). Antibiotic susceptibility Anaerobic cocci are usually susceptible to penicillin, metronidazole, imipenem, and chloramphenicol. They have intermediate susceptibility to broadspectrum cephalosporins, clindamycin, erythromycin, and Are resistant to the aminoglycosides (as are all anaerobes) Most infections are polymicrobic: broad-spectrum therapy against aerobic and anaerobic bacteria is usually selected. Anaerobic Rods Actinomyces Bifidobacterium Eubacterium Lactobacillus: They are found as part of the normal flora of the mouth, stomach, intestines, and genitourinary tract. Mobiluncus: The organisms colonize the genital tract in low numbers but are abundant in women with bacterial vaginosis (vaginitis). Propionibacterium propionicum: propionic acid is the primary metabolic product of fermentation Anaerobic, Non-Spore-Forming, Gram-Positive Rods Actinomyces spp.: Actinomycosis (cervicofacial, thoracic, abdominal, pelvic, central nervous system) Propionibacterium spp.: Acne, lacrimal canaliculitis, opportunistic infections Mobiluncus spp.: Bacterial vaginosis, opportunistic infections Lactobacillus spp.: Endocarditis, opportunistic infections Eubacterium spp.: Opportunistic infections Bifidobacterium spp.: Opportunistic infections Actinomyces They typically develop delicate filamentous forms or hyphae (resembling fungi) in clinical specimens or when isolated in culture Macroscopic colonies: grains of sand can frequently be seen in the abscesses These colonies, called sulfur granules: they appear yellow or orange, are masses of filamentous organisms bound together by calcium phosphate Disease caused by actinomyces: actinomycosis Actinomyces organisms colonize the upper respiratory, gastrointestinal, and female genital tracts. Have a low virulence potential and cause disease only when the normal mucosal barriers are disrupted by trauma, surgery, or infection. The cervicofacial type, thoracic, abdominal, pelvic Laboratory diagnosis Care must be used during collection of clinical specimens that they not become contaminated with actinomyces that are part of the normal bacterial population on mucosal surfaces. If sulfur granules are detected, the granule should be crushed between two glass slides, stained, and examined microscopically. Thin, gram-positive, branching rods can be seen along the periphery of the granules. Are fastidious and grow slowly (2 weeks) under anaerobic conditions; colonies appear white and have a domed surface. Anaerobic Gram-Negative Bacteria The most important gram-negative anaerobes that colonize the human upper respiratory, gastrointestinal, and genitourinary tracts They are the rods: Bacteroides, Fusobacterium, Porphyromonas, and Prevotella; the cocci in the genus Veillonella. Anaerobes are the predominant bacteria at each of these sites, outnumbering aerobic bacteria tenfold to 1000-fold. Among these pathogens, the most important is Bacteroides fragilis, the prototypical endogenous anaerobic pathogen. Bacteroides the genus Bacteroides consisted of almost 50 species A characteristic common to the current species remaining in the genus Bacteroides is that their growth is stimulated by 20% bile. Bacteroides have a typical gram-negative cell wall structure, which can be surrounded by a polysaccharide capsule. Bile-susceptible species: Porphyromonas, Prevotella Colonize the human body in large numbers These normal protective organisms produce serious disease when they move from their endogenous homes to normally sterile sites B. fragilis is commonly associated with pleuropulmonary, intraabdominal, and genital infections. Laboratory diagnosis MICROSCOPY: Microscopic examination of specimens from patients with suspected anaerobic infections can be useful. Although the bacteria may stain faintly and irregularly, the finding of pleomorphic, gramnegative rods can serve as useful preliminary information. CULTURE Specimens should be collected and transported to the laboratory in an oxygen-free system, Promptly inoculated onto specific media for the recovery of anaerobes, and incubated in an anaerobic environment Because most anaerobic infections are endogenous, it is important to collect specimens not contaminated with the normal bacterial population Most Bacteroides grow rapidly and should be detected within 2 days; Antibiotic susceptibility Virtually all members of the B. fragilis group, many Prevotella and Porphyromonas species, and some Fusobacterium isolates produce β-lactamases. This enzyme renders the bacteria resistant to penicillin and many cephalosporins. Antibiotics with the best activity: metronidazole, carbapenems (e.g., imipenem), and β-lactam-βlactamase inhibitors (e.g., piperacillin-tazobactam). Clindamycin resistance in Bacteroides, which is plasmid mediated, has become more prevalent (an average of 20% to 25% of the isolates)
