Yersinia and Pasteurella Overview PDF

# Yersinia - Gram(-), short, pleomorphic, non-motile - Bipolar staining - Catalase + - Oxidase - - Microaerophilic / Facultative anaerobe # Yersinia enterocolitica - Non-lactose fermenter - G(-) - Urease + - Oxidase - - Grow best at 25°C - Motile at 25°C but nonmotile at 37°C. - Transmission: e...

# Yersinia - Gram(-), short, pleomorphic, non-motile - Bipolar staining - Catalase + - Oxidase - - Microaerophilic / Facultative anaerobe # Yersinia enterocolitica - Non-lactose fermenter - G(-) - Urease + - Oxidase - - Grow best at 25°C - Motile at 25°C but nonmotile at 37°C. - Transmission: eating raw or undercooked pork # Pathogenesis and Clinical Findings - Incubation: 4-7 days - Ileum - Early symptoms: fever, abdominal pain, and diarrhea. - One to 2 weeks after onset, some patients with histocompatibility antigen HLA-B 27 develop arthralgia, arthritis, and erythema nodosum, suggesting an immunologic reaction to the infection. # Diagnostic Laboratory Tests - Culture – cefsulodin-irgasan-novobiocin (CIN) agar - Treatment: Self-limited - Susceptible to: aminoglycosides, chloramphenicol, tetracycline, TMP-SMX, piperacillin, third-generation cephalosporins, and fluoroquinolones; - Resistant to: ampicillin and first-generation cephalosporins # Neisseriae - Gram(-), nonmotile diplococcus - Aerobic, Acid Producing - Oxidase + # Neisseria gonorrhoeae | Growth on MTM, ML, or NYC Medium | Glucose | Maltose | Lactose | Sucrose or Fructose | DNAse | |---|---|---|---|---|---| | Neisseria gonorrhoeae | + | + | - | - | - | | Neisseria meningitidis | + | + | + | - | - | | Neisseria lactamica | + | + | + | + | - | | Neisseria sicca | + | + | + | + | - | | Neisseria subflava | + | + | - | 土 | - | | Neisseria mucosa | + | + | - | - | - | | Neisseria flavescens | - | - | - | - | - | | Neisseria cinerea | + | - | - | - | - | | Neisseria polysaccharea | + | + | + | - | - | | Neisseria elongata | -/w | - | - | - | - | | Moraxella catarrhalis | + | - | - | - | + | *ML, Martin-Lewis medium; MTM, modified Thayer-Martin medium; NYC, New York City medium.* # Diagnostic Laboratory Tests - Specimens: - Pus and secretions from the urethra, cervix, rectum, conjunctiva, throat, or synovial fluid for culture and smear. - Culture: - Modified Thayer-Martin medium [MTM] - Incubated in 5% CO2 at 37°C. - Transparent or opaque, nonpigmented, and nonhemolytic colonies - N. flavescens, N. cinerea, N. subflava, and N. lactamica yellow pigmentation. - N. sicca – opaque, brittle, wrinkled colonies - M catarrhalis – nonpigmented or pinkish gray opaque colonies. - NAAT, ELISA # Neisseria meningitidis - Most important serogroups: - A, B, C, X, Y, and W-135 - Gram(-) - Oxidase + - Kidney-shaped diplococcus with a polysaccharide capsule - Ability to use both glucose and maltose. # Neisseria meningitidis - Meningococci are piliated, but unlike gonococci, they do not form distinctive colony types indicating piliated bacteria. - Meningococcal LPS is responsible for many of the toxic effects found in meningococcal disease. # Neisseria meningitidis: Disease - Meningococcal meningitis - most prevalent in children 6 months to 2 years - Begins as mild pharyngitis - Fever, vomiting, headache, and stiff neck. - Pneumonia may be present. - A petechial eruption develops that progresses from erythematous macules to frank purpura. - Vasculitic purpura is the hallmark. # Pathogenesis, Pathology, Clinical Findings - Humans are the only natural hosts - The nasopharynx is the portal of entry. - Early symptoms may be like an upper RTI. - Fulminant meningococcemia is more severe, with high fever and hemorrhagic rash; there may be DIC and circulatory collapse (Waterhouse-Friderichsen syndrome). # Pathogenesis, Pathology, Clinical Findings - Meningitis is the most common complication of meningococcemia. - Sudden; with intense headache, vomiting, and stiff neck, and progresses to coma within a few hours - meninges are acutely inflamed, with thrombosis of blood vessels and exudation of PMNs, so that the surface of the brain is covered with a thick purulent exudate. - In meningococcemia, there is thrombosis of many small blood vessels in many organs, with perivascular infiltration and petechial hemorrhages - interstitial myocarditis, arthritis, and skin lesions # Meningococcal Disease - Two Most Common Manifestations & Their Symptoms* - Meningococcemia (Blood infection) - Meningitis (Spinal cord/brain infection) - Bacteria enters through the nose & throat - Purplish rash is a telltale symptom. # Neisseria spp.: Carbohydrate Utilization test | | Glucose | Maltose | Lactose | |---|---|---|---| | N. Gonorrhea | + | - | - | | N. Meningitides | + | + | - | # Neisseria gonorrhoeae - ANTIGENIC STRUCTURE - PILI (FIMBRIAE) – hair-like appendegas that enhance attachment to host cells and resistance to phagocytosis - POR – prevents phagosome-lysosome fusion, selectively binds to complement components C3b and C4b - OPA proteins – adhesion of gonococci within olonies and attachment to host receptos - RMP (Protein III) - Lipooligosaccharide – resistantance to killing by the human antibody-complement system and interferes with gonococcal binding to receptors on phagocytic cells. # Pathogenesis - Only piliated bacteria appear to be virulent. - Opaque colonies – from - men with symptomatic urethritis - uterine cervical cultures at mid cycle - Transparent colonies – from : - men with asymptomatic urethral infection - menstruating women - invasive forms of gonorrhea (salpingitis and disseminated infection) # Pathology - Gonococci attack mucous membranes of the genitourinary tract, eye, rectum, and throat → acute suppuration → tissue invasion → chronic inflammation and fibrosis. # Clinical Findings - MALES: urethritis, with yellow, creamy pus and painful urination → extend to the epididymis → if untreated, fibrosis occurs → urethral strictures. - FEMALES: infection in endocervix →urethra and vagina →mucopurulent discharge →uterine tubes →salpingitis, fibrosis, and obliteration of the tubes. # Clinical Findings - Gonococcal bacteremia → skin lesions (hemorrhagic papules and pustules) on the hands, forearms, feet, and legs and to tenosynovitis and suppurative arthritis (knees, ankles, and wrists) - Gonococcal ophthalmia neonatorum - during passage through an infected birth canal. # Treatment - UNCOMPLICATED GENITAL OR RECTAL INFECTIONS: - Ceftriaxone 1g IM as a single dose. - CONCOMITANT CHLAMYDIAL INFECTION: - Azithromycin 1g orally in a single dose or with doxycycline 100 mg orally twice a day for 7 days - Azithromycin has been found to be safe and effective in pregnant women, but doxycycline is contraindicated. # Pasteurella - Non-motile gram(-) coccobacilli - Bipolar staining - Aerobes or facultative anaerobes - Oxidase and Catalase + # Pasteurella - Most common presentation - history of animal bite followed within hours by an acute onset of redness, swelling, and pain. - Regional lymphadenopathy is variable - Fever often low grade. - Penicillin G - DOC - Tetracyclines and Fluoroquinolones - alternative # Pasteurella - P. multocida: - most common organism in human wounds inflicted by bites from cats and dogs. It - common causes of hemorrhagic septicemia in a variety of animals - P. bettyae: - from infections of the human genital tract and of newborns - P. pneumotropica: - normal flora of the respiratory tract and gut of mice and rats - cause pneumonia or sepsis when the host-parasite balance is disturbed - P. ureae: - mixed flora in human chronic respiratory disease or other suppurative infections. # Infections Caused by Anaerobic Bacteria - Anaerobic bacteria are found throughout the human body - skin, on mucosal surfaces, and in high concentrations in the mouth and Gl tract-as part of the normal microbiota | Genera | Anatomic Site | |---|---| | **Bacilli (rods)** | | | Gram negative | | | Bacteroides fragilis group |Colon, mouth | | Prevotella melaninogenica |Mouth, colon, genitourinary tract| | Fusobacterium |Mouth | | Gram positive | | | Actinomyces |Mouth | | Propionibacterium |Skin | | Clostridium |Colon | | **Cocci (spheres)** | | | Gram positive | | | Peptoniphilus |Colon, mouth, skin, genitourinary tract| | Peptostreptococcus |Colon, mouth, skin, genitourinary tract| | Peptococcus |Colon, mouth, skin, genitourinary tract| # Anaerobic Bacteria and Associated Representative Infections | | |---|---| | Brain abscesses | Peptostreptococci, Fusobacterium nucleatum, and others | | Oropharyngeal infections | Oropharyngeal anaerobes; Actinomyces, Prevotella melaninogenica, Fusobacterium species | | Pleuropulmonary infections | Peptostreptococci; Fusobacterium species; Prevotella melaninogenica, Bacteroides fragilis in 20-25%; others | | Intra-abdominal infections | | | Liver abscess | Mixed anaerobes in 40-90%; facultative organisms | | Abdominal abscesses | Bacteroides fragilis; other gastrointestinal flora | | Female genital tract infections | | | Vulvar abscesses | Peptostreptococci and others | | Tubo-ovarian and pelvic abscesses |Prevotella sp., peptostreptococci; others | | Skin, soft tissue, and bone infections | | | | Mixed anaerobic flora; Propionibacterium acnes | | Bacteremia | Bacteroides fragilis; peptostreptococci; propionibacteria; Fusobacteria; Clostridium; others | | Endocarditis | Bacteroides fragilis; Actinomyces | # DIAGNOSIS OF ANAEROBIC INFECTIONS - Clinical signs: - Foul-smelling discharge (caused by short-chain fatty-acid products of anaerobic metabolism) - Infection in proximity to a mucosal surface (anaerobes are part of the normal microbiota) - Gas in tissues (production of CO2 and H2) - Negative aerobic culture results # GRAM-NEGATIVE ANAEROBES: BACILLI - BACTEROIDES: - bile-resistant, nonspore forming, slender gram(-) rods that may appear as coccobacilli. - Normal flora of bowel and often implicated in intra-abdominal infections. - B fragilis, B thetaiotaomicron - PREVOTELLA - gram(-) bacilli and may appear as slender rods or coccobacilli. - P melaninogenica – URTI - P bivia and P disiens – female genital tract. - in brain and lung abscesses, in empyema, and in PID and TOA # GRAM-NEGATIVE ANAEROBES: BACILLI - PORPHYROMONAS - Normal oral flora - can be cultured from gingival and periapical tooth infections and, more commonly, breast, axillary, perianal, and male genital infections. - FUSOBACTERIA - Most human infections are caused by F. necrophorum and F. nucleatum. - F necrophorum cause severe infections of the head and neck that can progress to a complicated infection called Lemierre's disease. # GRAM-NEGATIVE ANAEROBES: COCCI - VEILLONELLA - small, anaerobic, gram-negative cocci - Normal flora of the mouth, nasopharynx, and probably the intestine. - Rarely the sole cause of an infection. # GRAM-POSITIVE BACILLI - ACTINOMYCES - A. israelii and A. gerencseriae - MC encountered. - Infections of the groin, urogenital area, breast, and axilla and postoperative infections of the mandible, eye, and head and neck. - Chronic suppurative and granulomatous infection that produces pyogenic lesions with interconnecting sinus tracts that contain granules composed of microcolonies of the bacteria embedded in tissue elements - DOC: Penicillin # GRAM-POSITIVE BACILLI - LACTOBACILLUS - normal flora of the vagina and rarely cause disease. - PROPIONIBACTERIUM - normal flora of the skin, oral cavity, large intestine, conjunctiva, and external ear canal. - opportunistic pathogen - acne vulgaris - Cause postsurgical wound infections (involving insertion of devices, such as prosthetic joint infections of the shoulder, CNS shunt infections, osteomyelitis, endocarditis, and endophthalmitis) # GRAM-POSITIVE BACILLI - EUBACTERIUM, EGGERTHELLA, BIFIDOBACTERIUM, & ARACHNIA - in mixed infections of oropharyngeal or bowel flora. - CLOSTRIDIUM - TETANI: ubiquitous, > 50% of cases follow minor injuries. - tetanospasmin, a potent neurotoxin. - preventable: active immunity is induced with tetanus toxoid (formalinized tetanus toxin). # GRAM-POSITIVE: COCCI - Peptostreptococcus - Opportunistic - In brain abscesses, pleuropulmonary infections, necrotizing fasciitis, and other deep skin and soft tissue infections, intra-abdominal infections, and infections of the female genital tract. # GRAM-POSITIVE BACILLI - CLOSTRIDIUM - BOTULINUM: preserved or canned foods with low oxygen levels, low ph, and nutrients that support growth. - neurotoxins - most potent toxins known but can be neutralized by specific antibodies. - PERFRINGENS: causes gas gangrene and food poisoning - All types produce the alpha toxin, a necrotizing, hemolytic exotoxin that is a lecithinase. # GRAM-POSITIVE BACILLI - CLOSTRIDIUM - DIFFICULE: causes pseudomembranous colitis, part of the normal Gl flora in 2-10% of humans. - from diarrhea alone to marked diarrhea and necrosis of mucosa with accumulation of inflammatory cells and fibrin, which forms the pseudomembrane.