Lecture 7 January 19.pptx

Spiral Shaped Bacteria Murray’s Basic Medical Microbiology, Chapter 10 January 19, 2024 Dr. Angela Benton Overview • Campylobacter jejuni • Helicobacter pylori • Treponema pallidum • Borrelia burgdorferi • Borrelia recurrentis • Leptospira spp. Campylobacter jejuni • Gram-negative rods, motile •...

Spiral Shaped Bacteria Murray’s Basic Medical Microbiology, Chapter 10 January 19, 2024 Dr. Angela Benton Overview • Campylobacter jejuni • Helicobacter pylori • Treponema pallidum • Borrelia burgdorferi • Borrelia recurrentis • Leptospira spp. Campylobacter jejuni • Gram-negative rods, motile • Most common cause of bacterial gastroenteritis • Consumption of contaminated food, milk, water • Poultry is a big culprit • Infections are zoonotic – many animals serve as reservoirs • Disease is most commonly seen in infants and young children • Second peak of disease in 20-to-40-year olds • Grows best at 42°C and reduced oxygen – differential test • Different than most bacterial species that prefer 37°C Pathogenesis – C. jejuni • Characteristically produces histologic damage to the mucosal surfaces of the jejunum, ileum, and colon • Mucosal surfaces appear ulcerated, edematous, and bloody • Crypt abscess form in the epithelial glands • Infiltration of the lamina propria with neutrophils, mononuclear cells, and eosinophils • Inflammatory process from invasion of bacteria into intestinal tissue Fun Facts – C. jejuni • Associated with Guillain-Barré syndrome • Antigenic cross-reactivity between surface LOS and peripheral nerve gangliosides • Characterized by development of symmetric weakness over several days – recovery takes months • Associated with reactive arthritis • Unrelated to severity of diarrheal disease • More common in patients that have the HLA-B27 phenotype • Characterized by joint pain and swelling of hands, ankles, and knees Clinical Disease – C. jejuni • Acute enteritis – most common thing to see • Diarrhea, fever, and severe abdominal pain • 10 or more bowel movements per day • Stools may be bloody • Generally self-limiting – symptoms may last for a week or longer • Can manifest as acute colitis and pseudoappendicitis Diagnosis – C. jejuni • Microscopy is difficult – thin, s-shaped organisms • Antigen detection • Commercial immunoassays • NAAT • Culture – tricky! • Elevated incubation temp (42°C) • Slow growing Treatment – C. jejuni • Typically managed by replacement of lost fluids and electrolytes • Antibiotics are used in severe infections/septicemia • Erythromycin or azithromycin for enteritis • People from endemic areas with chronic infection do show some protective antibody production Helicobacter pylori • Gram-negative, spiral rods • Highly motile – corkscrew motility • LPS aids bacteria in evading immune clearance • O side chain is antigenically similar to the Lewis blood group antigens – similar to our blood antigens • Humans are the primary reservoir • Life-long colonization unless specifically treated • Transmitted fecal-oral route H. pylori • Produce an abundance of urease • Important for survival in the gastric acids • Associated with gastritis, gastric ulcers, gastric adenocarcinoma, and gastric MALT lymphomas • >70% of patients are infected • Colonization appears to protect against GERD and adenocarcinomas of esophagus and gastric cardia – the urease neutralizes gastric acids Pathogenesis – H. pylori • Urease – neutralization of gastric acids • Localized tissue damage is mediated by urease Allow for colonization and by-products subsequent establishment of disease • Bacterial acid-inhibitory protein – blocks acid production • Motility allows for passage through gastric mucus • Adhesins allow for colonization and adherence to epithelial cells Virulence – H. pylori • Vacuolating cytotoxin A – VacA • Protein responsible for vacuole production after bacterial penetration into epithelial cells • Mediates localized tissue damage • Cytotoxin-associated gene – produces CagA • Injected into host cells by a type VI secretion system • Interferes with normal cytoskeletal structure of the epithelial cells • cag PAI gene induces IL-8 production • Attracts neutrophils  release protease and ROS • Thought to contribute to gastritis and gastric ulcers Clinical Disease – H. pylori • Gastritis • Infiltration of gastric mucosa by neutrophils/mononuclear cells • Acute phase • Feeling full, nausea, vomiting, and decreased acid production in the stomach • Can evolve into chronic gastritis • Chronic gastritis • Confined to the gastric antrum in patients with normal acid secretion • Whole stomach is involved if acid secretion is suppressed • 10-15% of these patients will develop ulcers Clinical Disease – H. pylori • Ulcers develop at the sites of intense inflammation • Gastric ulcer – Junction between corpus and antrum • Duodenal ulcer – Proximal duodenum • 85% of gastric ulcers and 95% of duodenal ulcers are a result of colonization • Barry Marshall* Clinical Disease – H. pylori • Gastric cancer • Chronic gastritis  replacement of normal gastric mucosa with fibrosa • Over proliferation of intestinal-type epithelium • Risk is increase 100-fol • cagA positive strains and high levels of IL-1 production are associated with higher risk for cancer • Infiltration of lymphoid tissue into gastric mucosa can evolve into MALT lymphoma Diagnosis – H. pylori • Microscopy of gastric biopsy specimen • Invasive! • Antigen detection for bacterial urease activity • Immunoassay for antigens – can test stool sample • Culture – difficult and time consuming Treatment – H. pylori • Combination of PPI, a macrolide, and a β-lactam • Omeprazole, clarithromycin, amoxicillin • 7-to-10-day treatment • Failure of treatment is most commonly associated with clarithromycin resistance Treponema pallidum • Thin, tightly coiled spirochetes • Difficult to see when Gram-stained or Giemsa stain • Found worldwide • Exclusive to humans • Etiological agent of syphilis • Transmitted by sexual contact Pathogenesis – T. pallidum • Enters the body through small abrasions on skin or mucous membranes • Local multiplication leads to infiltration of plasma cells, PMNs, and macrophages • Endarteritis can occur • Replicates very slowly – doubling time is ~30 hours • Incubation is ~ 3 weeks Clinical Disease – T. pallidum • Primary syphilis • 2 to 10 weeks after initial contact: • Bacteria multiply at site of infection • Primary chancre appears at site of infection – usually painless • Enlarged inguinal nodes • Proliferation of bacteria in regional lymph nodes • Spontaneous healing may/can occur • Patient still highly infectious Clinical Disease – T. pallidum • Secondary syphilis • 1-3 months after primary syphilis symptoms • Flu-like illness • Myalgia, fever, headache, mucocutaneous rash • Can spontaneously resolve • Multiplication of bacteria and production of lesions in: • Lymph nodes, liver, joints, muscles, skin, mucous membranes Clinical Disease – T. pallidum • Latent syphilis • ~2 to 6 weeks after secondary syphilis resolves • Treponemas are dormant in liver and spleen • Reactivation of treponemas leads to multiplication • Can last anywhere between 3 to 30 years Clinical Disease – T. pallidum • Tertiary syphilis • Progressive destructive disease • Dissemination and invasion • Cell mediated hypersensitivity • Neurosyphilis • “General paralysis of the insane” • Tabes dorsalis • Cardiovascular syphilis • Aortic lesions • Heart failure • Gummas in skin, bones, testes Clinical Disease – T. pallidum • Congenital syphilis • Infected mother transmits T. pallidum to baby in utero • Acquired after the first 3 months of pregnancy • Serious infection results in intrauterine death • Congenital abnormalities • Silent infection • Not apparent until about 2 years of age • Facial and tooth deformities Diagnosis – T. pallidum • T. pallidum can NOT be grown in laboratory • Depend on microscopy and serology • Exudate from primary chancre can be examined with dark-field microscopy – TEST • UV microscopy after staining with fluorescein antibodies • Silver staining can be done • Gram stain does not help diagnosis Syphilis Serology Tests • Non-specific tests – antigens are not from treponemas • Cardiolipin from beef hearts • Can give false positives • Sensitivity rate declines during tertiary syphilis • Specific tests – use recombinant proteins or treponemal antigens • • • • Confirm positive non-specific tests Used when clinical signs indicate disease Can remain positive for many years – good for latent/tertiary Can also give false positives Non-Specific Syphilis Tests • Cardiolipin allows for detection of anti-lipid IgG and IgM • Lipoidal material is released from damaged cells • Lipids in the surface of T. pallidum • VDRL test – the Venereal Disease Research Laboratory test • RPR test – rapid plasma reagin test • Positive within 4-6 weeks of infection • 1-2 weeks after primary chancre appears Specific Syphilis Tests • ELISA to detect IgM or IGG • FTA-ABS test – Fluorescent treponemal antibody absorption test • Patient’s serum is absorbed with nonpathogenic treponemes • Removes cross reacting antibodies • Detection of reaction with T. pallidum antigens • MHA-TP – microhemagglutination assay T. pallidum Treatment – T. pallidum • Penicillin is drug of choice • Reliably treats fetus when given to mother • Doxycycline if allergy to penicillin • Prevention of secondary and tertiary disease depends on early diagnosis and appropriate treatment • Congenital syphilis is treatable with early screening of mother • Treatment with penicillin Borrelia spp. • Neither Gram-positive or negative • Stain poorly • Microaerophilic and have complex nutritional needs • Makes them difficult to culture in the lab • Vectors are required for transmission to humans • B. burgdorferi – hard ticks • B. recurrentis – body louse Pathogenesis – B. burgdorferi – tick • Outer surface protein A (OspA) • Allows for binding specifically to the midgut of unfed ticks • When the ticks feed, the protein is downregulated – allows for passage in saliva • Outer surface protein C (OspC) • Critical for transmission from ticks to mammals • Upregulated during tick blood meal Clinical Disease – B. burgdorferi • Lyme disease • Begins as early localized infection – 3-to-30-day incubation • One or more skin lesions can develop at the site of the tick bite • Lesion begins as a small macule/papule • Enlarges over the next few weeks • Typically flat, red border, and central clearing • Erythema, vesicle formation, and central necrosis can also be seen • Lesion fades and disappears within weeks • May subsequently reappear Complications of Lyme Disease • Hematogenous dissemination will occur in untreated patients • Days to weeks of primary infection • Characterized by severe fatigue, headache, fever, malaise, arthritis and arthralgia, myalgia, erythematous skin lesions, cardiac dysfunction, and neurologic signs • Lyme arthritis develops in ~60% of untreated patients • 10-20% will develop neurological manifestations – facial nerve palsy • 5% will develop cardiac complications Diagnosis – B. burgdorferi • Microscopy/culture is not recommended • NAAT has mild success • Antibody detection – most commonly used • Immunofluorescence assay (IFA/EIA) • IgM antibodies appear 2-to-4-weeks after onset of symptoms Treatment – B. burgdorferi • Early manifestations of Lyme disease: • Amoxicillin, doxycycline, or cefuroxime • Lessens the likelihood and severity of late complications • Patients with recurrent arthritis or central/peripheral nervous system disease are treated with IV ceftriaxone, cefotaxime, or penicillin G • Post-Lyme disease syndrome is treated symptomatically • Antibiotics do not alleviate symptoms Pathogenesis – B. recurrentis • Lice become infected after feeding on an infected person • Organisms are ingested  pass through the wall of the gut • Multiply in the hemolymph • Disseminated disease does not occur in the louse • Human infection occur when the lice are crushed during feeding • Unsanitary conditions permit frequent contact with Clinical Disease – B. recurrentis • Relapsing fever • 1-week incubation period • Abrupt onset of shaking chills, fever, muscle aches, and headache • Splenomegaly and hepatomegaly are common • Bacteremic phase – resolve after 3-to-7-days • Bacteremia and fever return after ~1 week • Symptoms are generally milder and shorter Diagnosis – B. recurrentis • Microscopy • Blood specimen during febrile period with Giemsa-stain or Wright-stain • (+) in 70% of patients • Culture • Can be cultured on specialized media Treatment – B. recurrentis • Most effectively treated with tetracyclines or penicillins • Tetracyclines are preferred but contraindicated for pregnant people and children • Jarisch-Herxheimer reaction can occur in patients after treatment • Shock-like profile with rigors, leukopenia, increase in temp, decrease in BP • Rapid killing of borreliae and release of toxic products Leptospira spp. • Thin, coiled spirochetes • Characteristic hook at one or both ends • Motile! • 2 periplasmic flagella extending the length of bacteria • Anchored at the opposite ends • Obligate aerobes – optimum growth at 28°C to 30°C Leptospira • Worldwide distribution • Mandatory reporting of leptospirosis as of 2013 • Two types of hosts • reservoir host – endemic, chronic infections • incidental host – humans; person-to-person spread has not been documented • Most common reservoirs are rodents and small mammals • #1 zoonotic infection • Pathogenesis – Leptospira • Highly motile organisms • Penetrate intact mucous membrane or skin through cuts/abrasions • Spread to all tissues through blood • Including the CNS • Multiply rapidly and damage endothelium of small blood vessels • Results in major clinical manifestations • Clearance depends on humoral immunity development Clinical Disease – Leptospira • Leptospirosis • Infection is introduced through skin abrasions or conjunctiva • Symptomatic infection develop after a 1-to-2-week incubation period • Occurs in 2 phases • Initial phase is similar to influenza-like illness • Fever, myalgia, chills, headache, vomiting, diarrhea • Patient can progress to second phase – more severe disease • Sudden onset of headache, myalgia, chills, abdominal pain, conjunctival reddening • Vascular collapse, thrombocytopenia, hemorrhage, and hepatic/renal dysfunction are possible Clinical Disease – Leptospira • Weil disease – hepatitis • Icteric form of leptospirosis • Associated with a higher mortality (10-15%) • More severe form of disease • Hepatic necrosis is usually not seen • Surviving patients do no suffer from permanent hepatic damage Clinical Disease – Leptospira • Leptospirosis – in the CNS • Mistaken for aseptic viral meningitis • CSF is typically culture negative • Low mortality rate • Generally uncomplicated disease Diagnosis – Leptospira • Microscopy is not great • Leptospires are thin – difficult to see • Culture – possible but difficult • Require incubation for ~4 months • Antigen detection • Microscopic agglutination test 5-to-7 days after onset Treatment – Leptospira • IV penicillin or doxycycline • Doxy can be used to prevent disease after exposure • Eradication is difficult because of worldwide spread of disease • Wild and domestic animals • Vaccination of livestock and pets has been successful in reducing incidence of disease Intracellular Bacteria Murray’s Basic Medical Microbiology, Chapter 11 Overview • Rickettsia rickettsii • Coxiella burnetii • Chlamydia trachomatis Rickettsia rickettsii • Structurally similar to Gram-negative rods • Minimal peptidoglycan layer – poor staining • Grow ONLY in the cytoplasm of eukaryotic cells • Maintained in rodent hosts – reservoirs • Transmitted through ticks • Transovarian transmission occurs in the ticks- mom to child • 3 hard ticks are associated with disease in the US • Dog tick, brown dog tick, wood tick – TEST Pathogenesis – R. rickettsii • Outer membrane protein A (OmpA) • Expressed on the surface of the bacterium • Responsible for bacterial adherence to endothelial cells • Clinical manifestation are a result of bacterial replication in endothelial cells • Damage to cells and leakage of blood vessels • Cytokine-mediated intracellular killing and clearance by cytotoxic CD8 T cells are responsible for clearance Clinical Disease – R. rickettsii • Rocky Mountain Spotted Fever (RMSF) • Symptoms appear ~7 days after tick bite • High fever and headache – aggressively high fever • May also have malaise, myalgias, nausea, vomiting, abdominal pain, diarrhea • Hallmark of disease  macular rash after ~3 days • Initially wrists, arms, and ankles – spreads inward towards the trunk – • Spotted or petechial form • Complications can include neurological manifestations, pulmonary and renal failure, and cardiac abnormalities TORY YOU WILL BE TESTED ON THIS BACTERIA Diagnosis and Treatment – R. rickettsii • Diagnosis • Microimmunofluorescence • Detects antibodies directed against outer membrane proteins and LPS • Western blot immunoassay • Help determine specific species/strain • Treatment • Doxycycline – recommended for all patients with suspected disease regardless of age or pregnancy Coxiella burnetii • Gram-negative – but stain weakly • Grow intracellularly • Very slow replication inside the cell • Causative agent of Q fever • Farm animals and recently infected pets are the primary reservoir for human disease • Bacteria reach very high concentrations in placenta of infected livestock C. burnetii • Extremely stable bacterium • Survives in soil and milk for months • Human infection occurs after inhalation • Less commonly from contaminated milk • Very small infectious dose – < 10 bacteria • Ranchers, veterinarians, and food handlers are more likely to be infected • TICKS DO NOT TRANSMIT DISEASE TO HUMANS – TEST Q Phase Variation – C. burnetii • Two structural variants • Small cell variant – resistant to environmental stress – lives in soil and milk • Large cell variant – metabolically active form • Phase I • Observed in nature – Intact LPS • Prevent phagosome-lysosome fusion • Phase II • Mutation occurs resulting the absence of the outermost O-antigen sugars • Unable to prevent phagosome-lysosome fusion Pathogenesis – C. burnetii • Regulates cell signaling to prevent apoptosis • Acute vs chronic disease depends on intracellular survivability • Small cell variants attach to macrophages/monocytes • Internalized in a phagocytic vacuole • IFN-γ causes phagosome-lysosome fusion  bacterial death • Acute infection • IL-10 overproduction  no fusion • Intracellular survival – chronic infection Clinical Disease – C. burnetii • Q fever • Mild, nonspecific flulike symptoms • Abrupt onset of high-grade fever, fatigue, headache, myalgia • <5% need hospitalization • Common presentations in severe cases include hepatitis and pneumonia • Pneumonia is mild with nonproductive cough and nonspecific finding on radiographs Clinical Disease – C. burnetii • Chronic Q fever • Symptoms lasting >6 months • Develops months to years after initial exposure • Typically seen in patients with predisposing conditions • Underlying valvular heart disease or immunosuppression • Subacute endocarditis is the most common presentation • Difficult to diagnosis – lack of specific signs and symptoms Diagnosis – C. burnetii • Serology is the most commonly used diagnostic test • Microagglutination tests • Indirect immunofluorescence antibody • ELISA • Detection of immunoglobulins to phase II antigens  acute Q fever • Mutated LPS • Detection of immunoglobulins to phase I and II antigens  chronic Q fever • Phase 1 has intact LPS Treatment – C. burnetii • Doxycycline for 14 days • Chronic disease should be treated with combination of doxycycline and hydroxychloroquine • Vaccination available but only used on those who have never been infected • Increased stimulation of the immune system in those who have been previously infected- leads to cytokine storm Chlamydia trachomatis • Very small, intracellular bacteria • Exists in different forms • Elementary body (EB) – adapted for extracellular survival and initiation of infection • Reticulate body (RB) – adapted for intracellular multiplication C. trachomatis • Most common bacterial STI • Limited range of cells can be infected • Nonciliated columnar, cuboidal, and transitional epithelial cells • EBs are metabolically inactive INFECTIOUS forms • Cannot replicate • Accumulated RBs in the phagosome are called inclusions • Energy parasites • Use host ATP for energy requirements Sexually transmitted bacteria are D-K Know what the serotypes cause Serotypes of Chlamydia Trachoma – serious eye infection Cervicitis – infection/inflammation of cervix Urethritis – infection/inflammation of urethra Proctitis – infection/inflammation of prostate Conjunctivitis – infection/inflammation of conjunctiva; eye infection Pneumonia – infection in the lungs Lymphogranuloma venereum – chronic infection of the lymphatic Transmission – C. trachomatis • Most infections are genital • acquired through sexual contact • Neonates develop ocular infections from passage through birth canal • Adult ocular infections can also occur STORY YOU WILL BE TESTED ON THIS BACTERIA Nutting on her face can give her an eye infection Pathogenesis – C. trachomatis • Chlamydiae enter host through small abrasions in mucosal surfaces • Bind to specific receptors on host cell  “parasite induced” endocytosis Inside the cell lysosomal fusion is inhibited EB begins its developmental cycle EB differentiate into metabolically active RBs RBs divide and produce fresh EB progeny Released into extracellular environment Pathogenesis – C. trachomatis Infection – C. trachomatis • Clinical symptoms result from cell destruction • Host inflammatory response • Released EBs invade adjacent cells • If carried in blood/lymph – infect distant cells • Serotypes D-K restricted to columnar and transitional epithelial cells • Asymptomatic in most women • Symptomatic in men • Serotypes L1, L2,L3 can cause systemic disease Presentation – C. trachomatis • Most genital tract infections are asymptomatic • Can result in PID in women (Pelvic inflammatory disease= PID) • Clinical manifestations can include cervicitis and endometritis • Bartholinitis, perihepatitis, salpingitis, urethritis • Mucopurulent discharge is seen in symptomatic infections • Can be cultured! (If there is an active infection) Diagnosis – C. trachomatis • Microscopy using direct fluorescent antibody test • EBs stain bright yellow-green • Not sensitive for asymptomatic infections • Nucleic-acid-based tests are capable of directly testing • Nucleic acid probe and amplification tests • Specimen from cervix, urethra, urine, etc. can be used • Commercially available – rapid results Treatment – C. trachomatis • C. trachomatis is NOT susceptible to β-lactam antibiotics • Azithromycin is typically prescribed • Prescribed along with β-lactam antibiotics for concurrent infections • Prescribed to partners as well • Erythromycin should be used in babies • Prevention = condoms Lymphogranuloma venereum • Chronic state of inguinal lymphadenopathy • Systemic infection involving lymphoid tissue • Common in Africa, Asia, and South America • Sporadic in Europe, Australia, and North America • Affects males > females • Especially men who have sex with men • Caused by C. trachomatis serotypes L1, L2, L3 Lymphogranuloma venereum • Primary lesion is an ulcerating papule at the site of inoculation • Occurs after 1-4 weeks • Accompanied with fever, headache, myalgia • Lesion will heal quickly • Chlamydiae infect draining lymph nodes  inguinal buboes • Chlamydiae can disseminate from the lymph nodes to rectum • Proctitis • Systemic complication can include fever, hepatitis, pneumonitis, meningoencephalitis Lymphogranuloma venereum Complications • Untreated infection may resolve • Abscesses may form in lymph nodes • These can suppurate and discharge through skin • Chronic granulomatous reactions in lymphatics and neighboring tissues • Cause fistula in ano or genital elephantiasis Lymphogranuloma venereum Diagnosis and Treatment • Cell culture, immunofluorescence, nucleic-acid based tests for diagnosis • Same as with C. trachomatis • Treatment with doxycycline or erythromycin • Pregnant women and children < 9 years old should be treated with erythromycin Chlamydial Ocular Infections • Different serotypes of C. trachomatis cause inclusion conjunctivitis and trachoma • Serotypes D-K are responsible for inclusion conjunctivitis • Serotypes A, B, Ba, and C are responsible for trachoma Trachoma • Transmitted by contact • Contaminated flies, fingers and towels • Result of chronic repeated infection • Especially prevalent when there is poor access to water • ~200 million people worldwide suffer with trachoma • 10% are visually impaired • Trachoma is endemic in “resource-poor” countries Neonatal Conjunctivitis • Some serotypes can infect the urogenital tract as well as the conjunctiva • Can also cause pneumonia in the neonate • Newborns become infected during passage through an infected birth canal • Requires systemic treatment with ERYTHROMYCIN Chlamydial Conjunctivitis Diagnosis and Treatment • Nucleic acid amplification tests (NAATs) are the most accurate for laboratory diagnosis • Trachoma is diagnosed clinically • Treatment with topical or oral antibiotics • Azithromycin, doxycycline • NEONATES RECEIVE ERYTHROMYCIN (not doxy) – Chlamydia pneumoniae • Human pathogen – obligate intracellular pathogen • Person-to-person transmission via respiratory droplets • Elementary & reticulate bodies • Most infections are asymptomatic or mild bronchitis w/persistent cough, sinusitis, malaise • More severe respiratory infections – pneumonia • Typically involves a single lobe 80 Chlamydia psittaci • Zoonotic disease • Transmission by inhalation of dust contaminated with respiratory secretions or feces of infected birds, especially parrots – psittacosis or parrot fever • Bronchitis or pneumonia • Hepato/splenomegaly 81 82 Questions?