MEDICAL BACTERIOLOGY 2

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MEDICAL BACTERIOLOGY 2 by Mind Map: MEDICAL BACTERIOLOGY 2

1. Gram-negative Cocci (Neisseria)

1.1. Overview

1.1.1. Two pathogenic spesies

1.1.1.1. Neisseria gonorrhae (gonococci)

1.1.1.1.1. - oxidize glucose - transmitted mostly by sexual contact - not a part of normal flora - highly variable structure of pill - has other antigenic protein: Por, Opa, Rmp - cell wall consist of lipooligosaccharide which contributes to molecular mimicry - produce IgA1 protease with which inactivates IgA1 - ability to conduct rapid switching from one antigenic from to another contributes to its ability to escape from immune system - has more than two plasmids that encodes TEM-1 - can attack most mucosal membranes (producing acute suppuration) - diagnosis by finding Gram (-) diplococci intra and extracellular of PMN from Gram-stained smears

1.1.1.1.2. Lab diagnosis (WHO, 2012)

1.1.1.1.3. Treatment

1.1.1.1.4. Prevention and Control

1.1.1.2. Neisseria meningitides (meningococci)

1.1.1.2.1. - at least 13 serogroups has been identified - has 3 type of OMP which are comparable to gonococci's Por protein and helpful in bacterial attachment - Opa protein is comparable with gonococci - has pili, but is nit as distinctive as gonococci - has lipopolyasccharides on cell wall - can be part of normal flora in nasopharynx - mostly caused meningitis in susceptible host, with hemorrhagic rash in fulminant case

1.1.1.2.2. Treatment and Control

1.1.2. Appears as non-motile diplococci

1.1.3. Grows well in Thayer Martin selective medium after aerobic incubation for 48 hours

2. Gram-negative Bacilli (Enterobacteriaceae)

2.1. General chracteristic

2.1.1. - family Enterobacteriaceae consist of large number of species inhabiting both living and non-living environment - commonly lives in human GIT as opportunistic organism, thus also fequently described as enteric bacilli - some are responsible to nosocomial infections - most are facultative anaerobes - gives negative reaction to oxidase test

2.2. Morphology

2.2.1. - small (0.5 by 3.0 μm) - gram negative - non-spore-forming rods - most are motile (peritrichous flagella) - some posses well-defined capsule - most have fimbriae or pili - the cell wall is composed of murein and lipopolysaccharides; cell membrane consist of lipopotein, phospholipids and protein

2.3. Biochemical reactions

2.3.1. Act as identification method for Enterobacteriaceae (TSI - iMViC) - TSI (Triple Sugar Iron) - Indole - Methyl Red - Voges Proskauer - Citrate - Urease

2.3.2. Lactose fermentation also act as presumptive identification

2.4. Diagnosis

2.4.1. Specimens

2.4.1.1. sputum, tissue, pus, body fluids, rectal swabs or feces

2.4.2. These specimens must be cultured immediately or placed in an appropriate transport medium such as Stuart's or Amies medium

2.5. Culture Medium

2.5.1. Differential Medium

2.5.1.1. Eosin Methylene Blue (EMB)

2.5.2. Selective Differential Medium

2.5.2.1. Salmonella-Shigella (SS)

2.5.3. Highly Selective Medium

2.5.3.1. Bismuth Sulfite Agar (BSA)

2.5.4. Enrichment Medium

2.5.4.1. GN Broth

2.6. Antigenic Structure

2.6.1. Plays important role in epidemiology and classification

2.6.2. Major component consist of:

2.6.2.1. Antigen K

2.6.2.1.1. Capsular antigen

2.6.2.1.2. Vi antigen in S. Typhi

2.6.2.2. Antigen H

2.6.2.2.1. Flagellar antigen

2.6.2.3. Antigen O

2.6.2.3.1. Somatic antigen

2.6.2.3.2. Lipopolysaccharides

2.7. Pathogenicity

2.7.1. Exotoxin

2.7.1.1. usualy affect the small intestine, thus called enterotoxin

2.7.1.2. causing a transduction of fluid into the intestinal lumen (diarrhea)

2.7.2. Endotoxin

2.7.2.1. Lipopolysaccharides on cell wall

2.7.2.2. Toxicity resides in the lipid A

2.7.2.3. produce a variety of effects such as fever, fatal shock, leucocytuc alteration, regression of tumor

3. True Pathogens (Salmonella, Shigella, Yersinia)

3.1. Salmonella

3.1.1. - composed of serologically diverse group of microorganisms (over 2000 serotypes) - causes many clinical manifestations, mainly on GIT - mostly facultative intracellular bacteria

3.1.2. Characteristics

3.1.2.1. - unable to ferment lactose - most are motile (except S. gallinarum and S. pullorum) - produce H2S from inorganic sulfur source thiosulfate - most produce gas from glucose, except S. Typhi - intolerant to relatively large concentration of bile

3.1.3. Pathogenicity

3.1.3.1. Has antigenic structure as follow: H, O, Vi

3.1.3.2. Salmonella are complex organisms that produce variety of virulence factors including - surface antigens - factors contributing to invasiveness - endotoxin - cytotoxins - enterotoxins

3.1.4. Clinical Manifestations

3.1.4.1. Gastroenteritis

3.1.4.2. Septicemia

3.1.4.3. Enteric fever (typhoid fever)

3.1.5. Isolation and Diagnosis

3.1.5.1. Specimens

3.1.5.1.1. Blood, stool, urine or bone marrow aspirates, depends on patient condition

3.1.5.1.2. Specimens are isolated on culture mediums (identification using biochemical reactions)

3.1.5.2. Serology or CPR

3.1.6. Treatment

3.1.6.1. Gastroenteritis

3.1.6.1.1. - usually self-limited - supportive and symptomatic therapy

3.1.6.2. Typhoid fever of septicemia

3.1.6.2.1. - 1st line: ampicillin, chloramphenicol, cotrimaxazole - MDR case: fluoroquinolone, i.e. ciprofloaxacin - Cholecystostomy may be indicated for carrier

3.2. Shigella

3.2.1. - major cause of bacillary dysentery - genetically indistinguishable from Escherichia coli - divided into 4 major serogroups( S. dysenteriae, S. flexneri, S. boydii, S. sonnei) - mostly non-lactose fermenter except S. sonnei - nonmotile - most do not produce gas, exceptt S. flexneri serotype 6 - cannot produce lysine decarboxylase - cannot use acetate as carbon source - mostly infect local organ and rarely spread into other organs - can multiply within bowel up to 10^8/ml

3.2.2. Pathogenicity

3.2.2.1. Facultative intracellular bacteria

3.2.2.2. 4 major O antigenic groups: A, B, C, D

3.2.2.3. Virulent Shigella penetrates mucosa of colon

3.2.2.4. Shigella carries gene for Shiga-toxin (acts as neurotoxin, cytotoxin and enterotoxin)

3.2.2.5. Shigellosis has wide spectrum of manifestation from asymptomatic to serve bacillary dysentery

3.2.3. Isolation and Diagnosis

3.2.3.1. Most commonly isolated from clinical specimens (S. flexnery)

3.2.3.2. Specimens: recta swab or stool

3.2.3.3. The specimens are inoculated into differential media such as MacConkey, HE or SS agar

3.2.3.4. Confirmation is based on biochemical reactions and serologic typing

3.2.4. Treatment

3.2.4.1. Immidiate concern is shigellosis is rehydration

3.2.4.2. Drug of choice: ampicillin, amoxicillin, cotrimoxazole, tetracyline, chloramphenicol

3.2.4.3. Shigellosis prevention involves adequate sanitation and hygine, also detecion of carrier

3.3. Yersinia

3.3.1. - previously classified in the genus Pasteurella - three human pathogen species below are originally animal pathogens, but show ability to clinically manifest in human > Yersinia enterocolitica & Yersinia pseudotuberculosis (enteritis) > Yersinia pestis (pes/plague)

3.3.1.1. Y. enterocolitica & Y. pseudotuberculosis

3.3.1.1.1. Motil with peritrichous flagella

3.3.1.1.2. Never produce capsule, urease (+), H2S (-), TSI A/A

3.3.1.1.3. Both are transmitted by animals

3.3.1.1.4. Humans areinfected by ingestion of contaminated materials

3.3.1.1.5. Both need high load of bacteria to cause infection in human

3.3.1.1.6. Manifestation appears as diarrhea (from watery to bloody) with later onset of athralgia, arthitis and erythema nodosum

3.3.1.1.7. Specimens for diagnosis: stool, blood or other contaminated substance

3.3.1.1.8. Specimens must undergo cold enichment for 2-4 weeks in 4°C with pH 7.6

3.3.1.1.9. Mostly self-limited

3.3.1.1.10. Drug of choice: aminoglycosides, chloramphenicol, tetracycline, co-trimoxazole, third generation of cephalosporins, and fluroquinolones

3.3.1.1.11. It is typically resistant to ampicillin and first generation of cephalosporins

3.3.1.2. Y. pestis

3.3.1.2.1. Plague is originally a disease of wild rodents

3.3.1.2.2. Infect human by flea bites

3.3.1.2.3. Appears as facultative anaerobe nonmotile cocobacilli

3.3.1.2.4. Does not ferment lactose, but produce catalase and coagulase

3.3.1.2.5. Grows on wide range of temperature (0-43°C)

3.3.1.2.6. Specimens: bubi aspirates, sputum, blood, cerebrospinal fluid

3.3.1.2.7. Direct smear: Giemsa or Wayson

3.3.1.2.8. Drug of choice: steptomycin

4. Opportunistic Pathogens

4.1. Escherichia

4.1.1. - most known species: E. coli - motile and most appear as lactose-fermenter - grows easily in many culture medium and gives metallic sheen in EMB - generally resides in human as normal flora

4.1.2. Diagnosis and Treatment

4.1.2.1. Easily grows in many media

4.1.2.2. Culture and biochemical reactions are standard identification, infection of pathogenic E. coli can be considered in absence of true enteropathogen

4.1.2.3. Therpy consists of definitive, supportive and symptomative

4.2. Klebsiella

4.2.1. - most commonly isolated (K. pneumoniae) - most are lactose fermenting, except K. rhinosclerosis and K. ozaenae - nonmotile organisms with capsule - causes wide range of clinical condition and ofter multiresistant to antimicrobial agents - mostly produce beta-lactamase

4.3. Enterobacter

4.3.1. - inhabits human body and environment - motile and rapid lactose fermenter - some has capsule similar to Klebsiella - less frequently isolated than Klebsiella and E. coli and mostly associated with UTI (some cases are reported as sepsis) - commonly produce cephalosporinase which contributes to high resistance

4.4. Serratia

4.4.1. - easily distinguished from other Enterobacteriaceae from their ability to produce DNAse, lipase and gelatinase; also their resistance to colistin and cephalotin - mostly cause nosocomical infections - drug of choice is usually aminoglycosides, chloramphenicol, quinolon or contramoxazole

4.5. Proteus

4.5.1. - notable pathogen: P. mirabilis, P. vulgaris which are both motile and cause swarming in agar plates - all members can cause human infections, mostly occur as UTI with alkaline pH. The increasing pH may cause calculi formation - all members are resistant to tetracycline and most are sensitive to aminoglycoside and contrimoxazole