Microbes PDF

Microbes - Streptococcus pyogenes - Opportunistic pathogen - Frequently isolated from upper respiratory tract (normal flora) - Mode of transport: spreads by respiratory droplets - Causes strep throat - Symptoms: severe sore...

Microbes - Streptococcus pyogenes - Opportunistic pathogen - Frequently isolated from upper respiratory tract (normal flora) - Mode of transport: spreads by respiratory droplets - Causes strep throat - Symptoms: severe sore throat, enlarged tonsils, tonsillar exudates, tender cervical lymph nodes, and mild fever - Cause infections of inner ear (otitis media), mastitis (inflammation of mammary glands), and impetigo (infections of superficial layers of the skin - Causes rheumatic fever (linked to untreated or undertreated strep - Causes scarlet fever - Causes pink-red rashes to develop - Damages small blood vessels - Initiates fever - Can cause necrotizing fasciitis (rare) - Exotoxins A and B and superface M-protein act as superantigens - Cause streptococcal toxic shock-like syndrome - Symptoms: similar to TSS (fever, rash, vomiting, diarrhea - Cause respiratory distress syndrome - About 50% develop bacteremia and necrotizing fasciitis - Develops in patients with streptococcal soft-tissue infections - Streptococcus pneumoniae - Frequently isolated from upper respiratory tract (normal flora) - Causative agent of lung infections that develop as secondary infections to other respiratory disorders - Can cause meningitis (rare) - Cause pneumonia - Opportunistic pathogen - Some strains act as superantigens - Streptococcus agalactiae - Normal flora of female genital tract and lower gastrointestinal tract - Cause infections in neonates and pregnant women  - Occasionally colonizes upper respiratory tract (more in babies) - Causative agent of septic arthritis - Opportunistic pathogen - Infection in pregnant women usually involve postpartum infections like endometritis which can lead to pelvic abscesses and septic shock - Infections in neonate can be transmitted by: - Mother to baby: in utero or during delivery - Nosocomially: from mother, healthcare worker, or family member - Symptoms: sepsis, fever, meningitis, respiratory distress, lethargy, and hypotension - Two types: early onset (first 5 days of life) and late onset (7 days to 3 months after birth) - Streptococcus bovis - Veterinary pathogen - Causes mastitis - Rare for humans to have - Streptococcus salivarius and Streptococcus mitis - Non pathogenic (don’t cause disease) - Normal flora of the mouth - Obligate fermenters - Associated with formation of dental caries (tooth decay) - Enterococcus faecalis - Normal flora of intestinal tract - Non pathogenic - Isolated from fecal sample Microbes - Neisseria gonorrhoeae - Primary pathogen - Causative agent of gonorrhea - Sexually transmitted infection - Gonococcal infections primarily occur in the urethra, endocervix, anal canal, pharynx, and conjunctiva - Most common sexually transmitted bacterial infection in the U.S.  - Asymptomatic carriers are common (carry as normal flora) - Incubation period: 2 - 7 days - Disease in males: - 3%-5% are asymptomatic (95%-97% develop symptoms) - Acute urethritis (inflammation of urethra) - purulent discharge (from urethra) and dysuria (painful urination) - Complications: ascending infections including prostatitis and epididymitis - Disease in females: - Up to 50% are asymptomatic - Endocervix is site of infection - vaginal discharge, dysuria, lower abdominal pain, vaginal bleeding - Complications: pelvic inflammatory disease (inflammation of female reproductive organs) which can lead to sterility or ectopic pregnancy (fertilized egg does not drop) - Disease in neonates: - Ophthalmia neonatorum - gonococcal eye infection - Occurs during vaginal delivery through infected birth canal - May result in blindness - All neonates receive antibiotic drops in eyes right after birth for prevention - Disseminated infections: rare, cause arthritis, septicemia, fever, and rash - Other infections: anorectal and oropharyngeal infections - Treatment: penicillin (until 1976); ceftriaxone (since 1976) - Neisseria meningitis - Found in nasopharynx and oropharynx (normal flora) - Carrier rates vary with age, socioeconomic status, living conditions, etc - Causative agent of endemic and epidemic meningitis, meningococcemia, and pneumonia - Mode of transmission: respiratory droplets - Epidemic meningitis is mostly observed in young adults (teens - 20s)  - Symptoms: abrupt onset of frontal headaches, stiff neck, sensitivity to light, and sometimes fever - Petechial skin lesions may occur - Treatment: penicillin for patients; rifampin for close contacts - Branhamella catarrhalis - Opportunistic pathogen - Normal flora of respiratory tract - Associated with a number of infections: - Pneumonia (less likely, but possible) - Sinusitis: inflammation of sinuses - Acute otitis media: inner ear infection - Systemic disease - Formally known as Neisseria catarrhalis - Changed to Branhamella in 1974 - Late 1970s to early 1980s: changed to Moraxella - Listeria monocytogenes - Causes listeriosis - Found in soil, water, vegetation, and animal products - Uncommon but serious infection especially in: - Neonates - Pregnant women - Immunocompromised hosts - Can occur in healthy people (much less likely) - Disease in pregnant women: - Lead to miscarriage and stillborn neonates - Experience flu-like symptoms: - Body aches and pains - Lethargy - Fever - Headache - Myalgia (pain without known cause) - May progress and result in premature labor or septic abortion within 3-7 days after contracting listeriosis  - Infection is considered as self-limited because source of infection is eliminated when birth occurs - Disease in neonates: - Fatality rates are very high - 2 forms of neonatal listeriosis: - Early onset: result from intrauterine infection that can cause illness at or shortly after birth (hours or days); result is most often sepsis - Late onset: occurs several days to weeks after birth; infants are generally healthy and full term; most likely present as meningitis; lower fatality rate; by family or healthcare worker - Disease in immunocompromised: - Common manifestations are central nervous system infections and endocarditis - Affected patients usually present with meningitis, meningoencephalitis, or sepsis - Disease in healthy individuals - Occur via intestinal tract - Causes meningitis; fatality rate is high - Responds well to penicillins - Lactobacillus species - Non pathogenic - Normal flora of vaginal tract - Produce lactic acid and ferments sugars (glycogen and glucose) - Influence hormones - Corynebacterium xerosis - Commonly found on skin and mucocutaneous sites - Opportunistic pathogen - Bacteremia associated: - Intravenous catheters - Post-surgical wound infections - Pneumonia - Opportunistic infections:  - Prosthetic valve endocarditis - Corynebacterium ulcerans - Veterinary pathogen - Causes mastitis - Never really seen in humans unless they work with animals or ingest unpasteurized dairy - Corynebacterium jeikeium - Normal flora of the skin - Opportunistic pathogen - Common cause of diphtheroid prosthetic valve endocarditis in adults - Typically seen in people who are immunocompromised or have undergone invasive surgery - Antibiotic resistant (wide range) - Corynebacterium pseudotuberculosis - Veterinary pathogen - Causes something that looks like tuberculosis - Human cases are rare - Corynebacterium pseudodiphtheriticum - Normal flora of the human nasopharynx - Opportunistic pathogen - Rarely cause infection but when it does, it takes the form of endocarditis - Possible to have respiratory and urinary tract infections but only in people who are immunocompromised or worse - Corynebacterium diphtheriae - Causative agent of diphtheria - Primary pathogen - Produces a toxin (diphtheria toxin) - Strains that do not produce toxin are non-pathogenic - Humans are only host - Spread by respiratory droplets or hand-to-mouth contact - Carried in upper respiratory tract - Characterized by: - Fever  - Malaise (don’t feel like self) - Mild sore throat - Common site of infection are tonsils or pharynx - Treated by shot of antitoxin - Bacillus cereus - Can cause food poisoning - Opportunistic pathogen - Take 2 forms: - Diarrheal: ingestion of some kind of protein; abdominal pain, cramping, and many amounts of diarrhea - Strains produce heat-labile enterotoxin - Emetic: abdominal cramping, abdominal pain with vomiting; can be from food prepared in large quantities - Produce heat stable emetic toxin - Causes the vomiting - Two forms of illness are caused by 2 distinct enterotoxins produced by B. cereus; both forms are mild and self-limiting - Bacillus anthracis - Found in soil everywhere worldwide - Veterinary pathogen - Causes anthrax (in animals) - Cause skin infection, gastrointestinal infection, or respiratory (animals?) - 3 forms: (in humans) - Cutaneous: enter skin through some kind of break (scrape or cut) - Leads to tissue death because of the production of an anthrax toxin - Inhalation: rapid progression from mild flu-like symptoms (mild fever, aches and pains) to respiratory distress, death - Gastrointestinal: ingested in some kind of food source - Can cause severe diarrhea, vomiting, and bloody diarrhea - Produces complex toxin (edema factor, protective antigen, lethal factor - Edema factor + protective antigen = edema - Protective antigen + lethal factor = fatal infection (death) - Why? Toxic increases vascular permeability and interferes with phagocytosis