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Microbiologyof Bone & Joint InfectionsMyositisMyositis refers to any condition causing inflammation in one or more muscles

Weakness, swelling, and pain are the most common myositis symptoms

Myositis causes include infection, injury, autoimmune conditions, and drug side effects

Treatment of myositis varies according to the causeCauses of MyositisMyositis is caused by any condition that leads to inflammation in the muscles

Myositis causes can be divided into several major categories:

Inflammatory conditions causing myositisMyositis caused by microbial infectionMyositis caused by drugsMyositis due to injuryMyositis caused by microbial infectionKnown pathogens include the following:

ViralHIV (one of the most common causes of myositis), HTLV-1, Cytomegalovirus, Coxsackie B virus (epidemic myalgia), Influenza

BacterialS. aureus (most common, 70%); Streptococcus viridans; Salmonella enteritidis; Neisseria species , Yersinia species

SpirochetalBorrelia burgdorferi

MycobacterialMycobacterium avium

ParasiticEchinococcus granulosus, Taenia solium, T. cruzi

FungalCryptococcus neoformans, Candidaspecies, Histoplasma capsulatum, Aspergillusspecies

Symptoms of MyositisThe main symptom of myositis is muscle weakness that may be detectable with testing

Muscle pain (myalgias)

Dermatomyositis, polymyositis

The weakness affects large muscle groupsincluding the neck, shoulders, hips, and back

DermatomyositisDermatomyositis (DM) is a connective-tissue disease related to polymyositis (PM) that is characterized by inflammation of the muscles and the skin6

DermatomyositisThe weakness from myositis can lead to fallsmake it difficult to get up from a chair or after a fall

Other myositis symptoms that may be present with inflammatory conditions include:

RashFatigueThickening of the skin on the handsDifficulty swallowingDifficulty breathingDiagnosis of MyositisBlood testsMagnetic resonance imaging (MRI scan)Electromyography (EMG)Muscle biopsy

9OsteomyelitisOsteomyelitis is an infection in a bone

Infections can reach a boneby traveling through thebloodstream or spreadingfrom nearby tissue

Osteomyelitis can also beginin the bone itself if an injuryexposes the bone to germs

Osteomyelitis of the tibia of a young childIn childrenmost commonly affects the long bones of the legs and upper arm

In adultsmore likely to develop osteomyelitis in the bones that make up the spine

People who have diabetesmay develop osteomyelitisin their feet if they have foot ulcers

Plantar foot ulcers with a deep space infectionOnce considered an incurable condition, osteomyelitis can be successfully treated today

Most people require surgery to remove parts of the bone that have diedfollowed by strong antibioticsoften delivered intravenouslytypically for at least six weeksSymptomsSigns and symptoms of osteomyelitis include:

Fever or chillsIrritability or lethargy in young childrenPain in the area of the infectionSwelling, warmth and redness over the area of the infectionCausesMost cases of osteomyelitis are caused by staphylococcus bacteria

Germs can enter a bone in a variety of ways, including:Via the bloodstreamFrom a nearby infectionDirect contaminationVia the bloodstreamGerms in other parts of the body can travel through bloodstream to a weakened spot in a bone

From a nearby infectionSevere puncture wounds can carry germs deep inside the bodyIf such an injury becomes infected, the germs can spread into a nearby bone

Direct contamination

This may occur if a bone have broken so severely that part of it is sticking out through skin

Direct contamination can also occur during surgeries to replace joints or repair fractures16Disease causative agentAge groupMost common organismsNewborns(younger than 4 mo)S. aureus,Enterobacterspecies, andgroup AandB StreptococcusspeciesChildren (aged 4 mo to 4 y)S. aureus, group AStreptococcusspecies,Haemophilus influenzae, andEnterobacterspeciesChildren, adolescents (aged 4 y to adult)S. aureus(80%), group AStreptococcusspecies,H. influenzae, andEnterobacterspeciesAdultS. aureusand occasionallyEnterobacterorStreptococcus speciesSickle cell anemia patientsSalmonellaspecies are more common in patients with sickle cell disease than in normal patients. However, S. aureus is still most likely to occur.Acute Osteomyelitis Vertebral osteomyelitis can occur in adults secondary to a UTI or prostatitis

Candidemia from infected central venous catheters can lead to fungal osteomyelitis

Contiguous infectionBacteria related to primary focus, it includesGram positive cocci, Gram negative bacilli, Anaerobes, and Poly-microbial infection

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Risk factorsBones are normally resistant to infectionFor osteomyelitis to occur, a situation that makes your bones vulnerable must be present

Recent injury or orthopedic surgeryA severe bone fracture or a deep puncture woundSurgeryDeep animal bites19Circulation disordersWhen blood vessels are damaged or blockedWhat begins as a small cut can progress to a deep ulcer that may expose deep tissue and bone to infection

Diseases that impair blood circulation includePoorly controlled diabetesPeripheral arterial diseaseoften related to smokingSickle cell disease

Peripheral vascular diseaseProblems requiring intravenous lines or catheters

Examples of when this type of tubing might be used includeDialysis machinesUrinary cathetersLong-term intravenous tubing21Conditions that impair the immune system

Factors that may suppress your immune system includeChemotherapyPoorly controlled diabetesHaving had an organ transplantNeeding to take corticosteroidsFor unclear reasonspeople with HIV/AIDS don't seem to have an increased risk of osteomyelitis

Illicit drugsnonsterile needlesunsterilized skin before injections

ComplicationsOsteomyelitis complications may include:

Bone death (osteonecrosis)Septic arthritisImpaired growthSkin cancer

OsteonecrosisTests and diagnosisBlood testsImaging testsX-raysComputerized tomography (CT) scanMagnetic resonance imaging (MRI)Bone biopsy

Treatments and drugsThe most common treatments for osteomyelitis are antibiotics and surgery to remove portions of bone that are infected or deadHospitalization is usually necessary

Medications

A bone biopsy will reveal what type of germ is causing the infection

The antibiotics are usually administered through a vein for at least four to six weeks

Side effects may include nausea, vomiting and diarrhea

An additional course of oral antibiotics may also be needed for more-serious infectionsSurgery

Depending on the severity of the infection, osteomyelitis surgery may include one or more of the following procedures

Drain the infected areaRemove diseased bone and tissueRemove any foreign objectsAmputate the limbArthritisInfectious Arthritis is inflammation of the joint space

Generally affects a single jointand result insuppurative inflammation

Hematogenous seedingof joint is most common

Pain, swelling, limitation of movement common symptoms

Etiology, Epidemiology & Risk factorsGonococcal infection most common cause in young adults caused by Neisseria gonorrheae

Nongonococcal arthritis occurs in older adults

Occasionally results from direct trauma, procedures (arthroscopy) or from contiguous soft tissue infection

S. aureus is most common causeOther organisms : streptococci and aerobic Gram negative bacilli

Lyme disease in endemic areas

Risk factors: age, diabetes, immunosuppression, IV drug use, catheters, prior joint damage, sexually transmitted diseasesDiagnosis of Infectious ArthritisHistory/examination to exclude systemic illness

Blood culturesculture or DNA testing for N. gonorrheae

Urine may be used for DNA testing also

Culture of joint fluid, and skin lesions also indicated

Treatment & ManagementArthrocentesis with drainage of infected synovial fluid

Repeated therapeutic arthrocentesis often needed

Occassionally, arthroscopic or surgical drainage/debridement

Antimicrobial therapy should be directed at suspected and susceptibility resultsGonococcal arthritis: IV Ceftriaxone ( or Ciprofloxacin or Ofloxacin) then switch to oral Quinolone or Cefixime for 7-10 days

Nongonococcal infectiuos arthritis

MSSA: Nafcillin or Cefazolin.

MRSA: Vancomycin

Streptococci: Penicillin or Ceftriaxone or Cefazolin

Enterobacetriacae: Ceftriaxone or Fluroquinolone

Pesudomonas: Piperacillin and Aminoglycoside

Animal bite : Ampicillin-Sulbactam

Lyme disease arthritis: Doxycycline for 1 month

Prognosis & ComplicationsGonococcal arthritis has an excellent outcome

Nongonococcal arthritiscan result in scarring with limitation of movement, ambulation is affected in 50% of cases

Risk factors for longterm adverse sequellae include

Age, prior rheumatoid arthritis, poly-articular joint involvement, hip or shoulder involvement, virulent pathogens and delayed initiation or response to therapy

Acne vulgarisAcne vulgaris (cystic acne or simply acne)

A common human skin diseasecharacterized by areas ofscaly red skin, blackheadsand whiteheads,and possibly scarring

Acne affects mostly skinwith the densest populationof sebaceous folliclesthe face, the upper part of thechest, and the backSigns and symptomsScars Pigmentation

CauseHormonalGeneticPsychologicalInfectiousDiet

Different types of Acne Vulgaris: A: Cystic acne on the face, B: Subsiding tropical acne of trunk, C: Extensive acne on chest and shoulders.Infectious AgentPropionibacterium acnes (P. acnes) is the anaerobic bacterium species that is widely concluded to cause acne

Staphylococcus epidermidis has been universally discovered to play some role in acne formationMedications Benzoyl peroxideAntisepticsAntibioticsHormonesTopical retinoidsOral retinoidsAnti-inflammatories

Benzoyl peroxide cream