Anti-infective Drugs

Jan Bazner-Chandler

MSN, CNS, RN, CPNP

Bacteria

Bacteria

Gram-positive bacterium has a thick layer of peptioglycan.

Gram-negative bacterium has a thin peptioglycan layer and an outer membrane.

Common Bacterial Pathogens

Gram positive Staphylococcus aureus Streptocci Enterococci

Gram negative Escherichia coli or E-coli Klebsiella Proteus Pseudomonas

Empiric Therapy

Administration of antibiotics based on the practitioner’s judgment of the pathogens most likely to be causing the infection; it involves the presumptive treatment of an infection to avoid treatment delay before specific cuture information has been obtained.

Prophylactic Antibiotic Therapy Antibiotics taken before anticipated exposure

to an infectious organism in an effort to prevent the development of infection. IV antibiotics given prior to surgery

Superinfection

An infection occurring during antimicrobial treatment for another infection, resulting from overgrowth of an organism not susceptible to the antibiotic used.

A secondary infection that occurs due weakening of the patients immune system by the first infection.

Examples of Superinfections

Fungal or yeast infection Diarrhea due to diminished normal flora of

the gastrointestinal tract.

Laboratory Tests

Gram stain – microscopic identification of organism

Culture – identifies causative agent and susceptibility to specific antibiotics

Serology – titers or antibodies measured CBC – looking at WBC

Cultures

Throat Wound Urine Sputum Blood

Clinical Pearl

Always collect culture: urine, sputum, wound drainage, or blood prior to starting antibiotic therapy.

If technician is drawing blood make sure it has been done before starting antibiotics.

Antimicrobials

Drugs used to prevent or treat infection caused by pathogens

Two Classifications

Bactericidal drugs kill bacteria directly. Bacteriostatic drugs prevent bacteria from

dividing or inhibits their growth.

Infectious Disease

• Infections disease involves the presence of pathogen plus clinical signs and symptoms indicating infection.

• Microorganisms spread by direct contact with infected person or contaminated hands, food, water, or objects.

Opportunistic Infections

Severe burns Cancer HIV Indwelling IV catheter or urinary catheter Corticosteroid therapy Fungal or viral infections

Two Types of Bacteria

Aerobic – grow and live in presence of oxygen Staph & Strep

Anaerobic – cannot grow in presence of oxygen Deep wounds Characterized by abscess formation, foul-smelling

pus and tissue destruction

Community-Acquired Infection Less severe and easier to treat, although

drug resistant strains are increasing Remember Staph is everywhere – it is normal

flora on skin and in the upper respiratory tract

MRSA: methicillin-resistant-Staphylococcus aureus

Nosocomial Infections

More severe and difficult to manage because they often result from drug-resistant microorganisms and occur in clients whose resistance is impaired Pseudomonas Proteus

Bacterial Resistance

Bacteria develop the ability to produce substances which block the action of antibiotics or change their target or ability to penetrate the cells.

What causes resistance?

Widespread use of antimicrobial drug Interrupted or inadequate antimicrobial

treatment of infection Type of bacteria – gram-negative strains

have higher rates of resistance Re-occurring infections Condition of the host Location – critical care areas

Client History / Assessment

Allergies Previous drug reactions Baseline renal and liver function Review culture reports for appropriate

antibacterial drug choice Patient response to antibiotics therapy

Are they getting better? Any side effects?

Antibiotics

Sulfonamides Penicillins Cephalosporins Macrolides Fluoroquinolones Aminoglycosides Tetracyclines

Sulfonamides

Action: inhibit the growth of bacteria (bacteriostatic antibiotic) by inhibiting the growth of susceptible bacteria by preventing bacterial synthesis of folic acid.

Usually used in combination drugs. Trimethoprim / sulfamethoxazole: Trade name

Bactrim, Septra, TMP/SMX

Indications

Broad spectrum: can be used against gram negative and gram positive organisms

Very useful in treating kidney infections since they achieve a high concentration in the kidneys.

Susceptible organisms: Enterobacter, E.Coli, Klebsiella, Proteus

Problem: organisms becoming more resistant

Specific Use of Sulfa Drugs

HIV patients with pneumocystis carinii’ May be given Bactrim or Septra

prophylactically.

Contraindications

Drug allergy to sulfa Use of thiazide and loop diuretics Pregnant women Infants younger than 2 months of age

Adverse Effects

Most common is cutaneous reactions – can occur weeks after therapy started. Erythema multiforme (Stevens Johnson

Syndrome) Toxic epidermal necrolysis

Photosensitivity reactions: exposure to sunlight can result in severe sunburn

B-Lactam Antibiotics

Includes 4 major drug classifications penicillins cephalosporins carbapenes monobactams

Penicillin

Derived from mold fungus

Penicillin

First generation IM or IV Newer penicillins have been developed that

increase gastric acid stability of penicillin Good drug since it enters most bodily fluids:

joint, pleural, and pericardial. Not effective against intraocular (eye) or

cerebral spinal fluid infection (CSF)

Penicillin

Bactericidal action against sensitive bacteria Action: binds to bacterial wall, resulting in cell

death

Susceptible Bacteria

Gram-positive organisms Streptococcus Enterococcus Staphylococcus

Adverse Reactions

Most common reaction is GI (diarrhea) when administered orally.

Urticaria, pruritus, and angioedema Severe reaction: Steven’s Johns Syndrome Note: when giving IV or IM observe for ½ to 1

hour after giving for adverse reactions.

Combination Penicillin / B-lactamases Unasyn Augmentin Timentin Zosyn

Ampicillin – Synthetic Penicillin Broad spectrum effective against several

gram-positive and gram-negative bacteria E-coli, proteus, Salmonella, Shigella Not effective against staphylococci on

gonococci Bronchitis, sinusitis, and otitis media

Ampicillin

Bactericidal action – spectrum is broader than penicillin

Binds to bacterial wall resulting in cell death

Nursing Implications

Same as penicillin Ask client about oral contraceptive use – drug

may cause transient decrease in effectiveness

Advise to use additional BC – barrier protection during antibiotic therapy

Amoxicillin

Oral equivalent of Ampicillin Readily absorbed and reaches therapeutic

levels rapidly Drug of choice in prevention of bacterial

endocarditis Clients with total knee or hip replacement, heart

valve replacement need to take prior to any dental work, endoscopy exams

Dosing for Amoxicillin

Adults: 250 to 500 mg q8h Infants and children less than 20 kg:

20 – 40 mg / kg / day divided into doses q 8 hours

Cephalosporins

• Widely used drug derived from fungus• Used against gram–negative bacteria• Widely absorbed and distributed in most

bodily fluids – placenta and breast milk

Cephalosporin

First generation Cephalosporin drugs do not reach therapeutic levels in CSF (cerebral spinal fluid) but 2nd, and 3rd generation drugs do – especially important in treating meningitis

First Generation Cephalosporins

Bactericidal action – binds to bacterial cell wall, causing cell death Keflex (PO) still used extensively in treatment of

skin infections Ancef – often ordered preoperatively

First Generation Cephalosporins

Bactericidal action – binds to bacterial cell wall, causing cell death Keflex (PO) still used extensively in treatment of

skin infections Ancef – often ordered preoperatively

Keflex

First generation cephalosporin Action: binds to bacterial cell wall membrane,

causing cell death Therapeutic effect: bactericidal action against

susceptible bacteria Active against many gram-positive cocci –

step and staph

Client teaching

May be taken with or without food but food may minimize the GI irritation

Distribution: may cross placenta or enter breast milk in low concentrations.

Excreted entirely by the kidneys.

Keflex Dosing

Adults: 250 – 500 mg q 6 hours Children: 25 – 50 mg / kg / day in divided

doses q 6 h

Cefazolin or Ancef

Cefazolin – first generation cephalosporin Well absorbed following IM or IV

administration Crosses to placenta and breast milk in small

concentrations Minimal CSF penetration Excreted by kidneys

Ancef Dosing

IV Used for UTI, bone and skin infections,

endocarditis Not suitable for treatment of meningitis Perioperative prophylaxis

1 gram within 60 minutes of incision Post operatively every 8 hours for 24 hours (3 doses)

Second-Generation Cephalosporins More active against some gram-negative

organisms and anaerobic organisms than the first generation drugs.

May be effective in infections resistant to other antibiotics

Penetration into CSF is poor but adequate to be used in meningitis

Action: bactericidal – binds to cell wall

Third Generation Cephalosporin Drugs Similar to the second generation but has

increased activity against gram-negative pathogens even for drug resistant pathogens.

CSF penetration is better than the first two generation cephalosporin drugs.

Drug / Drug Allergies

If a client is allergic to penicillin there is a 1 to 18% chance they will be allergic to cephalosporin drugs.

Carbapenems

Has very broad antibacterial action Are often used for complicated body cavity

and connective tissue infections in the hospitalized patient. imipenem-cilastatin (Primaxin) meropenen (Merrem): only drug in this class used

in the treatment of bacterial meningitis.

Macrolides

Macrolides first developed in the 1950s with the drug: erythromycin. Four main drugs

azithromycin * Zithromax Clarithromcin * Biazin dirithromycin erythromycin

Macrolides

Two of the new drugs in the macrolide classification: azithromycin and clarithromycin have longer duration and improved resistance to acid degradation in the stomach. Dosing is less frequent GI effects decreased Better absorption than erythromycin

Macrolides

Action: work by inhibiting protein synthesis in susceptible bacteria.

Contraindications: drug allergy Adverse effect: two new drugs have lower GI

effects and are used in patients allergic to penicillin / cephalosporin drugs.

Ketaloids

Only one drug in this drug classification Generic: telithromycin Trade: Ketek Available for oral use only. Better acid stability and antibacterial

coverage than macrolides.

Tetracyclines

Action: binds to divalent (Ca2 + mg2) and Al3 mettalic ions to form insoluble complexes.

Why do you need to know this? When given with milk, antacids or iron there is a

reduction in oral absorption. Contraindicated in children under 8 years of age

because it can result in tooth discoloration.

Tetracyclines

When used? Syphilis and Lyme disease

Antibiotics Used to Treat Serious Infections IM or IV administration Have more toxic side effects Blood levels may need to be monitored to

determine therapeutic versus toxic levels of mediation in the blood.

Serious Adverse Effects

Nephrotoxicity: Toxicity to kidneys, often drug induced and manifesting in compromised kidney function.

Ototoxicity: Toxicity to the ears, often drug-induced and manifested by varying degrees of hearing loss than is likely to be permanent.

Pseudomembranous colitis: a necrotizing, inflammatory bowel condition associated with antibiotic therapy.

Aminoglycosides

Pharmacologic classification: Bactericidal drugs

Therapeutic classification: anti-infective Action: inhibits protein synthesis at the level

of the 30s ribosome Work primarily on dosing due to

concentration dependent killing of bacteria

Concentration Dependent

A property of some antibiotics, especially aminoglycosides and vancomycin, of achieving a relatively, high plasma drug concentration, results in the most effective bacterial kill.

Blood Plasma Levels

Peak levels: refers to amount of drug present in blood plasma within 15 to 30 minutes of IV drug administration 30 to 90 minutes of IM drug administration

Trough levels: refers to lowest level of drug present in the blood plasma. Since the drugs can cause severe adverse effects the

excretion of the drug needs to be monitored. Blood drawn just before the next dose given.

Adverse Effects Aminoglycosides Nephrotoxicity occurs in 5 to 25% and

ototoxicity (damage to VIII cranial nerve) occurs in 3 to 14%.

Aminoglycosides

gentamicin (Garamycin) tobramycin (Nobcin, TOBI) neomycin (Neo-Fradin)

used to irrigate bowel before major bowel surgery Topical applied to eye and skin infections

Floroquinolones

Action: destroys bacteria by altering their DNA.

Two most common drugs: ciproflxcin (Cipro) clindamycin (Cleocin)

Used in treatment of chronic infections or deep (anaerobic) abdominal infections and MRSA.

Major Adverse Side Effect

Clindamycin or Cleocin can cause pseudomembranous colitis

Signs and symptoms: abdominal pain and diarrhea

MRSA Infections

MRSA infection is caused by Staphylococcus aureus bacteria — often called "staph." MRSA stands for methicillin-resistant Staphylococcus aureus. It's a strain of staph that's resistant to the broad-spectrum antibiotics commonly used to treat it. MRSA can be fatal.

Vancomycin

Action: destroys bacteria by binding to the bacterial cell wall, producing immediate inhibition of cell wall synthesis and death.

Most common drug used in MRSA infections.

Adverse Effect

Red man syndrome has often been associated with rapid infusion of the first dose of the drug and was initially attributed to impurities found in vancomycin preparations. Even after improvement in vancomycin's purity, however, reports of the syndrome persist.

Flushing on upper chest, neck and face Intervention: slow the infusion rate.

Anti-viral Drugs

Kill or suppress viruses by either destroying virons or inhibiting their ability to replicate.

Does not irradiate the virus but helps the immune system to eliminate the virus.

Drugs to help with the Flu

Tamiflu and Relenza Uses: active against influenza virus types A

and B. Shown to reduce the duration of influenza

infection by a few days.

Herpes Zoster

Herpes simplex virus type 1: cold sore Herpes simplex virus type 2: genital herpes Human herpesvirus type 3: chicken pox or

shingles Human herpesvirus type 4: Espstein Barr

Virus Human herpesvirus type 5: CMV or

cytomegalovirus

Herpes Drugs

Generic: acyclovir Trade: Zovirax Action: interferes with DNA synthesis. Therapeutic effects: Inhibition of viral

replication, decreased viral shedding and reduced time for healing of lesions.

acyclovir

Comes in topical, po and IV preparations Should be started within 24 hours of

outbreak.