You are in: eMedicine Specialties > Infectious Diseases > MEDICAL TOPICS Staphylococcal InfectionsArticle Last Updated: Aug 20, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Thomas Herchline, MD, Professor of Medicine, Wright State University Boonshoft School of Medicine; Medical Director, Public Health, Dayton and Montgomery County, Ohio Thomas Herchline is a member of the following medical societies: American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America Editors: Klaus-Dieter Lessnau, MD, FCCP, Clinical Associate Professor of Medicine, New York University School of Medicine; Medical Director, Pulmonary Physiology Laboratory; Director of Research in Pulmonary Medicine, Department of Medicine, Section of Pulmonary Medicine, Lenox Hill Hospital; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; John L Brusch, MD, FACP, Assistant Professor of Medicine, Harvard Medical School; Consulting Staff, Department of Medicine and Infectious Disease Service, Cambridge Health Alliance; Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital; Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital Author and Editor Disclosure Synonyms and related keywords: staphylococcal infections, staph infection, MRSA, Staphylococcus aureus, S aureus, methicillin-resistant S aureus, methicillin-resistant Staphylococcus aureus, staphylococci, gram-positive cocci, S aureus bacteremia, staphylococcal toxic shock syndrome, Staphylococcus epidermis, S epidermis, staphylococcal skin infections, staphylococcal folliculitis, staphylococcal furuncles, staphylococcal bullous impetigo, staphylococcal wound infections, staphylococcal scalded skin syndrome, staphylococcal soft-tissue infections, staphylococcal pyomyositis, staphylococcal septic bursitis, staphylococcal septic arthritis, staphylococcal toxic shock syndrome, TSS, staphylococcal endocarditis, staphylococcal osteomyelitis, staphylococcal pneumonia, staphylococcal food poisoning, staphylococcal prosthetic infections, coagulase-negative staphylococci, staphylococcal urinary tract infection, UTI INTRODUCTIONSection 2 of 11
  BackgroundStaphylococcal infections are usually caused by the organism Staphylococcus aureus. However, the incidence of infections due to Staphylococcus epidermidis and other coagulase-negative staphylococci has been steadily increasing in recent years. This article focuses on S aureus but also discusses infections caused by coagulase-negative staphylococci when important differences exist. PathophysiologyS aureus is a gram-positive coccus that is both catalase- and coagulase-positive. Colonies are golden and strongly hemolytic on blood agar. They produce a range of toxins, including alpha-toxin, beta-toxin, gamma-toxin, delta-toxin, exfoliatin, enterotoxins, Panton-Valentine leukocidin (PVL), and toxic shock syndrome toxin–1 (TSST-1). The enterotoxins and TSST-1 are associated with toxic shock syndrome. PVL is associated with necrotic skin and lung infections but is not the major virulence factor.1 Coagulase-negative staphylococci, particularly S epidermidis, produce an exopolysaccharide (slime) that promotes foreign-body adherence and resistance to phagocytosis. FrequencyUnited StatesUp to 80% of people are eventually colonized with S aureus. Most are colonized only intermittently; 20-30% are persistently colonized. Colonization rates in health care workers, persons with diabetes, and patients on dialysis are higher than in the general population. The anterior nares are the predominant site of colonization in adults; other potential sites of colonization include the axilla, rectum, and perineum. InternationalS aureus infection occurs worldwide. Pyomyositis due to S aureus is more prevalent in the tropics. Mortality/MorbidityMortality due to staphylococcal infections varies widely. Untreated S aureus bacteremia carries a mortality rate that exceeds 80%. The mortality rate of staphylococcal toxic shock syndrome is 3-5%. Infections due to coagulase-negative staphylococci usually carry a very low mortality rate. Because these infections are commonly associated with prosthetic devices, the most serious complication is the need to remove the involved prosthesis, although prosthetic valve endocarditis may lead to death. RaceStaphylococcal infections have no reported racial predilection. SexThe vaginal carriage rate of staphylococcal species is approximately 10% in premenopausal women. The rate is even higher during menses. Age
CLINICALSection 3 of 11
HistoryCommon manifestations of staphylococcal infections include the following types of infections. The history obtained usually depends on the type of infection the organism causes.
Physical
CausesPredisposing factors for staphylococcal infections include the following:
Colonization with S aureus is common. Skin-to-skin and skin-to-fomite contact are common routes of acquisition.4 Isolates can be spread by coughing or sneezing.5 Evidence has also shown that S aureus can be spread during male homosexual sex.6 Pets can also serve as household reservoirs.7 DIFFERENTIALSSection 4 of 11
Brain Abscess Cellulitis Decubitus Ulcers Diabetic Ulcers Human Bite Infections Impetigo Influenza Liver Abscess Myocardial Abscess Nongonococcal Infectious Arthritis Perianal Abscess Perinephric Abscess Pneumococcal Infections Pneumonia, Bacterial Septic Shock Spinal Cord Abscess Splenic Abscess Streptococcus Group A Infections Streptococcus Group B Infections Toxic Shock Syndrome Urinary Tract Infection, Females Wound Infection
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| Drug Name | Nafcillin (Nafcil, Unipen, Nallpen) |
|---|---|
| Description | Preferred therapy for methicillin-susceptible S aureus (MSSA) staphylococci infections. Use parenteral therapy initially in severe infections. Oxacillin may be substituted for nafcillin based on hospital formulary. Change to oral therapy as condition warrants. |
| Adult Dose | 1-2 g IV q4h |
| Pediatric Dose | 100-200 mg/kg/d IV divided q4h |
| Contraindications | Documented hypersensitivity |
| Interactions | Associated with warfarin resistance when administered concurrently; effects may decrease with bacteriostatic action of tetracycline derivatives |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | To optimize therapy, determine causative organisms and susceptibility; duration of treatment should be at least 14 days in all patients with S aureus bacteremia to prevent sequelae (eg, endocarditis, osteomyelitis) |
| Drug Name | Vancomycin (Vancocin, Vancoled) |
|---|---|
| Description | Indicated for patients who cannot receive penicillins and cephalosporins or have infections with resistant staphylococci. To lessen the risk for toxicity, assay vancomycin trough levels after third dose drawn 0.5 h prior to next dosing. Use CrCl to adjust dose in patients diagnosed with renal impairment. |
| Adult Dose | 1 g or 15 mg/kg IV q12h |
| Pediatric Dose | 30-40 mg/kg/d IV divided q12h |
| Contraindications | Documented hypersensitivity |
| Interactions | Erythema, histaminelike flushing, and anaphylactic reactions may occur when administered with anesthetic agents; taken concurrently with aminoglycosides, risk of nephrotoxicity may increase above that with aminoglycoside monotherapy; effects in neuromuscular blockade may be enhanced when coadministered with nondepolarizing muscle relaxants |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Infuse slowly, rapid infusion may cause hypotension or tingling and flushing (red man syndrome); red man syndrome is caused by IV infusion that is too rapid but rarely happens when dose is administered as 2-h IV administration or with PO or IP administration; red man syndrome is not an allergic reaction; caution in renal failure and neutropenia |
| Drug Name | Cefazolin (Ancef, Kefzol) |
|---|---|
| Description | First-generation semisynthetic cephalosporin that arrests bacterial cell wall synthesis, inhibiting bacterial growth. Primarily active against skin flora, including S aureus (MSSA). Typically used alone for skin and skin-structure coverage. IV and IM dosing regimens are similar. |
| Adult Dose | 1 g IV q8h |
| Pediatric Dose | 50-100 mg/kg/d IV divided q8h |
| Contraindications | Documented hypersensitivity |
| Interactions | Probenecid prolongs effect; coadministration with aminoglycosides may increase renal toxicity; may yield false-positive result from urine dip test for glucose |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Adjust dose in renal impairment; superinfections and promotion of nonsusceptible organisms may occur with prolonged use or repeated therapy |
| Drug Name | Clindamycin (Cleocin) |
|---|---|
| Description | Lincosamide for treatment of serious skin and soft tissue staphylococci infections. Also effective against aerobic and anaerobic streptococci (except enterococcal) (MSSA). Inhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest. |
| Adult Dose | 150-300 mg PO q8h 300-600 mg IV q8h |
| Pediatric Dose | 25-40 mg/kg/d PO/IV divided tid |
| Contraindications | Documented hypersensitivity; regional enteritis, ulcerative colitis, or hepatic impairment (use caution) |
| Interactions | Increases duration of neuromuscular blockade induced by tubocurarine and pancuronium; erythromycin may antagonize effects; antidiarrheals may delay absorption |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Increases duration of neuromuscular blockade induced by tubocurarine and pancuronium; erythromycin may antagonize effects; antidiarrheals may delay absorption; all antimicrobials have been associated with development of pseudomembranous colitis |
| Drug Name | Dicloxacillin (Dycill, Dynapen) |
|---|---|
| Description | Binds to one or more penicillin-binding proteins, which, in turn, inhibits synthesis of bacterial cell walls. For treatment of infections caused by penicillinase-producing staphylococci susceptible to methicillin (MSSA). Also active against most nonenterococcal streptococci. May use to initiate therapy when staphylococcal infection is suggested. |
| Adult Dose | 500 mg PO q6h |
| Pediatric Dose | 25 mg/kg/d PO divided q6h |
| Contraindications | Documented hypersensitivity |
| Interactions | Decreases efficacy of oral contraceptives; increases effects of anticoagulants; probenecid and disulfiram may increase penicillin levels |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Monitor PT in patients taking anticoagulant medications; toxicity may increase in patients with renal impairment; usefulness limited by need for frequent dosing |
| Drug Name | Trimethoprim-sulfamethoxazole (Bactrim, Bactrim DS, Septra, Septra DS) |
|---|---|
| Description | Inhibits bacterial growth by inhibiting synthesis of dihydrofolic acid. Active against most staphylococci (MSSA), including some strains resistant to methicillin (MRSA). |
| Adult Dose | 160/800 mg PO q12h |
| Pediatric Dose | <2 years: Do not administer >2 years: 6-12 mg of trimethoprim/kg/d PO divided bid |
| Contraindications | Documented hypersensitivity; megaloblastic anemia due to folate deficiency |
| Interactions | May increase PT when used with warfarin (perform coagulation tests and adjust dose accordingly); coadministration with dapsone may increase blood levels of both drugs; coadministration of diuretics increases incidence of thrombocytopenia purpura in elderly persons; phenytoin levels may increase with coadministration; may potentiate effects of methotrexate in bone marrow depression; hypoglycemic response to sulfonylureas may increase with coadministration; may increase levels of zidovudine |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Discontinue at first appearance of skin rash or sign of adverse reaction; obtain CBC counts frequently; discontinue therapy if significant hematologic changes occur; goiter, diuresis, and hypoglycemia may occur with sulfonamides; prolonged IV infusions or high doses may cause bone marrow depression (if signs occur, give 5-15 mg/d leucovorin); caution in folate deficiency (eg, chronic alcoholism, elderly, anticonvulsant therapy, malabsorption syndrome); hemolysis may occur in persons with G-6-PD deficiency Persons with AIDS may not tolerate or respond to TMP-SMZ; caution in renal or hepatic impairment (perform urinalyses and renal function tests during therapy); give fluids to prevent crystalluria and stone formation |
| Drug Name | Minocycline (Minocin) |
|---|---|
| Description | Inhibits protein synthesis and thus bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria. Active against MSSA/MRSA. Less active against coagulase-negative staphylococci. Doxycycline (Vibramycin) may be used in place of minocycline |
| Adult Dose | 100 mg PO/IV q12-24h |
| Pediatric Dose | 2-4 mg/kg/d PO divided bid |
| Contraindications | Documented hypersensitivity |
| Interactions | Bioavailability decreases slightly with antacids containing aluminum, calcium, magnesium, iron, or bismuth subsalicylate; tetracyclines can increase hypoprothrombinemic effects of anticoagulants; tetracyclines can decrease effects of oral contraceptives, causing breakthrough bleeding and increased risk of pregnancy |
| Pregnancy | D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus |
| Precautions | Tetracycline use during tooth development (last half of pregnancy through 8 y) can cause permanent discoloration of teeth |
| Drug Name | Linezolid (Zyvox) |
|---|---|
| Description | Prevents formation of functional 70S initiation complex, which is essential for bacterial translation process. Bacteriostatic against staphylococci (MSSA/MRSA). |
| Adult Dose | 400-600 mg PO/IV q12h |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity |
| Interactions | May cause hypertension when used concomitantly with adrenergic agents, including pseudoepinephrine, sympathomimetic agents, vasopressors, or dopaminergic agents (reduce dose of dopamine or epinephrine if concurrent use required); serotonin syndrome may occur if used concomitantly with serotonergic agents, including TCAs, meperidine, dextromethorphan, trazodone, venlafaxine, and selective serotonin reuptake inhibitors |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Has mild MAOI properties and has potential to have same interactions as other MAOIs; caution in uncontrolled hypertension, pheochromocytoma, carcinoid syndrome, or untreated hyperthyroidism and in and patients who are at increased risk for bleeding, have preexisting thrombocytopenia, receive concomitant medications that may decrease platelet count or function, or who may require > 2 wk of therapy (monitor platelet counts); unnecessary use may lead to development of resistance to drug |
| Drug Name | Quinupristin/dalfopristin (Synercid) |
|---|---|
| Description | Belongs to the streptogramin group of antibiotics. Mechanism of action is similar to macrolides/lincosamides. Inhibits protein synthesis and is usually bacteriostatic. Also an option for methicillin-resistant S aureus (MRSA) infections. |
| Adult Dose | 7.5 mg/kg IV q8h |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity |
| Interactions | May decrease elimination and increase toxicity of cyclosporine A, midazolam, nifedipine, terfenadine astemizole, cisapride, alfentanil, alosetron, alprazolam, carbamazepine, delavirdine, diazepam, diltiazem, disopyramide, dofetilide, donepezil, erythromycin, ethinyl estradiol, felodipine, fexofenadine, indinavir, lidocaine, lovastatin, methylprednisolone, nevirapine, norethindrone, quinidine, ritonavir, saquinavir, simvastatin, tacrolimus, triazolam, trimetrexate, verapamil, vinblastine, and, possibly, other drugs |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Arthralgias and myalgias are common and may be severe; venous irritation common when administered through a peripheral line; administration through central venous line recommended; asymptomatic elevation of unconjugated bilirubin level may occur |
| Drug Name | Daptomycin (Cubicin) |
|---|---|
| Description | Indicated to treat complicated skin and skin structure infections caused by S aureus (including MRSA strains), Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus dysgalactiae, and Enterococcus faecalis. Also indicated for right-sided endocarditis due to S aureus. First of new antibiotic class called cyclic lipopeptides. Binds to bacterial membranes and causes rapid membrane potential depolarization, thereby inhibiting protein, DNA, and RNA synthesis and ultimately causing cell death. |
| Adult Dose | CrCl >30 mL/min: 4 mg/kg IV q24h infused over 30 min CrCl <30 mL/min: 4 mg/kg IV q48h (including hemodialysis or CAPD) |
| Pediatric Dose | <18 years: Not established >18 years: Administer as in adults |
| Contraindications | Documented hypersensitivity |
| Interactions | Coadministration with tobramycin slightly increases daptomycin Cmax and AUC and decreases tobramycin Cmax and AUC; may experience additive effects with other drugs (eg, HMG-CoA reductase inhibitors), causing myopathy |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Decrease dose with renal function <30 mL/min; pseudomembranous colitis may occur; may cause muscle pain or weakness; monitor CK levels and discontinue daptomycin with elevated CK and unexplained myopathy or marked CK elevation (10-times upper limits of reference range); not indicated for pneumonia (higher death rate in daptomycin-treated patients during phase III trials); not compatible with dextrose-containing solutions |
| Drug Name | Tigecycline (Tygacil) |
|---|---|
| Description | A glycylcycline antibiotic that is structurally similar to tetracycline antibiotics. Inhibits bacterial protein translation by binding to 30S ribosomal subunit, and blocks entry of amino-acyl tRNA molecules in ribosome A site. Indicated for complicated skin and skin structure infections and complicated intra-abdominal infections. Active against S aureus (including MRSA), as well as most streptococci, enterococci (including VRE), and gram-negative organisms (including anaerobes). |
| Adult Dose | Infuse each dose over 30-60 min 100 mg IV once, then 50 mg IV q12h Severe hepatic impairment (ie, Child Pugh class C): 100 mg IV once, then 25 mg IV q12h |
| Pediatric Dose | <18 years: Not established >18 years: Administer as in adults |
| Contraindications | Documented hypersensitivity |
| Interactions | Coadministration decreases warfarin clearance and increases warfarin Cmax and AUC (monitor aPTT and INR); coadministration of antibiotics with oral contraceptives may decrease contraceptive effect |
| Pregnancy | D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus |
| Precautions | Caution in severe hepatic impairment (reduce dose); may adversely effect tooth development; may permit clostridia overgrowth, resulting in antibiotic-associated colitis |
Many hospitals have implemented screening for methicillin-resistant S aureus (MRSA) infections upon admission to an intensive care unit. Topical decolonization therapy and contact isolation of patients who test positive for MRSA has been shown to decrease MRSA infection rates.4
| Media file 1: Embolic lesions in patient with Staphylococcus aureus endocarditis. | |
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| Media file 2: Close-up view of embolic lesions in patient with Staphylococcus aureus endocarditis. | |
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| Media file 3: Fifty-six-year-old man with erythema, edema, and drainage from below his right eye. | |
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| Media file 4: Gram stain in a 70-year-old woman with rheumatoid arthritis. | |
 | View Full Size Image | Media type: Histology |
Staphylococcal Infections excerpt
Article Last Updated: Aug 20, 2008
