Staphylococcus aureus has long been recognized as an important pathogen in human disease. Due to an increasing number of infections caused by methicillin-resistant S. aureus (MRSA) strains, therapy has become problematic. Therefore, prevention of staphylococcal infections has become more important. Carriage of S. aureus appears to play a key role in the epidemiology and pathogenesis of infection. The ecological niches of S. aureus are the anterior nares. In healthy subjects, over time, three patterns of carriage can be distinguished: about 20% of people are persistent carriers, 60% are intermittent carriers, and approximately 20% almost never carry S. aureus. The molecular basis of the carrier state remains to be elucidated. In patients who repeatedly puncture the skin (e.g., hemodialysis or continuous ambulatory peritoneal dialysis [CAPD] patients and intravenous drug addicts) and patients with human immunodeficiency virus (HIV) infection, increased carriage rates are found. Carriage has been identified as an important risk factor for infection in patients undergoing surgery, those on hemodialysis or CAPD, those with HIV infection and AIDS, those with intravascular devices, and those colonized with MRSA. Elimination of carriage has been found to reduce the infection rates in surgical patients and those on hemodialysis and CAPD. Elimination of carriage appears to be an attractive preventive strategy in patients at risk. Further studies are needed to optimize this strategy and to define the groups at risk.

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Nasal carriage of Staphylococcus aureus: epidemiology, underlying mechanisms, and associated risks.

Context.—Community-acquired methicillin-resistant Staphylococcus
aureus (MRSA) infections in children have occurred primarily in individuals
with recognized predisposing risks. Community-acquired MRSA infections in
the absence of identified risk factors have been reported infrequently.Objectives.—To determine whether community-acquired MRSA infections in children
with no identified predisposing risks are increasing and to define the spectrum
of disease associated with MRSA isolation.Design.—Retrospective review of medical records.Patients.—Hospitalized children with S aureus isolated
between August 1988 and July 1990 (1988-1990) and between August 1993 and
July 1995 (1993-1995).Setting.—The University of Chicago Children's Hospital.Main Outcome Measures.—Prevalence of community-acquired MRSA over time, infecting vs colonizing
isolates, and risk factors for disease.Results.—The number of children hospitalized with community-acquired MRSA disease
increased from 8 in 1988-1990 to 35 in 1993-1995. Moreover, the prevalence
of community-acquired MRSA without identified risk increased from 10 per 100000
admissions in 1988-1990 to 259 per 100000 admissions in 1993-1995 (P<.001), and a greater proportion of isolates produced clinical
infection. The clinical syndromes associated with MRSA in children without
identified risk were similar to those associated with community-acquired methicillin-susceptible S aureus. Notably, 7 (70%) of 10 community-acquired MRSA
isolates obtained from children with an identified risk were nonsusceptible
to at least 2 drugs, compared with only 6 (24%) of 25 isolates obtained from
children without an identified risk (P=.02).Conclusions.—These findings demonstrate that the prevalence of community-acquired
MRSA among children without identified risk factors is increasing.

https://jamanetwork.com/journals/jama/articlepdf/187279/joc71943.pdf

Community-acquired methicillin-resistant staphylococcus aureus in children with no identified predisposing risk

Antimicrobial resistance results in increased morbidity, mortality, and costs of health care. Prevention of the emergence of resistance and the dissemination of resistant microorganisms will reduce these adverse effects and their attendant costs. Appropriate antimicrobial stewardship that includes optimal selection, dose, and duration of treatment, as well as control of antibiotic use, will prevent or slow the emergence of resistance among microorganisms. A comprehensively applied infection control program will interdict the dissemination of resistant strains.

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Society for Healthcare Epidemiology of America and Infectious Diseases Society of America Joint Committee on the Prevention of Antimicrobial Resistance: Guidelines for the Prevention of Antimicrobial Resistance in Hospitals

Outbreaks of hospital-acquired infections caused by methicillin-resistant Staphylococcus aureus are being recognized with increasing frequency in the United States. Two thirds of outbreaks have been centered in critical care units. Infected and colonized inpatients appear to be the major institutional reservoir, and transient carriage on the hands of hospital personnel appears to be the most important mechanism of serial patient-to-patient transmission. In over 85% of hospitals into which they have been introduced, methicillin-resistant strains of S. aureus have become established as endemic nosocomial pathogens. A program designed to control a widespread outbreak in a university hospital used three surveillance methods to identify the major institutional reservoir of colonized and infected inpatients. Daily clinical laboratory surveillance, monthly prospective microbiology surveys of high-risk inpatients, and the recognition of previously infected 38%, 31%, and 31% of new cases, respectively. After control measures were instituted, the prevalence (p less than 0.001) and the number of acquisitions (p less than 0.002) of methicillin-resistant S. aureus declined over a 12-month period.

Epidemiology of Nosocomial Infections Caused by Methicillin-Resistant Staphylococcus aureus

To determine whether recommendations of infectious diseases specialists affect outcome for patients, we evaluated 244 hospitalized patients with Staphylococcus aureus bacteremia. We offered our management recommendations to each patient's physicians and then assessed the clinical outcome for both patients for whom our consultative advice was followed and those for whom our advice was not heeded. All patients were followed up for 12 weeks after their first positive blood culture. Our management advice was followed for 112 patients (45.9%) and partially or completely ignored for 132 patients (54.1%). Patients for whom our recommendations were followed were more likely to be cured of their S. aureus infection and less likely to relapse (P < .01), despite having significantly more metastatic infections (P < .01) at the outset of therapy, than were those for whom our recommendations were not followed. Failure to follow recommendations to remove an infected intravascular device was the most important risk for treatment failure. After controlling for other factors, logistic regression analysis revealed that patients whose intravascular device was not removed were 6.5 times more likely to relapse or die of their infection than were those whose device was removed. Our findings suggest that patient-specific management advice by infectious diseases consultants can improve the clinical outcome for patients with S. aureus bacteremia.

Outcome of Staphylococcus aureus bacteremia according to compliance with recommendations of infectious diseases specialists: experience with 244 patients.

The incidence of amikacin resistance among gram-negative bacilli isolated at the New York V.A. Medical Center increased from 2.0% to greater than 7% during an 18-month period from January 1980 to July 1981. This increase coincided with a threefold increase in amikacin use at this institution. The amikacin-resistant (AKR) isolates most frequently recovered in 1981 were species of Klebsiella, Serratia, and Pseudomonas. These organisms were recovered from multiple sites, including urine, sputum, wounds, blood, peritoneal fluid, and pleural fluid. The amikacin-modifying enzyme 6'-N-acetyltransferase was detected in 27 (67.5%) of 40 randomly selected AKR isolates. These data indicate that resistance to amikacin in this hospital is enzymatically mediated in most strains of AKR Klebsiella and Serratia and in about one-third of AKR strains of P. aeruginosa. This finding supports the conclusion that amikacin resistance is enhanced by the pressure of increased amikacin use.

Amikacin-Resistant Gram-Negative Bacilli: Correlation of Occurrence with Amikacin Use

Six strains of Staphylococcus aureus resistant to semisynthetic penicillins were recovered from clinical sources during a two-month period. Resistance was detected by standard disk sensitivity tests at 37 C. Two resistant strains were responsible for infections (one of which was fatal), and five strains were susceptible only to phage type 92. All of the strains produced penicillinase, which did not destroy oxacillin, and each was resistant to oxacillin at low inocula. Relative resistance to cephalosporin was demonstrable by the tube dilution assay but not by standard disk tests. The strains susceptible to phage type 92 were susceptible to vancomycin and to the synergistic action of oxacillin or cephalothin plus gentamicin.

Resistance of Staphylococcus aureus to Semisynthetic Penicillins and Cephalothin

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Staphylococcus Aureus Colonization in Intravenous Drug Abusers, Dialysis Patients and Diabetics

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Sam Schaefler

Papers

Amikacin-Resistant Gram-Negative Bacilli: Correlation of Occurrence with Amikacin Use

Resistance of Staphylococcus aureus to Semisynthetic Penicillins and Cephalothin

Staphylococcus Aureus Colonization in Intravenous Drug Abusers, Dialysis Patients and Diabetics

Staphylococcus Aureus Colonization in Intravenous Drug Abusers, Dialysis Patients and Diabetics