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PubMed2001

Fitness and competitive growth advantage of new gentamicin-susceptible MRSA clones spreading in French hospitals.

Since 1991, new epidemic methicillin-resistant Staphylococcus aureus (MRSA) strains characterized by the unexpected reappearance of heterogeneous phenotypic expression of resistance to methicillin and by susceptibility to gentamicin and various other antibiotics (GS-MRSA) have been reported in France. GS-MRSA strains have progressively replaced MRSA clones expressing homogeneous resistance to methicillin and resistance to gentamicin (GR-MRSA). In this study, we investigated the physiological characteristics of these new clones. In particular, we evaluated and compared the maximal growth rate and the deduced generation times (related to fitness of strains) of the major French epidemic MRSA clones. The population studied consisted of 79 isolates including (i) GR-MRSA that comprised six different types on the basis of PFGE; (ii) GS-MRSA the majority of which clustered into two PFGE types, A1 (usually resistant to erythromycin) and B (usually susceptible to erythromycin); (iii) methicillin-susceptible S. aureus (MSSA). GS-MRSA-A1 and MSSA strains were shown to have a significant fitness benefit (about 20%) with shorter generation times (theta = 23.7 +/- 0.1 and 22.9 +/- 0.05 min, respectively) than GR-MRSA and GS-MRSA-B strains (theta = 30.3 +/- 0.2 and 32.5 +/- 0.5 min, respectively). These data suggest that a link exists between genetic patterns, resistance profiles and physiological properties. In vitro competitive experiments indicated that GS-MRSA- A1 strains were able to rapidly outgrow GR-MRSA strains. The growth advantage observed should be taken into account in understanding the spread of some new clones of MRSA.

Anti-Bacterial Agents↗
PubMedDate not supplied

A comparison of previous antibiotic therapy following isolation of MRSA versus MSSA in nursing home residents: a preliminary investigation.

OBJECTIVE: Antibiotic exposure is a risk factor for isolation of methicillin-resistant Staphylococcus aureus (MRSA). We reasoned that this relationship might be especially strong if the comparison was targeted to antibiotics with activity against methicillin-sensitive Staphylococcus aureus (MSSA), but not MRSA. SUBJECTS: Forty-eight cases with initial MRSA clinical isolates (15 urinary, 19 wound, 11 sputum, 3 blood) were matched to 48 with MSSA clinical isolates from the same location. In addition, 10 whose MRSA was noted screening around an index case were matched to 10 with negative screening cultures sampled around the same index case. DESIGN: MSSA was always/usually sensitive to dicloxacillin, amoxicillin/clavulanate, cephalosporins, imipenem, quinolones, and erythromycin, whereas MRSA was always/usually resistant. These antibiotics were defined as "targeted" and would be expected to facilitate the proliferation of MRSA by suppressing competing bacteria. We compared the use of all antibiotics over 60 days in cases and controls. RESULTS: The comparison of antibiotic exposure in the 48 clinical isolates revealed that 29 (60%) with MRSA isolates versus 16 (33%) with MSSA isolates had received a targeted antibiotic (RR 1.81, CI 1.33-3.34, P = 0.006). Twelve (25%) with MRSA clinical isolates versus 3 with MSSA isolates (6%) had received a nontargeted antibiotic (RR 4.00, CI 2.10-14.18, P = 0.009). The comparison of antibiotic exposure in MRSA screening isolates versus negative controls revealed that 7 (70%) had received a targeted antibiotic versus 2 (20%) of controls (RR 3.50, CI 1.57-16.85, P = 0.009)). One in the screening group versus 2 controls had received a nontargeted antibiotic. Twenty-one (62%) of 34 with MRSA (urine or wound) isolates versus 4 MSSA controls (12%) had received a quinolone (RR 5.25, CI 1.80-15.30, P < 0.000). CONCLUSION: There was a significant association between antibiotic exposure and MRSA isolates. The association was especially strong for quinolones with urinary or wound isolation of MRSA. Our data do not support the hypothesis that targeted antibiotic use was more likely to be associated with MRSA isolation than nontargeted antibiotic use. The use of nontargeted antibiotics was low, with greater use in the MRSA clinical group.

Journal Article↗
PubMed1997

[Detection of methicillin-resistant Staphylococcus aureus (MRSA)--relation between respiratory tract and gastro-intestinal tract].

The study was conducted to elucidate the possibility of hospital infection of methicillin-resistant Staphylococcus aureaus (MRSA) through feces. Fecal cultures of 12 inpatients positive for MRSA in the respiratory tract and 11 inpatients negative for MRSA in the respiratory tract were performed from April to October in 1993. Fecal cultures of inpatients positive for MRSA in the respiratory tract were continued until September in 1996, finally a total of 50 cases were enrolled. MRSA was isolated from feces of 7 patients (58.3%) of the 12 patients positive for MRSA in the respiratory tract, while no MRSA was isolated from feces of 11 patients negative for MRSA in the respiratory tract. Twenty-seven patients (54.0%) of 50 patients positive for MRSA in the respiratory tract yielded MRSA in the feces. Twenty-three patients (85.2%) of the 27 patients positive for MRSA in the fecal flora had received H2-blocker, while 11 patients (47.8%) of the 23 patients negative for MRSA in the fecal flora received H2-blocker; these differences were statistically significantly (p < 0.01). These findings suggest the possible role of feces in hospital infection with MRSA and the necessity for careful administration of H2-blocker to patients positive for MRSA in the respiratory tract.

Aged↗
PubMed2006

Comparisons of community-associated methicillin-resistant Staphylococcus aureus (MRSA) and hospital-associated MSRA infections in Sacramento, California.

Methicillin-resistant Staphylococcus aureus (MRSA) has long been a common pathogen in healthcare facilities, but in the past decade, it has emerged as a problematic pathogen in the community setting as well. A retrospective case series study of patients from whom MRSA was isolated from December 1, 2003, through May 31, 2004, was conducted at the University of California, Davis, Medical Center. Patient data were collected from electronic medical records and traditional chart reviews to determine whether MRSA acquisition was likely to have been in the community or in the hospital. Antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE) were performed for all confirmed isolates. Skin and soft tissue were the most common infection sites for all MRSA patients. Among the 283 MRSA infections, 127 (44.9%) were defined as community-associated (CA)-MRSA. Ninety-six percent of the CA-MRSA isolates were susceptible to clindamycin. Double-disk diffusion tests were performed to examine inducible clindamycin resistance by erythromycin induction on both CA and hospital-associated (HA) clindamycin-susceptible and erythromycin-resistant isolates. Ten percent (17 of 183) were positive. Most CA-MRSA isolates were identified by PFGE as a unique strain, genotype USA300, which was not genetically related to the predominant genotype, USA100, in the HA-MRSA isolates. Injecting drug users accounted for 49% of CA-MRSA infections but only 19% of the HA-MRSA infections (odds ratio, 4.2; 95% confidence interval, 2.4 to 7.4). Our study shows that a single clone of CA-MRSA accounts for the majority of infections. This strain originated in the community and is not related to MRSA strains from healthcare settings. Injecting drug users could be a major reservoir for CA-MRSA transmission.

Adolescent↗
PubMed2006

Evaluation of the IDI-MRSA assay for detection of methicillin-resistant staphylococcus aureus from nasal and rectal specimens pooled in a selective broth.

Rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) by PCR can be performed directly from nasal specimens with the IDI-MRSA assay. To improve the efficiency of screening, we evaluated the performance of the IDI-MRSA assay for the detection of MRSA from pooled and unpooled specimens cultured in a selective broth. Of the 287 specimens evaluated, 71 were culture and PCR positive, 203 were culture and PCR negative, 3 were culture positive and PCR negative, 8 were culture negative and PCR positive, and 2 remained inhibited. A methicillin-susceptible Staphylococcus aureus isolate was recovered from five of the eight specimens with false-positive PCR results. Compared to the results of culture, the sensitivity, specificity, and positive and negative [corrected] predictive values of the IDI-MRSA assay for detection of MRSA from broth were 96%, 96%, 90%, and 98%, respectively. Following implementation of the IDI-MRSA assay, PCR-positive broths were subcultured for evaluation of assay performance. Of the 298 IDI-MRSA assay-positive broths, the results for 103 could not be confirmed by culture. A methicillin-susceptible S. aureus (MSSA) isolate was recovered from 77 of these 103 broths. Repeat testing by the IDI-MRSA assay directly with the MSSA isolates confirmed the original positive PCR result. The positive predictive value of the IDI-MRSA assay fell from 90% during the evaluation phase to 65% postimplementation. The IDI-MRSA assay performed well for the detection of MRSA from a selective broth compared to the performance of the detection of MRSA from culture. However, because of the burden associated with implementation of infection control precautions, cultures remain essential in confirming positive IDI-MRSA results.

Bacterial Typing Techniques↗
PubMed1998

An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) infection in HIV-seropositive persons.

Staphylococcus aureus is a cause of considerable morbidity and mortality in HIV-seropositive persons. Although methicillin-resistant S. aureus (MRSA) is encountered worldwide and in many areas of medical care, little has been reported on clinical infection with MRSA in patients with HIV. We report on an outbreak of MRSA infection in HIV antibody positive patients, using case reports to describe an outbreak of MRSA infection in HIV-seropositive persons. Six cases of clinical MRSA infection were reported over a 4-week period on patients on an HIV dedicated ward. All cases had previous AIDS diagnoses and low CD4 cell counts (median 8 x 10(6)/l; range 0 to 238). Two cases had infected skin lesions and 2 cases had infected indwelling central venous catheters with septicaemia. Two cases had pneumonia, one with concurrent infection at the entry site of a percutaneous endoscopic gastrostomy (PEG) feeding tube. Isolates of MRSA from the 6 cases were compared by pulsed-field gel electrophoresis of Sma1 chromosomal digests. The resultant banding pattern showed the same strain was responsible for all the infections. A seventh inpatient, the index case, had positive carriage with the same strain of MRSA. To define ongoing MRSA carriage after the outbreak, 29 consecutive ward patients were swabbed for MRSA: all were negative. All patients identified with MRSA infection responded to treatment with intravenous teicoplanin, although carriage was unaltered. Four of the 6 cases died within 7 weeks of diagnosis of MRSA. MRSA can cause severe morbidity in patients with end-stage HIV disease. A small outbreak of MRSA was controlled by simple precautionary measures with no subsequent ongoing transmission of MRSA.

AIDS-Related Opportunistic Infections↗
PubMed1993

Guidelines for management of patients with methicillin-resistant Staphylococcus aureus in acute care hospitals and long-term care facilities. The MRSA Interagency Advisory Committee in conjunction with the Connecticut Department of Public Health and Addiction Services, July 1993.

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that can colonize or infect people. MRSA strains are not more virulent than methicillin susceptible strains. Colonized and infected patients represent the most important reservoir of MRSA in hospitals. MRSA is transmitted by direct person-to-person contact, usually on the hands of health care workers. Limiting the spread of MRSA is desirable because the organism is resistant to oxacillin, nafcillin, cephalosporins, and imipenem. Treatment of choice for MRSA infection is usually intravenous vancomycin. The preferred methods for antimicrobial susceptibility testing of S. aureus include oxacillin-salt screening plates, microdilution broth tests with 2% NaCI, and disk diffusion tests incubated for 24 hours at 35 degrees C. Hospitals and LTCFs should monitor the incidence of nosocomial transmission of MRSA in their facility. Hospital admission because of MRSA infection is acceptable medical practice because treatment can best be accomplished in an acute care setting. However, given special circumstances, treatment of MRSA infection can be accomplished in an extended care facility or at home. This decision is based on the clinical judgement of the attending physician. Hospital admission solely because of MRSA colonization is unwarranted. MRSA colonization is not a contraindication to discharge from an acute care hospital to home or another facility. When a hospitalized patient who is colonized with MRSA no longer needs to receive acute nursing care (i.e. their MRSA infection and/or other acute medical problems are under control), they can be discharged. If they are discharged to another institution, that institution should be notified in advance that the patient is colonized with MRSA.

Cross Infection↗
PubMed2006

An audit demonstrating a reduction in MRSA infection in a specialised vascular unit resulting from a change in infection control protocol.

INTRODUCTION: In 2003, 18% of all admissions to our vascular ward were colonised by MRSA, with an MRSA infection rate of 10.6%. Standard practice was to segregate patients with proven MRSA from the rest of the patient pool. After a prospective audit, regression analysis was used to identify factors that could stratify patients into high and low risk for MRSA colonisation. A change in isolation policy was introduced that segregated patients according to their risk of MRSA acquisition, and isolated all patients undergoing prosthetic vascular reconstruction. Antibiotic policy was also altered. This audit reports the impact of these changes on MRSA colonisation and infection rates. METHODS: The MRSA status of patients during 777 in-patient episodes was prospectively recorded during three time spans; period 1 (November 2002-April 2003) before the change in isolation and antibiotic policy and, periods 2 (August-December 2003) and 3 (October 2004-January 2005) after the change in policy. RESULTS: Hospital acquired MRSA colonisation was reduced from 10.6% in period 1, to 1.1 and 1.4% in periods 2 and 3, respectively (p<0.001). Similarly, MRSA infection rates fell from 10.6 to 2.9 and 0.9% over the same time frame (p<0.001). The most dramatic changes in MRSA infection rates occurred in patients undergoing aneurysm repair (MRSA infection 30.1% in period 1 vs. 3.9 and 2.9% in periods 2 and 3) and lower limb revascularization (31 vs. 0 vs. 4.2%). Stepwise regression analysis revealed that the system of isolation was a significant factor reducing MRSA infection and colonisation rates (p<0.001). CONCLUSIONS: These data demonstrate that a change in infection control policy can significantly reduce MRSA infection in a vascular unit.

Amoxicillin-Potassium Clavulanate Combination↗
PubMed2004

Tackling contamination of the hospital environment by methicillin-resistant Staphylococcus aureus (MRSA): a comparison between conventional terminal cleaning and hydrogen peroxide vapour decontamination.

The hospital environment can sometimes harbour methicillin-resistant Staphylococcus aureus (MRSA) but is not generally regarded as a major source of MRSA infection. We conducted a prospective study in surgical wards of a London teaching hospital affected by MRSA, and compared the effectiveness of standard cleaning with a new method of hydrogen peroxide vapour decontamination. MRSA contamination, measured by surface swabbing was compared before and after terminal cleaning that complied with UK national standards, or hydrogen peroxide vapour decontamination. All isolation rooms, ward bays and bathrooms tested were contaminated with MRSA and several antibiogram types were identified. MRSA was common in sites that might transfer organisms to the hands of staff and was isolated from areas and bed frames used by non-MRSA patients. Seventy-four percent of 359 swabs taken before cleaning yielded MRSA, 70% by direct plating. After cleaning, all areas remained contaminated, with 66% of 124 swabs yielding MRSA, 74% by direct plating. In contrast, after exposing six rooms to hydrogen peroxide vapour, only one of 85 (1.2%) swabs yielded MRSA, by enrichment culture only. The hospital environment can become extensively contaminated with MRSA that is not eliminated by standard cleaning methods. In contrast, hydrogen peroxide vapour decontamination is a highly effective method of eradicating MRSA from rooms, furniture and equipment. Further work is needed to determine the importance of environmental contamination with MRSA and the effect on hospital infection rates of effective decontamination.

Cross Infection↗
PubMed2006

The throat: an important site for MRSA colonization.

In order to evaluate the value of bacterial cultures taken from the throat, 266 patients with MRSA were retrospectively assessed. At the time when MRSA was first detected in the patient, the most frequent sites positive for MRSA were a skin lesion (110 patients, 41%), the anterior nares (109 patients, 41%), and the throat (102 patients, 38%). In 26%, 17%, and 17% of the patients, a skin lesion, the anterior nares, and the throat, respectively, were the only site where MRSA was seen. In 123 patients cultured for MRSA because of a close contact with an already known MRSA patient, 65 patients (53%) were positive for MRSA in their throat and in 40 patients (33%), throat was the only sample site with MRSA at the time when the patient was found to be MRSA positive. 146 of the 266 patients (55%) were colonized with MRSA in the throat any time throughout the period they were MRSA positive. We conclude that throat is an important reservoir for MRSA and that samples taken from the throat should be included in screening patients for MRSA.

Adolescent↗
PubMedDate not supplied

The effect of G-CSF in an experimental MRSA graft infection in mice.

Wound infection after prosthetic material implantation is a troublesome complication with an incidence of 2% to 10%. The effect of granulocyte colony-stimulating factor (G-CSF) was studied in an experimental methicillin-resistant Staphylococcus aureus (MRSA) graft infection model. Eighty adult mice were used. Under general anesthesia an abdominal incision of 2 cm in length was performed. A subcutaneous cavity of 2 x 2 cm in size was created. Polypropylene mesh pieces of 2 x 1 cm and MRSA solution of 0.1ml of 10(8) CFU/mL were used. G-CSF was applied systemically or locally in a dosage of 0.02 MU/30 g body weight. There were 8 groups: group I, wound + MRSA; group II, wound + mesh + MRSA; group III, wound + mesh + MRSA + G-CSF (ip, 48 h before operation); group IV, wound + mesh + MRSA + G-CSF (ip, 24 h before operation); group V, wound + mesh + MRSA + G-CSF (locally, into the cavity); group VI, wound + mesh (incubated in G-CSF solution for 4 h) + MRSA; group VII, wound + mesh + MRSA + G-CSF, ip, 24 h from operation; and group VIII (positive control group), wound + mesh + MRSA + Teicoplanin (0.03 mg/30 g body weight, ip, 1/2 h before operation). Three days after, animals were killed and incisions were examined for possible infection or abscess formation and wound failure. Meshes were removed; after vortexing and dilution, samples were incubated with 5% agar media. Results of bacterial incubation were evaluated 24 h and 48 h later. There were symptoms of wound infection and abscess formation in all groups except group VIII. In group VIII, MRSA was isolated in 7 events with a colony count below 10(3). Bacterial counts were above 10(6) (10(6)-10(8)) in all other groups. Thus, it was observed that wound infection could be created with this model, but G-CSF could not prevent the development of wound infection, whether it was administered systemically or locally. Teicoplanin decreased the number of colony-forming units of MRSA, and prevents wound infection in this MRSA wound infection model.

Animals↗
PubMed1992

An epidemiological study of methicillin-resistant Staphylococcus aureus (MRSA) isolated from medical staff, inpatients, and hospital environment in one ward at our hospital.

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important causative microorganisms for nosocomial infections. Recently, the incidence of isolation of MRSA has been increasing every year in Japan and is, notably, much more frequently found in inpatients than in outpatients. Therefore, we have done epidemiological studies of MRSA isolated from medical staff, inpatients, and the hospital environment in one ward of our hospital. Thereafter, we examined the antibiotic susceptibility (ABPC, DMPPC, CET, CMZ, IPM, GM, MINO, OFLX, EM, CLDM, VCM), phage typing, and coagulase typing of these MRSA. MRSA were isolated more frequently from anterior nares of inpatients than from doctors and nurses. MRSA were isolated more frequently from the environment near carriers of MRSA. Coagulase type II and phage type N.T. (not typable) were the dominant types of MRSA in our hospital (69% and 61%). MRSA strains were resistant to most antibiotics with a few exceptions (VCM, IPM, CMZ, CET). The high isolation frequency of MRSA in our hospital seems to suggest that inpatients who are carrying MRSA spread MRSA throughout the hospital environment and that the anterior nares of inpatients are the major MRSA harbor.

Air Microbiology↗
PubMed2005

MRSA at an English children's hospital from 1998 to 2003.

AIMS: To investigate the epidemiological and clinical aspects of MRSA among inpatients and outpatients presenting to hospital. METHODS: Analysis of demographic, epidemiological, and clinical data collected on 385 children first identified as having MRSA between January 1998 and December 2003 in a 250 bed English children's hospital. RESULTS: There were 267 inpatients and 118 outpatients. The number of new cases of MRSA declined from 72 in 1998 to 52 in 2003, whereas hospital activity increased. Ninety nine (37.1%) inpatients acquired MRSA outside the hospital; a further 90 occurred among 31 clusters of cases. One hundred and seventy eight (66.7%) inpatients were aged <2 years; cardiac services and paediatric & neonatal surgery accounted for 59.6% of cases. Dermatology and A&E accounted for 51.7% of outpatients; 73.8% of outpatients had recently previously attended the hospital. A total of 13.9% of inpatients with MRSA developed bacteraemia; MRSA accounted for 15% of Staphylococcus aureus bacteraemias. The risk of MRSA bacteraemia in colonised patients, and the proportion of S aureus bacteraemias that were MRSA, varied between specialties. Intravascular devices were the most common source of MRSA bacteraemia (63.4% of cases). The mortality rate was 7.3%. CONCLUSIONS: Enhanced surveillance of MRSA can identify at-risk patient groups, thus facilitating targeting of control measures. The absence of a link between numbers of cases of acquisition of MRSA and bacteraemia suggests that the rise in MRSA bacteraemia may not solely reflect an increase in MRSA prevalence in children in the UK. The need for larger epidemiological studies is emphasised.

Age Distribution↗
PubMed2001

[A study of methicillin -- resistant staphylococcus aureus (MRSA) in a burn unit with repetitive -- DNA -- sequence -- based PCR fingerprinting].

OBJECTIVE: To investigate the distribution and spread of MRSA in a burn ward, so as to explore the measures of the prevention, surveillance and control of hospital infection in a burn ward. METHODS: Five hundred and four specimens were isolated from the wounds and nasal vestibules of burn patients, the hands and nasal vestibules of medical staffs and lay attendants and the surfaces of various equipments. From these specimens, 58 strains of MRSA and 43 methicillin -- sensitive staphylococcus aureus (MSSA) were isolated. The genome DNA of isolated MRSA strains was analyzed by repetitive DNA -- sequence -- based PCR analysis. RESULTS: MRSA strains were isolated from the burn wounds in 22 of 41 (53.7%) patients, and 5 from the nasal vestibules. Moreover, among 19 medical staffs, MRSA strains were isolated from the hands of 9 persons, but not from the nasal vestibules. From the hands in 9 of 43 lay attendants and the nasal vestibules in 2 MRSA strains were found. Thirteen MRSA strains were isolated from 193 specimens from the surrounding items. It was indicated by repetitive DNA -- sequence -- based PCR analysis of the genome DNA of isolated MRSA strains that there existed homologous strains around the patients' wounds, in the burn wounds, on the skin of medical staffs and lay attendants and also surrounding equipments. CONCLUSION: (1) There was wide spread presence of MRSA homologous strains in the burn ward. (2) It was indicated by repetitive DNA -- sequence -- based PCR analysis of the genome DNA of isolated MRSA strains that there was cross infection among burn patients. The source of the infection of MRSA in burn ward was burn patients, and the route of the infection was hands of medical staffs and lay attendants. (3) MRSA is wide -- spread. The contamination of the hands and the environment was potential risk factor of MRSA outbreak in the burn unit.

Burn Units↗
PubMed2002

DNA fingerprinting of methicillin-resistant Staphylococcus aureus (MRSA) by pulsed-field gel electrophoresis (PFGE) in a teaching hospital in Malaysia.

Methicillin-resistant Staphylococcus aureus (MRSA) has been prevalent in our hospital over the last three years. Differentiation among MRSA strains by DNA typing in addition to antibiotic resistance pattern surveillance is crucial in order to implement infection control measures. The aim of this study was to characterize MRSA isolates from patients admitted to Hospital Universiti Kebangsaan Malaysia (HUKM) by phenotypic (analyses of antibiotic susceptibility pattern) and genotypic (PFGE) techniques to determine the genetic relatedness of the MRSA involved and to identify endemic clonal profiles of MRSA circulating in HUKM. Seventy one MRSA strains collected between January to March 2000 from patients from various wards in HUKM were tested for antimicrobial resistance and typed by pulsed-field gel electrophoresis (PFGE). Four major types of PFGE patterns were identified (A, B, C and D) among MRSA strains. Two predominant PFGE types were recognised, Type A (59.2%) and Type B (33.8%). Most of these strains were isolated from ICU, Surgical wards and Medical wards. MRSA strains with different PFGE patterns appeared to be widespread among wards. Strains with the same antibiotype could be of different PFGE types. Most of isolates were resistant to ciprofloxacin, erythromycin, gentamicin and penicillin. One isolate with a unique PFGE pattern Type D and susceptible to gentamicin was identified as a different clone. Some isolates obtained from the same patient showed different PFGE subtypes suggesting that these patients were infected/colonized with multiple MRSA strains. PFGE analysis suggests that MRSA strains with different PFGE types was propagated within our hospital. The relationship between antibiotic susceptibility and PFGE patterns was independent. The ability of PFGE technique in differentiating our MRSA strains make it a method of choice for investigating the source, transmission and spread of nosocomial MRSA infection, and thus an appropriate control programme can be implemented to prevent the spread of MRSA infection.

DNA Fingerprinting↗
PubMed2006

The success of routine MRSA screening in vascular surgery: a nine year review.

AIM: Methicillin resistant Staphylococcus aureus (MRSA) infection in vascular patients is associated with increased morbidity and mortality. We investigated whether routine MRSA screening reduced complications related to MRSA infection. METHODS: Data was analysed for all MRSA positive (+ve) vascular patients admitted before (1996-2000) and after (2001-2004) routine MRSA screening was introduced. Outcome measures compared included wound infection, major limb amputation and mortality rates. RESULTS: There were 92 and 188 MRSA +ve patients in the pre- and postscreening periods, respectively. After the introduction of MRSA screening, MRSA wound infection in MRSA +ve elective admissions was significantly reduced from 55.6% (20/36) to 22.4% (15/67), (P=0.002, chi2 test); amputations were reduced from 27.8% (10/36) to 9% (6/67), P value 0.026, and mortality from 16.7% (6/36) to 9% (6/67), P value >0.05. In MRSA +ve emergency admissions wound infection was significantly reduced from 62.5% (35/56) to 43.8% (53/121), P value 0.042, amputations from 50% (28/56) to 38.8% (47/121), P value 0.26, and mortality from 25% (14/56) to 12.4% (15/121), P value 0.067. CONCLUSIONS: While the incidence of MRSA infection continues to rise, we have successfully demonstrated that MRSA screening identifies patients at risk of serious complications and is associated with a reduction in these complications following both elective and emergency surgery. Routine screening of all vascular admissions should be part of the strategy to combat MRSA infection.

Anti-Bacterial Agents↗
PubMed1993

[A clinical study of respiratory infection with methicillin-resistant Staphylococcus aureus (MRSA)].

We investigated patients with positive sputum for MRSA at Daido Hospital. The study was conducted from 1990 to 1991. The number of cases with positive sputum for MRSA is moderately increased. We classified 116 MRSA isolated cases into three groups, 67 cases of colonization with MRSA, 26 cases of suspected bronchopulmonary infection, and 23 cases of bronchopulmonary infection with MRSA. The coagulase types of MRSA were type II or type II + III. Examination of the susceptibility to antibiotics of MRSA showed that all MRSA strains were susceptible to sulfamethoxazole trimethoprim, arbekacin, and vancomycin. A few strains were resistant to rifampicin. There were no differences in coagulase types and susceptibility to antibiotics between the three groups. Bronchopulmonary infection with MRSA was frequently associated with underlying bronchopulmonary disease, whether malignant or not. Risk factors for MRSA bronchopulmonary infection could not be identified, but the prognosis of MRSA bronchopulmonary infection was poor in cases with higher grade of performance status. MRSA eradication rate in sputum after therapy was low, and was not improved by adding inhalation of antibiotics including vancomycin to systemic chemotherapy. This investigation demonstrates the importance of environmental prevention of MRSA infection in hospitals.

Adolescent↗
PubMed2026

Emergence of SCCmec variants causing false-negative MRSA results by Xpert SA Nasal Complete: a need for culture back-up?

BACKGROUND: Staphylococcus aureus (SA) is a major human pathogen and an important cause of healthcare-associated infections. Hospital-acquired methicillin-resistant S. aureus (MRSA) is associated with increased morbidity and mortality. Screening for nasal carriage of SA followed by decolonization has been shown to reduce healthcare-associated MRSA transmission and infection. Nucleic acid amplification assays (NAATs) are widely used for MRSA screening and are associated with shorter turnaround times, fewer isolation days, reduced MRSA-related infections, and improved clinical outcomes and cost savings. CASE SUMMARY: Two patients underwent preoperative nasal screening using Xpert SA Nasal Complete, and corresponding culture results were discordant with the molecular results. In both cases, the Xpert SA assay reported "SA detected and MRSA not detected," whereas culture and antimicrobial susceptibility testing (AST) demonstrated the presence of MRSA. Additional testing supported the culture-based identification of MRSA. Whole-genome sequencing and molecular typing revealed that both MRSA isolates harbored SCCmec variants that were not detected by the Xpert assay, leading to false-negative (FN) MRSA results. CONCLUSION: While NAATs remain highly sensitive and reliable tools for MRSA screening and the overall risk of FN MRSA detection may be low, our cases highlight the importance of ongoing surveillance of local MRSA epidemiology and understanding the genetic inclusivity of the molecular assays used for detection. In high-risk or targeted patients, consideration of reflex culture may be warranted.

MRSA screening↗