MRSA, Staph, Staff, Mersa, Methicillin Resistant Staphylococcus Aureus Symptoms & Treatment

CA MRSA doubles MRSA Colonisation Rate in 2 Years

Link: HighWire Press -- Medline Abstract.

Background. @nbsp; Staphylococcus aureus is a common cause of infection, particularly in persons colonized by this organism. Virulent strains of methicillin-resistant S. aureus (MRSA) have emerged in the general community. Methods. @nbsp; A nationally representative survey of nasal colonization with S. aureus was conducted from 2001 through 2004 as part of the National Health and Nutrition Examination Survey. MRSA isolates were identified by the oxacillin disk-diffusion method. The pulsed-field gel electrophoresis (PFGE) type was determined for all MRSA isolates. A t statistic was used to compare the prevalence of colonization across biennia and across population subgroups. Cofactors independently associated with colonization were determined with backward stepwise logistic modeling. Results. @nbsp; The prevalence of colonization with S. aureus decreased from 32.4% in 2001-2002 to 28.6% in 2003-2004 ([Formula: see text]), whereas the prevalence of colonization with MRSA increased from 0.8% to 1.5% ([Formula: see text]). Colonization with MRSA was independently associated with healthcare exposure in males and with having been born in the United States, age >/=60 years, diabetes, and poverty in females. In 2003-2004, a total of 19.7% (95% confidence interval, 12.4%-28.8%) of MRSA-colonized persons carried a PFGE type associated with community transmission. Conclusions. @nbsp; Nasal colonization with MRSA has increased in the United States, despite an overall decrease in nasal colonization with S. aureus. PFGE types associated with community transmission only partially account for the increase in MRSA colonization.

MRSA carriers 4 times more likely to develop infection than MSSA carriers

Link: HighWire Press -- Medline Abstract.

PURPOSE: Nasal, axillary, or inguinal colonization with Staphylococcus aureus generally precedes invasive infection. Some studies have found that colonization with methicillin-resistant S. aureus (MRSA) poses a greater risk of clinical infection than colonization with methicillin-susceptible S. aureus (MSSA). However, the magnitude of risk is unclear. METHODS: We undertook a systematic review to provide an overall estimate of the risk of infection following colonization with MRSA compared with colonization by MSSA. Ten observational studies, with a total of 1170 patients, were identified that provided data on both MSSA and MRSA colonization and infection. A random-effects model was used to obtain pooled estimates of the odds ratio and 95% confidence interval. RESULTS: Overall, colonization by MRSA was associated with a 4-fold increase in the risk of infection (odds ratio 4.08, 95% confidence interval, 2.10-7.44). Studies differed in the choice of patient population, severity of illness, and frequency of sampling to detect colonization. CONCLUSION: Further research is needed to identify effective methods for sustained eradication of MRSA carriage to reduce the high risk of subsequent infection.

Resistance growing to decolonisation treatment

Link: Emerging high-level mupirocin resistance among MRSA isolates in Ireland.

The antimicrobial drug mupirocin (an isoleucine analogue) is a protein synthesis inhibitor that acts by binding irreversibly to isoleucyl t-RNA synthetase (IleS) [1]. It is mainly used as an ointment (2% in paraffin base) and is very effective in eliminating methicillin-resistant Staphylococcus aureus (MRSA) from colonised nasal passages when used in conjunction with other MRSA decolonisation regimens [2]. Guidelines from the Strategy for the control of Antimicrobial Resistance in Ireland (SARI) Infection Control Subcommittee warn that the dosage (three times a day for five days) should not be repeated more than once to avoid emergence of resistance [2]. Two forms of resistance are reported: • Low-level resistance with minimum inhibitory concentrations (MIC) of 8 to 256 mg/L due to a mutation in IleS • High-level resistance (MIC ≥ 512 mg/L) due to acquisition of the plasmid-mediated mupA gene which encodes a second isoleucocyl t-RNA synthetase [1]. Ireland's National Methicillin-Resistant Staphylococcus aureus (MRSA) Reference Laboratory (NMRSARL) monitors rates of resistance to clinically useful antibiotics among MRSA isolates recovered from blood of patients in Irish hospitals [3]. High-level mupirocin resistance (MpR) was detected among 37 of 2,586 (1.4%) MRSA blood-stream isolates sent to NMRSARL between 1 January 1999 and 31 December 2005 (Period 1) compared with 29 of 997 isolates (2.9%) sent between 1 January 2006 and 31 December 2007 (Period 2) (p=0.005). In addition to this significant increase in the proportion of high-level mupirocin-resistant isolates, NMRSARL also noted a change in the epidemiological types associated with mupirocin-resistant MRSA [the antibiogram-resistogram-pulsed field group (AR-PFG) typing method used in NMRSARL is outlined below].

Scientists uncover staph survival in nose strategy

Link: Revealing How Superbug Staph Aureus Resists Our Natural Defenses.

Dr. Ferric Fang, UW professor of laboratory medicine and microbiology, and his UW colleagues Dr. Anthony Richardson and Dr. Stephen Libby set out to determine what makes Staph aureus a better pathogen than other bacteria. They focused on a chemical compound called nitric oxide (NO), a natural antibiotic that our cells excrete to protect us from pathogens. For most bacteria, NO creates an environment that keeps invading microbes from undergoing respiration or fermentation, vital chemical processes that allow bacteria to grow. The researchers found that Staph aureus has a mechanism that allows it to produce lactic acid in the presence of NO, which allows it to maintain its chemical balance and keep growing and thriving in the harsh host environment. When Staph aureus is exposed to NO, it produces the novel enzyme responsible for lactic acid production, along with another enzyme that converts NO to non-toxic products. NO is commonly found in the nose and nasal passages, and is meant to protect people against disease-causing microbes. But Staph aureus is commonly found in the nose despite the presence of NO, the researchers explained. When the researchers modified Staph aureus to take away its ability to make lactic acid, the bacteria could no longer tolerate NO. The modified bacteria also lost their ability to survive in host immune cells and cause lethal disease in mice.

Overlapping Population Structures of Nasal Isolates of Staphylococcus aureus

Link: Overlapping Population Structures of Nasal Isolates of Staphylococcus aureus from Healthy Dutch and American Individuals -- Melles et al. 46 (1): 235 -- Journal of Clinical Microbiology.

This result identifies differences in the local prevalence of certain S. aureus genotypes. AFLP clusters II and III, which represent multilocus sequence typing clonal complexes 30 and 45, respectively, account for 46.4% of all MSSA isolates in the study, suggesting that these two lineages have evolved as extremely successful pandemic colonizers of humans. In conclusion, the overall population structures of American and Dutch nasal carriage isolates of S. aureus are surprisingly similar, despite subtle geographic differences in the prevalence of certain S. aureus genotypes.

Nasal treatment eases MRSA burden for sick patients

Link: Intranasal mupirocin for reduction of Staphylococcus aureus infections in surgical patients with nasal carriage: a systematic review -- Rijen et al., 10.1093/jac/dkm480 -- Journal of Antimicrobial Chemotherapy.

CENTRAL, EMBASE and MEDLINE were searched for the keywords mupirocin, pseudomonic acid or bactroban, combined with nasal or intranasal. Only randomized controlled studies investigating surgical patients were included. Titles and abstracts were screened independently by two reviewers. S. aureus infection data in nasal carriers with and without mupirocin treatment were pooled in the meta-analysis. Results: The literature search resulted in 211 hits, of which 4 articles met the inclusion criteria. Among the 686 mupirocin-treated surgical patients with S. aureus nasal carriage, there were 25 S. aureus infections (3.6%), compared with 46 (6.7%) in the controls (RR 0.55, 95% CI 0.34–0.89; P = 0.02). Conclusions: Prophylactic intranasal mupirocin significantly reduced the rate of post-operative S. aureus infections among surgical patients who were S. aureus carriers.

Dermatitis patients MRSA prone

Link: HighWire Press -- Medline Abstract.

Eighty seven (75.4%) of 115 patients contained cultivable S. aureus, of which 16 (18.3%) were MRSA. All MRSA were susceptible to chloramphenicol, rifampin, cotrimoxazole, and ciprofloxacin. While MSSA were composed of 23 isolates of singular types and 9 clusters comprising 48 isolates, MRSA isolates were typed into three clones; 8 isolates of pulsotype A-agr1-SCCmec IV, 5 isolates of pulsotype B-agr3-SCCmec IIb-etb-positive, and 3 isolates of pulsotype C-agr3-SCCmec IV. Three SCCmec IVA-MRSA were tst-positive but none were positive for the pvl or eta. Among 71 MSSA isolates, 7 isolates were tst-positive, of which 6 were pulsotype F-agr3, and 9 of 10 agr4-isolates were eta-positive. The average ages of patients carrying MSSA, SCCmec IVA-MRSA and SCCmec IIb-MRSA were 7.7 /-4.6, 3.1 /-1.5 and 8.2 /-3.1 years, respectively. Among the patients carrying MRSA, two patients had been treated with oral antimicrobials and one had been admitted to hospital 18 months ago. In conclusion, CA-MRSA isolates of a few clones colonized AD skin of the patients without risk factors for acquisition of HA-MRSA, which suggested that the AD skin of children may represent a significant reservoir of MRSA colonization in community.

New Spray could beat early stage MRSA without antibiotics

Link: New Anti-Infective Drug Aims to Fight Drug-Resistant Bacteria at the Source.

NovaBay Pharmaceuticals, Inc. announces results from a Phase I clinical trial with NVC-422, a new compound with potent activity against numerous pathogens, including MRSA. NVC-422, whose trade name is AgaNase™, is unique in that it is an anti-infective, but technically not an antibiotic. Nasal colonization by Staphylococci is an important risk factor that predisposes carriers to nosocomial infections. NovaBay hopes that by greatly reducing this layer of colonizing bacteria, hospital patients will be less likely to experience serious MRSA infections. NVC-422 rapidly destroys a range of pathogens that includes Gram-positive and Gram-negative bacteria, yeasts, and viruses. Because it kills pathogens on contact and not through typical antibiotic mechanisms, it is believed that bacteria and viruses are unlikely to develop resistance to NVC-422 treatment. This “non-antibiotic” strategy is critical for maintaining the efficacy of antibiotic therapies for life-threatening infections.

1 in 3 with MRSA not nasally colonised

Link: Prediction of methicillin-resistant Staphylococcus aureus involvement in disease sites by concomitant nasal sampling -- Robicsek et al., 10.1128/JCM.01746-07 -- Journal of Clinical Microbiology.

Retrospective review of 5,779 nasal MRSA tests obtained within 24 hours before or after a clinical culture growing any organism. Results. A positive nasal MRSA test strongly predicted MRSA involvement in a clinical site (relative risk 12.9, 95% CI, 10.4, 16.1). Nasal MRSA colonization also strongly predicted antimicrobial resistance in other organisms. A negative nasal test was less useful; only 217 (67.2%, 95% CI 61.8, 72.3) of 323 patients with clinical cultures involving MRSA had detectable concomitant nasal MRSA colonization. Patients with clindamycin-susceptible MRSA were less likely (59%) to have nasal colonization than those with clindamycin-resistant MRSA (71%, P = 0.042). Conclusions. Patients nasally colonized with MRSA were substantially more likely to have antibiotic resistant flora in clinical isolates and this should be considered when initiating therapy. However, nearly a third of MRSA-infected patients were not nasally colonized, suggesting that nasal colonization need not precede disease and that a negative test for nasal colonization would not rule out MRSA disease in settings of moderate or high prevalence.

New Nasal treatment could help rid millions of MRSA

Link: NovaBay Announces Positive Phase I Study Results with Its Lead Aganocide Compound.

(AMEX & TSX: NBY, http://novabaypharma.com), a biopharmaceutical company developing products for the treatment or prevention of a wide range of bacterial and viral infections, reports results from a Phase I trial studying the lead Aganocide compound, NVC-422, a novel non-antibiotic anti-infective that has shown potent in vitro activity against major pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). Nasal colonization of Staphylococcus aureus, including MRSA, is an important risk factor that predisposes the carrier to infections during invasive hospital procedures. The results of the Phase I trials show that when topically applied to the anterior nares (the lower nasal passages), NVC-422 appears safe and well tolerated with undetectable systemic exposure. Based on these results, NovaBay has commenced a second Phase I trial to test the safety of NVC-422 at a higher dose and expects to have results from this second study by early 2008. In parallel with the second Phase I study, NovaBay expects to commence a Phase IIa study by January 2008 in healthy volunteers that are carriers of Staphylococcus aureus in their nasal passages.