Molecular determination of carriage of the mecA locus in coagulase negative staphylococci in screening swabs from patients in an intensive care unit

Phenotypic detection, antimicrobial susceptibility and virulence profile of staphylococci in the pig production setting, Makurdi, Nigeria

Livestock, particularly pigs, have increasingly been recognized as important reservoirs for zoonotic transmission of pathogenic bacteria, including staphylococci. Livestock production systems in developing countries of sub-Saharan Africa, including Nigeria, are characterized by high misuse/abuse of antimicrobials and a close association between humans and these animals, which promotes the emergence and transmission of resistant and potentially virulent bacteria. In the present study, we investigated the occurrence and characteristics (species distribution, virulence and resistance profile) of staphylococci from smallholder backyard pig farms, slaughter slabs and pig handlers in Makurdi, Nigeria. A total of 330 nasal swabs originating from 300 pigs and 30 in-contact humans were collected and processed. One hundred and thirteen samples [34.2 %; 95 % confidence interval (CI): 29.1–39.6] comprising 103 (34.3 %; 95 % CI: 29.0–40.0) and 10 (33.3 %; 95 % CI: 17.3–52.8 %) samples from pigs and humans, respectively, were positive for staphylococci, yielding 120 isolates (pigs n=110, humans n=10). The 120 isolates were distributed into 15 species with Staphylococcus aureus (n=25) followed by Staphylococcus cohnii (n=19) and Staphylococcus sciuri (n=14) occurring more frequently. All isolates were resistant to β-lactam (100 %) antibiotics. Resistance to some critical antimicrobials, including linezolid (22 %), vancomycin (19.2 %), gentamicin (7.5%) and the fluoroquinolones ciprofloxacin (75.8 %) and enrofloxacin (66.7 %), was also observed. Majority (99.2 %) of the isolates displayed a multidrug resistance phenotype with the AMP-C-CIP-E-ENR-FOX-OX-P-S-SXT-TE phenotype being predominant. Overall, 70 % of the isolates expressed the methicillin resistance phenotype, out of which 20 % (n=17) were MRSA. Resistance to serum bactericidal activity and biofilm production were respectively observed in 45 (100 %) and 5 (11.3 %) of the coagulase-positive staphylococci. Our findings demonstrated the occurrence of a high diversity of staphylococci expressing multidrug resistance and potentially virulent phenotypes among healthy swine and pig handlers in small-scale backyard farms in North-Central Nigeria. These findings underscore the potential role of pig production settings in the emergence and dissemination of potentially virulent staphylococci and the importance of the development of antimicrobial resistance monitoring systems/implementation of control measures in developing countries. Proper hygienic practices and control of indiscriminate use and misuse of antibiotics are recommended.

Survival of epidemic strains of healthcare (HA-MRSA) and community-associated (CA-MRSA) meticillin-resistant Staphylococcus aureus (MRSA) in river-, sea- and swimming pool water

The aim of this study was to examine the survival dynamics of several epidemic healthcare (HA) and community-associated (CA) meticillin-resistant Staphylococcus aureus (MRSA) in river, sea and swimming pool waters. Six different phage-types of HA-MRSA (Irish 1, Irish 2, EMRSA 15, EMRSA 16, distinct type and non-typable), as well as a community-associated MRSA (CA-MRSA), were examined in this study. Two strains of each type were examined resulting in a total of 14 organisms being examined. Cells were harvested from overnight cultures of Columbia blood agar (Oxoid) supplemented with 5% [v/v] defibrinated blood to make a 0.5 McFarland inoculum standard. An inoculum of each MRSA isolate was added individually to each water microcosm to give log(10)5 (10(5)) colony forming units (cfu/ml water) and water was stored in the dark at ambient temperature for up to 14 days. Recovery experiments were unable to isolate any of HA- or CA-MRSA in the swimming pool water after 24 h storage. This study demonstrates that all 14 epidemic HA and CA MRSA studied can survive in sea and river water environments up to at least 14 days post inoculation. There was no significant differences in the survival dynamics between CA-MRSA and HA-MRSA in any water environment, but all MRSA died off more quickly in river water, compared to sea water, with decimal (D(10)) reduction values of 3.53 and 7.4 days, for river- and sea water, respectively. This study indicates that contaminated sea and river water may serve as potential reservoirs of HA- and CA-MRSA, if such water sources become contaminated with these organisms.

Bactericidal activity of denture-cleaning formulations against planktonic health care-associated and community-associated methicillin-resistant Staphylococcus aureus

The aim of this study was to examine the survival dynamics of several epidemic health care-associated (HA) and community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) in planktonic state in widely employed denture-cleaning solutions. The bacteriocidal activity of five widely employed denture-cleaning formulations were examined against five phage-types of HA-MRSA (EMRSA 15, EMRSA 16, Irish 1, Irish 2, unique type), as well as a CA-MRSA strain, in this study. Viable MRSA cells (circa 10(5) cfu/mL) were coincubated with optimum recommended working concentrations of denture-cleaning solutions for up to 17 hours (overnight). Recovery experiments were unable to isolate any of the inoculated MRSA organisms 10 minutes post inoculation. The significance and impact of this short study indicates that HA-MRSA and CA-MRSA are not able to remain culturable for 10 minutes in planktonic form, in commonly used denture-cleaning formulations widely available on the UK High Street, suggesting that these formulations may be useful in lowering the numbers of MRSA. Further work is however required to examine the more complex survival dynamics of MRSA in naturally derived denture biofilm, associated with dental plaque and the use of such cleaning formulations.

Survival of epidemic strains of nosocomial- and community-acquired methicillin-resistant Staphylococcus aureus on coins

BACKGROUND

The aim of this study was to examine the survival dynamics of several epidemic nosocomial and community-acquired methicillin-resistant Staphylococcus aureus (MRSA) strains on copper alloy coins.

METHODS

Six different phage types of nosocomial MRSA (Irish 1, Irish 2, EMRSA 15, EMRSA 16, distinct type, and untypeable), as well as community-acquired MRSA, were examined in this study. Two isolates of each type were studied, resulting in a total of 14 organisms being examined. Cells were harvested from overnight cultures of Columbia blood agar (Oxoid) supplemented with 5% (wt/vol) defibrinated blood to make a 0.5 McFarland inoculum standard. An inoculum of each MRSA isolate in 5-microl volume was added to washed, dried, and presterilized 1-penny copper-plated steel coins, equating to log(10) 5 colony-forming units (cfu) and allowed to dry naturally at ambient temperatures in the dark.

RESULTS

Recovery experiments were unable to isolate any of the inoculated organisms 4 hours postinoculation. To ascertain whether this was a toxic effect from the copper alloy of the coins or a physical desiccation effect, experiments were repeated on glass and plastic, and similar results were demonstrated. The effect of soil was investigated by repeating the experiment with (60)Co irradiated pus and sterile blood, and we were able to demonstrate the survival of all organisms after at least 2 weeks storage in the dark at ambient temperature, during which the quantitative counts were reduced by approximately 1-log unit and 2-log units for blood and pus, respectively.

CONCLUSION

This study demonstrates that all epidemic nosocomial- and community-acquired MRSA do not survive when no organic protection is offered but survive well when soil (pus and blood) is present, thus offering protection from drying. This study indicates that contaminated coins may serve as potential vehicles for MRSA.