The phenotypes and genotypes associated with biofilm formation among methicillin-susceptible Staphylococcus aureus (MSSA) isolates collected from a tertiary hospital in Terengganu, Malaysia

Methicillin-susceptible Staphylococcus aureus (MSSA) is an important nosocomial pathogen worldwide. This study aims to investigate the in vitro biofilm-forming ability of clinical MSSA isolated from various sources in the main public tertiary referral hospital in Terengganu, Malaysia and to detect the presence of biofilm-associated and regulatory genes among these isolates. A total of 104 MSSA isolates [pus (n = 75), blood (n = 24), respiratory secretions (n = 2), eye (n = 2), and urine (n = 1)] were investigated for slime production and biofilm formation using Congo red agar and crystal violet microtitre plate, respectively. Fifteen MSSA isolates with varying degrees of biofilm formation were selected for validation via a real-time cell analyser. All isolates were screened for microbial surface components recognising adhesive matrix molecules (MSCRAMM) and accessory gene regulator (agr) using polymerase chain reaction assay. A total of 76.0% (79/104) isolates produced slime layer, while all isolates developed biofilm as follows: 52.8% (55/104) strong biofilm producers, 40.4% (42/104) intermediate biofilm producers, and 6.7% (7/104) weak biofilm producers. A total of 98.1% (102/104) isolates carried at least one of the screened MSCRAMM gene(s) with the eno gene detected at the highest rate (87.5%, 91/104), while the sasG gene was significantly associated with strong biofilm production (p = 0.015). Three agr groups, 1, 2, and 3, were detected among the MSSA isolates with a predominance of agr-3 (32.7%, 34/104). In conclusion, biofilm formation varied greatly among clinical MSSA isolates, and the presence of sasG gene and agr-1 may play important role in initiating MSSA infections via biofilm formation.

spa diversity of methicillin-resistant and -susceptible Staphylococcus aureus in clinical strains from Malaysia: a high prevalence of invasive European spa-type t032

Background

Staphylococcus aureus is one of the important pathogens causing nosocomial infection. spa typing allows identification of S. aureus clones in hospital isolates and is useful for epidemiological studies and nosocomial infection control. This study aims to investigate the spa types in Malaysian S. aureus isolates obtained from various clinical specimens.

Method

A total of 89 methicillin-resistant S. aureus (MRSA) [pus (n = 55), blood (n = 27), respiratory (n = 5), eye (n = 2)] isolates and 109 methicillin-susceptible S. aureus (MSSA) [pus (n = 79), blood (n = 24), respiratory (n = 3), eye (n = 2) and urine (n = 1)] isolates were subjected to spa typing with sequences analysed using BioNumerics version 7.

Results

The spa sequence was successfully amplified from 77.8% of the strains (154/198) and 47 known spa types were detected. The distribution of known spa types in MRSA (36.2%, 17/47) was less diverse than in MSSA (70.2%, 33/47). The most predominant spa types were t032 (50%) in MRSA, and t127 (19%) and t091 (16.7%) in MSSA, respectively. spa type t091 in MSSA was significantly associated with skin and soft tissue infections (p = 0.0199).

Conclusion

The previously uncommon spa type t032 was detected in the Malaysian MRSA strains, which also corresponded to the most common spa type in Europe and Australia, and has replaced the dominant spa type t037 which was reported in Malaysia in 2010.

NUMB localizes in the basal cortex of mitotic avian neuroepithelial cells and modulates neuronal differentiation by binding to NOTCH-1

The importance of lateral inhibition mediated by NOTCH signaling is well demonstrated to control neurogenesis both in invertebrates and vertebrates. We have identified the chicken homolog of Drosophila numb, which suppresses NOTCH signaling. We show that chicken NUMB (c-NUMB) protein is localized to the basal cortex of mitotic neuroepithelial cells, suggesting that c-NUMB regulates neurogenesis by the modification of NOTCH signaling through asymmetrical cell division. Consistent with this suggestion, we show (1) that c-NUMB interferes with the nuclear translocation of activated c-NOTCH-1 through direct binding to the PEST sequence in the cytoplasmic domain of c-NOTCH-1 and (2) that c-NUMB interferes with c-NOTCH-1-mediated inhibition of neuronal differentiation.