Gram Positive Bacilli

Cocci

Corynebacterium Spp.Clostridium spp. Listeria spp.Bacillus spp.

Catalase negativeStreptococcaceae(strepto-cocay-see-eye)

γ (gamma)-hemolytic EnterococcusE. faecalisE. faecium

β-hemolytic (clear) S. Pyogenes Group ABacitracin sensitive

S. agalactiae Group BBacitracin resistant

α-hemolytic (green)S. Pneumoniae Optochin sensitiveBile-soluble capsule (Quellung)

S. viridans, S. Mutans, S. sanguisOptochin resistantBile-insoluble No capsule

Catalase positiveStaphylococcus

Coagulase positive

Coagulase negative

S. epidermidisNovobiocin sensitive

S. saprophyticusNovobiocin resistant

S. aureus

Methods

Nasopharyngeal and oropharyngeal swabs were plated onto CNA (colistin–nalidixic acid) agar (Biolife), sheep blood agar (Biolife) and Sabouraud dextrose agar (Biolife).

Sabouraud plates were incubated at 36 C in ambient air,

whereas CNA and sheep blood plates were incubated at

1. 36 C in ambient air,

2. anaerobically

3. and in an atmosphere of 5% CO2.

All plates were examined after 24, 48 and 72 h.

After 24 h of incubation, α-haemolytic colonies belonging to the same streptococcal species had grown, under each of the three atmospheric growth conditions. The isolate was identified as S. pneumoniae. (Vitek2; bioMe´rieux), and confirmation of the identification was provided by inhibition of the isolate by optochin.

Optochin susceptibility testing was performed in ambient air, anaerobically and in an atmosphere of 5% CO2, to prevent misidentification of Streptococcus pseudo-pneumoniae as true S. pneumoniae (Balsalobre et al., 2006).

In Kirby-Bauer testing, white wafers containing antibiotics are placed on a plate of bacteria. Circles of poor bacterial growth surround some wafers indicating susceptibility to the antibiotic