Use of Mueller-Hinton Broth and Agar in the Germ Tube Test

Abstract

Candida albicans is often isolated from clinical samples, thus its presumptive differentiation from other species of the same genus can be based on its ability to form the germ tube in human serum. Nevertheless, there are two other species that share this characteristic: C. dubliniensis and C. africana. The aim of this study was to compare four different substrates to perform the germ tube (GT) test. The Candida spp. isolates were identified using a manual system (135 C. albicans, 24 C. tropicalis and one C. dubliniensis). The germ tube test was performed with fresh, previously frozen serum and Mueller-Hinton (MH) broth and agar. GT was observed in 96% (130/136) of the isolates through the fresh serum technique, 94% (128/136) through previously frozen serum, 92% (125/136) in MH agar, and 90% (122/136) in MH broth. The sensitivity of each test was higher than 90%, with 100% specificity. Both the MH agar and broth were able to identify the true positives, and false positives were not found. However, some C. albicans isolates were not identified. MH agar and broth may be used in laboratory for the rapid presumptive identification of C. albicans, as an alternative method for germ tube test.

Species identification and antifungal susceptibility pattern ofCandidaisolates in cases of vulvovaginal candidiasis

“…43 However, this test gives also positive results in case of C. dubliniensis. 44 Consistent with our GTT results, some studies 45,46 reported similar sensitivity rates but with 100% specificity. Other studies 47 reported lower sensitivity and specificity rates (79.3% and 69.2%, respectively), or higher rates ranging from 92 to 98.8% and 99 to 100%, respectively.…”

Evaluation Of Mueller-Hinton Agar For Germ Tube Test

“…Germ tüp oluşumu için en sık kullanılan insan serumu dışında, farklı serum tipleri ve besiyerleri araştırılmıştır. At, tavşan, koyun, keçi, domuz ve fetal sığır serumu, peptonlu su, triptik soy buyyon, beyin kalp infüzyon buyyonu, Sabouraud glukoz buyyon, Mueller-Hinton buyyon (MHB), Mueller-Hinton agar, pirinç oxgall-tween 80 agar ve RPMI besiyeri gibi çok sayıda serum ve besiyeri çeşidi, optimum GTT için araştırılmıştır 6,10,12,13 .…”

“…Bu test insan veya tavşan serumu içerisine bir miktar maya kolonisi eklenmesi ve 37 o C'de 2-3 saat inkübe edilerek germ tüp oluşumunun incelenmesi esasına dayanır 4 . Serum kullanımı esnasında meydana gelebilecek bulaş riski ve taze serum bulunmasındaki zorluk nedeniyle, GTT için insan serumu yerine agar temelli besiyerleri kullanımı ile ilgili çalışmalar yapılmaktadır [6][7][8][9][10] .…”

Identification of Candida and Trichosporon species by oxidase and coagulase test.

“…For example, the serum has to be fresh or frozen; the yeast inoculum has to contain <10 7 cells mL -1 , otherwise, the germ tube production is inhibited. In addition, the handling of pooled human serum includes the possible risk of infection with HIV or hepatitis virus and different batches of serum may produce different results (8) .…”