Chlamydia muridarum enters a viable but non-infectious state in amoxicillin-treated BALB/c mice

Abstract

In culture, exposure to penicillin and other stressors induce chlamydiae to enter a non-infectious but viable state termed persistence. Chlamydiae may reenter their normal developmental cycle after stressor removal. Though aberrant RB similar to those present in culture models of persistence have been observed within infected tissues, the existence of persistent chlamydiae has not been definitively demonstrated in vivo. As a result, the role of persistent organisms in pathogenesis is undefined. In order to establish an experimentally tractable model of in vivo persistence, C. muridarum vaginally-infected mice were gavaged with either water or amoxicillin (amox). Vaginal swabs were collected for chlamydial titration and RNA isolated for quantification of pre-16s rRNA. Uterine tissue was analyzed by transmission electron microscopy (TEM). Although amox-treatment reduced vaginal shedding by >99%, C. muridarum pre-16s rRNA accumulation was unchanged by treatment. These data indicate that the amox-exposed organisms were viable but not infectious. Furthermore, TEM analyses demonstrated that inclusions in amox-treated animals contained primarily large, aberrant RB, but those observed in untreated control animals were normal. Collectively, these data suggest that amoxicillin treatment induces C. muridarum to enter the persistent state in vivo. This model also represents the first experimentally tractable animal model of chlamydial persistence.

Induction of the Chlamydia muridarum Stress/Persistence Response Increases Azithromycin Treatment Failure in a Murine Model of Infection

“…As expected, mock-infected animals did not shed infectious chlamydiae (not shown). Additionally, shedding was undetectable immediately after AMX stress but resumed thereafter in all mice receiving AMX alone (persistently infected controls), as previously observed (4). Taken together, these data suggest that persistent/stressed chlamydiae are more resistant to AZM in vivo, as reported in cell culture (5).…”

“…In our model, AMX treatment decreased vaginal shedding of infectious chlamydiae by Ͼ99% without affecting viability. Shedding of infectious EBs resumed within 1 week after treatment cessation (4). These data demonstrate that AMX can be used to reversibly induce chlamydial persistence in vivo.…”

“…To determine a dose of AZM adequate to eradicate chlamydial shedding, 6-week-old, progesterone-treated, female BALB/c mice were vaginally infected with 10 Mice were vaginally swabbed every third day, and swabs were used to determine infectious IFU shed, via subculture titer assay and antilipopolysaccharide staining as described previously (4). Both 16 mg/kg, which was selected based on its approximation of a typical human dose (10), and 80 mg/kg, which is a commonly published dosage used in mice (11), failed to eradicate productive infection (Fig.…”

Collateral Damage: Detrimental Effect of Antibiotics on the Development of Protective Immune Memory

“…However, Chlamydia trachomatis is not a natural pathogen of mice, and many laboratories therefore choose to examine immunity to Chlamydia muridarum , which causes an ascending reproductive tract infection following vaginal inoculation. Chlamydia bacteria have the ability to fuse and form noninfectious aberrant bodies under antibiotic pressure, and this form of the pathogen is known to be refractory to antibiotic killing (71, 72). There is also evidence that Chlamydia can persist in the intestine during an immune response or antibiotic treatment that can effectively clear bacteria from the reproductive tract (73, 74).…”

Subversion of Cell-Autonomous Host Defense by Chlamydia Infection

“…During each round of the developmental cycle, Chlamydia produce hundreds of infectious progeny which would cause a rapid spread and progression of the infection. Nevertheless, clinical Chlamydia infections tend to remain asymptomatic and slowly progressing, in line with frequent persistence and reactivation phases and non-continuous chlamydial replication in the patient (Beatty et al 1994b;Phillips Campbell et al 2012). …”